Response inhibition in Extinction

In three experiments, rats were given a nonreinforced choice between two instrumental responses, in the presence of stimuli that had separately signalled the various outcomes those responses had earned. Whether those stimuli had been trained in a Pavlovian or instrumental procedure, they selectively enhanced the transfer response with which they shared an outcome. However, a subsequent test showed that this greater responding to a stimulus during extinction produced a reduced ability of that stimulus to augment its transfer response. These results are consistent with the development of an inhibitory S-R association during extinction.     

Simultaneous and sequential conditioned inhibition in autoshaping

Two experiments examined sequential and simultaneous conditioned inhibition in an autoshaping preparation. In Experiment 1, a 5-sec coloured keylight (A) was reinforced when presented alone. However, reinforcement was withheld from trials on which A was preceded by one grid pattern or presented simultaneously with another pattern. A third (control) pattern was presented separately without reinforcement. Inhibition developed most strongly to the grid pattern presented simultaneously with A. However, a transfer test with another excitatory coloured keylight found both inhibitors to be equally strong whether they were tested in simultaneous or in sequential compound. Experiment 2 compared grid patterns that consistently had sequential or simultaneous relations to the excitor with one that was sometimes presented in sequential and sometimes in simultaneous compound. The mixed treatment pattern showed levels of inhibition like the simultaneous or sequential pattern, depending on the temporal relation it bore to A on a particular trial. These results suggest that sequential and simultaneous relations between inhibitors and excitors yield similar amounts of inhibition. However, that inhibition is better exhibited when tested in simultaneous compound with the excitor.     

Within-subject Partial Reinforcement Extinction Effect in Autoshaping

Three autoshaping experiments explored the extinction of various keylight stimuli conditioned with partial and continuous reinforcement within the same pigeon subjects. Extinction of autoshaped keypecking proceeded more slowly in a stimulus trained with 50% (Experiment 1) and 25% (Experiment 2) reinforcement compared with a stimulus given 100% reinforcement. Experiment 3 found conditioning with 75% reinforcement to generate more rapid extinction than that with 25% reinforcement. These results have both theoretical and methodological implications for the study of extinction.     

Unequal associative changes when excitors and neutral stimuli are conditioned in compound

In four experiments a compound of a previously conditioned excitor and a neutral stimulus was either reinforced with food or nonreinforced. Two experiments used a magazine approach procedure in rats, and two used an autoshaping procedure in pigeons. All experiments employed a novel compound test procedure, which permitted evaluation of the size of the associative change that took place for the excitatory and neutral stimuli. Reinforcement of the compound resulted in greater increments in the associative strength of the neutral stimulus than of the excitor. Nonreinforcement of the compound resulted in greater decrements in the associative strength of the excitor than of the neutral stimulus. These results agree with earlier experiments with compounds of excitors and inhibitors and provide an additional challenge to contemporary error-correction models of conditioning.     

The role of context in intertrial interval effects in autoshaping

Two experiments evaluated the role of differential conditioning of the context in mediating the effect of intertrial interval (ITI) in autoshaping. In Experiment 1 pigeons were given acquisition with two keylights, each presented in a particular context. A given keylight/context combination had associated with it either a short (10-sec) or a long (2-min) ITI. Acquisition was more rapid with the long ITI. Tests with those keylights in a common third context indicated that the longer ITI had resulted in greater conditioning. On the other hand, pigeons trained on keylights with mixed ITIs in a third context evoked more responding when they were tested in the short ITI context compared with the long ITI context. That suggests that a context with a history of a short ITI enhances performance. In Experiment 2, two keylights were initially conditioned with mixed ITIs and then extinguished in different contexts under different ITI lengths. Extinction was more rapid for the keylight presented with a short ITI. That difference persisted when the keylights were tested with mixed ITIs in a common third context, suggesting a difference in associative strength of the keylights. The results are interpreted in terms of differential context conditioning resulting in differences in learning about the keylight.     

Elemental and configural encoding of the conditioned stimulus.

Five experiments explored the effect of conditioning AB and CD compounds on responding to transfer AD and BC compounds and to elements. These experiments used several conditioning procedures: flavour aversion and instrumental discriminative learning in rats and autoshaping in pigeons. All of the experiments found greater responding to the trained AB and CD than to the transfer AD and BC compounds, a result that agrees with some configural models, but not with an elemental model. All experiments also found greater responding to the transfer AD and BC compounds than to the elements, a result that agrees with elemental, but not configural, models.     

Full Preservation of a Response-Outcome Association through Training with a Second Outcome

In two experiments rats were trained to make instrumental responses, with each response earning first one and then a second outcome. Subsequent devaluation of either the first or the second earned outcome had a depressive effect on responding. The magnitude of the effect was similar, whichever outcome was devalued. This result suggests that initially trained response-outcome associations are fully preserved despite the same response being trained with a second outcome.