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• Published: 17 October 2022

How animal minds can help reveal the human mind

• Andrew B. Barron   ORCID: orcid.org/0000-0002-8135-6628 1  

Nature Reviews Psychology volume  1 ,  pages 687–688 ( 2022 ) Cite this article

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The field of animal cognition does far more than simply extend cognition into zoology. Studying animal cognition helps researchers to comprehend the human mind.

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Skinner’s Box Experiment (Behaviorism Study)

We receive rewards and punishments for many behaviors. More importantly, once we experience that reward or punishment, we are likely to perform (or not perform) that behavior again in anticipation of the result. 

Psychologists in the late 1800s and early 1900s believed that rewards and punishments were crucial to shaping and encouraging voluntary behavior. But they needed a way to test it. And they needed a name for how rewards and punishments shaped voluntary behaviors. Along came Burrhus Frederic Skinner , the creator of Skinner's Box, and the rest is history.

What Is Skinner's Box?

The "Skinner box" is a setup used in animal experiments. An animal is isolated in a box equipped with levers or other devices in this environment. The animal learns that pressing a lever or displaying specific behaviors can lead to rewards or punishments.

This setup was crucial for behavioral psychologist B.F. Skinner developed his theories on operant conditioning. It also aided in understanding the concept of reinforcement schedules.

Here, "schedules" refer to the timing and frequency of rewards or punishments, which play a key role in shaping behavior. Skinner's research showed how different schedules impact how animals learn and respond to stimuli.

Who is B.F. Skinner?

Burrhus Frederic Skinner, also known as B.F. Skinner is considered the “father of Operant Conditioning.” His experiments, conducted in what is known as “Skinner’s box,” are some of the most well-known experiments in psychology. They helped shape the ideas of operant conditioning in behaviorism.

Law of Effect (Thorndike vs. Skinner) 

At the time, classical conditioning was the top theory in behaviorism. However, Skinner knew that research showed that voluntary behaviors could be part of the conditioning process. In the late 1800s, a psychologist named Edward Thorndike wrote about “The Law of Effect.” He said, “Responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation, and responses that produce a discomforting effect become less likely to occur again in that situation.”

Thorndike tested out The Law of Effect with a box of his own. The box contained a maze and a lever. He placed a cat inside the box and a fish outside the box. He then recorded how the cats got out of the box and ate the fish. 

Thorndike noticed that the cats would explore the maze and eventually found the lever. The level would let them out of the box, leading them to the fish faster. Once discovering this, the cats were more likely to use the lever when they wanted to get fish. 

Skinner took this idea and ran with it. We call the box where animal experiments are performed "Skinner's box."

Why Do We Call This Box the "Skinner Box?"

Edward Thorndike used a box to train animals to perform behaviors for rewards. Later, psychologists like Martin Seligman used this apparatus to observe "learned helplessness." So why is this setup called a "Skinner Box?" Skinner not only used Skinner box experiments to show the existence of operant conditioning, but he also showed schedules in which operant conditioning was more or less effective, depending on your goals. And that is why he is called The Father of Operant Conditioning.

How Skinner's Box Worked

Inspired by Thorndike, Skinner created a box to test his theory of Operant Conditioning. (This box is also known as an “operant conditioning chamber.”)

The box was typically very simple. Skinner would place the rats in a Skinner box with neutral stimulants (that produced neither reinforcement nor punishment) and a lever that would dispense food. As the rats started to explore the box, they would stumble upon the level, activate it, and get food. Skinner observed that they were likely to engage in this behavior again, anticipating food. In some boxes, punishments would also be administered. Martin Seligman's learned helplessness experiments are a great example of using punishments to observe or shape an animal's behavior. Skinner usually worked with animals like rats or pigeons. And he took his research beyond what Thorndike did. He looked at how reinforcements and schedules of reinforcement would influence behavior. 

About Reinforcements

Reinforcements are the rewards that satisfy your needs. The fish that cats received outside of Thorndike’s box was positive reinforcement. In Skinner box experiments, pigeons or rats also received food. But positive reinforcements can be anything added after a behavior is performed: money, praise, candy, you name it. Operant conditioning certainly becomes more complicated when it comes to human reinforcements.

Positive vs. Negative Reinforcements 

Skinner also looked at negative reinforcements. Whereas positive reinforcements are given to subjects, negative reinforcements are rewards in the form of things taken away from subjects. In some experiments in the Skinner box, he would send an electric current through the box that would shock the rats. If the rats pushed the lever, the shocks would stop. The removal of that terrible pain was a negative reinforcement. The rats still sought the reinforcement but were not gaining anything when the shocks ended. Skinner saw that the rats quickly learned to turn off the shocks by pushing the lever. 

About Punishments

Skinner's Box also experimented with positive or negative punishments, in which harmful or unsatisfying things were taken away or given due to "bad behavior." For now, let's focus on the schedules of reinforcement.

Schedules of Reinforcement 

We know that not every behavior has the same reinforcement every single time. Think about tipping as a rideshare driver or a barista at a coffee shop. You may have a string of customers who tip you generously after conversing with them. At this point, you’re likely to converse with your next customer. But what happens if they don’t tip you after you have a conversation with them? What happens if you stay silent for one ride and get a big tip? 

Psychologists like Skinner wanted to know how quickly someone makes a behavior a habit after receiving reinforcement. Aka, how many trips will it take for you to converse with passengers every time? They also wanted to know how fast a subject would stop conversing with passengers if you stopped getting tips. If the rat pulls the lever and doesn't get food, will they stop pulling the lever altogether?

Skinner attempted to answer these questions by looking at different schedules of reinforcement. He would offer positive reinforcements on different schedules, like offering it every time the behavior was performed (continuous reinforcement) or at random (variable ratio reinforcement.) Based on his experiments, he would measure the following:

• Response rate (how quickly the behavior was performed)
• Extinction rate (how quickly the behavior would stop) 

He found that there are multiple schedules of reinforcement, and they all yield different results. These schedules explain why your dog may not be responding to the treats you sometimes give him or why gambling can be so addictive. Not all of these schedules are possible, and that's okay, too.

Continuous Reinforcement

If you reinforce a behavior repeatedly, the response rate is medium, and the extinction rate is fast. The behavior will be performed only when reinforcement is needed. As soon as you stop reinforcing a behavior on this schedule, the behavior will not be performed.

Fixed-Ratio Reinforcement

Let’s say you reinforce the behavior every fourth or fifth time. The response rate is fast, and the extinction rate is medium. The behavior will be performed quickly to reach the reinforcement. 

Fixed-Interval Reinforcement

In the above cases, the reinforcement was given immediately after the behavior was performed. But what if the reinforcement was given at a fixed interval, provided that the behavior was performed at some point? Skinner found that the response rate is medium, and the extinction rate is medium. 

Variable-Ratio Reinforcement

Here's how gambling becomes so unpredictable and addictive. In gambling, you experience occasional wins, but you often face losses. This uncertainty keeps you hooked, not knowing when the next big win, or dopamine hit, will come. The behavior gets reinforced randomly. When gambling, your response is quick, but it takes a long time to stop wanting to gamble. This randomness is a key reason why gambling is highly addictive.

Variable-Interval Reinforcement

Last, the reinforcement is given out at random intervals, provided that the behavior is performed. Health inspectors or secret shoppers are commonly used examples of variable-interval reinforcement. The reinforcement could be administered five minutes after the behavior is performed or seven hours after the behavior is performed. Skinner found that the response rate for this schedule is fast, and the extinction rate is slow. 

Skinner's Box and Pigeon Pilots in World War II

Yes, you read that right. Skinner's work with pigeons and other animals in Skinner's box had real-life effects. After some time training pigeons in his boxes, B.F. Skinner got an idea. Pigeons were easy to train. They can see very well as they fly through the sky. They're also quite calm creatures and don't panic in intense situations. Their skills could be applied to the war that was raging on around him.

B.F. Skinner decided to create a missile that pigeons would operate. That's right. The U.S. military was having trouble accurately targeting missiles, and B.F. Skinner believed pigeons could help. He believed he could train the pigeons to recognize a target and peck when they saw it. As the pigeons pecked, Skinner's specially designed cockpit would navigate appropriately. Pigeons could be pilots in World War II missions, fighting Nazi Germany.

When Skinner proposed this idea to the military, he was met with skepticism. Yet, he received $25,000 to start his work on "Project Pigeon." The device worked! Operant conditioning trained pigeons to navigate missiles appropriately and hit their targets. Unfortunately, there was one problem. The mission killed the pigeons once the missiles were dropped. It would require a lot of pigeons! The military eventually passed on the project, but cockpit prototypes are on display at the American History Museum. Pretty cool, huh?

Examples of Operant Conditioning in Everyday Life

Not every example of operant conditioning has to end in dropping missiles. Nor does it have to happen in a box in a laboratory! You might find that you have used operant conditioning on yourself, a pet, or a child whose behavior changes with rewards and punishments. These operant conditioning examples will look into what this process can do for behavior and personality.

Hot Stove: If you put your hand on a hot stove, you will get burned. More importantly, you are very unlikely to put your hand on that hot stove again. Even though no one has made that stove hot as a punishment, the process still works.

Tips: If you converse with a passenger while driving for Uber, you might get an extra tip at the end of your ride. That's certainly a great reward! You will likely keep conversing with passengers as you drive for Uber. The same type of behavior applies to any service worker who gets tips!

Training a Dog: If your dog sits when you say “sit,” you might treat him. More importantly, they are likely to sit when you say, “sit.” (This is a form of variable-ratio reinforcement. Likely, you only treat your dog 50-90% of the time they sit. If you gave a dog a treat every time they sat, they probably wouldn't have room for breakfast or dinner!)

Operant Conditioning Is Everywhere!

We see operant conditioning training us everywhere, intentionally or unintentionally! Game makers and app developers design their products based on the "rewards" our brains feel when seeing notifications or checking into the app. Schoolteachers use rewards to control their unruly classes. Dog training doesn't always look different from training your child to do chores. We know why this happens, thanks to experiments like the ones performed in Skinner's box. 

Related posts:

• Operant Conditioning (Examples + Research)
• Edward Thorndike (Psychologist Biography)
• Schedules of Reinforcement (Examples)
• B.F. Skinner (Psychologist Biography)
• Fixed Ratio Reinforcement Schedule (Examples)

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Animal Behavior

Reviewed by Psychology Today Staff

The study of animal behavior is a cornerstone of psychology for several reasons. Ethology, or the study of animals in their natural habitats, sheds light on how animals interact with each other and their environments, and why they behave the way they do. By studying animal behavior, humans can also learn more about their own behavior—a field known as comparative psychology.

• Do Animals Have Thoughts and Emotions?
• Understanding Animal Behavior
• Are Pets Good For Your Health?

Many researchers who study animal cognition agree that animals “think”—that is, they perceive and react to their environment, interact with one another, and experience different emotions, like stress or fear . Whether they are “conscious” in the same way that humans are, however, has been widely debated in both the fields of ethology (the study of animal behavior) and psychology.

Animals can communicate emotion to one another, but this does not qualify as language. Language is an exchange of information using non-fixed symbols (speech). Animals produce innate signals to warn or manipulate other animals (such as the screech of an eagle when it encounters predators). They cannot vary these sounds to create new signals that are arbitrary and content-rich, as do humans.

Charles Darwin with his theory of evolution was one of the first scientists to acknowledge animals’ mental and emotional capacities. Since then, there have been many discoveries of animals that can think : Chimpanzees can make tools and help each other, parrots can talk, newborn chicken can calculate, dolphins can recognize themselves in the mirror, and scrub jays can plan for the future.

Some animal species, such as chimpanzees and goats , are self-aware. They have clearly demonstrated a Theory of Mind —they understand that others have different perspectives, beliefs, and desires, and they can attribute mental states to others as well as themselves.

Among the most intelligent non-human species are chimpanzees, great apes, elephants, New Caledonian Crows, and dolphins.

While scientists haven’t proven conclusively whether animals love, the evidence that they feel grief suggests they can form attachments. Mammals have the same brain areas required to feel emotions as humans do, and bird brains contain similar structures for thinking and feeling. Animals may also go out of their way to spend time with specific individuals when it’s not necessary for their survival—a possible indication of affection.

Many animals will make vocalizations that sound like laughter while playing or for the purpose of social bonding. For instance, domesticated foxes can laugh , a trick they learned by observing people. Additionally, some dog breeds appear to have a sense of humor and will exhibit playful behaviors to amuse humans.

Practically all living creatures shed tears to clear debris and other irritants from their eyes; however, there is some debate over whether non-human animals cry to express emotions, like sadness or grief . Some experts claim that wild animals who cry make themselves vulnerable, so they are more likely to mask their emotions.   

Animals demonstrate through their actions that they are impacted by the loss of a loved one, but it’s unclear whether they understand death or know they’re going to die. Anecdotally, there are examples of animals that hide themselves when it’s time to die, as well as individual animals that kill themselves shortly after a great loss (raising questions about animal suicide ).

