Blocking of Stimulus Control and Conditioned Reinforcement

Abstract

Stimuli with no specific biological relevance for the organism can acquire multiple functions through conditioning procedures. Conditioning procedures involving compound stimuli sometimes result in blocking, related to the phenomenon of overshadowing. This can affect the establishment of conditioned stimuli in classical conditioning and discriminative stimuli in operant conditioning. The aim of the current experiment was to investigate whether a standard blocking procedure might block the establishment of a conditioned reinforcer-in addition to blocking discriminative control by that stimulus in rats. We used successive discrimination training to establish a tone or a light as a discriminative stimulus for chain pulling, upon which an unconditioned reinforcer (water) was contingent. Next, we trained a tone-light compound stimulus the same way. Finally, we conducted two tests, one for stimulus control and one for a conditioned reinforcing effect on a new response. Little or no discriminative control was evident by the second stimulus, which was added to the previously established discriminative stimulus later during training. The subsequent test showed blocking of conditioned reinforcement in five of the seven rats. Procedures that generate blocking can have a practical impact on attempts to establish discriminative stimuli and/or conditioned reinforcers in applied settings and needs careful attention.

Blocking of Stimulus Control in Children with Autism

“…Replication of the stimulus control test showed the same consistent result: The S 1 + , which was established during the first phase of the discrimination training, was still effective, whereas S 2 + , which was added during the second phase, was not. The results of the present study are in accord with the results of previous studies that have demonstrated blocking of discriminative control in animals (e.g., Vandbakk et al, 2020;vom Saal & Jenkins, 1970) and in humans. However, results of previous experiments with humans have varied, and so have the procedures used in those experiments.…”

“…Moreover, the added stimulus did not show reinforcing properties when contingent upon a novel response. Thus, Vandbakk et al (2020) supported previous research on the blocking effect in animals using an operant discrimination training procedure.…”

“…Blocking of conditioned reinforcers is shown in pigeons (e.g., Palmer, 1988) and rats (e.g., Vandbakk et al, 2020), and is strongly indicated in children with autism (e.g., Lovaas et al, 1966). In applied contexts, it is likely that the conditioning of a new stimulus as a reinforcer will sometimes fail: for example, if a smile already functions as a reinforcer, establishing "Great!"…”

“…In a recent study, Vandbakk, Olaff, and Holth (2020) demonstrated blocking of stimulus control in rats using an operant conditioning procedure. In the first phase of a go/no-go procedure, either of two single stimuli, one auditory and one visual, was established as a positive discriminative stimulus (S+) for chain pulling, and the second as a negative discriminative stimulus (S-or S-delta).…”

“…The authors of this article suggest that procedures that facilitate blocking of stimulus control may influence the establishment of stimulus control and conditioned reinforcers in applied settings. The present study aimed to replicate parts of Vandbakk et al (2020) in an applied context. Thus, we investigated whether blocking could be demonstrated in children with autism during the establishment of stimulus control, using a standard operant discrimination procedure (e.g., Seraganian & vom Saal, 1969;Vandbakk et al, 2020;vom Saal & Jenkins, 1970).…”