Thorndike’s Law of Effect

One of the first principles associated with learning and behaviour was developed by Edward Lee Thorndike and this has become known as Thorndike’s Law of Effect. Thorndike was a pioneer not only in behaviorism and in studying learning, but also in using animals in psychology experiments.

This states that behaviours that lead to satisfying outcomes are likely to be repeated, whereas behaviors that lead to undesired outcomes are less likely to recur.

Edward Lee Thorndike (1874-1949)

Thorndike theorised that animals learn by trial and error.

In his experiments, Thorndike used 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 placed a cat inside the puzzle box. He then placed a piece of meat outside the box and watched the cat’s efforts to escape and get the food. He recorded how long each cat took to work 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. Thorndike noticed 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. He said,

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 to the situation weakened, so that, when it recurs, they will be less likely to occur. The greater the satisfaction or discomfort, the greater the strengthening or weakening of the bond.

Thorndike’s discovery had a big influence on the development of behaviorism and Burrhus Frederic Skinner based his theory of operant conditioning on the Law of Effect. Skinner introduced a new term into the Law of Effect – reinforcement. Behaviour which is reinforced tends to be repeated (i.e. strengthened); behavior which is not reinforced tends to die out-or be extinguished (i.e. weakened).

Both Thorndike’s and Skinner’s theories have many similarities and differences. Both recognise that consequences due to behaviours have a direct impact on conditioning human behaviour.  However, in Skinner’s theory, a behaviour is likely to reoccur based on a reinforcer rather than whether the stimulus is positive or negative.

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