A wide range of animal species—including whales, dolphins, horses, cats, dogs, rabbits, birds, elephants, monkeys, and chimpanzees— exhibit grieving behavior after the death of a mate or other member of their family or social group. They might sit motionless, withdraw or seek seclusion, lose interest in food or sex , or remain with the carcass for days.

Animal behavior research is particularly relevant to the study of human behavior when it comes to the preservation of a species, or how an animal’s behavior helps it survive. The behavior of animals in stressful or aggressive situations can be studied to help find solutions for humans in similar circumstances; it may also provide insight for dealing with depression, anxiety , or similar mental health disorders.

Animal-assisted therapy , in which dogs, horses, and other domestic animals help facilitate different forms of therapy, can be helpful for individuals who are socially isolated, living with a diagnosis on the autism spectrum, or suffering from a mood disorder or post- traumatic stress. Interacting with animals has been found to increase humans' levels of oxytocin , a hormone that enhances social bonding. Animal behaviorists are also interested in the ways in which animals themselves may benefit from relationships with humans.

Animal behavior is a result of biology and environment. Behavioral changes are triggered by an internal or external cue, such as the appearance of a threat nearby. Animal responses are driven by the primal urges to survive and reproduce. While animal behavior can vary widely based on the individual, certain behavioral traits, like attention seeking and chasing prey, are genetically inherited, as with dog behavior.

While some animal behavior scholars perform experiments and study animals in a laboratory setting, others advocate watching animals in their natural habitats to get a clearer sense of what they do and how they allocate their time.

Innate behaviors are genetically hardwired and can be performed in response to stimuli without any prior experience. Learned behaviors are acquired by social learning , often by watching and imitating adult members of their species. Through natural selection, animals are more likely to pass on skills that will help their young survive and thrive.

Animals are motivated to fulfill basic survival needs for shelter, food, warmth, and community. Through a combination of genetics and social learning , they acquire skills based on their species’ preferences (e.g., some animals forage, while others hunt). Other animal behaviors include migrating to warmer climates during the winter, establishing a group pecking order, and imprinting on a parental figure. 

Humans share planet Earth with other non-human animals, many of whom are in danger of going extinct . Learning more about animal behavior can help people conserve nature and better coexist with animals. Additionally, observations about animal behavior may provide fresh insights on why people behave the way they do, and how they can change for the better.

Like humans, animals acquire the necessary skills to survive by watching and imitating adult members of their species. Social learning is quicker and more effective than having to figure out how to do something through trial-and-error, and it gives individuals and the species as a whole a better chance at survival.

Inherited behaviors may vary between species and even among individuals. In dogs, for example, many behaviors are strongly inherited , including trainability, aggression towards strangers, attachment , and attention-seeking.

Animals learn from the behavior of more experienced individuals in their family or social group to figure out which behaviors are likely to be punished and which rewarded. They are motivated to avoid pain and seek out pleasure. They can also be conditioned by people to behave in a certain way using a system of rewards and punishments.

Animal sampling is taking a group of animals from a larger population for measurement. The findings are then used to make generalized conclusions about the whole population. Smaller sample sizes tend to be more problematic and prone to error than larger ones.

Humans and house pets such as dogs have co-evolved ever since humans first domesticated animals some 14,000 years ago. Dogs and cats are beloved creatures the world over and are the lynchpin of a multi-billion-dollar pet product industry.

The so-called pet effect is the widespread belief that owning a pet will make one healthier and happier. This effect may be more anecdotal than reality-based, as many studies find no support or even counter-evidence for the idea that living with a pet enhances human quality of life. In rare cases, pets can transmit serious disorders, such as toxoplasmosis via cat's litter boxes or autoimmune disorders associated with pet birds.

That said, in an era when contact with the natural world is on the decline for many, humans' complex and loving relationships with house pets will endure.

Generally yes. Despite some mixed results in studies, kids with pets seem mostly better off. They have fewer behavioral and learning problems, are less moody, are more physically active, are more obedient, and have improved health overall. They also tend to come from wealthier families and enjoy other socioeconomic advantages.

Pets can provide affection and positive interactions that alleviate feelings of loneliness and isolation. Having a pet can teach children about responsibility and caretaking , while also offering an instant friend and playmate. Pet love can be a powerful emotional resource, particularly during periods of insecurity and self-doubt.

While pets are not a panacea, evidence shows that companion animals can help people who are struggling with mental health problems. They can provide comfort, relieve worry, and ward off a sense of loneliness or isolation; they also prove a source of physical activity and social interactions. Furthermore, caring for a pet can build up a person’s identity and self-worth .

The “Pet Effect” is the rapidly spreading notion that people who have pets live longer and healthier lives. Many people credit their pets with an increase in well-being and health benefits, which include reduced stress, lower levels of cortisol, and higher levels of dopamine and oxytocin, aka the “love hormone.” However, research aimed at proving whether the “Pet Effect” is real remains inconclusive.

When pets are unruly, a person may feel guilty or frustrated that they can’t manage the undesirable behavior. Pets also restrict one’s freedom, making it more logistically difficult to travel or take spontaneous outings. There can be heavy financial and emotional costs to sharing one’s life with a companion animal, including coping with their eventual loss.

Sedentary youngsters are vulnerable to fast-food as the French are discovering,

A fascinating and sobering experiment on how rats cope with stress has far-ranging implications. Can we humans, who tend to react in similar ways, do better?

Discover the intriguing connection between narcissism and pet guardianship, exploring how these dynamics impact both animals and their people in surprising ways.

Research shows careful anthropomorphism helps us better understand animals for who they are—sentient beings—while the timeworn arguments of critics ignore what we actually know.

Balanced dog training using positive reinforcement (rewards-based) methods and aversives (physical punishment) is no better than simply using force-free positive methods and love.

Championed by civil rights icons like Rosa Parks and Angela Davis, Black veganism intertwines with social justice and nonviolence.

Some animals communicate with others and use a few tools, which may be signs of culture. But humans have hundreds of millions of cultural products. Why the enormous difference?

Human brains are biased toward the comfort of similarity, but in horses and life, differences are more important.

Cathryn Michon helps people deal with losing a dog because it's always too soon. Rather than focusing on inevitable grief, she explains how to cherish that they're forever present.

We know that dogs experience different emotions. Here’s how dog guardians can take that into account with training, enrichment, and helping the dog to feel safe.

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Pavlov's Dogs and the Discovery of Classical Conditioning

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• Pavlov's Theory

Pavlov's dog experiments played a critical role in the discovery of one of the most important concepts in psychology: Classical conditioning .

While it happened quite by accident, Pavlov's famous experiments had a major impact on our understanding of how learning takes place as well as the development of the school of behavioral psychology. Classical conditioning is sometimes called Pavlovian conditioning.

Pavlov's Dog: A Background

How did experiments on the digestive response in dogs lead to one of the most important discoveries in psychology? Ivan Pavlov was a noted Russian physiologist who won the 1904 Nobel Prize for his work studying digestive processes.

While studying digestion in dogs, Pavlov noted an interesting occurrence: His canine subjects would begin to salivate whenever an assistant entered the room.

The concept of classical conditioning is studied by every entry-level psychology student, so it may be surprising to learn that the man who first noted this phenomenon was not a psychologist at all.

In his digestive research, Pavlov and his assistants would introduce a variety of edible and non-edible items and measure the saliva production that the items produced.

Salivation, he noted, is a reflexive process. It occurs automatically in response to a specific stimulus and is not under conscious control.

However, Pavlov noted that the dogs would often begin salivating in the absence of food and smell. He quickly realized that this salivary response was not due to an automatic, physiological process.

Pavlov's Theory of Classical Conditioning

Based on his observations, Pavlov suggested that the salivation was a learned response. Pavlov's dog subjects were responding to the sight of the research assistants' white lab coats, which the animals had come to associate with the presentation of food.

Unlike the salivary response to the presentation of food, which is an unconditioned reflex, salivating to the expectation of food is a conditioned reflex.

Pavlov then focused on investigating exactly how these conditioned responses are learned or acquired. In a series of experiments, he set out to provoke a conditioned response to a previously neutral stimulus.

He opted to use food as the unconditioned stimulus , or the stimulus that evokes a response naturally and automatically. The sound of a metronome was chosen to be the neutral stimulus.

The dogs would first be exposed to the sound of the ticking metronome, and then the food was immediately presented.

After several conditioning trials, Pavlov noted that the dogs began to salivate after hearing the metronome. "A stimulus which was neutral in and of itself had been superimposed upon the action of the inborn alimentary reflex," Pavlov wrote of the results.

"We observed that, after several repetitions of the combined stimulation, the sounds of the metronome had acquired the property of stimulating salivary secretion."

In other words, the previously neutral stimulus (the metronome) had become what is known as a conditioned stimulus that then provoked a conditioned response (salivation).

To review, the following are some key components used in Pavlov's theory:

• Conditioned stimulus : This is what the neutral stimulus becomes after training (i.e., the metronome was the conditioned stimulus after Pavlov trained the dogs to respond to it)
• Unconditioned stimulus : A stimulus that produces an automatic response (i.e., the food was the unconditioned stimulus because it made the dogs automatically salivate)
• Conditioned response (conditioned reflex) : A learned response to previously neutral stimulus (i.e., the salivation was a conditioned response to the metronome)
• Unconditioned response (unconditioned reflex) : A response that is automatic (i.e., the dog's salivating is an unconditioned response to the food)

Impact of Pavlov's Research

Pavlov's discovery of classical conditioning remains one of the most important in psychology's history.

In addition to forming the basis of what would become behavioral psychology , the classical conditioning process remains important today for numerous applications, including behavioral modification and mental health treatment.

Principles of classical conditioning are used to treat the following mental health disorders:

• Obsessive-compulsive disorder (OCD)
• Panic attacks and panic disorder
• Substance use disorders

For instance, a specific type of treatment called aversion therapy uses conditioned responses to help people with anxiety or a specific phobia.

A therapist will help a person face the object of their fear gradually—while helping them manage any fear responses that arise. Gradually, the person will form a neutral response to the object.

Pavlov’s work has also inspired research on how to apply classical conditioning principles to taste aversions . The principles have been used to prevent coyotes from preying on domestic livestock and to use neutral stimulus (eating some type of food) paired with an unconditioned response (negative results after eating the food) to create an aversion to a particular food.

Unlike other forms of classical conditioning, this type of conditioning does not require multiple pairings in order for an association to form. In fact, taste aversions generally occur after just a single pairing. Ranchers have found ways to put this form of classical conditioning to good use to protect their herds.

In one example, mutton was injected with a drug that produces severe nausea. After eating the poisoned meat, coyotes then avoided sheep herds rather than attack them.

A Word From Verywell

While Pavlov's discovery of classical conditioning formed an essential part of psychology's history, his work continues to inspire further research today. His contributions to psychology have helped make the discipline what it is today and will likely continue to shape our understanding of human behavior for years to come.

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Fanselow MS, Wassum KM.  The origins and organization of vertebrate Pavlovian conditioning .  Cold Spring Harb Perspect Biol.  2015;8(1):a021717. doi:10.1101/cshperspect.a021717

Nees F, Heinrich A, Flor H.  A mechanism-oriented approach to psychopathology: The role of Pavlovian conditioning .  Int J Psychophysiol.  2015;98(2):351-364. doi:10.1016/j.ijpsycho.2015.05.005

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By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

SPECIALTY GRAND CHALLENGE article

The challenges of understanding animal minds.

• Center for Adaptive Behavior and Cognition, Max Planck Institute for Human Development, Berlin, Germany

Comparative psychology is by nature an interdisciplinary science that lies at the crossroads of psychology and biology but also draws from other fields in the natural, social, and cognitive sciences. The study of the psychology of animals has been labeled animal cognition, comparative cognition, animal learning, animal psychology, and animal intelligence. Here, comparative psychology is used interchangeably with these terms, encompassing all fields that explore the psychological mechanisms underlying animal behavior, including human behavior.

The primary goal of comparative psychology is to understand the cognitive, emotional, and motivational processes of the animal mind. How do other animals perceive, learn about, and make decisions in their worlds? From our pets to exotic animals portrayed in nature documentaries, we are inherently curious about other animals. Comparative psychology both provides a window into their minds, as well as offers a unique perspective on the human mind. Which aspects of our psychology do animals share? Human uniqueness is constantly challenged as we learn more about the psychology of animal minds. Once distinctive human abilities – such as tool use, language, and mental time travel – appear, at least to a degree, in other species. Though other species exhibit elements of these abilities, the central question for comparing humans and animals remains, do humans and other animals share the same psychological mechanisms?

Comparative psychology explores many of the same topics as human psychology. From learning and memory to communication and decision making, the field investigates a number of key questions, for example:

• How do animals understand causal relationships in their environments?

• Can animals represent the perceptions, intentions, and beliefs of others?

