ON THE CONTRIBUTIONS OF RESPONDING AND REINFORCEMENT TO WITHIN-SESSION PATTERNS OF RESPONDING

Operant responding may change systematically within experimental sessi ons even when the contingencies of reinforcement remain constant acros s the session. In two experiments, eight pigeons pecked a key for mixe d grain delivered by variable interval or multiple variable interval s chedules. Experiment 1 showed that changes in the rate at which reinfo rcers were delivered altered the within-session patterns even when the total amount of reinforcement presented per session was held constant . Experiment 2 showed that changing the overall rate of responding did not alter within-session response patterns. These results question th e idea that within-session patterns of responding are produced by simp le interpretations of satiation or fatigue. If within-session changes in responding were produced by satiation, then subjects receiving equa l amounts of reinforcement should have shown similar within-session pa tterns of responding, but they did not (Experiment 1). If within-sessi on changes were produced by fatigue, then the patterns should have dif fered when the overall response rate differed, bur they did not (Exper iment 2). The present study confirms that within-session patterns of r esponding are sensitive to changes in rate of reinforcement. (C) 1995 Academic Press, Inc.