Forward and Backward Blocking in Human Contingency Judgement

Three experiments investigated whether a process akin to Kamin's (1969) blocking effect would occur with human contingency judgements in the context of a video game. Subjects were presented with sets of trials on each of which they could perform a particular action and observe whether the action produced a particular outcome in a situation in which there was an alternative potential cause of the outcome. In Experiment 1 it was found that prior observation of the relationship between the alternative cause and the outcome did indeed block or reduce learning about the subsequent action-outcome relationship. However, exposure to the relationship between the alternative cause and the outcome after observing the association between the action and the outcome also reduced judgements of the action–outcome contingency (backward blocking), a finding at variance with conditioning theory. In Experiment 2 it was found that, just as is the case with forward blocking, the degree of backward blocking depended on how good a predictor of the outcome the alternative cause was. Finally, in Experiment 3 it was shown that the backward blocking effect was not the result of greater forgetting about the action–outcome relationship in the experimental than in the control condition. These results cast doubt upon the applicability of contemporary theories of conditioning to human contingency judgement.