FIXED VERSUS VARIABLE SEQUENCES OF FOOD AND STIMULUS PRESENTATION IN SECOND‐ORDER SCHEDULES¹

Abstract

Three pigeons were exposed to a second-order schedule in which the behavior specified by a fixed-interval component schedule was reinforced according to a ratio overall schedule. The completion of components not followed by food was signalled by a brief stimulus never paired with food. Food and the stimulus occurred in a random sequence or in fixed alternation, but the overall schedules (variable ratio 2 or fixed ratio 2) ensured that an equal number of food and brief-stimulus presentations occurred in each session. The control exerted by the food and by the brief stimulus was measured by overall response rates, mean pauses, frequency distributions of pauses, and response patterning across components. In general, the stimulus controlled patterns of behavior more similar to those controlled by food when food and the stimulus occurred in a random sequence than when they occurred in fixed alternation.Key words: second-order schedules, fixed-interval components, nonpaired brief stimuli, schedule control, conditioned reinforcement, omission effect, key peck, pigeons Kelleher (1966b) 1972). The study of second-order schedules with these brief stimuli is important in the investigation of conditioned reinforcement, because this procedure enables a clear demonstration that a previously neutral stimulus can acquire the power to act like a primary reinforcer in maintaining appropriate schedulecontrolled patterns of responding over long periods of time. The effects of brief nonpaired stimuli in second-order schedules are more equivocal, however. Although several reports have suggested that nonpaired stimuli do not control behavior similar to that controlled by food (e

Effects of Fixed‐time Shocks and Brief Stimuli on Food‐maintained Behavior of Rats

“…This behavior developed although the stimulus was never paired with shock. There is a parallel between this phenomenon and the control of behavior on second-order schedules in which the unit schedule is reinforced on a VR schedule and nonreinforced units end with a nonpaired brief stimulus (e.g., Corfield-Sumner & Blackman, 1976). In both cases brief stimulus presentation occurs unpredictably and signals that another time interval must elapse, or unit schedule be completed, before the next occasion at which shock, or the reinforcer, may be received.…”

Separating the Reinforcing and Discriminative Properties of Brief‐stimulus Presentations in Second‐order Schedules

“…The discriminative interpretation stems from research showing that a stimulus not paired with food may also engender response patterning; and further, that pairing the brief stimulus with food has no effect on response 149 1979, 322 149-156 NUMBER 2 (MUrMMBER) patterning (e.g., Cohen, Hughes, & Stubbs, 1976;Corfield-Sumner & Blackman, 1976;Staddon & Innis, 1969;Stubbs, 1971;Stubbs & Cohen, 1972). Stubbs (1971) has argued that in a second-order schedule with a fixed temporal relationship between brief-stimulus and food presentations (e.g., fixed interval or fixed ratio) the brief stimulus acquires discriminative properties.…”