Duration of signals for intertrial reinforcement and nonreinforcement in random control procedures.

Abstract

In the random control procedure, responding to a conditioned stimulus (target CS) is prevented when the probability of unsignaled, unconditioned stimuli (USs) in the intertrial interval (ITI) is equal to the probability of the US in the presence of the target CS. Three experiments used an autoshaping procedure with White Carneaux pigeons to examine the effects of the temporal duration of signals for the ITI USs (cover CSs) and for concomitant periods of nonreinforcement. In Experiment 1, a short duration cover, but not a long duration cover, resulted in responding to the target CS. In Experiment 2, an explicit CS- cue during periods of nonreinforcement did not affect target acquisition. In Experiment 3, a long CS-, but not a short cover CS, was a sufficient condition for the acquisition of responding to the target CS. These results imply that the acquisition of responding to a target CS requires a discriminable period of nonreinforcement that is long relative to the target CS duration.

The Cover-Stimulus Effect: Role of Similarity in Durations of The CS and Cover Cues

“…It is possible that this difference can be attributed to species differences and/or the relatively more nonspecific response measure (proportion of time spent on the side of a shuttle box containing the CS) used by Williams. The present results are quite similar to those of Cooper et al (1990) who studied pigeon autoshaped responding, as in the present study. Durlach (1983) also studied autoshaped behavior and reported comparatively high levels of responding; however, unique to that study was cover-cue pretraining.…”

“…Under the signaled random procedure, both the CS and context acquire value as they do under the unsignaled random procedure, but the effective associative strength of the context is weakened owing to the presence of the cover cue whenever the US is presented. In Cooper et al (1990), for example, the cover cue weakens the context by deleting the US with which it is paired from the calculation of background strength.…”

“…For example, Durlach (1983) showed that the competition model of Rescorla and Wagner (1972) provided a good account for her data. In contrast, Cooper et al (1990) presented data that were not readily accounted for by the Rescorla-Wagner model, but that could be accommodated by the deletion comparator model, a version of Scalar Expectancy Theory (Gibbon & Balsam, 1981). In the General Discussion of this report, we evaluate the performance of competition and comparator models in accounting for the effects of relative durations of CS and cover cues.…”

“…Under the signaled random procedure (Cooper, Aronson, Balsam, & Gibbon, 1990;Durlach, 1982Durlach, , 1983Williams, 1994), a random temporal relation between the CS and US is arranged such that the CS and US are occasionally paired, but p(USICS) = p(USIGS). All unpaired US presentations, however, are preceded by a second cue, called the cover stimulus.…”

“…Cooper et al (1990, Experiment 1) exposed two groups of pigeons to a signaled random autoshaping procedure. Duration of the CS was 12 s, and the cover stimulus was either 12 s (short group) or 48 s (long group) in duration.…”