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  • Author: Pieter J.A. Unema x
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Robert R.A. van Doorn and Pieter J.A. Unema

A display gain setting defines the mapping of a movement to the real-time visual display. In two experiments we investigated how the acquired adaptation to low and high display gain affected motor control of single aimed stylus movements. Experiments differed with respect to how gain was varied. In Experiment 1, gain was realized by manipulating the surface displacements with a constant display. The results show an expected linear decrease of movement time and spatial accuracy, which is in sharp contrast with the often-reported U-shaped relation. Experiment 2 was run to study the influence of visual feedback in low- and high-gain conditions. The manipulation of gain was realized by display variation with unaltered surface displacements. The linear increase of movement time and feedback processing with gain and the unaltered spatial accuracy across conditions, suggested that participants actively adapted to the displayed visual information in altered gain conditions.

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Robert R.A. van Doorn and Pieter J.A. Unema

The present study showed that movement execution depends on the direct visual environment. We replicated findings of an earlier study that showed a difference between real time information via a trace of the unfolding trajectory, and cursor feedback constituting real time information about the changing movement location. Detailed analyses involving subdividing a movement into four successive sections revealed that movements governed by trace feedback were typically slower and required more feedback guidance near the occurrence of peak velocity. The present study further showed that movement behavior under the two visual modes diverged even more due to the presence of a static object positioned within the action area of the movement. Movements in the trace feedback condition were affected by the presence of an object in the second half of the movement trajectory when the movement reached peak deceleration. Discussion focuses on the differences between the two modes of online visual information.