8.6 Evolutionary Thinking in Psychology
Darwin was a dualist and he applied his theory of evolution to both the mind and body (1). His influence in the later development of psychology was particularly felt in psychoanalysis, functionalism, and behaviorism. He made a direct contribution to psychology in his theory of emotion developed in his book Expression of Emotion in Man and Animals. Darwin, also, prepared the foundation for ethology and comparative psychology.
Sigmund Freud (1856-1939), the physician founder of psychoanalysis, was influenced by the deterministic implication of Darwin's natural selection in formulating his theories on the development of the human's normal and neurotic personalities. Freud also based his conception of the irrational nature of the human's instincts on the evolutionary kinship between animals and humans.
Freud divided a person's mental apparatus into three categories: the id, the ego, and the superego. The id is the primary unconscious pleasure principle that includes the instincts. It acts like a spoiled child who wants immediate gratification of all desires. The ego is the secondary process evolved out of the control of the id in facing reality in which the superego has to be placed in balance with the id. The ego is partly conscious and partly unconscious. The superego is the product of moral principles learned from society and is totally conscious. It consists of the conscience, which tells what is wrong, and the ego-ideal, which tells what is right (2).
Freud developed his theories on instincts according to a more or less biological outlook. He distinguished two classes of instincts. The first instincts are the life instincts that find their source in the physiological  needs of the organism for survival. The second instincts are the death instincts that are based on the decay process in biological degradation of tissues (3).
The functionalists took from Darwin the theme that behavior is adaptable and in order to survive psychologically, humans have to be able to adjust to their environment both physically and mentally. They stressed the survival values of the solution of a mental problem. To them, psychology is concerned with mental functions rather than contents, and these functions are adjustments and adaptations to the environment. They emphasized the utilitarian aspect of psychology that asks the question of applicability of mental functions. They also saw a close relationship between mental and physical responses, the biological and psychological understanding of humans in terms of interaction between mind and body (4). The evolutionary philosophy of pragmatism also contributed much to the functionalist's thinking through William James (1842-1910) and John Dewey (1859-1952). In addition, the functionalists influenced later theories of perception, e.g., James J. Gibson's writings (5).
The application of Darwinian evolutionary ideas to both mind and body led to a controversy on whether an animal has consciousness and, if so, to what extent, and at what point on the scale to simpler forms consciousness ceases. The behaviorists solved this problem by confining psychology to the studies of observable behavior and leaving open the question of whether mind exists.
In one of the animal- and man-consciousness studies Ivan Petrovich Pavlov (1849-1936) experimented with the salivation of dogs in response to food and pioneered the techniques of conditioning (6). Early behaviorist James Broadus Watson (1878-1958) stressed the continuity between humans and animals. He elevated the experimental aspect of psychology at the expense of introspection and consciousness as the only tool in the behaviorist method (7). Contemporary outspoken behaviorist B. F. Skinner elaborated the art of conditioning and stressed the manipulatability of human behavior. To him, the autonomous agent to which behavior has traditionally been attributed is replaced. The new agent is the environment where the species evolves and that same environment shapes and maintains the species behavior (8). In the fifties behaviorism emerged as the dominant view of psychological thinking.
1. Darwin, C. The expression of education in man
and animals. London: Murray; 1973.
2. Freud, S. An outline of psychoanalysis. New York: Norton, 1949.
3. Freud, S. Beyond the pleasure principle. London: Hogarth; 1955.
4. Lundin, R. W. Theories and systems of psychology. Lexington, MA: Heath; 1972 (chap. 9).
5. Gibson, J. J. The senses considered as perceptual systems. Boston: Houghton Mifflin; 1966.
6. Pavlov, I. P. Conditioned reflex. London: Oxford Univ. Press; 1927.
7. Watson, J. B. Psychology as the behaviorist views it. Psychological Review. 20:158; 1913.
8. Skinner, B. F. Beyond freedom and dignity. New York: Banton; 1971.