If you stroke a cat's fur in a manner that is pleasing to the cat it will purr. The cat's purring may act as a positive reinforcer, causing you to stroke the cat's fur in the same manner in the future.
When a child says "please" and "thank you" to his/her mother, the child may not have to engage in his/her dreaded chore of setting the table. Therefore, not having to set the table will act as a negative reinforcer and increase the likelihood of the child saying "please" and "thank you" in the future.
A behavior (operant response) is sometimes more likely to occur in the future as a result of the consequences that follow that behavior. Events that increase the likelihood of a behavior occurring in the future are called reinforcers.
A positive reinforcer is an appetitive event whose presentation follows an operant response. The positive reinforcer increases the likelihood of that behavior occurring again under the same circumstances.
Click here for an example of a positive reinforcer.
A negative reinforcer is an aversive event whose removal follows an operant response. The negative reinforcer increases the likelihood of that behavior occurring again under the same circumstances.
Click here for an example of a negative reinforcer.
A primary reinforcer is a reinforcer that is biologically pre-established to act as reinforcement.
Food, water, and sex are all primary reinforcers because they satisfy biological desires.
A conditioned reinforcer is a previously neutral stimulus. If the neutral stimulus is paired with a primary reinforcer it acquires the same reinforcement properties associated with the primary reinforcer.
Money is a conditioned reinforcer. The actual paper bills are not themselves reinforcing. However, the paper bills can be used to acquire primary reinforcers such as food, water, and shelter. Therefore, the paper bills become reinforcers as a result of pairing them with the acquisition of food, water, and shelter.