Uncontrollable shock proactively increases sensitivity to response-reinforcer independence in rats

Learned helplessness theory predicts that animals exposed to inescapable shock acquire an expectancy of response-reinforcer independence, which proactively interferes with learning of response-reinforcer dependence. The theory also predicts that this expectancy can increase sensitivity to subsequent instances of response-reinforcer independence. These experiments test the latter prediction in a paradigm that minimizes the confounding effects of shock-induced activity deficits. Rats were trained to respond for food, then given either escapable, inescapable, or no shock. Subsequently, they received two sessions of response-contingent food followed by sessions of noncontingent food deliveries. During this phase, inescapably shocked animals decreased responding faster than did controls. Experiment 2 replicated this finding with a different schedule of food delivery and a procedure that more directly minimized the possibility that the outcome is due to either direct or indirect shock-induced activity changes. These results support the prediction that uncontrollable aversive events can increase an animal's sensitivity to noncontingent response-reinforcer relationships.     

The influence of biased exposure to forgone outcomes

After making decisions, we often get feedback concerning forgone outcomes (what would have happened had we chosen differently). Yet, many times, our exposure to such feedback is systematically biased. For example, your friends are more likely to tell you about a party you missed if it was fun than if it was boring. Despite its prevalence, the effects of biased exposure to forgone outcomes on future choice have not been directly studied. In three studies (five experiments) using a simplified learning task, we study the basic influence of biased exposure to forgone outcomes in the extreme case in which decision makers can easily infer the missing information such that the biased exposure carries almost no informational value. The results in all studies suggest that nevertheless, the biased exposure to forgone outcomes affected choice. Exposure to forgone outcomes only when they were better than the obtained outcomes (Only-Better-Forgone) increased selections of the forgone option compared with exposure to forgone outcomes only when they were worse than the obtained outcome (Only-Worse-Forgone). Moreover, relative to an unbiased exposure to all forgone outcomes, the effect of exposure to Only-Worse-Forgone was larger than the effect of exposure to Only-Better-Forgone feedback. However, these effects were not universal: In environments that include rare negative events (“disasters”), biased exposure to forgone outcomes had very little effect. We raise potential explanations and further discuss implications for marketing and risk awareness.     

Learned helplessness and immunization: sensitivity to response-reinforcer independence in immunized rats

In experiments 1 and 2, we examined the learned helplessness and immunization effects using a test in which appetitive responding was extinguished by delivering noncontingent reinforcers. Contrary to learned helplessness theory, "immunized" animals showed performance virtually identical to that of animals exposed only to inescapable shock, and different from nonshocked controls. Experiment 2 suggests that the helplessness effect and the lack of immunization are not due to direct response suppression resulting from shock. In Experiment 3, where the immunization effect was assessed by measuring the acquisition of a response to obtain food when there was a positive response-reinforcer contingency, immunization was observed. These results cannot be explained on the basis of proactive interference, but suggest that animals exposed to the immunization procedure acquire an expectancy of response-reinforcer independence during inescapable shock. Thus, immunization effects may reflect the differential expression of expectancies, rather than their differential acquisition as learned helplessness theory postulates.     

The Effects of a Pretrained Excitatory Stimulus on Schedule-Induced Polydipsia in the Rat

The purpose of the present study was to test two predictions derived from the application of Pavlovian conditioning principles to the schedule-induced polydipsia (SIP) phenomena. The first prediction was that a pretrained excitatory signal for pellet delivery would facilitate the development of SIP. A second prediction was that phenomena which are typically observed in Pavlovian conditioning experiments, such as learned irrelevance, latent inhibition, and the US preexposure effect, would also be observed in the SIP paradigm. The results indicated that a group given excitatory pretraining to a tone failed to develop SIP more rapidly than controls when this tone was used to signal pellet deliveries during SIP training. However, learned irrelevance, latent inhibition, and the US preexposure effect were demonstrated. Thus, these data generally support the predictions derived from the Pavlovian conditioning view of SIP.