SOME EFFECTS OF RESPONSE‐DEPENDENT CLOCK STIMULI IN A FIXED‐INTERVAL SCHEDULE¹

Abstract

Two experiments studied the effects of brief response-dependent clock stimuli in fixedinterval schedules of reinforcement. In the first experiment, two pigeons were exposed to a fixed-interval schedule. Two conditions were compared. In both conditions each peck on the key produced a brief stimulus. In one condition, pecks produced a different stimulus in successive sixths of the interval. This was the clock condition. In the other condition, the same stimulus was produced throughout the interval. Response riates were lower and the pause after reinforcement was longer in the clock condition. In the second experiment, a two-key optional clock procedure was used. Responding on the clock key produced one of three stimuli correlated with the three successive minutes of a fixedinterval schedule. A response on the other key produced grain at the end of the 3 min. When the final stimulus was removed from the situation and pecking produced nothing during the third minute, responding to the clock key declined to a very low rate. When the first two stimuli were removed and the third one replaced, responding to the clock key was resumed.

Stimulus functions within a fixed-interval clock schedule: Reinforcement, punishment, and discriminative stimulus control

“…Moreover, when brief clock stimuli were response-dependent, the dara suggested that the early stimuli functioned as S-s and conditioned punishers, perhaps because of their temporal distance from food, whereas the later stimuli (especially the terminal clock stimulus) functioned as S + s and conditioned reinforcers, presumably because of their temporal proximity to food. 1 A systematic replication of Segal's experiment by Kendall (1972) showed that the control exerted by the brief stimuli of a response-dependent FI clock schedule is particularly evident when one compares response rates under successive portions of a clock condition with response rates during corresponding portions of a single stimulus condition. Kendall trained pigeons to respond on an FI schedule where each peck on the key produced either the same brief visual stimulus (single stimulus condition) or a different brief visual stimulus (clock condition) during successive sixths of the Fl schedule.…”

“…More recent studies of Fl clock schedules (Farmer & Schoenfeld, 1966;Hendry & Dillow, 1966;Hendry, Yarczower & Switalski, 1969;Kendall, 1972;Laties & Weiss, 1966;Segal, 1962) have used a discontinuous clock where, for instance, an Fl schedule might be divided into four equal parts by four successive, distinctive, visual stimuli reliably correlated with the passage of time. The stimuli may either be responseindependent or response-dependent.…”

“…In an experiment (Kendall, 1972, Experiment 2) using a two-key optional clock procedure (Hendry & Dillow, 1966), responding on the "dock key" 117 briefly produced one of three stimuli correlated with the three successive minutes of an FI schedule. The first response on a second key following the end of the interval produced food.…”

“…Although both Kendall (1972) and Segal (1962) have suggested that response-dependent brief stimuli correlated with the early portions of an FI clock schedule are punishing (cf. Dews, 1970), direct evidence of suppression relative to baseline responding is unavailable.…”

Signaled reinforcement effects on fixed-interval performance of the rat

“…Rats in the yoked group received the signal when their paired master rats received the signal and the reinforcement. This procedure, however, might have introduced some artifacts because a stimulus in the interval affects the rate and pattern ofFI responding (e.g., Eckerman & McGourty, 1969;Farmer & Schoenfeld, 1966a, 1966bFerster & Skinner, 1957;Kendall, 1972;Segal, 1962). Thus, we used as an appropriate control the unsignaled group instead of the yoked one.…”