alpha responses Nonassociative responses that follow the presentation of the conditioned stimulus. They are nonassociative in the same way that unconditioned responses are nonassociative in that they are innate reflexes to the presentation of a stimulus. However, unconditioned responses do not show much habituation. In other words, repeated presentations of the unconditioned stimulus will continue to induce unconditioned responses. Alpha responses quickly habituate, which means that after a few presentations of the conditioned stimulus, they no longer occur. Ideally, conditioned stimuli are chosen because they are neutral (i.e., do not initially elicit a response). However, sometimes it is preferable to use a particular conditioned stimulus even if it temporarily results in alpha responses.

amplitude The magnitude of the conditioned response or unconditioned response. For example, in eyeblink conditioning the amplitude is expressed as the distance the eyelid moves in millimeters. Accordingly, a conditioned response of 2 mm has a greater amplitude than a conditioned response of only 1 mm.

conditioned response A learned response that is elicited by the conditioned stimulus.

conditioned stimulus A stimulus that signals the unconditioned stimulus. Initially the conditioned stimulus does not cause a response, but eventually it elicits a conditioned response.

conditioned stimulus-alone test trial A conditioned stimulus-alone test trial is a trial in which the unconditioned stimulus is omitted, leaving only the conditioned stimulus presentation. Conditioned stimulus-alone test trials are sometimes used because the presentation of the unconditioned stimulus and subsequent unconditioned response can obscure or mask the conditioned response.

extinction training Extinction training can be presented following the acquisition of the conditioned response. Conditioned responses are formed by pairing a conditioned stimulus and an unconditioned stimulus. During extinction training only the conditioned stimulus is presented (i.e., the unconditioned stimulus is omitted). Extinction training will gradually result in the disappearance of the conditioned response. This is referred to as extinction "training" because the conditioned response is not forgotten but inhibited. In other words, extinction is an active process. Evidence that extinction training is different from forgetting comes from paired conditioned stimulus and unconditioned stimulus trials. This results in the rapid reinstatement of the conditioned response. The reinstatement occurs much more rapidly than the original acquisition of the conditioned

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response. Therefore, the conditioned response is not forgotten but, rather, inhibited.

interstimulus interval Sometimes called the conditioned stimulus-unconditioned stimulus interval, the interstimulus interval is the amount of time between the onset of the conditioned stimulus and the onset of the unconditioned stimulus.

intertrial interval A classical conditioning trial begins with the onset of the conditioned stimulus and ends with the offset of the unconditioned stimulus. The intertrial interval is the amount of time between each individual trial and is usually an average amount of time. The exact time between trials is usually varied within a restricted range in order to prevent "time" from becoming a conditioned stimulus as it is in temporal conditioning.

latency The amount of time between one event and another event. For example, the latency of the conditioned response is the amount of time between the onset of the conditioned stimulus and the onset of the conditioned response. The latency of the unconditioned response is the time between the onset ofthe unconditioned stimulus and the onset of the unconditioned response.

pseudoconditioning Classical conditioning results in conditioned responses when an association forms between the conditioned stimulus and the unconditioned stimulus. However, sometimes responses that appear to be conditioned responses, in that they follow the presentation of a conditioned stimulus, result from experience with the unconditioned stimulus only and not because of an association between the conditioned stimulus and the unconditioned stimulus. This is known as pseudoconditioning.

spontaneous recovery Spontaneous recovery is related to the process of extinction. Extinction training will result in the disappearance of the conditioned response. However, when the subject is given further extinction training following a break, the conditioned response will initially reemerge or spontaneously recover. Continued extinction training will more quickly result in the disappearance of the conditioned response until spontaneous recovery no longer occurs.

unconditioned response An innate response that is elicited by the unconditioned stimulus.

unconditioned stimulus A stimulus that is signaled by the conditioned stimulus. The unconditioned stimulus always elicits an unconditioned response.

unconditioned stimulus-alone test trial In unconditioned stimulus-alone test trials, the conditioned stimulus is omitted, leaving only the unconditioned stimulus presentation. In many classical conditioning experiments, the amplitude of the unconditioned response is an important measure (e.g., as a test to evaluate if a manipulation such as a brain lesion affects the ability of the subject to make a completely normal response). However, in a subject that is emitting conditioned responses, it is not possible to obtain an accurate measure of the unconditioned response amplitude because of contamination from the presence of conditioned responses. Unconditioned stimulus-alone test trials allow an uncontaminated measure of unconditioned response amplitude in subjects that are emitting conditioned responses.

Classical conditioning is a basic form of associative learning in which the organism learns something about the causal fabric of the environment or, in an experimental setting, the relationship of stimuli. Stimuli can be arranged so that one stimulus provides the organism with information concerning the occurrence of another stimulus. This type of associative learning is most commonly referred to as classical conditioning, but it has also been termed Pavlovian conditioning, respondent conditioning, and conditioned reflex type I conditioning, or type S conditioning.

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