Line Bisection and Perceptual Asymmetries in Normal Individuals: What You See Is Not What You Get

Abstract

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. © 1995 American Psychological Association.