THE RELATION BETWEEN SPEED OF VISUAL PERCEPTUAL PROCESSING AND INTELLIGENCE IN NORMAL POPULATIONS
LAUX, LILA FITZGERALD
Doctor of Philosophy
The idea that there is an association between speed of visual perceptual processing and general intelligence is intuitively appealing, but success in establishing the relationship empirically has been only partially successful. Although it has been shown that retardates and normals differ in the speed with which they can perform simple tasks requiring rapid visual perceptual processing, when the same tasks are used to assess processing speed in normal populations individual differences in processing speed are not related to scores on measures of intelligence. Researchers interested in the correlates of reading ability, however, have had consistent success in establishing a relationship between levels of reading ability and individual differences in speed of visual perceptual processing in normal populations when the perceptual processing tasks involved locating or identifying letters in briefly presented multi-element arrays. This suggests that although the tasks used by intelligence and reading researchers are superficially similar, the processing demands of the tasks differ. As intelligence and reading ability are substantially correlated in normal populations, it was hypothesized that the consistently reported correlation between reading ability and speed of visual perceptual processing is mediated by the relation between reading ability and intelligence. This study examined the relationship between performance on tasks requiring subjects to either locate or identify targets in briefly presented arrays and Raven's Standard Progressive Matrices scores and scores on the Nelson Denny Reading Comprehension and Speed Test in a group of typical high school students. Accuracy of performance on tasks which required subjects to report the location or identity of uncued targets in arrays correlated with Raven's scores but not with reading ability scores. This supports the hypothesis that correlations between reading ability and visual perceptual processing speed are mediated by individual differences in general intelligence. More importantly, performance as assessed by two measures which have been shown to suffer decrements when attentional load is increased accounted for significant proportions of variance in Raven's scores.