Advances in Understanding Brain Behavior in Animals

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Advances in Understanding Brain Behavior in Animals


Understanding the behavior of animals is essential to the work of scientists today. Animal models are used in many areas to study anatomy as well as behavior. Knowing the workings of animal brains led to the founding of psychology and neurology as distinct disciplines. Several scientists devoted their efforts to the study of brain behavior in animals. Russian physiologist Ivan Petrovich Pavlov (1839-1936) is known for his development of the concept of conditioned reflex. German-born American biologist Jacques Loeb (1859-1924) studied animal responses that he coined "tropisms." And American psychologist B. F. Skinner (1904-1990) experimented with scientific measurement of animal behavior that led to the development of a major branch called behaviorism. Behaviorism is not only a philosophy of the past but of the future. For example, computer-assisted instruction is based on the work of the behaviorists.


The scientific study of brain behavior in animals has philosophical roots in the observations of French philosopher René Descartes (1594-1650). As a soldier in Amsterdam, Descartes lived next to a butcher's quarters and became fascinated with animal dissection. His dissections led him to develop an early mechanistic account of the nervous system that included a model of reflex concepts. Later, the study of animal behavior as a branch of psychology developed from the merging of two fields: 1) ethology, the study of characteristic behavior patterns of animals; and 2) comparative psychology, a field of comparing responses. Influenced by Charles Darwin (1809-1882), ethologists—mostly in Europe—studied the behavior of insects, fishes, and birds and became fascinated with the evolution of instinct and genetics. The comparative psychologists—mostly in America—focused on behavior in laboratory animals such as guinea pigs, mice, rats, and monkeys. They were much more interested in environmental aspects than genetics. These two fields merged in the 1950s with the realization that both environment and genetics are of fundamental importance.

Scientists who worked with animals also were not satisfied with just studying the behavior of animals but sought to relate this to human behavior. Ivan Pavlov is a famous name in psychology books for his development of the conditioned reflex. Pavlov, the son of a parish priest of the Russian Orthodox Church, was born in Ryazan, Russia, and received an M.D. at the Imperial Academy of Saint Petersburg. His research and dissertation on how the nervous system regulated circulation earned him a two-year travel scholarship to Germany. There, he was influenced by German physiologists who used animal models for their various studies.

Back in Russia, he met I. M. Sechenov (1829-1905), who had published his extensive work in his book Reflexes of the Brain. Pavlov had observed how many individual body functions are reflexive in nature, coordinated by the brain and nervous system. A reflex is an automatic response. For example, blinking and jerking away from a hot object are reflexes. Pavlov developed a "theory of nervism" that guided him through many experiments relating to digestion and behavior. A skilled surgeon, he developed procedures to study digestive processes in unanesthetized animals. He noted that when he would simply approach the laboratory dogs with a piece of meat, they began to produce saliva or salivate at the sight of food or even with the sounds of footsteps.

From about 1898 to 1930 Pavlov measured the salivary secretion of his dogs to study their brain function. For example, in one experiment, he rang a bell at the same time the food was presented; the dog would salivate. Then he would ring the bell without the food. The dog would still salivate. He called this a "conditioned reflex," in contrast to the unconditioned reflex that occurred when the dog had a natural flow of saliva. He proposed that these conditionings constituted the animal basis of behavior. Pavlov also found that the dogs would respond to bells of different pitch—one that would signal food and the other that would not be related to food. If the sounds of the bells were too much alike, the animal would receive mixed messages, become confused, and behave strangely. He called this erratic behavior "neurosis." Increased exposure to the confusing stimuli would cause great irritability in the nerves of the cerebral cortex. If this confusion continued, it affected the entire nervous system, and the behavior of the animal became abnormal.

During this time Pavlov came into contact with the work of British scientist Charles Sherrington (1857-1952). Sherrington had extensively studied spinal reflexes, which are any reflexes relating to the spinal cord. Sherrington proposed that the spinal reflex is made of integrated actions of several parts. Pavlov added to Sherrington's work the relation of the stimulus to reception in the cortex, the outer area of the brain, as well as the subcortex on the inner part of the brain. He proposed that sleep had a great effect and that neurotic disturbances were caused from the conflict or collision between being excited and then being inhibited at the same time.

