Edward L. Thorndike

Edward Lee Thorndike (August 31, 1874 - August 9, 1949) was an American psychologist who spent nearly his entire career at Teachers College, Columbia University. His work on animal behaviour and the learning process led to the theory of connectionism.

Among Thorndike's most famous contributions were his research on how cats learned to escape from puzzle boxes and his related formulation of the law of effect. The law of effect states that responses that are closely followed by satisfying consequences become associated with the situation, and are more likely to reoccur when the situation is subsequently encountered. Conversely, if the responses are followed by aversive consequences, associations to the situation become weaker. The puzzle box experiments were motivated in part by Thorndike's dislike for statements that animals made use of extraordinary faculties such as insight in their problem solving: "In the first place, most of the books do not give us a psychology, but rather a eulogy of animals. They have all been about animal intelligence, never about animal stupidity." (Animal Intelligence, 1911).

Thorndike meant to distinguish clearly whether or not cats escaping from puzzle boxes were using insight. Thorndike's instruments in answering this question were 'learning curves' revealed by plotting the time it took for an animal to escape the box each time it was in the box. He reasoned that if the animals were showing 'insight,' then their time to escape would suddenly drop to a negligible period, which would also be shown in the learning curve as an abrupt drop; while animals using a more ordinary method of trial and error would show gradual curves. His finding was that cats consistently showed gradual learning.

Thorndike interpreted the findings in terms of associations. He asserted that the connection between the box and the motions the cat used to escape was 'strengthened' by each escape. A similar, though radically reworked idea was taken up by B. F. Skinner in his formulation of operant conditioning. The associative analysis went on to figure largely in behavioral work through mid-century, and is now evident in some modern work in behavior as well as modern connectionism.

Law of Effect

The law of effect is a principle of psychology described by Edward Thorndike in 1898. It holds that responses to stimuli that produce a satisfying or pleasant state of affairs in a particular situation are more likely to occur again in the situation. Conversely, responses that produce a discomforting, annoying or unpleasant effect are less likely to occur again in the situation

The law is important in understanding learning, especially as it relates to operant conditioning. However its status is controversial. Particularly in relation to animal learning, it is not obvious how to define a "satisfying state of affairs" or an "annoying state of affairs" independent of their ability to induce instrumental learning, and the law of effect has therefore been widely criticised as logically circular. In the study of operant conditioning, most psychologists have therefore adopted B. F. Skinner's proposal to define a reinforcer as any stimulus which, when presented after a response, leads to an increase in the future rate of that response. On that basis, the law of effect follows tautologically from the definition of a reinforcer.

In an influential paper of 1970, R. J. Herrnstein proposed a quantitative relationship between response rate (B) and reinforcement rate (Rf):

B = k Rf / (Rf₀ + Rf)

where k and Rf₀ are constants. Herrnstein proposed that this formula, which he derived from the matching law he had observed in studies of concurrent schedules of reinforcement, should be regarded as a quantification of the law of effect. While the qualitative law of effect may be a tautology, this quantitative version is not.

References

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Herrnstein, R. J. (1970). On the law of effect. Journal of the Experimental Analysis of Behavior, 13, 243-266.

External links

• Edward Thorndike biography

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