The Detection of Inhibition Using the Resistance to Reinforcement Method

Abstract

Pigeons learned to discriminate between a stimulus which signalled a variable-interval (VI) schedule of reinforcement and a stimulus which signalled extinction. In Experiment 1, for one group of four pigeons, a line- tilt stimulus was associated with extinction, and for another group of four pigeons this stimulus was uncorrelated with the availability of reinforcement. During a resistance to reinforcement phase, responses to this line-tilt stimulus and to a novel stimulus were reinforced on a VI schedule. Statistical comparisons of the response rates to these test stimuli indicated that subjects consistently responded at a higher rate to the line-tilt stimulus than to the novel stimulus. Between-groups comparisons of response rates to the line-tilt stimulus indicated no reliable differences. These results indicated that a novel stimulus had strong response suppression or inhibition effects when compared to stimuli to which the subjects had had previous exposure. However, stimuli which were correlated or uncorrelated with the availability of reinforcement were equivalent in their inhibitory or response suppression effects.

Experiment 2 used a within-subject design to replicate and extend the findings of Experiment 1. The data from Experiment 2 also indicated that a novel stimulus was a very strong suppressor of responding. However, these data also indicated that a stimulus that had signalled extinction was a stronger inhibitor of responding than a stimulus that had been uncorrelated with reinforcement. These findings are discussed in terms of the stimulus- reinforcer and response-reinforcer contingency arrangements which produce inhibitory stimulus control. Methodological considerations for the detection of inhibition are also discussed.