Abstract
Tool actions are characterized by a transformation (of spatio-temporal and/or force-related characteristics) between movements and their resulting consequences in the environment. This transformation has to be taken into account, when planning and executing movements and its existence may affect performance. In the present study we investigated how angular gain transformations between movement and visual feedback during circling movements affect coordination performance. Participants coordinated the visual feedback (feedback dot) with a continuously circling stimulus (stimulus dot) on a computer screen in order to produce mirror symmetric trajectories of them. The movement angle was multiplied by a gain factor (0.5–2; nine levels) before it was presented on the screen. Thus, the angular gain transformations changed the spatio-temporal relationship between the movement and its feedback in visual space, and resulted in a non-constant mapping of movement to feedback positions. Coordination performance was best with gain = 1. With high gains the feedback dot was in lead of the stimulus dot, with small gains it lagged behind. Anchoring (reduced movement variability) occurred when the two trajectories were close to each other. Awareness of the transformation depended on the deviation of the gain from 1. In conclusion, the size of an angular gain transformation as well as its mere presence influence performance in a situation in which the mapping of movement positions to visual feedback positions is not constant. When designing machines or tools that involve transformations between movements and their external consequences, one should be aware that the mere presence of angular gains may result in performance decrements and that there can be flaws in the representation of the transformation.
Highlights
Movements of the limbs are limited by the speed and the distance they can cover without moving the whole body at the same time
Comparisons of the MoFast gains showed no significant differences in Instructed Mode (IM) between gains at 0.8 Hz speed, but a significant decline in IM was observed between gain = 0.75 and 0.6 at 1.0 www.frontiersin.org indicated that participants were more in advance/lagged less behind the stimulus with lower speed with higher speed (0.8 Hz: M = 18.2◦, 1.0 Hz: M = 6.5◦, 1.2 Hz: M = −1.2◦, pmax = 0.002)
The interaction between Visual Speed and Location, F(6,78) = 9.94, p < 0.001, η2p = 0.43, together with the significant interaction between Gain, Visual Speed, and Location F(48,624) = 2.55, p < 0.001, η2p = 0.16, indicated that the difference between locations in variable error (VE) increased with increasing speed in MoFast gains, but no significant increase was found in gain = 1 and MoSlow gains
Summary
Movements of the limbs are limited by the speed and the distance they can cover without moving the whole body at the same time. We can reach distances out of bodily reach or achieve movement effects in the environment which are faster or slower than our actual movements. Tool use requires that an adjustment to some type of transformation between motor activity and resulting consequences in external space takes place. The consequences in external space happen in a different location than the actual motor activity. When using a computer mouse motor activity takes place on a mouse-pad but the resulting consequences happen on a computer screen. When using a computer mouse or a touchpad the cursor on the screen covers a larger distance than the actual movement (correspondingly, the speed of the feedback is faster than the actual movement, gain larger than 1). The transformation itself seems to be an important part of the cognitive representation of tool-use actions (Massen and Prinz, 2007)
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