The dissociation between the recall of stimulus frequencies and the judgment of contingency allows the placement of the competition effect in the final causal processing stages

In the predictive learning and causal reasoning literature it has been suggested that the processing of events is under the control of a competitive mechanism. However, little is known about whether the competitive mechanism operates at the encoding or near the response stages. The present work suggests that measures based on the recall of frequencies of the cells in the contingency table could help us in the placement of the competition principle within the processing stages. As the contingency judgment about a constant symptom-illness relation changed according to the validity of a second different symptom, we concluded in favour of a competition mechanism. However, estimated frequencies did not change as a result of such manipulation. This dissociation suggests that the competitive mechanism operates near the response stage rather than at the stimulus encoding period. In the predictive learning and causal reasoning literature it has been suggested that the processing of events is subject to a competitive mechanism. According to this principle, the causal or predictive relationship attributed to an element is engaged in a relative way to other potential agents. The competition principle was in fact evidenced in a systematic way in the frame of the relative validity paradigm (Wagner, 1969). In this procedure (see Baker, Valle-Tourangeau and Murphy, 2000) it is usual to present two stimuli (A and B) as potential predictors of an outcome, and two experimental conditions. In both conditions the contingency of stimulus A is kept constant, whereas the contingency of stimulus B is changed from one condition to the other. The competition is computed by analysing the differences of the contingency judgment for stimulus A. Competition effects such as blocking, relative validity or discounting are interpreted as a coding or learning problem, as implicated by the Rewcorla-Wagner model (see Cobos, Cano, Lopez, Luque,