The law of effect is a principle of the psychology of learning described by Edward Thorndike (1911):

"Of several responses made to the same situation, those which are accompanied or closely followed by satisfaction to the animal will, other things being equal, be more firmly connected with the situation, so that, when it recurs, they will be more likely to recur; those which are accompanied or closely followed by discomfort to the animal will, other things being equal, have their connections with that situation weakened, so that, when it recurs, they will be less likely to occur" (p. 244).^[1]

It holds that responses that produce a satisfying or pleasant state of affairs in a particular situation are more likely to occur again in a similar 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 instrumental 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 circular. In the study of operant conditioning, most psychologists have therefore adopted B. F. Skinner's proposal to define a reinforcer as any stimulus that, 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, R. J. Herrnstein (1970)^[2] proposed a quantitative relationship between response rate (B) and reinforcement rate (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.

[edit] References

1. ^ Thorndike, E. L. (1911). Animal intelligence: Experimental studies. New York : Macmillan. Retrieved June 18, 2009, from http://www.archive.org/details/animalintelligen00thor
2. ^ Herrnstein, R. J. (1970). On the law of effect. Journal of the Experimental Analysis of Behavior, 13, 243-266.