The Effect of the Instrumental Training Contingency on Susceptibility to Reinforcer Devaluation

Two experiments investigated performance of instrumental lever pressing by rats following post-conditioning devaluation of the sucrose reinforcer produced by establishing an aversion to it. In Experiment I rats responded less in an extinction test after being averted from the sucrose following training on a ratio schedule, but not following an equivalent amount of training on an interval schedule. This was true even though the devalued sucrose would not act as an effective reinforcer on either the ratio or interval schedule. Experiment II provided a further investigation of the insensitivity of interval responding to reinforcer devaluation by comparing test performance under simple extinction with responding when the devalued reinforcer was presented on either a response-contingent or non-contingent schedule during the test. Once again simple extinction performance was unaffected by prior reinforcer devaluation. Furthermore, neither non-contingent nor contingent presentations of the devalued reinforcer significantly depressed responding below the level seen in the extinction condition. Ratio, but not interval performance appears to be controlled by knowledge about the instrumental contingency that encodes specific properties of the training reinforcer.

Feedback in Discriminative Avoidance Learning: Mechanistic versus Cognitive Views

Presentation of a feedback stimulus, a non-aversive event never paired with shock, following an avoidance response has been found to be an effective reinforcer in avoidance learning. Alternative formulations of the feedback effect, one a version of the traditional S-R mechanistic, two-factor theory and the other a cognitive (informational) theory, were evaluated with a view toward determining which type of formulation provides a more viable explanation of avoidance learning. The conclusion reached, however, was that both informational and fear-reduction positions operationalize their critical concepts in the same manner, and to date there are no empirical grounds for distinguishing these different views.

Interaction of Anxiety and Note-Taking on Verbal Conditioning in Clinical Interviews

Using 60 male psychiatric patients, the interaction between three levels of anxiety and note-taking as a reinforcer was explored within a verbal conditioning paradigm. Results showed a curvilinear relationship between anxiety and reinforcement with high-average anxiety subjects conditioning better than either high or low-average subjects This supported the authors' prediction and showed note-taking to be an effective reinforcer of verbal behavior in an interview situation. Unexpectedly, subjects of low-average anxiety who conditioned less well than those of high-average anxiety showed a larger drop in emission rate during extinction, dropping to a level significantly below initial baserate.

Locus of the Effect of a Surprising Reinforcer in the Attenuation of Blocking

Previous experiments on conditioned suppression in rats have shown that prior conditioning to one element of a compound conditioned stimulus paired with shock may block or prevent conditioning to the other element. Reliable conditioning may, however, occur to the added element (blocking may be attenuated), if a surprising second shock is added shortly after each compound trial. Experiment I confirmed this finding, and further showed that blocking was attenuated only when the second shock occurred 10 s after the compound trial, not when it occurred 100 s later. Experiment II showed that the surprising omission of an expected second shock 10 s after each compound trial would also attenuate blocking, thus implying that the surprising event does not itself act to reinforce conditioning to the added element, but rather permits the unconditioned stimulus (the first shock) to play its normal role as an effective reinforcer. This conclusion was confirmed by Experiment III, which showed that a surprising second shock does not produce any increase in conditioning to the added element on the trial on which it occurs; rather it serves to ensure adequate conditioning to that element on a subsequent compound trial. The implication is that the surprising event acts proactively to prevent subjects learning to ignore an otherwise redundant stimulus.

Influence of Three Stimulus Conditions upon the Strength of a Secondary Reinforcement Effect

Animals were trained to approach a water dipper at the onset of a light and a tone, water being received following approach on an intermittent schedule. For three groups of animals bar-pressing was then reinforced on an intermittent schedule, using three stimulus conditions: light and tone only; light, tone, and dry dipper; and light, tone, and interrupted presentation of dry dipper. The interrupted presentation proved to be the most effective reinforcer. Ss in other groups which did not at first show a strong effect did so when switched to this condition.