What is animal experimentation in the field of psychology?

Introduction

Before the general acceptance of Charles Darwin’s theory of evolution in the late nineteenth century, in much of the Western world, animals were considered to be soulless machines with no thoughts or emotions. Humans, on the other hand, were assumed to be qualitatively different from other animals because of their abilities to speak, reason, and exercise free will. Therefore, it was thought that nothing could be learned about the mind by studying animals.

After Darwin, however, people began to recognize that although each species is unique, the chain of life is continuous, and species have similarities as well as differences. Because animal brains and human brains are made of the same kinds of cells and have similar structures and connections, it was reasoned, the mental processes of animals must be similar to the mental processes of humans. This new insight led to the introduction of animals as psychological research subjects around 1900. Since then, animal experimentation has yielded much new knowledge about the brain and the mind, especially in the fields of learning, memory, motivation, and sensation.

Psychologists who study animals can be roughly categorized into three groups: biopsychologists (psychobiologists), learning theorists, and ethologists and sociobiologists. Biopsychologists, or physiological psychologists, study the genetic, neural, and hormonal controls of behavior, for example, eating behavior, sleep, sexual behavior, perception, emotion, memory, and the effects of drugs. Learning theorists study the learned and environmental controls of behavior, for example, stress, stimulus-response patterns, motivation, and the effects of reward and punishment. Ethologists and sociobiologists concentrate on animal behavior in nature, for example, predator-prey interactions, mating and parenting, migration, communication, aggression, and territoriality.

Reasons for Using Animal Subjects

Psychologists study animals for a variety of reasons. Sometimes they study the behavior of a particular animal to solve a specific problem. They may study dogs, for example, to learn how best to train them as police dogs; chickens to learn how to prevent them from fighting one another in coops; and wildlife to learn how to regulate populations in parks, refuges, or urban areas. These are all examples of what is called applied research.

Most psychologists, though, are more interested in human behavior but study animals for practical reasons. A developmental psychologist, for example, may study an animal that has a much shorter life span than humans do so that each study takes a much shorter time and more studies can be done. Animals may also be studied when an experiment requires strict controls; researchers can control the food, housing, and even social environment of laboratory animals but cannot control such variables in the lives of human subjects. Experimenters can even control the genetics of animals by breeding them in the laboratory; rats and mice have been bred for so many generations that researchers can special order from hundreds of strains and breeds and can even obtain animals that are basically genetically identical to one another.

Another reason psychologists sometimes study animals is that there are fewer ethical considerations than in research with human subjects. Physiological psychologists and neuropsychologists, in particular, may use invasive procedures (such as brain surgery, hormone manipulation, or drug administration) that would be unethical to perform on humans. Without animal experimentation, much of this research simply could not be conducted. Comparable research on human victims of accident or disease would have less scientific validity and would raise additional ethical concerns.

A number of factors make animal research applicable for the study of human psychology. The first factor is homology. Animals that are closely related to humans are likely to have similar physiology and behavior, because they share the same genetic blueprint. Monkeys and chimpanzees are the animals most closely related to humans and thus are homologically most similar. Monkeys and chimpanzees make the best subjects for psychological studies of complex behaviors and emotions. However, they are expensive and difficult to keep, and there are serious ethical considerations when using them, so they are not used when another animal would be equally suitable.

The second factor is analogy. Animals that have a lifestyle similar to that of humans are likely to have some of the same behaviors. Rats, for example, are social animals, as are humans; cats are not. Rats also show similarity to humans in their eating behavior (which is one reason rats commonly live around human habitation and garbage dumps); thus, they can be a good model for studies of hunger, food preference, and obesity. Rats, however, do not have a similar stress response to that of humans; for studies of exercise and stress, the pig is a better animal to study.

The third factor is situational similarity. Some animals, particularly dogs, cats, domesticated rabbits, and some domesticated birds, adapt easily to experimental situations such as living in a cage and being handled by humans. Wild animals, even if reared by humans from infancy, may not behave normally in experimental situations. The behavior of a chimpanzee that has been kept alone in a cage, for example, may tell something about the behavior of a human kept in solitary confinement, but it will not necessarily be relevant to understanding the behavior of most people in typical situations.

By far the most common laboratory animal used in psychology is Rattus norvegicus, the Norway rat. Originally, the choice of the rat was something of a historical accident. Because the rat has been studied so thoroughly, it is often the animal of choice so that comparisons can be made from study to study. Fortunately, the rat shares many features analogous with humans. Other animals frequently used in psychological research include pigeons, mice, hamsters, gerbils, cats, monkeys, and chimpanzees.

