Effect of a visual distractor on line bisection.

Previous studies have shown that a flanking distractor produces a spatial bias during line bisection. In the present study, we investigated whether that bias depends on perceptual or motor components. Participants were asked to bisect a horizontal line, or to reach towards a dot, with or without vision of their hand. The line and the target could be flanked by a distractor. Movement trajectories and endpoints were consistently deviated away from the location of the distractor in the bisection task, but not in the reaching task, irrespectively of whether the participants had online visual feedback from their moving hand. It is suggested that flanking distractors influence perceptual localization of the subjective mid-point during line bisection.