Lateral asymmetries of orientation to track control in extrapersonal space

In an initial experiment, subjects were asked to make simple lateral lever responses to left and right verbal and arrow directions with the preferred hand. No asymmetries were found. In two subsequent experiments, subjects guided a track through a left or right turn in one of four orientations under instructions which were direct, compass points, or physical referents, by either a rotary or a discrete control. Asymmetries of direction of turn were observed. Rotary control produced a response bias towards the body midline, but independently of this factor there was a powerful bias towards right turns of track direction in extrapersonal space. Discrimination in the horizontal plane was more difficult than in the vertical plane especially when the instructions were compass points. Within the horizontal plane, together with the bias to right turns of track direction, a bias towards the right of the display was present. The interaction of these factors is believed to underlie reported errors in route finding and direction giving situations.