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Two experiments were conducted to examine pseudoneglect as reflected in line bisection (LB) errors made by normal individuals and the relationship between LB and perceptual asymmetries.In Study 1, 63 dextral and 48 sinistral participants transected lines significantly to the left, and sinistrals' biases were stronger than dextrals' biases. Hemispatial effects were also present. Perceptual asymmetries for chimeric faces, dot-filled rectangles, and comparisons of Muller-Lyer illusion lines to arrows did not correlate with LB scores. In Study 2, 24 dextral participants had leftward bisection errors for a paper-and-pencil version of LB but not a computer version, although scores were correlated. Average perception of prebisected lines was unbiased, and correlations between this and LB tasks were lower than correlations between paper-and-pencil and computer LB tasks. These findings suggest that some nonperceptual, and possibly motor, factor contributes to the LB bias.

Interhemispheric cooperation in the processing of nonsense syllables projected simultaneously to both hemispheres was investigated in 2 experiments. Stimuli were projected unilaterally in the left and right visual fields (LVF, RVF) and bilaterally (the same syllable in both fields, BVF; Experiment 1, 64 right-handed subjects) or centrally (CVF; Experiment 2, 32 right-handed subjects). Accuracy and error patterns differed for the LVF and RVF. Error patterns were intermediate for the BVF-CVF and were partly shifted toward the RVF for subjects with large RVF advantages and toward the LVF for those with small asymmetries. Regression analyses showed that variance in BVF-CVF error patterns was jointly predicted by LVF and RVF variances. Both hemispheres, as demonstrated by means and regression analyses, contribute to the processing of bihemispherically presented syllables.

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College students screened for psychosis-proneness using the Chapman scales were compared on 4 free-vision tasks that typically yield left-spatial-field biases. The tasks included 2 chimeric face tests, consisting of happy/neutral faces and male/female faces, and 2 nonface tasks, consisting of pairs of dot-filled or gradient-filled rectangles. Participants endorsing perceptual aberration items, magical ideation items, or both (n = 98) and control participants (n = 112) were left-biased on all tasks but gradients and were most biased on emotion faces; in contrast, i.e., social anhedonia participants (n = 40) displayed very little or no left-field biases. For all groups, task intercorrelations were greatest between the 2 face tasks and between the 2 nonface tasks. These findings suggest patterns of atypical perceptual asymmetry in psychosis-prone individuals.