STIMULUS-CONTROL OF BEHAVIOR DURING THE POST-REINFORCEMENT PAUSE OF FI SCHEDULES

Pigeons were given the opportunity to terminate certain segments of fixed intervals by pecking a control key. When 30-sec segments of negative and positive stimuli alternated across the interreinforcement interval (Experiment 1), most birds terminated a large proportion of negative segments. However, few control-key responses were made during the negative segment immediately following food presentation. Under schedules during which only one negative segment was programmed, during the first 30 sec of 1-min intervals (Experiment 2), control-key responses, when they occurred at all, were made after several seconds of the interval had elapsed. Similar findings were obtained when a peck on the control key merely changed the color on the food key (Experiment 3). These findings suggest that the post-reinforcement extinction state (Schneider, 1969) during fixed-interval schedules consists of two phases: an immediate postreinforcement inhibitory phase, followed by a second phase during which a control-key response may occur. These two phases and their associated behavior may be related to Staddon's (1977) distinction between interim and facultative activities. © 1979 Psychonomic Society, Inc.