Individual differences in the classification of stimuli by dimensions.

In two experiments, adults differing in general mental abilities ("intelligence") were given multidimensional classification tasks: aural and visual free-classification tasks that allowed grouping of triads or trends by conflicting criteria of dimensional identity or overall similarity, and a speeded classification task that required the filtering of variation in an irrelevant dimension. Four principal results are reported: (a) Individual differences in the tendency to use similarity criteria in free classification were systematic across modalities and stimulus dimensions; (b) filtering performance, measured as the effect of irrelevant variation on speeded classification, did not correlate with free-classification performance (percent similarity responses); (c) the tendency to use similarity criteria in free classification was not correlated with intelligence; and (d) the amount of interference in speeded classification was correlated negatively with intelligence. The results taken together suggest that there are two dimensions of individual differences in perceptual analysis, one having to do with ability and the other with style or preference. This suggestion was supported by an additional analysis. The results also raise questions about the convergence of measures of multidimensional stimulus processing.