Set-size and frequency-of-occurrence judgements in young and older adults: the role of the availability heuristic.

Two experiments examined the cognitive processes underlying judgements of set size and judgements of frequency of occurrence in young (Experiments 1 and 2) and older (Experiment 2) adults. Previous research has implicated the availability heuristic in set-size judgements, whereas an automatic processing mechanism has been implicated in judgements of frequency of occurrence. In the current experiments, path analysis was employed to investigate the role of an availability bias in performance on the judgement tasks. In Experiments 1 and 2, both types of judgement were influenced by repetition frequency of words independent of the availability (recall) of specific exemplars. Experiment 2 extended the investigation to include age differences. Although older adults' recall performance was poorer overall, the availability bias was age invariant, and there were no age differences in either set-size or frequency-of-occurrence judgements. Our results indicate that both set-size and frequency-of-occurrence judgements are independent of the availability bias evident in recall, and they support the notion that an automatic processing mechanism underlies both types of judgement.