Scientific Value

One of the most important topics for which psychologists use animal experimentation is the study of interactive effects of genes and the environment on the development of the brain and subsequent behavior. These studies can be done only if animals are used as subjects, because they require subjects with a relatively short lifespan that develop quickly, they may involve invasive procedures to measure cell and brain activity, or they may require the manipulation of major social and environmental variables in the life of the subject.

In the 1920s, Edward C. Tolman and Robert Tryon began a study of the inheritance of intelligence using rats. They trained rats to run a complex maze and then, over many generations, bred the fastest learners with one another and the slowest learners with one another. From the beginning, offspring of the bright rats were substantially faster than offspring of the dull rats. After only seven generations, there was no overlap between the two sets, showing that intelligence is at least partly genetic and can be bred into or out of animals just as size, coat color, or milk yield can be.

Subsequent work with selectively bred rats, however, found that high-performing rats would outperform the slower rats only when tested on the original maze used with their parents and grandparents; if given a different task to measure their intelligence, the bright rats were in some cases no brighter than the dull rats. These studies were the first to suggest that intelligence may not be a single attribute that one either has much or little of; there may instead be many kinds of intelligence.

Over the years researchers have developed selectively bred rats as models of a variety of interesting human characteristics. Of particular value are animal models of human psychopathology. For example, genetic lines of rats have been developed that serve as models for susceptibility to depression, anxiety, alcoholism, and attention-deficit hyperactivity disorder (ADHD). These models are important not only in understanding genetic, environmental, and physiological factors associated with these disorders, but also in serving as early tests for possible drug treatments for them. Indeed, the area of behavioral pharmacology, where drug effects on behavior are studied in animal models, is an important and growing area of research.

Brain Studies

Another series of experiments that illustrate the role of animal models in the study of brain and behavior is that developed by David Hubel and Torsten Wiesel, who studied visual perception (mostly using cats). Hubel and Wiesel were able to study the activity of individual cells in the living brain. By inserting a microelectrode into a brain cell of an immobilized animal and flashing visual stimuli in the animal’s visual field, they could record when the cell responded to a stimulus and when it did not.

Over the years, scientists have used this method to map the activities of cells in several layers of the visual cortex, the part of the brain that processes visual information. They have also studied the development of cells and the cell connections, showing how early experience can have a permanent effect on the development of the visual cortex. Subsequent research has demonstrated that the environment has major effects on the development of other areas of the brain as well. The phrase “use it or lose it” has some accuracy when it comes to development and maintenance of brain connections and mental abilities.

Harlow’s Experiments

Perhaps the most famous psychological experiments on animals were those done by Harry Harlow in the 1950s.
Harlow was studying rhesus monkeys and breeding them in his own laboratory. Initially, he would separate infant monkeys from their mothers. Later, he discovered that, in spite of receiving adequate medical care and nutrition, these infants exhibited severe behavioral symptoms: They would sit in a corner and rock, mutilate themselves, and scream in fright at the approach of an experimenter, a mechanical toy, or another monkey. As adolescents, they were antisocial. As adults, they were psychologically ill-equipped to deal with social interactions: Male monkeys were sexually aggressive, and female monkeys appeared to have no emotional attachment to their own babies. Harlow decided to study this phenomenon (labeled “maternal deprivation syndrome”) because he thought it might help to explain the stunted growth, low life expectancy, and behavioral symptoms of institutionalized infants which had been documented earlier by René Spitz.

Results of the Harlow experiments profoundly changed the way psychologists think about love, parenting, and mental health. Harlow and his colleagues found that the so-called mothering instinct is not very instinctive at all but rather is learned through social interactions during infancy and adolescence. They also found that an infant’s attachment to its mother is based not on its dependency on food but rather on its need for “contact comfort.” Babies raised with both a mechanical “mother” that provided milk and a soft, cloth “mother” that gave no milk preferred the cloth mother for clinging and comfort in times of stress.

Through these experiments, psychologists came to learn how important social stimulation is, even for infants, and how profoundly the lack of such stimulation can affect mental health development. These findings played an important role in the development of staffing and activity requirements for foundling homes, foster care, day care, and institutions for the aged, physically and mentally disabled, and mentally ill. They have also influenced social policies that promote parent education and early intervention for children at risk.

