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要旨:
We investigated the effect of various viewpoints on remapping visuo-motor space. Subjects tapped targets on a touch monitor that was placed horizontally in front of them. The targets appeared at one of seven positions at a fixed distance from the starting position of the hand. Subjects viewed the monitor and their hand through video glasses attached to a camera that was placed at a fixed radius from the centre of the monitor and elevated 45°. On each trial, the camera was randomly positioned at one of seven azimuths (–90° to +90° in 30° steps). We recorded tapping errors and movement times. Both errors and movement times were described by a U-shaped curve when plotted as a function of camera position: performance progressively decreased with larger azimuths. However, the minimum of the curve was shifted to the right of the central camera position. In a second experiment, we found that this bias of camera position depended on the hand that subjects used to tap the targets rather than on handedness: if subjects used their left hand, the bias shifted towards the left of the central camera position. In order to perform the task, subjects could use 'static information', consisting of the lay-out of the scene with the monitor and the hand. In principle, this information specified the camera position and the location of the target in space. In addition, subjects could use 'dynamic information' which involves the visual feedback of moving the hand in a certain direction. Subjects could use this information to adjust their movements online to reach the target. We hypothesise that the U-shaped curve and bias are caused by the dependence of these strategies on camera position.
