Effects of spatiotopic factors on bisection of radial lines.

Under visual guidance normal subjects usually misbisect radial lines farther than the true midpoint (distal bias). We investigated whether this distal bias is constant across the peripersonal space or it varies by varying the distance of the stimulus from the subject. Subjects were asked to bisect radial lines presented below eye level either in the near or far peripersonal space. The results showed an increase of distal bias in the far-space. This finding suggests that the influence of spatial factors on bisection of radial lines is not constant across the peripersonal space. Distal bias increases as a function of the distance of the stimulus from the subject, according to a spatiotopic processing scheme.