• Do animals plan for the future?

• Can animals use referential communication?

• How do animals track time and number?

• Do animals maintain a cognitive map of their environment?

• Do animals attend to the well being of others?

• How do animals categorize objects in their world?

• Which emotional and motivational factors underly animal behavior?

Studying the psychology of other species is not easy. With rare exceptions, we cannot ask directly about their psychological states. Instead, we must make inferences about the psychology of animals based on their behavior. Inferring internal mechanisms from external behavior results in a number of challenges for comparative psychologists. Though we have met a number of these challenges, several remain, slowing our progress in advancing comparative psychology. To push forward, we must meet these conceptual and practical challenges head on.

The Complexity of Parsimony

The difficulties of making inferences about internal mechanisms has spawned two general approaches to studying cognitive aspects of animal behavior. The animal learning approach emphasizes the general learning principles, such as instrumental, and Pavlovian conditioning, espoused by Hull, Spence, Tolman, and Skinner. The cognitive approach examines other forms of cognition such as perception, attention, memory, categorization, navigation, timing, number, communication, decision making, and social cognition. Though learning mechanisms often are considered simpler explanations, some cognitive mechanisms are more complex, requiring an organism to generate a mental representation. Since Morgan’s (1903) admonition to opt for the most parsimonious explanation supported by the data, the learning tradition has set the benchmark for parsimonious explanations. If a simpler, learning account can explain the data, then we should not invoke a more complex explanation. This stringent benchmark has set a high bar for researchers in the cognitive tradition to reject simple learning explanations. Occasionally, the bar is raised higher and higher, sometimes to the extent that the learning mechanism becomes quite complex. How complex does a parsimonious explanation need to be before we accept a representational one? How do we define the complexity of a mechanism? One solution is to sidestep the parsimony/complexity question completely. Rather than resorting to a scale of psychological complexity, we can develop and test more precise models of the phenomena of interest.

Even after excluding simpler explanations for phenomena, the question arises, under what circumstances do animals use the more complex form of cognition? Possessing a particular psychological ability does not imply using it at every opportunity. In many cases, animals may use simpler mechanisms, reserving the more complex mechanisms for situations in which the simpler mechanisms do not work. The circumstances under which animals use different mechanisms remains an open question in comparative psychology.

Individual Differences

A hallmark of data in comparative psychology is variation across individuals. Despite this, we have very little understanding of the sources of variation in psychological mechanisms. Evolutionary models predict individual differences in behavior ( Wolf et al., 2007) , but few models explore why cognition and emotion should vary across individuals. A number of questions arise when developing a theoretical understanding of individual differences. Is there really variation in animal psychological abilities or only in the expression of these abilities? To what extent is this variation adaptive? To what extent does the variation result from environmental influences? Are there general reasons for variation in psychology or do we need to consider each ability separately? Researchers of animal behavior investigate individual differences under the headings of animal personality, behavioral syndromes, and temperament. We must now extend this study of variation at the psychological level and explore the sources of such variation.

Putting the Comparative Back into Comparative Psychology

Despite the name and origins of the field, comparative psychology lacked many comparative studies during much of the twentieth century. Only a handful of species acted as the workhorses of the field: the pigeon, the rat, and the rhesus macaque. Focusing on a few species offers a more in-depth and cumulative method for understanding the psychology of those species. This restriction, however, limits our broader understanding of psychological mechanisms in animals. Comparative psychologists have lamented this lack of diversity for decades ( Beach, 1950 ; Cook, 1993 ; Shettleworth, 1993 ), and, more recently, researchers have tested a number of interesting questions in a wide variety of species, ranging from insects and octopods to tortoises and manatees. We should continue to meet the challenge of casting a wide taxonomic net.

Cataloging the abilities of various species provides a necessary first step in understanding the psychology of animals. However, comparative does not mean simply collecting information on a broad range of species; it also implies active comparison across species ( Shettleworth, 1993) . The implicit comparison in the early days of comparative psychology was between a single animal species and humans. Comparisons have become more explicit recently, borrowing methods directly from fields such as cognitive psychology, developmental psychology, social psychology, and economics. When testing questions of human psychology in animals, we should strive to make the experiments as comparable as possible across species.

Comparing not just to humans but across animal species opens a host of new questions to investigation. In particular, the comparative method allows the testing of evolutionary questions regarding the origins of and ecological pressures on psychological mechanisms. Do phylogenetically closely related species share similar psychological mechanisms? What kinds of evolutionary pressures shape psychological mechanisms across species? Does the social environment play a special role in shaping psychology? How can we test whether species share actual mechanisms rather than just general psychological abilities? Comparisons across species pose difficulties and require great care regarding the species tested and the experimental methods used. Nevertheless, the fruits of this labor will yield valuable insights into the nature of animal psychology.

Ecological Relevance

Simon (1990) argued that a serious study of cognition must explore both the mind and the environment in which the mind interacts. He likened this to two blades in a pair of scissors that cannot function unless both blades are present. This provides an important lesson for comparative psychology as well. Studies of comparative psychology frequently face criticism for overly artificial task environments. Using simple stimuli in impoverished apparatuses offers clear advantages in terms of reducing the likelihood of confounding variables. Unfortunately, this gain in internal validity comes at the price of reducing external validity. Striking a balance between careful control over the experimental situation and eliciting meaningful responses is critical to understanding animal psychology ( Cook, 1993) . The right balance starts with asking ecologically relevant questions. What kinds of mechanisms do animals need to navigate through their physical and social worlds?

The next step is to develop experimental stimuli and tasks that tap the natural abilities of animals. Though simple artificial stimuli offer complete control over the features presented to animal subjects, Cook (1993) argues that more naturalistic stimuli of intermediate complexity can offer a reasonable balance between control and ecological relevance. In addition, Hare (2001) argues that we must consider the natural ecology of the species to develop appropriate experimental tasks. When placed in unnatural situations, animals may not demonstrate the relevant psychological mechanism. Though not easy to conduct, field experiments can offer the most naturalistic circumstances for testing psychological mechanisms in animals. Developing tasks that tap natural behaviors and situations can yield more valid studies of comparative psychology.

Strong Inference

Much of comparative psychology is based on existence proofs: Do animals have theory of mind, metacognition, episodic memory, empathy, or other-regarding preferences? To further mature, however, the field needs to develop more sophisticated models of how psychological mechanisms work, not just whether they are present and what influences them. Weisman (2008) offers an important challenge to the young researchers in behavioral and cognitive science: embrace Platt’s (1964) notion of strong inference. Strong inference emphasizes the development of multiple hypotheses and the design of critical experiments allowing for alternative outcomes that will exclude some of the hypotheses. Currently, many behavioral scientists rely on testing a single hypothesis against a null hypothesis, despite the pitfalls of this approach ( Marewski and Olsson, 2009) . Rather than only testing for the presence or absence of a psychological ability or for factors that influence an ability, we need to explore how the processes work. To this end, testing a series of formal process-based models allows a precise understanding of psychological mechanisms. Though formal models are common in the animal learning tradition (e.g., models of timing), other areas of comparative psychology have yet to use these models to their full potential.

Developing and testing multiple hypotheses yields more careful inferences because more powerful statistical techniques can be used. Instead of relying on the weak null hypothesis testing paradigm, we can use competitive model testing techniques to discriminate between hypotheses. Incorporating process models and competitive model selection into the strong inference approach can only raise the level of rigor for comparative psychology.

Replication and Reproducible Research

Around the turn of the twentieth century, a horse named Clever Hans captivated first Germany and then the world with amazing feats of arithmetic skill. Alas, the even more clever Pfungst (1911) debunked the horse by demonstrating that Hans simply used inadvertent cues from his owner or others during the questioning. This story is often the first cautionary tale learned by all comparative psychologists as they enter the field. It reminds us that the wishes and biases of the observer can influence the observation. It also has encouraged meticulous methodologies for researching animal psychology. Our field could improve, however, in fostering replication and reproducible research.

A core principle of experimental research methods is to replicate studies. This is common practice in human psychology experiments, perhaps because a new pool of participants is available each semester at the university. The typically small sample sizes used in comparative psychology can make replication difficult. Nevertheless, we should encourage the general practice of replicating our work and publishing these replications, even if they result in different findings. As one solution to facilitating replications, we can grant free access to experimental methods. The Comparative Mind Database 1 offers a systematic attempt to maintain free access to experimental methods in comparative psychology by archiving experimental protocols and video clips of experimental sessions. This database facilitates comparative studies by standardizing experimental procedures such that researchers may use similar protocols across species. In addition to exact replications of methods, we need to replicate our studies using different methods. As scientists, we often become enamored with our methodologies. Yet, the use of a single method to test a hypothesis can result in a biased view of the phenomenon of interest. Returning to Simon’s scissors, cognition cannot be understood fully without accounting for the environment, and ensuring that our findings generalize across multiple experimental environments is crucial. Replicating our work within laboratories, between laboratories, and across methodologies strengthens the integrity of our conclusions.

Allowing free access to data and data analyses is equally important in advancing comparative psychology because it allows for reproducible research ( de Leeuw, 2001) . With the available electronic technologies, scientists can include data files either as supplementary materials published on a journal’s website or posted on the author’s website. In addition to publishing the data, granting access to how the data were analyzed can be useful for other scientists. Some statistical software programs, including the freely available R software for statistical computing 2 , allow the reporting of not only statistical results but also the code used to generate the results. Making this code freely available facilitates both error checking and direct reproduction of data analysis. Thus, posting experimental protocols, example videos, data files, and analysis code maintains the transparent nature of science. In the spirit of the mission of open access, we at Frontiers in Comparative Psychology encourage the publication of methods, data, and data analysis along with scientific articles.

Looking Ahead

Comparative psychology explores the fascinating topic of the animal mind. The field has made great strides in the recent years, though more work remains. We face exciting conceptual challenges such as grappling with issues of parsimony and complexity, exploring individual differences, and posing careful comparative questions of psychological mechanism. We also share more practical challenges with other areas in behavioral science and beyond, including developing more naturalistic experimental paradigms, implementing strong inference techniques, and producing reproducible and transparent research. No single piece of scientific work will likely address all of these challenges. Nevertheless, to advance comparative psychology into the twenty-first century, we must carefully craft our questions and continually be mindful of the most rigorous means to achieve our goal of delving into the minds of animals.

Acknowledgments

I wish to thank Lael Schooler, Sara Shettleworth, and Alison Stevens for comments on this paper.

• ^ http://www.cmdbase.org/
• ^ http://www.r-project.org/

Beach, F. A. (1950). The Snark was a Boojum. Am. Psychol. 5, 115–124.

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de Leeuw, J. (2001). Reproducible Research: The Bottom Line . Department of Statistics Papers, University of California, Los Angeles.

Hare, B. (2001). Can competitive paradigms increase the validity of experiments on primate social cognition? Anim. Cogn. 4, 269–280. doi: 10.1007/s100710100084.

Marewski, J. N., and Olsson, H. (2009). Beyond the null ritual: formal modeling of psychological processes. J. Psychol. 217, 49–60. doi: 10.1027/0044-3409.217.1.49.

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Citation: Stevens JR (2010) The challenges of understanding animal minds. Front. Psychology 1 :203. doi: 10.3389/fpsyg.2010.00203

Received: 15 September 2010; Accepted: 28 October 2010; Published online: 19 November 2010.

Copyright: © 2010 Stevens. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

*Correspondence: jstevens@mpib-berlin.mpg.de, jeffrey.r.stevens@gmail.com

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

Pavlov’s Dogs Experiment and Pavlovian Conditioning Response

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

Like many great scientific advances, Pavlovian conditioning (aka classical conditioning) was discovered accidentally. Ivan Petrovich Pavlov (1849–1936) was a physiologist, not a psychologist.

During the 1890s, Pavlov researched salivation in dogs in response to being fed. He inserted a small test tube into the cheek of each dog to measure saliva when the dogs were fed (with a powder made from meat).

Pavlov predicted the dogs would salivate in response to the food in front of them, but he noticed that his dogs would begin to salivate whenever they heard the footsteps of his assistant, who was bringing them the food.

When Pavlov discovered that any object or event that the dogs learned to associate with food (such as the lab assistant) would trigger the same response, he realized that he had made an important scientific discovery.

Accordingly, he devoted the rest of his career to studying this type of learning.

Pavlovian Conditioning: Theory of Learning

Pavlov’s theory of learning, known as classical conditioning, or Pavlovian conditioning, posits that behaviors can be learned through the association between different stimuli.

Classical conditioning (later developed by Watson, in 1913) involves learning to associate an unconditioned stimulus that already brings about a particular response (i.e., a reflex) with a new (conditioned) stimulus, so that the new stimulus brings about the same response.

