Pointing in Stereoscopic Space

Abstract

Movements in virtual stereoscopic space tend to be difficult and slow. To shed some light on the origins of these difficulties, we studied open-loop pointing with targets presented in a mirror stereoscope. Whilst targets were placed in a virtual horizontal plane, movement end-points were located in an inclined plane. The inclination of this plane was a stable individual characteristic. Amplitude errors gave no evidence of a contraction bias. Open-loop movements had fairly straight trajectories, but closed-loop movements were strongly curved so that they ended in a horizontal plane rather than in an inclined one. Effects of closed-loop movements on subsequent open-loop movements (calibration effects) were only small. These findings reveal that movements in a virtual environment exhibit a number of characteristics also seen in real environments, but in addition they reflect specific visual illusions. Extensive calibration procedures are needed to overcome such errors for the reliance on closed-loop control of pointing to be relaxed.