Individual variation in directional bias in visual perception

Directional biases in visual perception were examined for individual differences in sixty-five subjects on two tasks. One task required judgments of the onset asynchrony of pairs of dots presented at random, either one dot in each visual field, or both in the left visual field (LVF), or the right visual field (RVF). The second task required the recall of four letter strings presented randomly in either visual field. Dot-asynchrony judgments were influenced by two main biases: first, an outward from the centre bias in both visual fields, and second, a lateral bias which was significantly from left to right (L-R) in the total sample. A substantial minority of subjects were biased to judge the dots as occurring in right to left (R-L) order. Accuracy of letter report decreased fairly consistently from L-R in the RVF but varied in the LVF. Some subjects showed a L-R report gradient, some a R-L gradient, and some a U-shaped recall pattern. Significant correlations between measures of L-R and R-L biases on the two tasks show that the biases have some stable foundation. The findings suggest that there are directional biases affecting visual perception which are due neither to learned reading habits, nor to cerebral specialization of function.