What concept did Thorndike formulate from his animal puzzle-box experiments?

Thorndike formulated the law of effect from his animal puzzle-box experiments.

The law of effect states that a response followed by a satisfying consequence becomes more likely in the same situation, while a response followed by an unpleasant consequence becomes less likely. Thorndike reached this idea after measuring how animals gradually escaped from boxes by trial and error.

In the experiments, cats were placed in enclosures that could be opened by pulling a loop, pressing a lever, or performing another simple action. Early attempts involved many ineffective movements. Across repeated trials, escape times generally fell, suggesting that successful responses were strengthened by the satisfying consequence of release and access to food.

Thorndike’s 1898 work described the puzzle-box results and precursors of the principle; his later writings gave the law a more explicit formulation. The concept became an important ancestor of instrumental and operant conditioning. It is distinct from the Gestalt laws of similarity, proximity, and closure, which describe perceptual organization rather than learning from consequences.