About individual differences in vision

In cognition, audition, and somatosensation, performance strongly correlates between different para-digms, which suggests the existence of common factors. In contrast, visual performance in seeminglyvery similar tasks, such as visual and bisection acuity, are hardly related, i.e., pairwise correlationsbetween performance levels are low even though test-retest reliability is high. Here we show similarresults for visual illusions. Consistent with previous findings, we found significant correlations betweenthe illusion magnitude of the Ebbinghaus and Ponzo illusions, but this relationship was the only signif-icant correlation out of 15 further comparisons. Similarly, we found a significant link for the Ponzo illu-sion with both mental imagery and cognitive disorganization. However, most other correlations betweenillusions and personality were not significant. The findings suggest that vision is highly specific, i.e., thereis no common factor. While this proposal does not exclude strong and stable associations between certainillusions and between certain illusions and personality traits, these associations seem to be the exceptionrather than the rule.