Effects of coextensivity of the neutral stimulus with different lengths of the discriminative time in a temporally-defined schedule

Abstract

An experiment was conducted with 4 male albino Wistar rats. The effect of presenting a differential neutral stimulus coextensively to the tD subcycle in a temporally-defined schedule was evaluated. All rats were exposed to four experimental phases, in which the length of the T cycle was varied (60, 80, 120, and 60 s). The value for T was always 0.5, and the P values for water delivery were 1.0 and 0.0 for tD and tD respectively. Each phase consisted of 30 sessions, 60 cycles each one. Water was delivered to the first response in tD. However, the stimulus correlated with tD remained until the end of the subcycle. The same occurred with the stimulus correlated with tD . Results show that rats emitted the same number of responses across the experiment, irrespectively of the cycle’s length. It was also observed that no stimulus control developed but, unlike previous studies, the number of responses in tD and tD was similar. Overall number of responses was a function of the number of water deliveries obtained during the first 20 cycles of each session. There were more tD than tD subcycles with at least one response. These results are examined in terms of different stimulus functions developed in temporal stimulus schedules and in traditional reinforcement schedules.