A law proposed by Edward Thorndike stating that any behavior that has good consequences will tend to be repeated, and any behavior that has bad consequences will tend to be avoided.

The idea that instrumental or operant responses are influenced by their effects. Responses that are followed by a pleasant state of affairs will be strengthened and those that are followed by discomfort will be weakened. Nowadays, the term refers to the idea that operant or instrumental behaviors are lawfully controlled by their consequences.