What Is the Law of Effect?

Cat in box
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The law of effect principle developed by Edward Thorndike suggested that responses closely followed by satisfaction will become firmly attached to the situation and, therefore, more likely to reoccur when the situation is repeated. Conversely, if the situation is followed by discomfort, the connections to the situation will become weaker, and the behavior of response is less likely to occur when the situation is repeated.

Imagine that you arrive early to work one day by accident. Your boss notices and praises your diligence. The praise makes you feel good, so it reinforces the behavior. You start showing up for work a little bit early each day to keep receiving your boss’s commendations. Because a pleasing consequence followed the behavior, the action became more likely to be repeated in the future.

How Was the Law of Effect Discovered?

While we often associate the idea that consequences lead to changes in behavior with the process of operant conditioning and B.F. Skinner, this notion has its roots in the early work of psychologist Edward Thorndike. In his experiments, Thorndike utilized what are known as puzzle boxes to study how animals learn. The boxes were enclosed but contained a small lever that, when pressed, would allow the animal to escape.

Thorndike would place a cat inside the puzzle box and then place a piece of meat outside the box and then observe the animal’s efforts to escape and obtain the food.

He recorded how long each animal took to figure out how to free itself from the box.

Eventually, the cats would press the lever, and the door would open so that the animal could receive the reward. Even though first pressing the lever occurred simply by accident, the cats became likely to repeat it because they had received an award immediately after performing the action.

Thorndike noted that with each trial, the cats became much faster at opening the door. Because pressing the lever had led to a favorable outcome, the cats were much more likely to perform the behavior again in the future.

Thorndike termed this the “Law of Effect,” which suggested that when satisfaction follows an association, it is more likely to be repeated. If an unfavorable outcome follows an action, then it becomes less likely to be repeated.

There are two key aspects of the law of effect:

  1. Behaviors immediately followed by favorable consequences are more likely to occur again. In our earlier example, being praised by a supervisor for showing up early for work made it more likely that the behavior would be repeated.
  2. Behaviors followed by unfavorable consequences are less likely to occur again. If you show up late for work and miss an important meeting, you will probably be less likely to show up late again in the future. Because you view the missed meeting as a negative outcome, the behavior is less likely to be repeated.

    The Law of Effect’s Influence on Behaviorism

    Thorndike’s discovery had a major influence on the development of behaviorism. B.F. Skinner based his theory of operant conditioning on the law of effect. Skinner even developed his own version of a puzzle box which he referred to as an operant conditioning chamber (also known as a Skinner box). In operant conditioning, behaviors that are reinforced are strengthened, while those that are punished are weakened. The law of effect clearly had a major influence on the development of behaviorism, which went on to become the dominant school of thought in psychology for much of the twentieth-century.

    More Psychology Definitions: The Psychology Dictionary

    Also Known As: Thorndike's Law of Effect


    Thorndike, E.L. (1898). Animal intelligence: An experimental study of the associative processes in animals. The Psychological Review: Monograph Supplements, 2(4), i-109.

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