Sunday, January 04, 2009

Operant conditioning

Operant conditioning is the use of consequences to modify the occurrence and form of behavior. Operant conditioning is distinguished from classical conditioning (also called respondent conditioning, or Pavlovian conditioning) in that operant conditioning deals with the modification of "voluntary behavior" or operant behavior. Operant behavior "operates" on the environment and is maintained by its consequences, while classical conditioning deals with the conditioning of respondent behaviors which are elicited by antecedent conditions. Behaviors conditioned via a classical conditioning procedure are not maintained by consequences.

Reinforcement and punishment, the core tools of operant conditioning, are either positive (delivered following a response), or negative (withdrawn following a response). This creates a total of four basic consequences, with the addition of a fifth procedure known as extinction (i.e. no change in consequences following a response).

It's important to note that organisms are not spoken of as being reinforced, punished, or extinguished; it is the response that is reinforced, punished, or extinguished. Additionally, reinforcement, punishment, and extinction are not terms whose use is restricted to the laboratory. Naturally occurring consequences can also be said to reinforce, punish, or extinguish behavior and are not always delivered by people.
- Reinforcement is a consequence that causes a behavior to occur with greater frequency.
- Punishment is a consequence that causes a behavior to occur with less frequency.
- Extinction is the lack of any consequence following a behavior. When a behavior is inconsequential, producing neither favorable nor unfavorable consequences, it will occur with less frequency.

Four contexts of operant conditioning: Here the terms "positive" and "negative" are not used in their popular sense, but rather: "positive" refers to addition, and "negative" refers to subtraction. What is added or subtracted may be either reinforcement or punishment. Hence positive punishment is sometimes a confusing term, as it denotes the addition of punishment (such as spanking or an electric shock), a context that may seem very negative in the lay sense. The four procedures are:
1. Positive reinforcement occurs when a behavior (response) is followed by a favorable stimulus (commonly seen as pleasant) that increases the frequency of that behavior. In the Skinner box experiment, a stimulus such as food or sugar solution can be delivered when the rat engages in a target behavior, such as pressing a lever.
2. Negative reinforcement occurs when a behavior (response) is followed by the removal of an aversive stimulus (commonly seen as unpleasant) thereby increasing that behavior's frequency. In the Skinner box experiment, negative reinforcement can be a loud noise continuously sounding inside the rat's cage until it engages in the target behavior, such as pressing a lever, upon which the loud noise is removed.
3. Positive punishment (also called "Punishment by contingent stimulation") occurs when a behavior (response) is followed by an aversive stimulus, such as introducing a shock or loud noise, resulting in a decrease in that behavior.
4. Negative punishment (also called "Punishment by contingent withdrawal") occurs when a behavior (response) is followed by the removal of a favorable stimulus, such as taking away a child's toy following an undesired behavior, resulting in a decrease in that behavior.

- Avoidance learning is a type of learning in which a certain behavior results in the cessation of an aversive stimulus. For example, performing the behavior of shielding one's eyes when in the sunlight (or going indoors) will help avoid the aversive stimulation of having light in one's eyes.
- Extinction occurs when a behavior (response) that had previously been reinforced is no longer effective. In the Skinner box experiment, this is the rat pushing the lever and being rewarded with a food pellet several times, and then pushing the lever again and never receiving a food pellet again. Eventually the rat would cease pushing the lever.
- Noncontingent reinforcement refers to delivery of reinforcing stimuli regardless of the organism's (aberrant) behavior. The idea is that the target behavior decreases because it is no longer necessary to receive the reinforcement. This typically entails time-based delivery of stimuli identified as maintaining aberrant behavior, which serves to decrease the rate of the target behavior. As no measured behavior is identified as being strengthened, there is controversy surrounding the use of the term noncontingent "reinforcement".


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