Born Aug. 31, 1874, in Williamsburg, Mass.; died Aug. 9, 1949, in Montrose, N.Y. American psychologist.

A professor at Columbia University from 1904, Thorndike worked primarily in the field of comparative psychology and learning. He devised a system for the study of animal behavior in which problem boxes were used—that is, cages equipped with a hidden mechanism, the secret of which the animal itself must discover. A new type of experiment was thus introduced, wherein movements were registered as responses to a problem situation. Thorndike came to the conclusion that animal behavior lacks goal-directedness—that is, the characteristically human faculty of sudden understanding and decision-making on the basis of a single trial. Picturing the mind of an animal as an instrument for its adaptation to the environment, Thorndike formulated the trial-and-error principle: chance behavior in a trial, when successful, is subsequently reinforced, creating the appearance of purposeful behavior.

Thorndike’s work was instrumental in overcoming anthropomorphic interpretations of animal behavior and introducing objective research methods in the study of behavior. In essence, Thorndike laid down the foundations of behaviorism, although behaviorists have criticized him for not fully eliminating the subjective approach. The limitations of the trial-and-error principle have been demonstrated in Soviet psychology, as well as in works by J. Piaget, G. S. Hall, and E. C. Tolman. The principle has been shown to be applicable only within the narrow sphere of artificially constructed situations.

Thorndike’s Educational Psychology (1903) was a seminal work in the development of learning theory in the United States; the range of its influence included the concept of programmed learning. Thorndike regarded learning as a process of individual adaptation to the environment—that is, from the biological point of view; a central concept in his work was the “law of effect, ” according to which the degree of reinforcement of a reaction depends on the extent or lack of satisfaction that is obtained as a result.