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Video Clip: Thorndike’s Puzzle Box

16 February, 2016 - 09:24

When Thorndike placed his cats in a puzzle box, he found that they learned to engage in the important escape behavior faster after each trial. Thorndike described the learning that follows reinforcement in terms of the law of effect.

The influential behavioral psychologist B. F. Skinner (1904–1990) expanded on Thorndike’s ideas to develop a more complete set of principles to explain operant conditioning. Skinner created specially designed environments known as operant chambers (usually called Skinner boxes) to systemically study learning. A Skinner box (operant chamber) is a structurethat is big enough to fit a rodent or bird and that contains abar or keythat theorganism can press or peck to releasefood or water. It also contains a deviceto record theanimals responses.

The most basic of Skinner’s experiments was quite similar to Thorndike’s research with cats. A rat placed in the chamber reacted as one might expect, scurrying about the box and sniffing and clawing at the floor and walls. Eventually the rat chanced upon a lever, which it pressed to release pellets of f ood. The next time around, the rat took a little less time to press the lever, and on successive trials, the time it took to press the lever became shorter a nd shorter. Soon the rat was pressing the lever as fast as it could eat the food that appeared. As predicted by the law of effect, the ra t had learned to repeat the action that brought about the f ood and cease the actions that did not.

Skinner studied, in detail, how animals changed their behavior through reinforcement and punishment, and he developed terms that explained the processes of operant learning (). Skinner used the termreinforcer to refer to Table 7.1any event that strengthens or increases thelikelihood of abehavior and the term punisher to refer to anyevent that weakens or decreases thelikelihood of a behavior. And he used the terms positiveand negativeto refer to whether a reinforcement was presented or removed, respectively. Thus positive reinforcement strengthens a responseby presenting something pleasant after theresponseand negative reinforcement strengthens a responsebyreducing or removing something unpleasant. For example, giving a child praise for completing his homework represents positive reinforcement, whereas taking aspirin to reduced the pain of a headache represents negative reinforcement. In both cases, the reinforcement makes it more likely that behavior will occur again in the future.

Operant conditioningterm




Table 7.1 How Positive and Negative Reinforcement and Punishment Influence Behavior

Positive reinforcement

Add or increase a pleasant stimulus

Behavior is strengthened

Giving a student a prize after he gets an A on a test

Negative reinforcement

Reduce or remove an unpleasant stimulus

Behavior is strengthened

Taking painkillers that eliminate pain increases the likelihood that you will take painkillers again

Positive punishment

Present or add an unpleasant stimulus

Behavior is weakened

Giving a student extra homework after she misbehaves in class

Negative punishment

Reduce or remove a pleasant stimulus

Behavior is weakened

Taking away a teen’s computer after he misses curfew


Reinforcement, either positive or negative, works by increasing the likelihood of a behavior. Punishment, on the other hand, refers to anyeventthat weakens or reducesthelikelihood of abehavior. Positive punishment weakens a responsebypresenting somethingunpleasant after the response, whereasnegative punishment weakensa responsebyreducing or removing something pleasant. A child who is grounded after fighting with a sibling (positive punishment) or who loses out on the opportunity to go to recess after getting a poor grade (negative punishment) is less likely to repeat these behaviors.

Although the distinction between reinforcement (which increases behavior) and punishment (which decreases it) is usually clear, in some cases it is difficult to determine whether a reinforcer is positive or negative. On a hot day a cool breeze could be seen as a positive reinforcer (because it brings in cool air) or a negative reinforcer (because it removes hot air). In other cases, reinforcement can be both positive and negative. One may smoke a cigarette both because it brings pleasure (positive reinforcement) and because it eliminates the craving for nicotine (negative reinforcement).

It is also important to note that reinforcement and punishment are not simply opposites. The use of positive reinforcement in changing behavior is almost always more effective than using punishment. This is because positive reinforcement makes the person or animal feel better, helping create a positive relationship with the person providing the reinforcement. Types of positive reinforcement that are effective in everyday life include verbal praise or approval, the awarding of status or prestige, and direct financial payment. Punishment, on the other hand, is more likely to create only temporary changes in behavior because it is based on coercion and typically creates a negative a nd adversarial relationship with the person providing the reinforcement. When the person who provides the punishment leaves the situation, the unwanted behavior is likely to return.