Pavlov developed some rather unfriendly technical terms to describe this process:

• Neutral Stimulus (NS) : A stimulus that initially does not elicit a particular response or reflex action. In other words, before any conditioning takes place, the neutral stimulus has no effect on the behavior or physiological response of interest. For example, in Pavlov’s experiment, the sound of a metronome was a neutral stimulus initially, as it did not cause the dogs to salivate.
• Unconditioned Stimulus (UCS): This is a stimulus that naturally and automatically triggers a response without any learning needed. In Pavlov’s experiment, the food was the unconditioned stimulus as it automatically induced salivation in the dogs.
• Conditioned Stimulus (CS): This is a previously neutral stimulus that, after being repeatedly associated with an unconditioned stimulus, comes to trigger a conditioned response. For instance, in Pavlov’s experiment, the metronome became a conditioned stimulus when the dogs learned to associate it with food.
• Conditioned Response (CR): This is a learned response to the conditioned stimulus. It typically resembles the unconditioned response but is triggered by the conditioned stimulus instead of the unconditioned stimulus. In Pavlov’s experiment, salivating in response to the metronome was the conditioned response.
• Unconditioned Response (UR): This is an automatic, innate reaction to an unconditioned stimulus. It does not require any learning. In Pavlov’s experiment, the dogs’ automatic salivation in response to the food is an example of an unconditioned response.

Pavlov’s Dog Experiment

Pavlov (1902) started from the idea that there are some things that a dog does not need to learn. For example, dogs don’t learn to salivate whenever they see food. This reflex is ‘hard-wired’ into the dog.

Pavlov showed that dogs could be conditioned to salivate at the sound of a bell if that sound was repeatedly presented at the same time that they were given food.

Pavlov’s studies of classical conditioning have become famous since his early work between 1890 and 1930. Classical conditioning is “classical” in that it is the first systematic study of the basic laws of learning (also known as conditioning).

Pavlov’s dogs were individually situated in secluded environments, secured within harnesses. A food bowl was positioned before them, and a device was employed to gauge the frequency of their salivary gland secretions.

The data from these measurements were systematically recorded onto a rotating drum, allowing Pavlov to meticulously monitor the rates of salivation throughout the course of the experiments.

First, the dogs were presented with the food, and they salivated. The food was the unconditioned stimulus and salivation was an unconditioned (innate) response. (i.e., a stimulus-response connection that required no learning).

Unconditioned Stimulus (Food) > Unconditioned Response (Salivate)

In his experiment, Pavlov used a metronome as his neutral stimulus. By itself, the metronome did not elicit a response from the dogs. 

Neutral Stimulus (Metronome) > No Response

Next, Pavlov began the conditioning procedure, whereby the clicking metronome was introduced just before he gave food to his dogs. After a number of repeats (trials) of this procedure, he presented the metronome on its own.

As you might expect, the sound of the clicking metronome on its own now caused an increase in salivation.

Conditioned Stimulus (Metronome) > Conditioned Response (Salivate)

So, the dog had learned an association between the metronome and the food, and a new behavior had been learned.

Because this response was learned (or conditioned), it is called a conditioned response (and also known as a Pavlovian response). The neutral stimulus has become a conditioned stimulus.

Temporal contiguity

Pavlov found that for associations to be made, the two stimuli had to be presented close together in time (such as a bell).

He called this the law of temporal contiguity. If the time between the conditioned stimulus (bell) and the unconditioned stimulus (food) is too great, then learning will not occur.

‘Unconditioning’ through experimental extinction

In extinction, the conditioned stimulus (the bell) is repeatedly presented without the unconditioned stimulus (the food).

Over time, the dog stops associating the sound of the bell with the food, and the conditioned response (salivation) weakens and eventually disappears.

In other words, the conditioned response is “unconditioned” or “extinguished.”

Spontaneous recovery

Pavlov noted the occurrence of “spontaneous recovery,” where the conditioned response can briefly reappear when the conditioned stimulus is presented after a rest period, even though the response has been extinguished.

This discovery added to the understanding of conditioning and extinction, indicating that these learned associations, while they can fade, are not completely forgotten.

Generalization

The principle of generalization suggests that after a subject has been conditioned to respond in a certain way to a specific stimulus, the subject will also respond in a similar manner to stimuli that are similar to the original one.

In Pavlov’s famous experiments with dogs, he found that after conditioning dogs to salivate at the sound of a bell (which was paired with food), the dogs would also salivate in response to similar sounds, like a buzzer.

This demonstrated the principle of generalization in classical conditioning.

However, the response tends to be more pronounced when the new stimulus closely resembles the original one used in conditioning.

This relationship between the similarity of the stimulus and the strength of the response is known as the generalization gradient.

This principle has been exemplified in research, including a study conducted by Meulders and colleagues in 2013.

Impact of Pavlov’s Research

Ivan Pavlov’s key contribution to psychology was the discovery of classical conditioning, demonstrating how learned associations between stimuli can influence behavior.

His work laid the foundation for behaviorism, influenced therapeutic techniques, and informed our understanding of learning and memory processes.

Behaviorism: Pavlov’s work laid the foundation for behaviorism , a major school of thought in psychology. The principles of classical conditioning have been used to explain a wide range of behaviors, from phobias to food aversions.

Therapy Techniques: Techniques based on classical conditioning, such as systematic desensitization and exposure therapy , have been developed to treat a variety of psychological disorders, including phobias and post-traumatic stress disorder (PTSD).

In these therapies, a conditioned response (such as fear) can be gradually “unlearned” by changing the association between a specific stimulus and its response.

• Little Albert Experiment : The Little Albert experiment, conducted by John B. Watson in 1920, demonstrated that emotional responses could be classically conditioned in humans. A young child, “Little Albert,” was conditioned to fear a white rat, which generalized to similar objects. 

Educational Strategies: Educational strategies, like repetitive learning and rote memorization, can be seen as applications of the principles of classical conditioning. The repeated association between stimulus and response can help to reinforce learning.

Marketing and Advertising: Principles from Pavlov’s conditioning experiments are often used in advertising to build brand recognition and positive associations.

For instance, a brand may pair its product with appealing stimuli (like enjoyable music or attractive visuals) to create a positive emotional response in consumers, who then associate the product with it.

Critical Evaluation

Pavlovian conditioning is traditionally described as learning an association between a neutral conditioned stimulus (CS) and an unconditioned stimulus (US), such that the CS comes to elicit a conditioned response (CR). This fits many lab studies but misses the adaptive function of conditioning (Domjan, 2005).

From a functional perspective, conditioning likely evolves to help organisms effectively interact with biologically important unconditioned stimuli (US) in their natural environment.

For conditioning to happen naturally, the conditioned stimulus (CS) can’t be arbitrary, but must have a real ecological relationship to the US as a precursor or feature of the US object.

Pavlovian conditioning prepares organisms for important biological events by conditioning compensatory responses that improve the organism’s ability to cope.

The critical behavior change from conditioning may not be conditioned responses (CRs), but rather conditioned modifications of unconditioned responses (URs) to the US that improve the organism’s interactions with it.

Evidence shows conditioning occurs readily with naturalistic CSs, like tastes before illness, infant cues before nursing, prey sights before attack. This conditioning is more robust and resistant to effects like blocking.

Traditional descriptions of Pavlovian conditioning as simply the acquired ability of one stimulus to evoke the original response to another stimulus paired with it are inadequate and misleading (Rescorla, 1988).

New research shows conditioning is actually about learning relationships between events, which allows organisms to build mental representations of their environment.

Just pairing stimuli together doesn’t necessarily cause conditioning. It depends on whether one stimulus gives information about the other.

Conditioning rapidly encodes relations among a broad range of stimuli, not just between a neutral stimulus and one eliciting a response. The learned associations allow complex representations of the world.

Recently, Honey et al. (2020, 2022) presented simulations using an alternative model called HeiDI that accounts for Rescorla’s findings. HeiDI differs by allowing reciprocal CS-US and US-CS associations. It uses consistent learning rules applied to all stimulus pairs.

The simulations suggest HeiDI explains Rescorla’s results via two mechanisms:

• Changes in US-CS associations during compound conditioning, allowing greater change in some US-CS links
• Indirect influences of CS-CS associations enabling compounds to recruit associative strength from absent stimuli

HeiDI integrates various conditioning phenomena and retains key Rescorla-Wagner insights about surprise driving learning. However, it moves beyond the limitations of Rescorla-Wagner by providing a framework to address how learning translates into performance.

HeiDI refers to the authors of the model (Honey, Dwyer, Iliescu) as well as highlighting a key feature of the model – the bidirectional or reciprocal associations it proposes between conditioned stimuli and unconditioned stimuli.

H – Honey (the lead author’s surname), ei – Bidirectional (referring to the reciprocal associations), D – Dwyer (the second author’s surname), I – Iliescu (the third author’s surname).

• Domjan, M. (2005). Pavlovian conditioning: A functional perspective.  Annu. Rev. Psychol. ,  56 , 179-206.
• Honey, R.C., Dwyer, D.M., & Iliescu, A.F. (2020a). HeiDI: A model for Pavlovian learning and performance with reciprocal associations. Psychological Review, 127, 829-852.
• Honey, R. C., Dwyer, D. M., & Iliescu, A. F. (2022). Associative change in Pavlovian conditioning: A reappraisal .  Journal of Experimental Psychology: Animal Learning and Cognition .
• Meulders A, Vandebroek, N. Vervliet, B. and Vlaeyen, J.W.S. (2013). Generalization Gradients in Cued and Contextual Pain-Related Fear: An Experimental Study in Health Participants .  Frontiers in Human Neuroscience ,  7 (345). 1-12.
• Pavlov, I. P. (1897/1902). The work of the digestive glands. London: Griffin.
• Pavlov, I. P. (1928). Lectures on conditioned reflexes . (Translated by W.H. Gantt) London: Allen and Unwin.
• Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex . Translated and edited by Anrep, GV (Oxford University Press, London, 1927).
• Rescorla, R. A. (1988). Pavlovian conditioning: It’s not what you think it is .  American Psychologist ,  43 (3), 151.
• Pavlov, I. P. (1955). Selected works . Moscow: Foreign Languages Publishing House.
• Watson, J.B. (1913). Psychology as the behaviorist Views It. Psychological Review, 20 , 158-177.
• Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions.  Journal of experimental psychology ,  3 (1), 1.

Further Reading

• Logan, C. A. (2002). When scientific knowledge becomes scientific discovery: The disappearance of classical conditioning before Pavlov. Journal of the History of the Behavioral Sciences, 38 (4), 393-403.
• Learning and Behavior PowerPoint

What was the main point of Ivan Pavlov’s experiment with dogs?

The main point of Ivan Pavlov’s experiment with dogs was to study and demonstrate the concept of classical conditioning.

Pavlov showed that dogs could be conditioned to associate a neutral stimulus (such as a bell) with a reflexive response (such as salivation) by repeatedly pairing the two stimuli together.

This experiment highlighted the learning process through the association of stimuli and laid the foundation for understanding how behaviors can be modified through conditioning.

What is Pavlovian response?

The Pavlovian response, also known as a conditioned response, refers to a learned, automatic, and involuntary response elicited by a previously neutral stimulus through classical conditioning. It is a key concept in Pavlov’s experiments, where dogs learned to salivate in response to a bell.

When did Pavlov discover classical conditioning?

Ivan Pavlov discovered classical conditioning during his dog experiments in the late 1890s and early 1900s. His seminal work on classical conditioning, often called Pavlovian conditioning, laid the foundation for our understanding of associative learning and its role in behavior modification.

10 of the most famous animals in Psychology

This Digest feature post is a celebration of the contribution that animals have made to psychology.

21 December 2017

By Christian Jarrett

Psychologists have long studied chimps and other animals with two principal, related aims: to find out the capabilities of the animal mind, and to discover what makes us truly unique, if anything. This is a challenging field. As any pet owner knows, it's tempting to project a human interpretation onto animal behaviour. Researchers, especially when they've spent many years studying the same animal, can fall victim to this very bias (you'll see a theme of this field is the powerful, close bonds frequently formed between psychologist and animal). At the same time, though, there is also a temptation to overestimate our human uniqueness. Which emotions and capabilities are exclusively human? Tool use, perspective taking and deceit were once contenders, but no more, and the list is getting shorter all the time.

This Digest feature post is a celebration of the contribution that animals have made to psychology, including eight that we've come to know on first-name terms:

Hans the Horse

The extent to which animals are truly capable of human-like intelligence has dogged psychologists for over a hundred years. A horse nicknamed Clever Hans (Der Kluge Hans in his native tongue) seemed to answer that question in dramatic fashion through his public performances in Berlin in early 1900s. Trained by a maths teacher Wilhelm Von Ofsten for four years, Hans appeared not only capable of simple arithmetic and telling the time, but by using hoof taps to correspond to letters, he performed even more astonishing feats, like identifying artists from their paintings or the composers of melodies. The German board of Education launched an 18-month long enquiry and found no evidence of fraud. However, the psychologist Oscar Pfungst eventually deduced that Hans must be reading tell-tale cues from whomever was questioning him because he could only answer correctly when his interrogator was visible.

