In the match/mismatch model, recently formulated by Rachman and coworkers, it is stated that incorrectly predicted aversive experiences are generally followed by an immediate adjustment of the predictions concerning aversiveness of the next experience. This model can be considered to reflect a psychological process of the formation of expectations. In the present article it is argued that a simple H0 model, assuming that predictions are completely randomly generated by the subject, may account for the same effects. This H0 model is used in a stringent test of empirical data to determine if there are any effects of the discrepancy between prediction and experience on next prediction that exceed the effects explained by the H0 model. Although the H0 model produces effects very similar to the empirically observed effects, there is clear support for the hypothesized influence of the discrepancy between prediction and experience. Therefore, the model appears to reflect 'real' psychological processes and not chance findings.