Contingency judgment: primacy effects and attention decrement.

Subjects made judgments concerning the strength and direction of the contingency between two dichotomous variables in a situation in which no contingency actually existed. The judgments exhibited a significant primacy effect. The effects of warning and not warning the subjects that they would be required to recall the frequencies of observed event co-occurrences implied that this primacy effect was due to ‘attention decrement’ (Anderson 1981). According to this hypothesis, attention to contingency-relevant information diminishes after the subject is exposed to only a small portion of the available information.