This revelation highlighted some of the problems that have plagued animal psychology research ever since. Animals are highly receptive to human cues and many animal behaviours that seem impressive on the surface – and which seem to reveal complex animal cognition – may often have a simpler explanation (though Hans' ability to read cues, even when humans tried to conceal them, remains an incredible feat in itself). Unfortunately, the story ends sadly. Hans was recruited into the German war effort and, depending on which account you believe, was killed in action or eaten by hungry soldiers.

Pavlov's Dogs

I'm cheating a little with this (and the final) entry by including a group of famous animals rather than an individual, but it only seems right to mention the dogs studied by the Russian physiologist Ivan Pavlov given their contribution to psychology. The reason Pavlov's dogs feature in almost every introductory psychology class and textbook is because they revolutionised our understanding of learning, especially the principle of classical conditioning (detailed in a  classic paper  from 1927). Pavlov discovered classical conditioning almost by accident, when he noticed that his research dogs salivated when they heard cues that indicated to them that dinner was on the way. Pavlov soon found that he could get the dogs to salivate in response to almost any kind of previously meaningless cue, such as a bell, simply by pairing the bell repeatedly with the arrival of food. A challenge for later psychology research has often been to show that something more than basic learning processes, such as classical conditioning, are at play when animals perform apparently impressive feats of human-like intelligence.

See also ' The kingdom of dogs '

Washoe the Chimp

A long-running question in animal psychology has been whether human language can be taught to animals. Early in the last century, one idea was that our primate cousins might well be capable of human language if only they were raised in human culture. This prompted the wife and husband team of Luella and Winthrop Kellogg to raise the chimp  Gua  in their home alongside their son. It ended in failure of course, with Gua unable to speak. Decades later – it's strange it took so long – animal researchers realised non-human primates would never speak because of the anatomy of their mouth and vocal chords.

Recognition of this anatomical fact led to an intense period of several decades of work that attempted to teach apes sign language and, later, communication by symbols on a picture board. The first chimp to be taught sign language was Washoe (hence why I've chosen her for this list, rather than other famous research chimps including Kanzi and Nim Chimpsky). Washoe hailed from West Africa and was adopted by another spousal psychologist team, Allen and Beatrix Gardner. Washoe eventually learned to use over 250 different signs (her obituary in the  New York Times  in 2007 was headlined:  Washoe, a Chimp of Many Words, Dies at 42 ). There is disagreement over whether Washoe ever really invented new words, such as the time she allegedly signed "water", "bird" at the sight of a swan. However, witnessing this apparent linguistic improvisation was according to at least one commentator (Harvard psychologist Roger Brown) "like getting an SOS from outer space".

Koko the Gorilla

Most of the ape language studies have involved chimps, but one particularly famous exception is Koko the Gorilla, who has been taught sign language (and exposed to spoken English) for decades by the psychologist Francine "Penny" Patterson. A few years ago Koko made headlines around the world when it was alleged by the Gorilla Foundation in California that she was mourning the passing of actor and comedian Robin Williams, who she'd met for an afternoon in 2001. A YouTube clip of their encounter (see above) has been viewed over three million times. Koko has also starred in her own books, including a children's book,  Koko's  Kitten, and been the subject of several film documentaries, most recently a BBC programme,  Koko: The Gorilla Who Talks To People . "What we can really learn from this extraordinary science experiment turned love affair?" asks the film, highlighting in a nutshell one key problem with this entire field – the emotional closeness between researchers and the animals they study, challenging the pursuit of scientific objectivity.

The sad thing about the story of Koko and the other apes made famous by their part in psychological study is that the whole field has crashed, not only because of methodological criticism (most notably a  devastating critique  published in  Science  in 1979 by Herbert Terrace, leader of the Nim Chimpsky project, in which he argued that ape language is not human-like and doesn't feature real syntax), but also amid accusations of animal mistreatment. A recent  Slate   article  summed up the situation: "No new studies have been launched in years, and the old ones are fizzling out. A behind-the-scenes look at what remains of this research today reveals a surprisingly dramatic world of lawsuits, mass resignations, and dysfunctional relationships between humans and apes." Similarly, a major new  paper  in  Annual Reviews of Anthropology  by Don Kulick says, "The threadbare field left today is an alarming not-so-funhouse of intrigue, betrayal, accusation, threats, litigation, dismissals, obese apes (unsurprising when most of their signing seems to be concerned with obtaining food rewards), dead apes, mass resignations, and even, inevitably, sex."

Peter the Dolphin

Sex is also a surprising theme of dolphin research that took place in the 1960s at a lab known as Dolphin House, built on the Caribbean island of Saint Thomas. There, John Lilley and his wife conducted investigations into whether dolphins are capable of mimicking human speech, and later into the effects of LSD on dolphins (to their surprise, the drug seemed to have no effect). As part of the language research, a woman called Margaret Howe Lovatt moved into a specially designed dolphinarium with a young male dolphin called Peter, living there more or less 24 hours a day in an office that overhang his water tank. The idea was that with constant human contact, it would perhaps be possible for a dolphin to fully grasp and imitate human language.

One problem: the pup's burgeoning sexual needs began to interrupt the language lessons. At first Peter was intermittently relocated to spend time with female dolphins in another tank, but Lovatt found that this interfered too much with her research and the bond she was trying to establish. So she began to satisfy Peter's needs herself. "It wasn't sexual on my part. Sensuous perhaps,"  she told Christopher Riley , the producer and director of the BBC documentary  The Girl Who Talked To Dolphins . "It seemed to me that it made the bond closer," she continued. "Not because of the sexual activity, but because of the lack of having to keep breaking. And that's really all it was. I was there to get to know Peter. That was part of Peter."

This isn't just an odd tale, but a sad one. As Lovatt's experiment was coming to an end, news came that funding was being withdrawn from the lab (Riley says this is because of wider concerns about the welfare of all the resident dolphins). The following year, Dolphin House lab was forced to close. The story goes that after being moved to claustrophobic surroundings in Miami, Peter took his own life.

Alex the Parrot

Language skills and a keen intelligence are not only the preserve of apes and dolphins, as shown – to many experts' surprise at the time – by the remarkable achievements of the African Grey parrot Alex (an acronym for "Avian Learning Experiment"), who was studied for 30 years by the psychologist Irene Pepperberg, until the parrot's death in 2007 at the age of 31.

Pepperberg, who bought Alex from a pet store in 1977, was apparently inspired to study Alex because she'd read about the linguistic achievements of Washoe (see above) and other animals. As well as being famous for his one liners, Alex apparently learned over 100 words, could name over 50 objects and knew his colours and shapes. He starred in several BBC and PBS documentaries. Like many of his ape peers in the research world, Alex also received notable obituaries upon his death.  The Economist  referred to him as science's " best known parrot ". The  New York Times  ran with " Brainy Parrot Dies, Emotive To The End ", in reference to the fact that Alex's last words to Pepperberg the night he died were "You be good, see you tomorrow. I love you."

Compared with his ape peers, it seems that Alex contributed to research that is more likely to stand the test of time. He featured in dozens of quality peer-reviewed papers by Pepperberg (by contrast, it's over 20 years since the on-going Koko project published a significant language paper in a peer-reviewed journal, and that was in the  Russian Journal of Foreign Psychology ). In his recent review of human-animal communication, anthropologist Don Kulick wrote the "… emphasis on cognition and downplaying of language seem to have protected Pepperberg's studies [of Alex] from the sort of critical onslaught that pulverized ape-language research".

Betty the Crow

Alex is far from being the only smart bird in town. Betty, the New Caledonian crow, though less famous than the parrot, made headlines around the world in 2002 when it was reported that she had shown the ingenuity to make a hook out of a straight piece of wire, to reach food in a plastic tube (another crow had taken off with the hook provided by the researchers). This was considered a big deal because, as one of the researchers  told the  BBC , "Although many animals use tools, purposeful modification of objects to solve new problems, without training or prior experience, is virtually unknown". In fact, the researchers claimed Betty's tool-making was more impressive than the tool use seen among chimps.

However, as is usually the way with animal research of this kind, doubts have since been raised about the way Betty's feat was interpreted. Last year, a different team of researchers  studied 18 New Caledonian crows  as they made tools with the branches they use in the wild. Crucially, the researchers observed that most of the birds performed the same final modification – to create a hook shape – as seen by Betty in the lab. In other words, Betty's feat was not entirely spontaneous, but probably part of her species' natural repertoire. Meanwhile, while we're talking about corvids, an honourable mention should go to psychologist Nicky Clayton's scrub-jays, who have been observed demonstrating many behaviours previously considered uniquely human, such as advanced deceit. For instance, a jay will re-hide her food stash if a potential thief was nearby when she first hid it.

Chaser the Border Collie

Not to be outdone by the birds and the apes, a dog named  Chaser the Border Collie  can reportedly recognise over 1000 words, having been trained extensively through play by the psychologists Alliston Reid and John Pilley. "We have found that play is infinitely greater than food [for training]. It's not as distracting and dogs don't satiate on play" says Pilley in a promotional video (see above) for his  New York Times  best-selling book,  Chaser: Unlocking the Genius of The God Who Knows a Thousand Words . Are Chaser's skills an example of true animal intelligence? Pilley thinks so: "These kind of findings definitely show that lower animals, especially dogs, are not machines with blood. They have emotions, they have mental processes." But again, anyone watching Pilley with his research subject will see the common problem of an emotional bond between scientist and animal, potentially blurring objectivity and making it difficult to interpret research findings. That said, in the formal  published paper  detailing Chaser's achievements, Pilley claims to have ruled out the possibility that Chaser relies on visual cues, "Clever Hans style".  Chaser's fame continues to grow through regular documentary appearances, including on 60 Minutes and National Geographic and on the BBC.

Echo the Elephant

Echo the elephant died in 2009 at the age of 64 having been filmed and observed in Kenya's Amboseli National Park for several decades, making her the world's most studied elephant (although, strictly speaking she was the subject of ethological rather than psychological study). Echo, who was her tribe's matriarch for about 36 years, starred in at least four documentaries, including David Attenborough's  Echo: An Unforgettable Elephant . The principal researcher was ethologist Cynthia Moss who, like many of the other researchers mentioned in this list, formed a powerful emotional bond with Echo. Moss learned from Echo and the other elephants of Amboseli about their emotional lives, their transmission of cultural practices and their capacity for future planning and teamwork. This is illustrated in the clip above, in which Echo marshals the support of her tribe's adult females to execute an apparently daring rescue of her daughter, Ebony, who had been kidnapped by a rival tribe.

Harlow's Monkeys

I'm going to cheat again for this last entry and rather than name a specific creature, include a group of animals who helped us better understand a fundamental fact about ourselves.

The importance of physical touch between mother and baby is today widely recognised, but back in the 1950s this wasn't the case, thanks in part to the influence of Freud and his ideas that an infant bonds with her mother primarily because she satisfies her basic needs of thirst and hunger. The American psychologist Harry Harlow's research in the 1950s with rhesus monkeys changed this. Though ethically controversial, it provided a powerful demonstration of the importance of physical contact in mother-infant attachment.

Inspired by his observation that monkeys separated from their mothers grew highly attached to and possessive of their blankets, Harlow created two forms of surrogate mother: one made of wire that provided milk, another warm and soft that provided comfort but no milk. Given the choice, infant monkeys spent the majority of their time with the soft, warm version. However, without their mothers, even the monkeys who clinged to the cloth-covered surrogates developed serious behavioural problems later, lending graphic evidence to support the British psychologist John Bowlby's claims about the importance of early maternal care.

Which animals would you have included on this list and why?  Answers via comments or tweet us @ResearchDigest  #famouspsychologyanimals

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Animal Studies of Attachment: Lorenz and Harlow

Last updated 22 Mar 2021

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In the 1950s research which used animal subjects to investigate early life experiences and the ability for organisms to form attachments contributed significantly to the field of developmental psychology. Two of the most well-known animal studies were conducted by Konrad Lorenz and Harry Harlow.

Lorenz (1952)

Lorenz’s research suggests that organisms have a biological propensity to form attachments to one single subject.

Lorenz conducted an experiment in which goslings were hatched either with their mother or in an incubator. Once goslings had hatched they proceeded to follow the first moving object that they saw between 13 & 16 hours after hatching; in this case, Lorenz.

It supports the view that having a biological basis for an attachment is adaptive as it promotes survival.

This would explain why goslings imprint after a matter of minutes due to their increased mobility; human babies are born immobile and therefore there is less call for them to form an attachment straight away, and so, this develops later (8-9 months).

Harlow (1958)

Harlow conducted research with 8 rhesus monkeys which were caged from infancy with wire mesh food dispensing and cloth-covered surrogate mothers, to investigate which of the two alternatives would have more attachment behaviours directed towards it.

Harlow measured the amount time that monkeys spent with each surrogate mother and the amount time that they cried for their biological mother.

