Instructed Human Fixed-Interval Performance: The Effects of the Experimental Setting

Abstract

Four experimentally naive human subjects were exposed to three fixed-interval (FI) schedules of reinforcement: FI 600 s, FI 300 s, and FI 60 s. The subjects were given instructions specifying the fixed interval based nature of the schedules and the behavior required to obtain points, later exchangeable for money. The experimental setting comprised of three rooms: Room A contained reading material, food snacks, and a variety of nonalcoholic beverages; Room B contained a computer keyboard; and Room C contained a monitor connected to the keyboard in Room B. The subjects were instructed to type “FEED” on the keyboard in Room B and then immediately check the monitor in Room C for the delivery of points. During exposure to the FI 600-s schedule all subjects produced pause-respond local response rates. These patterns persisted when subjects were transferred to the FI 300-s schedule. For a number of sessions during exposure to the FI 300-s schedule Room A was locked. The introduction of these “two-room” sessions decreased response rates and increased the postreinforcement pauses (PRPs) for three subjects. The FI 60-s schedule produced low response rates and extended PRPs for all four subjects. With a return to the FI 600 s, all subjects reverted to the pause-respond pattern. These results emphasize the importance of the experimental setting in human operant studies.