Summary: Operant Conditioning

Operant conditioning is distinguished from classical conditioning in several ways, including the country of origin (the United States instead of Russia), the type of behavior involved (learned instead of biologically inborn), and the prototypical experimental set-up (an operant chamber instead of Pavlov's dog). Operant conditioning is also called instrumental conditioning, because the animal uses its own behavior as an "instrument" to pursue some goal.

An operant is defined as a behavior producing a certain effect on the environment. Thus a bar-press operant is any behavior which results in a bar press, whether it is accomplished (for example) with the animal's paw or the animal's nose.

In a "rat lab" students start by teaching a rat to find food pellets in a small enclosure, the food magazine. Next the rat is reinforced (given food pellets) for any behavior that brings it close to the bar that sticks out of the cage wall. Then the rat is required to actually press the bar, to receive a pellet. This process of gradually reinforcing steps toward a desired behavior is called shaping.

A reinforcing stimulus is a stimulus that makes the behavior it follows more frequent. Extinction occurs when the reinforcer that maintains a behavior is stopped, and the behavior goes away. A punishing stimulus is one that makes the behavior it follows less frequent or probable. It is not the same thing as negative reinforcement. Negative reinforcement is a form of reinforcement (therefore it makes behavior more frequent). Negative reinforcement occurs when the reinforcing event is removal of a stimulus. "Negative punishment" or response cost occurs when the removal of a stimulus after a behavior makes the behavior less frequent.

Antecedents-stimuli that come before a behavior-are also used in operant conditioning. An S+ is a stimulus that indicates reinforcementis available if a behavior is performed. An S- is a stimulus that indicates reinforcement is not available. An S+ or an S- can be called a discriminative stimulus, because it helps the animal discriminate between situations when reinforcement is or is not available.

When animals learn to perform a behavior to escape from pain or other aversive stimulation, this is called escape conditioning. When animals receive a stimulus indicating something aversive is about to happen, they will try to escape ahead of time to avoid the unpleasant event. This is called avoidance learning. Avoidance conditioning is marked by its persistence. The relief produced by avoidance is reinforcing, so avoidance behavior tends to continue forever even when the original threat is no longer relevant.

Operant conditioning can occur through observational learning. Modeling is the process of demonstrating a behavior that others learn by observation. This is a talent uniquely well developed in primate species, perhaps because of specialized nerve cells called mirror neurons that respond the same way whether an action is (1) performed by the animal itself, or (2) observed being performed by a different animal.


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