Stimulus Control

A primary objective of psychology is the prediction of behavior. Operationally, this means that what an individual will do in a particular situation can be anticipated. To the degree that this is possible, the individual is under stimulus control. The fact that people seldom are surprised by the actions of those with whom they interact is an indication that others are behaving as expected. This entry briefly discusses how this stimulus control is acquired. It progresses from simple reflexive actions to those resulting from the differential consequences of one's behavior in different situations. For example, one learns to use different language and manners when speaking to a teacher than when speaking to a fellow student.

The simplest form of stimulus control is those unlearned responses naturally elicited by an unconditioned stimulus (UCS). Thus, an air puff to the eye will produce an eye blink, contact with a hot stove will result in rapid retraction of one's hand, and food in the mouth will elicit salivation. However, as I. P. Pavlov showed, this control can be transferred to stimuli that precede, and therefore predict, these naturally eliciting events. For example, stimulus control is revealed when a dog salivates to a tone that precedes food and when the child who burned his or her hand on the hot stove becomes afraid of stoves. Both are examples of classical conditioning and illustrate that this type of associative learning is capable of (a) bringing a particular reflexive response under the control of a conditioned stimulus (CS) that was originally neutral with respect to that behavior, and (b) creating motive states related to the signaled events—repulsion (“fear”) in the case of aversive events and attraction with those that are positive. Recall being drawn into a bakery when you had no interest in food prior to experiencing the aroma of your favorite, fresh-baked pastry. This incentive-motivation is clearly under the control of stimuli signaling positive (attractive) or aversive (repelling) events significant to the individual.

Traditionally, students of stimulus control have been most interested in operant conditioning that is concerned with when, whether, and in what way an individual's behavior will be affected by particular environmental consequences or events related to that behavior. C. B. Ferster and B. F. Skinner pioneered the study of these relationships, whereby operant reinforcement contingencies describe the relationships between emitted behavior and consequences. Those operant behaviors that produce a reinforcer (e.g., an attractive event such as food, approval, or a safety signal) will increase in frequency. In contrast, behaviors that produce an aversive situation (e.g., a repelling event such as shock, rejection, or a time-out from reinforcement signal) decrease the probability of those behaviors.

In nature, there tend to be cues in the environment that signal when a specific contingency is in operation and one's behavior will therefore produce the consequence(s) specified by that contingency. Differential reinforcement of a particular behavior pattern under a limited range of environmental conditions is what produces operant stimulus control. For example, pressing a lever may produce food pellets for a deprived rat only when a house light is on, just as a speaker is likely [Page 948]to get an answer to his or her question only when he or she has a listener's attention. This can be represented schematically by the three-term contingency: SD • R → Sr, which states that a behavior (R) (e.g., asking a question), emitted in the presence of a discriminative stimulus (SD) (e.g., an attentive, prepared listener), will produce a reinforcer (Sr) (e.g., an answer). This also implies that when the SD is absent (e.g., a listener isn't present, or the one who is isn't attentive or prepared), these responses will be ineffective.

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