Visuospatial neglect in normal subjects: altered spatial representations induced by a perceptual illusion.

Previous studies have suggested that the representation of space is distorted in patients with hemispatial neglect. To examine the nature of the altered spatial representation, we developed an analog of neglect in normal subjects using bisections of the Judd visual illusion (e.g., <---<) whose direction (facing left/right/both) and fin angle (14 degrees/45 degrees/76 degrees) were orthogonally varied. Subjects made bisection errors that deviated significantly in a direction opposite to that in which the fins pointed, and these deviations decreased as fin angle increased. We replicated these findings in a second task in which subjects were given the midpoint and placed the two fins at the ends of an imaginary shaft (e.g., < x <, note: dot = true center). These findings suggest that the geometric properties of the display have a strong influence on the representation of space, and thus may be used to induce a distorted perception of space analogous to that observed in patients with visuospatial neglect.