Harlow’s findings revealed that separated infant rhesus monkeys would show attachment behaviours towards a cloth-covered surrogate mother when frightened, rather than a food-dispensing surrogate mother. Monkeys were willing to explore a room full of novel toys when the cloth-covered monkey was present but displayed phobic responses when only the food-dispensing surrogate was present.

Furthermore, Harlow reviewed infant monkeys that were reared in a social (non-isolated) environment and observed that these monkeys went on to develop into healthy adults, while the monkeys in isolation with the surrogate mothers all displayed dysfunctional adult behaviour, including:

a) Being timid

b) Unpredictable with other monkeys

c) They had difficulty with mating

d) The females were inadequate mothers

Implications of Animal Studies of Attachment

The fact that the goslings studies imprinted irreversibly so early in life, suggests that this was operating within a critical period, which was underpinned by biological changes. The longevity of the goslings’ bond with Lorenz would support the view that, on some level, early attachment experiences do predict future bonds. The powerful instinctive behaviour that the goslings displayed would suggest that attachments are biologically programmed into species according to adaptive pressures; goslings innately follow moving objects shortly after hatching, as this would be adaptive given their premature mobility.

The rhesus monkeys’ willingness to seek refuge from something offering comfort rather than food would suggest that food is not as crucial as comfort when forming a bond. The fact that isolated monkeys displayed long-term dysfunctional behaviour illustrates, once more, that early attachment experiences predict long-term social development. Despite being fed, isolated monkeys failed to develop functional social behaviour, which would suggest that animals have greater needs that just the provision of food.

Evaluating Animal Studies of Attachment

Humans and monkeys are similar

Green (1994) states that, on a biological level at least, all mammals (including rhesus monkeys) have the same brain structure as humans; the only differences relates to size and the number of connections.

Important practical applications

Harlow’s research has profound implications for childcare. Due to the importance of early experiences on long-term development, it is vital that all of children’s needs are catered for; taking care of a child’s physical needs alone is not sufficient.

Results cannot be generalised to humans

It is questionable whether findings and conclusions can be extrapolated and applied to complex human behaviours. It is unlikely that observations of goslings following a researcher or rhesus monkeys clinging to cloth-covered wire models reflects the emotional connections and interaction that characterises human attachments.

Research is unethical

The use of animals in research can be questioned on ethical grounds. It could be argued that animals have a right not to be researched/ harmed. The pursuit of academic conclusions for human benefits could be seen as detrimental to non-human species.

• Types of attachment
• Explanations of Attachment: Learning Theory
• Ethical guidelines

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The Flaws and Human Harms of Animal Experimentation

Nonhuman animal (“animal”) experimentation is typically defended by arguments that it is reliable, that animals provide sufficiently good models of human biology and diseases to yield relevant information, and that, consequently, its use provides major human health benefits. I demonstrate that a growing body of scientific literature critically assessing the validity of animal experimentation generally (and animal modeling specifically) raises important concerns about its reliability and predictive value for human outcomes and for understanding human physiology. The unreliability of animal experimentation across a wide range of areas undermines scientific arguments in favor of the practice. Additionally, I show how animal experimentation often significantly harms humans through misleading safety studies, potential abandonment of effective therapeutics, and direction of resources away from more effective testing methods. The resulting evidence suggests that the collective harms and costs to humans from animal experimentation outweigh potential benefits and that resources would be better invested in developing human-based testing methods.

Introduction

Annually, more than 115 million animals are used worldwide in experimentation or to supply the biomedical industry. 1 Nonhuman animal (hereafter “animal”) experimentation falls under two categories: basic (i.e., investigation of basic biology and human disease) and applied (i.e., drug research and development and toxicity and safety testing). Regardless of its categorization, animal experimentation is intended to inform human biology and health sciences and to promote the safety and efficacy of potential treatments. Despite its use of immense resources, the animal suffering involved, and its impact on human health, the question of animal experimentation’s efficacy has been subjected to little systematic scrutiny. 2

Although it is widely accepted that medicine should be evidence based , animal experimentation as a means of informing human health has generally not been held, in practice, to this standard. This fact makes it surprising that animal experimentation is typically viewed as the default and gold standard of preclinical testing and is generally supported without critical examination of its validity. A survey published in 2008 of anecdotal cases and statements given in support of animal experimentation demonstrates how it has not and could not be validated as a necessary step in biomedical research, and the survey casts doubt on its predictive value. 3 I show that animal experimentation is poorly predictive of human outcomes, 4 that it is unreliable across a wide category of disease areas, 5 and that existing literature demonstrates the unreliability of animal experimentation, thereby undermining scientific arguments in its favor. I further show that the collective harms that result from an unreliable practice tip the ethical scale of harms and benefits against continuation in much, if not all, of experimentation involving animals. 6

Problems of Successful Translation to Humans of Data from Animal Experimentation

Although the unreliability and limitations of animal experimentation have increasingly been acknowledged, there remains a general confidence within much of the biomedical community that they can be overcome. 7 However, three major conditions undermine this confidence and explain why animal experimentation, regardless of the disease category studied, fails to reliably inform human health: (1) the effects of the laboratory environment and other variables on study outcomes, (2) disparities between animal models of disease and human diseases, and (3) species differences in physiology and genetics. I argue for the critical importance of each of these conditions.

The Influence of Laboratory Procedures and Environments on Experimental Results

Laboratory procedures and conditions exert influences on animals’ physiology and behaviors that are difficult to control and that can ultimately impact research outcomes. Animals in laboratories are involuntarily placed in artificial environments, usually in windowless rooms, for the duration of their lives. Captivity and the common features of biomedical laboratories—such as artificial lighting, human-produced noises, and restricted housing environments—can prevent species-typical behaviors, causing distress and abnormal behaviors among animals. 8 Among the types of laboratory-generated distress is the phenomenon of contagious anxiety. 9 Cortisone levels rise in monkeys watching other monkeys being restrained for blood collection. 10 Blood pressure and heart rates elevate in rats watching other rats being decapitated. 11 Routine laboratory procedures, such as catching an animal and removing him or her from the cage, in addition to the experimental procedures, cause significant and prolonged elevations in animals’ stress markers. 12 These stress-related changes in physiological parameters caused by the laboratory procedures and environments can have significant effects on test results. 13 Stressed rats, for example, develop chronic inflammatory conditions and intestinal leakage, which add variables that can confound data. 14

A variety of conditions in the laboratory cause changes in neurochemistry, genetic expression, and nerve regeneration. 15 In one study, for example, mice were genetically altered to develop aortic defects. Yet, when the mice were housed in larger cages, those defects almost completely disappeared. 16 Providing further examples, typical noise levels in laboratories can damage blood vessels in animals, and even the type of flooring on which animals are tested in spinal cord injury experiments can affect whether a drug shows a benefit. 17

In order to control for potential confounders, some investigators have called for standardization of laboratory settings and procedures. 18 One notable effort was made by Crabbe et al. in their investigation of the potential confounding influences of the laboratory environment on six mouse behaviors that are commonly studied in neurobehavioral experiments. Despite their “extraordinary lengths to equate test apparatus, testing protocols, and all possible features of animal husbandry” across three laboratories, there were systematic differences in test results in these labs. 19 Additionally, different mouse strains varied markedly in all behavioral tests, and for some tests the magnitude of genetic differences depended on the specific testing laboratory. The results suggest that there are important influences of environmental conditions and procedures specific to individual laboratories that can be difficult—perhaps even impossible—to eliminate. These influences can confound research results and impede extrapolation to humans.

The Discordance between Human Diseases and Animal Models of Diseases

The lack of sufficient congruence between animal models and human diseases is another significant obstacle to translational reliability. Human diseases are typically artificially induced in animals, but the enormous difficulty of reproducing anything approaching the complexity of human diseases in animal models limits their usefulness. 20 Even if the design and conduct of an animal experiment are sound and standardized, the translation of its results to the clinic may fail because of disparities between the animal experimental model and the human condition. 21

Stroke research presents one salient example of the difficulties in modeling human diseases in animals. Stroke is relatively well understood in its underlying pathology. Yet accurately modeling the disease in animals has proven to be an exercise in futility. To address the inability to replicate human stroke in animals, many assert the need to use more standardized animal study design protocols. This includes the use of animals who represent both genders and wide age ranges, who have comorbidities and preexisting conditions that occur naturally in humans, and who are consequently given medications that are indicated for human patients. 22 In fact, a set of guidelines, named STAIR, was implemented by a stroke roundtable in 1999 (and updated in 2009) to standardize protocols, limit the discrepancies, and improve the applicability of animal stroke experiments to humans. 23 One of the most promising stroke treatments later to emerge was NXY-059, which proved effective in animal experiments. However, the drug failed in clinical trials, despite the fact that the set of animal experiments on this drug was considered the poster child for the new experimental standards. 24 Despite such vigorous efforts, the development of STAIR and other criteria has yet to make a recognizable impact in clinical translation. 25

Under closer scrutiny, it is not difficult to surmise why animal stroke experiments fail to successfully translate to humans even with new guidelines. Standard stroke medications will likely affect different species differently. There is little evidence to suggest that a female rat, dog, or monkey sufficiently reproduces the physiology of a human female. Perhaps most importantly, reproducing the preexisting conditions of stroke in animals proves just as difficult as reproducing stroke pathology and outcomes. For example, most animals don’t naturally develop significant atherosclerosis, a leading contributor to ischemic stroke. In order to reproduce the effects of atherosclerosis in animals, researchers clamp their blood vessels or artificially insert blood clots. These interventions, however, do not replicate the elaborate pathology of atherosclerosis and its underlying causes. Reproducing human diseases in animals requires reproducing the predisposing diseases, also a formidable challenge. The inability to reproduce the disease in animals so that it is congruent in relevant respects with human stroke has contributed to a high failure rate in drug development. More than 114 potential therapies initially tested in animals failed in human trials. 26

Further examples of repeated failures based on animal models include drug development in cancer, amyotrophic lateral sclerosis (ALS), traumatic brain injury (TBI), Alzheimer’s disease (AD), and inflammatory conditions. Animal cancer models in which tumors are artificially induced have been the basic translational model used to study key physiological and biochemical properties in cancer onset and propagation and to evaluate novel treatments. Nevertheless, significant limitations exist in the models’ ability to faithfully mirror the complex process of human carcinogenesis. 27 These limitations are evidenced by the high (among the highest of any disease category) clinical failure rate of cancer drugs. 28 Analyses of common mice ALS models demonstrate significant differences from human ALS. 29 The inability of animal ALS models to predict beneficial effects in humans with ALS is recognized. 30 More than twenty drugs have failed in clinical trials, and the only U.S. Food and Drug Administration (FDA)–approved drug to treat ALS is Riluzole, which shows notably marginal benefit on patient survival. 31 Animal models have also been unable to reproduce the complexities of human TBI. 32 In 2010, Maas et al. reported on 27 large Phase 3 clinical trials and 6 unpublished trials in TBI that all failed to show human benefit after showing benefit in animals. 33 Additionally, even after success in animals, around 172 and 150 drug development failures have been identified in the treatment of human AD 34 and inflammatory diseases, 35 respectively.

The high clinical failure rate in drug development across all disease categories is based, at least in part, on the inability to adequately model human diseases in animals and the poor predictability of animal models. 36 A notable systematic review, published in 2007, compared animal experimentation results with clinical trial findings across interventions aimed at the treatment of head injury, respiratory distress syndrome, osteoporosis, stroke, and hemorrhage. 37 The study found that the human and animal results were in accordance only half of the time. In other words, the animal experiments were no more likely than a flip of the coin to predict whether those interventions would benefit humans.

In 2004, the FDA estimated that 92 percent of drugs that pass preclinical tests, including “pivotal” animal tests, fail to proceed to the market. 38 More recent analysis suggests that, despite efforts to improve the predictability of animal testing, the failure rate has actually increased and is now closer to 96 percent. 39 The main causes of failure are lack of effectiveness and safety problems that were not predicted by animal tests. 40

Usually, when an animal model is found wanting, various reasons are proffered to explain what went wrong—poor methodology, publication bias, lack of preexisting disease and medications, wrong gender or age, and so on. These factors certainly require consideration, and recognition of each potential difference between the animal model and the human disease motivates renewed efforts to eliminate these differences. As a result, scientific progress is sometimes made by such efforts. However, the high failure rate in drug testing and development, despite attempts to improve animal testing, suggests that these efforts remain insufficient to overcome the obstacles to successful translation that are inherent to the use of animals. Too often ignored is the well-substantiated idea that these models are, for reasons summarized here, intrinsically lacking in relevance to, and thus highly unlikely to yield useful information about, human diseases. 41

Interspecies Differences in Physiology and Genetics

Ultimately, even if considerable congruence were shown between an animal model and its corresponding human disease, interspecies differences in physiology, behavior, pharmacokinetics, and genetics would significantly limit the reliability of animal studies, even after a substantial investment to improve such studies. In spinal cord injury, for example, drug testing results vary according to which species and even which strain within a species is used, because of numerous interspecies and interstrain differences in neurophysiology, anatomy, and behavior. 42 The micropathology of spinal cord injury, injury repair mechanisms, and recovery from injury varies greatly among different strains of rats and mice. A systematic review found that even among the most standardized and methodologically superior animal experiments, testing results assessing the effectiveness of methylprednisolone for spinal cord injury treatment varied considerably among species. 43 This suggests that factors inherent to the use of animals account for some of the major differences in results.