By the 1920s Pavlov began to extend his theory of animal behavior to human psychology. He believed that all learned behavior related to the construction and integration of interconnected chains of conditioned reflexes. For example, language reflects these long chains of conditioning involving words. Excessive nerve excitation and inadequate inhibition of the cerebral cortex causes neurosis or psychosis. The person with the psychosis develops a protective mechanism—shutting out the external world that would include all the extreme stimuli he or she had received. From this Pavlov determined that a chief treatment for people with mental illness should be quiet rest, without the exciting stimuli. He supported institutional treatment for mental illness.

Jacques Loeb, German born and educated at the University of Strasbourg, moved to the United States in 1891. He was a mechanist who believed that many complicated life happenings could be explained in simple biochemical terms. Loeb applied the term "tropism" to mean a movement or response to a stimulus. He believed that all behavior of organisms is composed of tropisms or involuntary relationships. For example, some organisms naturally will go to the light while others will turn from the light. Other tropisms include darkness, heat, cold, or chemicals. Loeb was particularly interested in problems of instinct and free will. The unlearned behavior reaction to an environment is called a "stereotyped response." Instinct is one of these.

As the term tropism began to be used to relate to plants, later researchers used the term taxes—singular taxis—to refer to animal responses rather than those of plants. Burrhus Frederic (B. F.) Skinner, an American psychologist, became interested in the work of John B. Watson (1878-1958) as a student at Harvard. He studied intensely the work of Ivan Pavlov on conditioned reflexes and was fascinated by the essays of philosopher Bertrand Russell (1872-1970) on behaviorism. Watson, the founder of a school called behaviorism, became his mentor.

During World War II Skinner concentrated research on training pigeons and developed a device called the "Skinner box." This box enabled him to scientifically study the behavior of animals using controls and accurate measurements. He introduced the ideas of stimulus-response, or S-R connection. This proposed that the learning process is a basic matter of receiving a stimulus and being rewarded with a reinforced response. Skinner then applied his animal theories to humans. As a professor at Indiana University, Bloomington, he received public attention when he introduced his Air-Crib, sort of a Skinner box for human beings. The Air-Crib was a large, soundproof, germ-free, air-conditioned box that was a baby keeper for the first two years. It was supposed to provide the best environment for the growth of a child. In 1948 he published a controversial book called Walden Two, in which he showed a community modeled after these principles of social engineering. He went back to Harvard in 1948 and became one of the greatest influences on a generation of psychologists. He continued his work with animals and trained them to perform complex and even amazing feats—all using his S-R theories. For example, he trained a group of his pigeons to play ping-pong.


The work of Pavlov, Loeb, and Skinner had a profound impact on modern theories of animal behavior and brain development. Although Pavlov received the Nobel Prize for medicine in 1904 for his work on digestive secretions, he is most remembered for his pioneering studies in human behavior. He set the stage for other psychologists to study behavior using objective methods and describing in physiological terms. He also provided psychology with a basic unit that explains complex behavior. American psychologist John B. Watson used Pavlov's work as the foundation of behaviorist psychology, which is still a viable part of educational psychology. As for Skinner, his famous box is now used in pharmaceutical research to show how different drugs affect animal behavior.

The systematic theory of the behaviorists led Skinner to develop a system called programmed learning, using teaching machines. In programmed learning, a person is given the stimulus—a question. After the person answers, he/she is then given immediate reinforcement—positive (moving on to a new question) if the answer was correct or negative (not moving on) if the answer was incorrect. The student progresses through a systematic series of questions/answers at his or her own rate of speed. Central are the ideas of immediate reinforcement or reward and learning in limited, incremental steps.

Modern-day computerized-assisted instruction (CAI) is based on this same theory—using computers instead of the old teaching machines. The term now used to describe the behavior is mastery learning or learning by objective. During the first half of the twentieth century the experiments of Pavlov, Loeb, and Skinner advanced the study of animal behavior and brain development. The ideas of the behaviorists are prominent today in a school called neo-behaviorism, led by Albert Bandura.


Further Reading

Gray, Jeffrey A. Ivan Pavlov. New York: Penguin, 1981.

Skinner, B. F. Science and Human Behavior. New York: Macmillan, 1953.

Skinner, B. F. The Shaping of a Behaviorist. New York: Knopf, 1979.

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Advances in Understanding Brain Behavior in Animals

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Advances in Understanding Brain Behavior in Animals