Editing Operant conditioning (section)

====Discriminated avoidance learning====
A discriminated avoidance experiment involves a series of trials in which a neutral stimulus such as a light is followed by an aversive stimulus such as a shock. After the neutral stimulus appears an operant response such as a lever press prevents or terminate the aversive stimulus. In early trials, the subject does not make the response until the aversive stimulus has come on, so these early trials are called "escape" trials. As learning progresses, the subject begins to respond during the neutral stimulus and thus prevents the aversive stimulus from occurring. Such trials are called "avoidance trials." This experiment is said to involve classical conditioning because a neutral CS (conditioned stimulus) is paired with the aversive US (unconditioned stimulus); this idea underlies the two-factor theory of avoidance learning described below.