Limitations and Ethical Concerns

However, there are drawbacks to using animals as experimental subjects. Most important are the clear biological and psychological differences between humans and nonhuman animals; results from a study using nonhuman animals simply may not apply to humans. In addition, animal subjects cannot communicate directly with researchers; they are unable to express their feelings, motivations, thoughts, and reasons for their behavior. If a psychologist must use an animal instead of a human subject for ethical or practical reasons, the scientist will want to choose an animal that is similar to humans in the particular behavior being studied.

For the same reasons that animals are useful in studying psychological processes, however, people have questioned the moral justification for such use. Because it is now realized that vertebrate animals can feel physical pain and that many of them have thoughts and emotions as well, animal experimentation has become politically controversial.

Psychologists generally support the use of animals in research. The American Psychological Association (APA) identifies animal research as an important contributor to psychological knowledge. The majority of individual psychologists would tend to agree. In 1996, S. Plous surveyed nearly four thousand psychologists and found that fully 80 percent either approved of or strongly approved of the use of animals in psychological research. Nearly 70 percent believed that animal research was necessary for progress in the field of psychology. However, support dropped dramatically for invasive procedures involving pain or death. Undergraduate students majoring in psychology produced largely similar findings. Support was less strong among newer rather than more established psychologists and was also less strong in women than in men.

Some psychologists would like to see animal experimentation in psychology discontinued altogether. In 1981, psychologists formed an animal rights organization called Psychologists for the Ethical Treatment of Animals (PsyETA), which was later renamed the Society and Animals Forum. It is highly critical of the use of animals as subjects in psychological research and has strongly advocated improving the well-being of those animals that are used through publication (with the American Society for the Prevention of Cruelty to Animals) of the Journal of Applied Animal Welfare Science. The organization is also a strong advocate for the developing field of human-animal studies, in which the relationship between humans and animals is explored. Companion animals (pets) can have a significant impact on psychological and physical health, and they can be used as a therapeutic tool with, for example, elderly people in nursing homes and emotionally disturbed youth. In this field of study, animals themselves are not the subjects of the experiment; rather, it is the relationship between humans and animals that is the topic of interest.

Regulations

In response to such concerns regarding the use of animals in experiments, the US Congress amended the Animal Welfare Act in 1985 so that it would cover laboratory animals as well as pets. (Rats, mice, birds, and farm animals are specifically excluded.) Although these regulations do not state specifically what experimental procedures may or may not be performed on laboratory animals, they do set standards for humane housing, feeding, and transportation. Later amendments were added in 1991 in an effort to protect the psychological well-being of nonhuman primates.

In addition, the Animal Welfare Act requires that all research on warm-blooded animals (except those specifically excluded) be approved by a committee before it can be carried out. Each committee (known as Institutional Animal Care and Use Committees, or IACUCs) is composed of at least five members and must include an animal researcher; a veterinarian; someone with an area of expertise in a nonresearch area, such as a teacher, lawyer, or member of the clergy; and someone who is unaffiliated with the institution where the experimentation is being done and who can speak for the local community. In this way, those scientists who do animal experiments must justify the appropriateness of their use of animals as research subjects.

The APA has its own set of ethical guidelines for psychologists conducting experiments with animals. The APA guidelines are intended for use in addition to all pertinent local, state, and federal laws, including the Animal Welfare Act. In addition to being a bit more explicit in describing experimental procedures that require special justification, the APA guidelines require psychologists to have their experiments reviewed by local IACUCs and do not explicitly exclude any animals. About 95 percent of the animals used in psychology are rodents and birds (typically rats, mice, and pigeons), which are not governed by the Animal Welfare Act. It seems likely that federal regulations will change to include these animals at some point, and according to surveys, the majority of psychologists believe that they should be. Finally, psychologists are encouraged to improve the living environments of their animals and consider nonanimal alternatives for their experiments whenever possible.

Alternatives to animal experimentation are becoming more widespread as technology progresses. Computer modeling and bioassays (tests using biological materials such as cell cultures) cannot replace animal experimentation in the field of psychology, however, because computers and cell cultures will never exhibit all the properties of mind that psychologists want to study. At the same time, the use of animals as psychological research subjects will never end the need for study of human subjects. Although other animals may age, mate, fight, and learn much as humans do, they will never speak, compose symphonies, or run for office. Animal experimentation will thus always have an important, though limited, role in psychological research.

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