Abstract

"Blocking" refers to judgments of a moderate contingency being lowered when contrasted with a strong contingency. The Rescorla-Wagner model and causal model theory account for blocking through different mechanisms. To examine the predictions from these two models, seven experiments tested the extent to which "causal scenario" and "causal order" would influence whether blocking was observed in human contingency learning tasks. "Causal scenario" was manipulated by contrasting responses to two causes of one effect or to one cause of two effects; "causal order" was defined as causes preceding effects or effects preceding causes. The four conjunctions of these two factors were investigated separately in Experiments 1 to 5. In Experiments 1 and 2, two causes preceded one effect and two effects preceded one cause, respectively. Blocking was observed regardless of whether the predictors were causes or effects. In Experiments 3, 4 and 5, participants were presented with one antecedent cue and made separate predictions about each of the trial's two outcomes. Blocking was not observed, irrespective of whether the antecedent cue was a cause or an effect. These initial results were consistent with the Rescorla-Wagner model. An alternative explanation was that blocking failed to occur in Experiments 3 to 5 because participants were asked questions between the predictor and two outcomes. Predicting the outcomes might have implicitly led participants to monitor them separately and to report on subsets of the data at the time of judgment. To address this issue, the volunteers in Experiment 6 observed the events on each trial but did not make any predictions about the outcomes. Blocking was observed, signifying that the intervening questions between the antecedent and consequent cues constitute an important variable influencing cue competition effects. In Experiment 7, all four conjunctions of causal scenario and causal order were tested simultaneously. Furthermore, participants w.