Even rats from the same strain but purchased from different suppliers produce different test results. 44 In one study, responses to 12 different behavioral measures of pain sensitivity, which are important markers of spinal cord injury, varied among 11 strains of mice, with no clear-cut patterns that allowed prediction of how each strain would respond. 45 These differences influenced how the animals responded to the injury and to experimental therapies. A drug might be shown to help one strain of mice recover but not another. Despite decades of using animal models, not a single neuroprotective agent that ameliorated spinal cord injury in animal tests has proven efficacious in clinical trials to date. 46

Further exemplifying the importance of physiological differences among species, a 2013 study reported that the mouse models used extensively to study human inflammatory diseases (in sepsis, burns, infection, and trauma) have been misleading. The study found that mice differ greatly from humans in their responses to inflammatory conditions. Mice differed from humans in what genes were turned on and off and in the timing and duration of gene expression. The mouse models even differed from one another in their responses. The investigators concluded that “our study supports higher priority to focus on the more complex human conditions rather than relying on mouse models to study human inflammatory disease.” 47 The different genetic responses between mice and humans are likely responsible, at least in part, for the high drug failure rate. The authors stated that every one of almost 150 clinical trials that tested candidate agents’ ability to block inflammatory responses in critically ill patients failed.

Wide differences have also become apparent in the regulation of the same genes, a point that is readily seen when observing differences between human and mouse livers. 48 Consistent phenotypes (observable physical or biochemical characteristics) are rarely obtained by modification of the same gene, even among different strains of mice. 49 Gene regulation can substantially differ among species and may be as important as the presence or absence of a specific gene. Despite the high degree of genome conservation, there are critical differences in the order and function of genes among species. To use an analogy: as pianos have the same keys, humans and other animals share (largely) the same genes. Where we mostly differ is in the way the genes or keys are expressed. For example, if we play the keys in a certain order, we hear Chopin; in a different order, we hear Ray Charles; and in yet a different order, it’s Jerry Lee Lewis. In other words, the same keys or genes are expressed, but their different orders result in markedly different outcomes.

Recognizing the inherent genetic differences among species as a barrier to translation, researches have expressed considerable enthusiasm for genetically modified (GM) animals, including transgenic mice models, wherein human genes are inserted into the mouse genome. However, if a human gene is expressed in mice, it will likely function differently from the way it functions in humans, being affected by physiological mechanisms that are unique in mice. For example, a crucial protein that controls blood sugar in humans is missing in mice. 50 When the human gene that makes this protein was expressed in genetically altered mice, it had the opposite effect from that in humans: it caused loss of blood sugar control in mice. Use of GM mice has failed to successfully model human diseases and to translate into clinical benefit across many disease categories. 51 Perhaps the primary reason why GM animals are unlikely to be much more successful than other animal models in translational medicine is the fact that the “humanized” or altered genes are still in nonhuman animals.

In many instances, nonhuman primates (NHPs) are used instead of mice or other animals, with the expectation that NHPs will better mimic human results. However, there have been sufficient failures in translation to undermine this optimism. For example, NHP models have failed to reproduce key features of Parkinson’s disease, both in function and in pathology. 52 Several therapies that appeared promising in both NHPs and rat models of Parkinson’s disease showed disappointing results in humans. 53 The campaign to prescribe hormone replacement therapy (HRT) in millions of women to prevent cardiovascular disease was based in large part on experiments on NHPs. HRT is now known to increase the risk of these diseases in women. 54

HIV/AIDS vaccine research using NHPs represents one of the most notable failures in animal experimentation translation. Immense resources and decades of time have been devoted to creating NHP (including chimpanzee) models of HIV. Yet all of about 90 HIV vaccines that succeeded in animals failed in humans. 55 After HIV vaccine gp120 failed in clinical trials, despite positive outcomes in chimpanzees, a BMJ article commented that important differences between NHPs and humans with HIV misled researchers, taking them down unproductive experimental paths. 56 Gp120 failed to neutralize HIV grown and tested in cell culture. However, because the serum protected chimpanzees from HIV infection, two Phase 3 clinical trials were undertaken 57 —a clear example of how expectations that NHP data are more predictive than data from other (in this case, cell culture) testing methods are unproductive and harmful. Despite the repeated failures, NHPs (though not chimpanzees or other great apes) remain widely used for HIV research.

The implicit assumption that NHP (and indeed any animal) data are reliable has also led to significant and unjustifiable human suffering. For example, clinical trial volunteers for gp120 were placed at unnecessary risk of harm because of unfounded confidence in NHP experiments. Two landmark studies involving thousands of menopausal women being treated with HRT were terminated early because of increased stroke and breast cancer risk. 58 In 2003, Elan Pharmaceuticals was forced to prematurely terminate a Phase 2 clinical trial when an investigational AD vaccine was found to cause brain swelling in human subjects. No significant adverse effects were detected in GM mice or NHPs. 59

In another example of human suffering resulting from animal experimentation, six human volunteers were injected with an immunomodulatory drug, TGN 1412, in 2006. 60 Within minutes of receiving the experimental drug, all volunteers suffered a severe adverse reaction resulting from a life-threatening cytokine storm that led to catastrophic systemic organ failure. The compound was designed to dampen the immune system, but it had the opposite effect in humans. Prior to this first human trial, TGN 1412 was tested in mice, rabbits, rats, and NHPs with no ill effects. NHPs also underwent repeat-dose toxicity studies and were given 500 times the human dose for at least four consecutive weeks. 61 None of the NHPs manifested the ill effects that humans showed almost immediately after receiving minute amounts of the test drug. Cynomolgus and rhesus monkeys were specifically chosen because their CD28 receptors demonstrated similar affinity to TGN 1412 as human CD28 receptors. Based on such data as these, it was confidently concluded that results obtained from these NHPs would most reliably predict drug responses in humans—a conclusion that proved devastatingly wrong.

As exemplified by the study of HIV/AIDS, TGN 1412, and other experiences, 62 experiments with NHPs are not necessarily any more predictive of human responses than experiments with other animals. The repeated failures in translation from studies with NHPs belie arguments favoring use of any nonhuman species to study human physiology and diseases and to test potential treatments. If experimentation using chimpanzees and other NHPs, our closest genetic cousins, are unreliable, how can we expect research using other animals to be reliable? The bottom line is that animal experiments, no matter the species used or the type of disease research undertaken, are highly unreliable—and they have too little predictive value to justify the resultant risks of harms for humans, for reasons I now explain.

The Collective Harms That Result from Misleading Animal Experiments

As medical research has explored the complexities and subtle nuances of biological systems, problems have arisen because the differences among species along these subtler biological dimensions far outweigh the similarities , as a growing body of evidence attests. These profoundly important—and often undetected—differences are likely one of the main reasons human clinical trials fail. 63

“Appreciation of differences” and “caution” about extrapolating results from animals to humans are now almost universally recommended. But, in practice, how does one take into account differences in drug metabolism, genetics, expression of diseases, anatomy, influences of laboratory environments, and species- and strain-specific physiologic mechanisms—and, in view of these differences, discern what is applicable to humans and what is not? If we cannot determine which physiological mechanisms in which species and strains of species are applicable to humans (even setting aside the complicating factors of different caging systems and types of flooring), the usefulness of the experiments must be questioned.

It has been argued that some information obtained from animal experiments is better than no information. 64 This thesis neglects how misleading information can be worse than no information from animal tests. The use of nonpredictive animal experiments can cause human suffering in at least two ways: (1) by producing misleading safety and efficacy data and (2) by causing potential abandonment of useful medical treatments and misdirecting resources away from more effective testing methods.

Humans are harmed because of misleading animal testing results. Imprecise results from animal experiments may result in clinical trials of biologically faulty or even harmful substances, thereby exposing patients to unnecessary risk and wasting scarce research resources. 65 Animal toxicity studies are poor predictors of toxic effects of drugs in humans. 66 As seen in some of the preceding examples (in particular, stroke, HRT, and TGN1412), humans have been significantly harmed because investigators were misled by the safety and efficacy profile of a new drug based on animal experiments. 67 Clinical trial volunteers are thus provided with raised hopes and a false sense of security because of a misguided confidence in efficacy and safety testing using animals.

An equal if indirect source of human suffering is the opportunity cost of abandoning promising drugs because of misleading animal tests. 68 As candidate drugs generally proceed down the development pipeline and to human testing based largely on successful results in animals 69 (i.e., positive efficacy and negative adverse effects), drugs are sometimes not further developed due to unsuccessful results in animals (i.e., negative efficacy and/or positive adverse effects). Because much pharmaceutical company preclinical data are proprietary and thus publicly unavailable, it is difficult to know the number of missed opportunities due to misleading animal experiments. However, of every 5,000–10,000 potential drugs investigated, only about 5 proceed to Phase 1 clinical trials. 70 Potential therapeutics may be abandoned because of results in animal tests that do not apply to humans. 71 Treatments that fail to work or show some adverse effect in animals because of species-specific influences may be abandoned in preclinical testing even if they may have proved effective and safe in humans if allowed to continue through the drug development pipeline.

An editorial in Nature Reviews Drug Discovery describes cases involving two drugs in which animal test results from species-specific influences could have derailed their development. In particular, it describes how tamoxifen, one of the most effective drugs for certain types of breast cancer, “would most certainly have been withdrawn from the pipeline” if its propensity to cause liver tumor in rats had been discovered in preclinical testing rather than after the drug had been on the market for years. 72 Gleevec provides another example of effective drugs that could have been abandoned based on misleading animal tests: this drug, which is used to treat chronic myelogenous leukemia (CML), showed serious adverse effects in at least five species tested, including severe liver damage in dogs. However, liver toxicity was not detected in human cell assays, and clinical trials proceeded, which confirmed the absence of significant liver toxicity in humans. 73 Fortunately for CML patients, Gleevec is a success story of predictive human-based testing. Many useful drugs that have safely been used by humans for decades, such as aspirin and penicillin, may not have been available today if the current animal testing regulatory requirements were in practice during their development. 74

A further example of near-missed opportunities is provided by experiments on animals that delayed the acceptance of cyclosporine, a drug widely and successfully used to treat autoimmune disorders and prevent organ transplant rejection. 75 Its immunosuppressive effects differed so markedly among species that researchers judged that the animal results limited any direct inferences that could be made to humans. Providing further examples, PharmaInformatic released a report describing how several blockbuster drugs, including aripiprazole (Abilify) and esomeprazole (Nexium), showed low oral bioavailability in animals. They would likely not be available on the market today if animal tests were solely relied on. Understanding the implications of its findings for drug development in general, PharmaInformatic asked, “Which other blockbuster drugs would be on the market today, if animal trials would have not been used to preselect compounds and drug-candidates for further development?” 76 These near-missed opportunities and the overall 96 percent failure rate in clinical drug testing strongly suggest the unsoundness of animal testing as a precondition of human clinical trials and provide powerful evidence for the need for a new, human-based paradigm in medical research and drug development.

In addition to potentially causing abandonment of useful treatments, use of an invalid animal disease model can lead researchers and the industry in the wrong research direction, wasting time and significant investment. 77 Repeatedly, researchers have been lured down the wrong line of investigation because of information gleaned from animal experiments that later proved to be inaccurate, irrelevant, or discordant with human biology. Some claim that we do not know which benefits animal experiments, particularly in basic research, may provide down the road. Yet human lives remain in the balance, waiting for effective therapies. Funding must be strategically invested in the research areas that offer the most promise.

The opportunity costs of continuing to fund unreliable animal tests may impede development of more accurate testing methods. Human organs grown in the lab, human organs on a chip, cognitive computing technologies, 3D printing of human living tissues, and the Human Toxome Project are examples of new human-based technologies that are garnering widespread enthusiasm. The benefit of using these testing methods in the preclinical setting over animal experiments is that they are based on human biology. Thus their use eliminates much of the guesswork required when attempting to extrapolate physiological data from other species to humans. Additionally, these tests offer whole-systems biology, in contrast to traditional in vitro techniques. Although they are gaining momentum, these human-based tests are still in their relative infancy, and funding must be prioritized for their further development. The recent advancements made in the development of more predictive, human-based systems and biological approaches in chemical toxicological testing are an example of how newer and improved tests have been developed because of a shift in prioritization. 78 Apart from toxicology, though, financial investment in the development of human-based technologies generally falls far short of investment in animal experimentation. 79

The unreliability of applying animal experimental results to human biology and diseases is increasingly recognized. Animals are in many respects biologically and psychologically similar to humans, perhaps most notably in the shared characteristics of pain, fear, and suffering. 80 In contrast, evidence demonstrates that critically important physiological and genetic differences between humans and other animals can invalidate the use of animals to study human diseases, treatments, pharmaceuticals, and the like. In significant measure, animal models specifically, and animal experimentation generally, are inadequate bases for predicting clinical outcomes in human beings in the great bulk of biomedical science. As a result, humans can be subject to significant and avoidable harm.

