THE INFLUENCE OF CENTER-OF-MASS EFFECT ON THE DISTRIBUTION OF SPATIALATTENTION IN THE VERTICAL AND HORIZONTAL DIMENSIONS

Normal subjects attend toward the middle of grouped items (center of m ass effect). In order to learn if mass effect could influence performa nce on line bisection tasks and if the spatial orientation of the line (vertical vs. horizontal) could influence center of mass effect, we a dministered bisection tasks to 16 normal subjects using either lines c omposed of two unequal segments (one thick and one thin) or unsegmente d lines. When the longer segment was to the right, left, up, or down, subjects erred by deviating their bisection toward the longer segment (center of mass effect). Our results demonstrate that the center of ma ss effect can be seen with bisection tasks and is greater in the verti cal than in the horizontal dimension. (C) 1997 Academic Press.