Testing the Reinforcing Properties of S—: A Replication of Lieberman's Procedure

Abstract

A critical issue in testing theories of observing is whether the stimulus associated with extinction (the S-) reinforces observing responses. In previous experiments, subjects have been trained to make observing responses that produce both the S- and the stimulus correlated with reinforcement (the S+). Then, either the S+ or the S- has been withheld. Conflicting results have been attributed to differences among species. In the present experiments, pecking one key by master pigeons was reinforced with grain on a variable-ratio extinction schedule. Yoked pigeons received the grain on a variable-interval, extinction schedule controlled by the variable-ratio performances of the master birds. For both groups, concurrent pecking on a second key was reinforced on a variable-interval schedule with displays of discriminative stimuli. Subsequently, either the S+ or the S- was eliminated from the procedure. Omission of S+ produced a large decrease, as predicted by traditional conditioned reinforcement accounts of observing. By itself, S- did not maintain observing. A smaller and less reliable decrease, comparable to that obtained by Lieberman (1972) with rhesus monkeys, occurred when S- was eliminated. This replication with pigeons of Lieberman's results indicates that they are not species-specific, and the fact that observing was not maintained by S- alone suggests that the decrease obtained when S- was omitted is not attributable to the reinforcing power of S-.

The Effect of Negative Stimulus Presentations on Observing‐response Rates

“…Similar results have been obtained using pigeons (Mueller & Dinsmoor, 1984). However, when the response-contingent S-is eliminated from an observing procedure, both the presentations of the S-and the contingency between observing and the Sare eliminated.…”

“…The food deliveries were contingent on pecking one of two keys; pecks on the second, observing key produced stimulus displays, also delivered on a VI schedule, When the S + was omitted and only the S -could be produced by pecking the observing key, observing rates quickly and reliably dropped to zero. Subsequent studies have produced comparable results using other schedules of reinforcement (Auge, 1974;Mueller & Dinsmoor, 1984). Similar failures to maintain observing responses have been reported when the responses were followed by stimuli that accompanied a smaller magnitude (Auge, 1973) or lower density of reinforcement (Jwaideh & Mulvaney, 1976).…”

“…The present series of experiments has demonstrated (1) that presentations of S-are sufficient to raise observing rates, whether or not the S-is produced by the observing responses; (2) that the S -raises rates by a local-contrast-like effect, in which bursts of responses occur following offsets of S -; and (3) if only the contingency between S -and observing is eliminated, with the presence of S -held constant, higher rates of observing occur. Thus, the results obtained by Lieberman (1972) and by Mueller and Dinsmoor (1984) were probably due to the elimination of the presence of S -, as opposed to the elimination of the contingency between observing and S-.…”

“…Nine birds had no previous experience in observing procedures and were recruited from an experiment in which pecking had been autoshaped with a white key as CS+ and a white key with a black dot as CS-. The remaining seven birds had served in previous experiments similar to the one reported here, but without the free mixed stimulus (e.g., Mueller & Dinsmoor, 1984, Experiment 2). Subjects were maintained at 75% of their free-feeding weights by postsession feeding.…”

Decrease of Precurrent Behavior as Training Increases: Effects of Task Complexity

“…Despite this general similarity, research on observing behavior has been primarily concerned with testing different hypotheses (conditioned reinforcement or information) related to the variables that maintain observing responses rather than identifying the variables responsible for their decrease. As a matter of fact, in those few experiments in which the frequency of observing responses decreased with increasing training, this result has been regarded as unexpected and difficult to explain (e.g., Bickel, Higgins, & Hughes, 1991;D' Amato, Etkin, & Fazzaro, 1968;Mueller & Dinsmoor, 1984;Ohta, 1987). The experimental situations used to investigate observing behavior seem also to differ from the situations in which responses such as looking-up-in-the-directory occur.…”