Reinforcement

Reinforcement is a term in operant conditioning and behavior analysis for the process of increasing the rate or probability of a behavior (e.g., pulling a lever more frequently) in the form of a "response" by the delivery or emergence of a stimulus (e.g. a candy) immediately or shortly after performing the behavior.

The response strength is assessed by measuring frequency, duration, latency, accuracy, and/or persistence of the response after reinforcement stops. Experimental behavior analysts measured the rate of responses as a primary demonstration of learning and performance in non-humans (e.g., the number of times a pigeon pecks a key in a 10-minute session).

A reinforcer is the stimulus, event, or situation that is presented or otherwise emerges when the response behavior is performed.

Positive and negative reinforcement

As Skinner discussed, positive reinforcement is superior to punishment in altering behavior. He maintained that punishment was not simply the opposite of positive reinforcement; positive reinforcement results in lasting behavioral modification, whereas punishment changes behavior only temporarily and presents many detrimental side effects.

The accepted model of reinforcement began shifting in 1966 when Azrin and Holz contributed a chapter to Honig's volume on operant conditioning. Skinner defined reinforcement as creating situations that a person likes or removing a situation he doesn't like, and punishment as removing a situation a person likes or setting up one he doesn't like. Thus the distinction was based on the appetitive or aversive nature of the stimulus. Azrin and Holz defined punishment "as 'a reduction of the future probability of a specific response as a result of the immediate delivery of a stimulus for that response'."This new definition of punishment encroached on Skinner's definition of reinforcement, but most textbooks now only present examples of the 1966 model summarized below:

Helpful definitions:

• Appetitive stimulus: a pleasant outcome
• Aversive stimulus: an unpleasant outcome

A positive reinforcer is a consequence that increases the frequency of a behavior or maintains the frequency. What is reinforcing is defined by what happens to the frequency of the behavior. It has nothing to do with whether the organism finds the reinforcer 'pleasant' or not. For example, if a child gets slapped whenever he/she says a 'naughty' word but the frequency of naughty words increases, the slap is a positive reinforcer.

A 'pleasant' consequence is not necessarily a positive reinforcer. Getting a birthday gift is not a positive reinforcer. There is no behavior that will increase (or be maintained) in frequency. When deciding whether or not something is a reinforcer or not, the basic criteria is whether there is a behavior that is increasing or being maintained in the frequency of its occurrence.

Consequences are not universally reinforcing. For example, happy face stickers may be effective reinforcers for some children. Other children may find them silly.

A negative reinforcer increases or maintains the frequency of a behavior. It is not punishment. These terms are often confused. A negative reinforcer increases or maintains the frequency of the behavior that terminates the negative reinforcer. In this case the negative reinforcer is present before the behavior. The organism performs a behavior that terminates the negative reinforcer. The behavior that terminates the negative reinforcer is likely to increase or be maintained in frequency. Suppose someone has a headache (negative reinforcer). The person takes two aspirin but nothing happens. Then the person takes two Tylenol tablets and the headache goes away. The next time the person has a headache it is likely the person will take Tylenol. That is the behavior that has been reinforced.

Forms of operant conditioning:

• Positive reinforcement: the adding of an appetitive stimulus to increase a certain behavior or response.
  Example: Father gives candy to his daughter when she picks up her toys. If the frequency of picking up the toys increases or stays the same, the candy is a positive reinforcer.
• Positive punishment: the adding of an aversive stimulus to decrease a certain behavior or response.
  Example: Mother yells at a child when running into the street. If the child stops running into the street the yelling is positive punishment.
• Negative reinforcement: the taking away of an aversive stimulus to increase certain behavior or response.
  Example: Turning off distracting music when trying to work. If the work increases when the music is turned off, turning off the music is a negative reinforcer.
• Negative punishment (omission training): the taking away of an appetitive stimulus to decrease a certain behavior.
  Example: A teenager comes home an hour after curfew and the parents take away the teen's cell phone for two days. If the frequency of coming home after curfew decreases, the removal of the phone is negative punishment.