The data showing the unreliability of animal experimentation and the resultant harms to humans (and nonhumans) undermine long-standing claims that animal experimentation is necessary to enhance human health and therefore ethically justified. Rather, they demonstrate that animal experimentation poses significant costs and harms to human beings. It is possible—as I have argued elsewhere—that animal research is more costly and harmful, on the whole, than it is beneficial to human health. 81 When considering the ethical justifiability of animal experiments, we should ask if it is ethically acceptable to deprive humans of resources, opportunity, hope, and even their lives by seeking answers in what may be the wrong place. In my view, it would be better to direct resources away from animal experimentation and into developing more accurate, human-based technologies.

Aysha Akhtar , M.D., M.P.H., is a neurologist and preventive medicine specialist and Fellow at the Oxford Centre for Animal Ethics, Oxford, United Kingdom.

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79. There is no direct analysis of the amount of money spent on animal testing versus alternatives across all categories; however, in 2008 the Chronicle of Higher Education reported that funding of research involving animals (under basic research) of the National Institute of Health (NIH) remained steady at about 42 percent since 1990. See Monastersky R. Protesters fail to slow animal research. Chronicle of Higher Education 2008:54. In 2012, NIH director Francis Collins noted that the NIH’s support for basic research has held steady at 54 percent of the agency’s budget for decades. The remainder of the NIH’s budget is heavily funded toward clinical research, suggesting that preclinical human-based testing methods are much less funded. See also Wadman M. NIH director grilled over translational research centre. Nature News Blog 2012 Mar 20. Available at http://blogs.nature.com/news/2012/03/nih-director-grilled-over-translational-research-center.html (last accessed 5 Mar 2015). There is no data that suggests that the NIH’s funding of animal experimentation has decreased. A 2010 analysis estimates that at least 50 percent of the NIH’s extramural funding is directed into animal research; see Greek R, Greek J. Is the use of sentient animals in basic research justifiable? Philosophy, Ethics, and Humanities in Medicine 2010; 5 :14 [ PMC free article ] [ PubMed ] [ Google Scholar ] .

80. For a helpful discussion on animal pain, fear, and suffering, see DeGrazia D. Taking Animals Seriously: Mental Lives and Moral Status . New York: Cambridge University Press; 1996:116–23. [ Google Scholar ]

81. See Akhtar A. Animals and Public Health: Why Treating Animals Better Is Critical to Human Welfare . Hampshire, UK: Palgrave Macmillan; 2012:chap. 5.

Raccoons in the Laboratory

The lab rat is now a symbol of science, but psychologists once believed that raccoons presented unique potential in the study of animal intelligence.

By the middle of the twentieth century, psychologists were putting rats through myriad experiments, trying to understand how the mind worked. But earlier in the century, some thought that raccoons held the key to understanding intelligence.

Historian Michael Pettit argues that the rejection of raccoons as test subjects was a deliberate “disciplinary choice” in the history of psychology. This choice was due to important shifts in psychological theory and methods, and it may have influenced decades of research.

Pettit explains that around the turn of the century, Darwinism generated interest in finding the roots of human intelligence. Psychologists began experimenting on a variety of animals, and raccoons in particular seemed promising.

People had long considered raccoons to be intelligent. Indigenous American folklore portrayed the raccoon as a “deceptive and cunning trickster figure,” writes Pettit. In colonial America, people often kept raccoons as pets. Their place in American domestic life persisted into the twentieth century, when President Calvin Coolidge kept a pet raccoon named Rebecca in the White House .

While others spent time hunting raccoons, Pettit points out that pretty much everyone agreed that they possessed “cunning, mischief and curiosity, nurtured by an acute sense of touch.”

In 1907, two psychologists published studies about raccoon intelligence, including Lawrence W. Cole. Based in Oklahoma, Cole conducted “puzzle box” experiments, which involved starving animals and observing their attempts to escape confinement. But Cole’s research also involved his observations of raccoon behavior at home, where, as Pettit puts it, “these scientific objects partially lived the lives of pets.” Cole’s research emphasized curiosity and touch, and convinced some psychologists “that animals may possess minds.” But around this time, behaviorism was emerging.

Behaviorists held that animal behavior was largely a function of conditioning, and they favored a tightly controlled laboratory setting. Cole’s research on raccoons was problematic to them, partly because of his relationship with the animals.

Around this time, Walter S. Hunter began research at the University of Chicago. He ran experiments testing the ability to maintain an association between a light bulb and food after a delay. His test subjects included rats, dogs, raccoons, and children.

The raccoons performed almost as well as the children, but Hunter’s interpretation diverged from Cole’s. Rather than seeing a mind at work, Hunter simply saw a complex sensory response. Cole pushed back on Hunter’s methods, explains Pettit, expressing concern that Hunter was creating “a laboratory psychology that could never travel outside such spaces.”

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But Cole and his raccoons lost relevance as behaviorism became dominant. Pettit emphasizes that the raccoon existed in various “borderlands,” including between lab and field science, and this contributed to exclusion. In tightly controlled spaces, researchers struggled with the escape-artist raccoons. Rats and pigeons were easier to manage in large numbers.

As the raccoon faded from the lab, so did the idea that curiosity and touch contributed to learning. “The abandonment of the raccoon as a model was symptomatic of the neglect of these aspects of learning,” Pettit writes, “of how behaviourism produced ignorance about them.”

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President's Column

The importance of research with nonhuman animals

APA is a leader in supporting ethical research that enhances the lives of humans and nonhumans alike

By Antonio E. Puente, PhD, APA president

October 2017, Vol 48, No. 9

Print version: page 6

• Animal Research

As a neuropsychologist, I have a keen appreciation for the contributions of basic research with nonhuman animals to our understanding of the brain and behavior. Such work is not only central to basic research in experimental psychology, behavioral neuroscience and psychopharmacology, but has also led to important applications in a wide range of fields including clinical psychology (e.g., behavioral therapies), pediatrics (e.g., touch stimulation for premature infants), rehabilitation (e.g., enhancing motor function in stroke patients), human factors (e.g., vision and traffic safety) and, of course, clinical neuropsychology (e.g., animal models of dementia).

Psychologists and APA have long been interested in the well-being of research animals. The precursor to APA's current Committee on Animal Research and Ethics (CARE) was established in 1925. CARE's mission includes safeguarding responsible research with nonhuman animals, disseminating accurate information about such research, reviewing the ethics of such research and recommending guidelines for its ethical conduct, and protecting the welfare of nonhuman animals in research, teaching and practical applications.

In the United States, laboratory research with nonhuman animals is strongly regulated by the federal government to ensure it is scientifically valid and that animals are treated humanely. Of course, it is also the ethical obligation of researchers and their institutions to appropriately care for animals. According to Sara Jo Nixon, PhD, chair of APA's Board of Scientific Affairs, "The issue of continuing support for the conduct of ethical animal research is critical and will no doubt require ongoing attention."

Some groups are opposed to all research with nonhuman animals, and some have even threatened and harassed scientists and destroyed labs—a form of terrorism. APA has and will continue to condemn such acts and to speak out against such threats. I was particularly pleased that in August APA's Council of Representatives renewed this commitment when it adopted the "Resolution Reaffirming Support for Research and Teaching with Nonhuman Animals." The resolution emphasizes both the value of research with nonhuman animals and the need to pursue such research ethically. It notes, among other things, the many ways such research contributes to our understanding of cognitive, emotional and social processes and to the development of clinical interventions. This research not only benefits people, but also enhances the lives of nonhuman animals by improving animal care practices and guiding conservation efforts. I am proud of APA's continued leadership in supporting research with nonhuman animals.

Letters to the Editor

• Send us a letter

10 Pros and Cons of Animal Experimentation

Millions of animals are being used for experiments in the US each year. Those who support this legal practice say that it is for a good cause, implying that it is better to use animals than human beings for testing. But on the other side of the coin, critics are also pushing their reasons why the practice should not be continued, with animal suffering and ethical issues as their biggest concerns. After all, it cannot be denied that the conditions of these test subjects are truly monotonous, unnatural and stressful, causing them to feel uncomfortable, suffer and even die. Basically, whether this practice is good or bad really depends on who you are asking. To come up with a well-informed opinion, let us take a look at the pros and cons of animal experimentation.

List of Pros of Animal Experimentation

1. It contributes to cures and treatments that save human lives. Proponents claim that most medical breakthroughs in the last century were direct results of animal experimentation. For example, insulin was discovered through a test where dogs had their pancreases removed. The Anderson Cancer Center also associated the hepatitis B vaccine with tests that were conducted on chimpanzees. Without these experimentations, these people say that thousands, if not millions, of hepatitis B and diabetic patients would have died each year. Moreover, the center said that chimpanzees are humanity’s only hope for finding a vaccine for hepatitis C.

2. It provides an ethical alternative solution to testing. It is widely believed that it is unethical to use humans for invasive experiments, especially when it could result in death. Human lives should not be put at risks by letting them volunteer for testing medicines for potential toxicity or side effects, as well as for manipulating genes. To prevent unfavorable consequences, animal testing is done to precede human trials.

3. It allows researchers to study test subjects for an entire life span. Considering that human beings can live up to 80 years or more, scientists who are conducting tests would be dead before they can gather results. On the other hand, laboratory animals, particularly rats, can only live for 2 to 3 years, which give researchers the opportunity to study the effects of treatments and genetic manipulation over an entire lifetime. In other cases, they can even continue to conduct experiments across several generations, which is why lab animals have been used for long-term research on cancer.

4. It uses animals that are identical to humans in some way. According to scientists, chimpanzee DNA is 99% similar with humans, while it is 98% for mice in terms of genetics. As you can see, people and animals are biologically similar, having the same set of organs, central nervous system and bloodstream, which is why both are affected by virtually the same health conditions and diseases. Considering these facts, animals are being accepted as appropriate research subjects.

5. It provides benefits to the animals themselves. If vaccines were not tested on animals, a lot of them could have died from diseases and health conditions, such as hepatitis, rabies, leukemia, anthrax, parvo, hip dysplasia, glaucoma, etc. Aside from this, animal experimentation helped keep some endangered species from becoming extinct. This is the reason of the American Veterinary Medical Association to endorse this practice.

List of Cons of Animal Experimentation

1. It uses cruel and inhumane treatment. Generally, testing protocols are often painful to the animal test subjects, where they are deprived of food and water, force-fed, physically restrained in long periods, inflicted with pain and wounds to test for healing process effects and remedies, and even purposely killed as part of the process. For instance, to evaluate irritation caused by cosmetics, rabbit’s eyes are held open by clips for days, so they will not be able to blink while the products are being assessed. Some experiments also include the administration of lethal doses of certain chemicals to determine how much would kill animals.

2. It uses animals that make poor test subjects. This directly contradicts what proponents believe about the closeness of animals and humans in an anatomical and biological sense, as both have many cellular, metabolic and anatomical differences. According to Thomas Hartung of the Johns Hopkins University, using rats to test for toxicity should not be accepted as reliable, as these animals are nowhere close to being 70 kilograms. This is further supported by the Archives of Toxicology study in 2013, stating that the lack of direct comparison of human data versus that of a rat puts in question the usefulness of research data.

3. It risks completing a misleading research. Some products and medicines that have the potential to harm animals are actually useful to humans, such as the aspirin. As you can see, the drug was almost shelved because it proved dangerous for animals, which could have lead to the difficulty of lowering the risk of organ rejection during transplants.

4. It uses animals that are not protected by the Animal Welfare Act (AWA). As only over 1 million animals are covered by the AWA as of 2010, around 25 million more are left unprotected from abuse and mistreatment. And because animal experimentations are being regulated by the committee that is selected by the facility itself, animal subjects are even put at a bigger risk of being treated poorly for their entire existence.

5. It is performed despite the existence of less expensive alternatives. There are alternatives to animal experimentation that are considered viable, such cell cultures in a petri dish and in vitro testing, which can even produce more relevant results than those from vivisection. The same thing goes to using artificial human skin, where virtual reconstructions of human molecular structures are done through computer models. And for testing adverse reactions, there is also the method called microdosing, where small doses are being administered on humans themselves.

Indeed, animal experimentation offers some benefits, where medical treatments have been developed through it, but it also comes with significant problems, with those related to ethics being the biggest, which need to be carefully addressed. And with the pros and cons listed above, we can surely come up with a considerable opinion about this subject matter.

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