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Authors
John M. Foley

Visually directed action

publication date
May 2021
Category
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Abstract/Introduction

When people throw or walk to targets in front of them without visual feedback, they often respond short. With feedback, responses rapidly become approximately accurate. To understand this, an experiment is performed with four stages. 1) The errors in blind walking and blind throwing are measured in a virtual environment in light and dark cue conditions. 2) Error feedback is introduced and the resulting learning measured. 3) Transfer to the other response is then measured. 4) Finally, responses to the perceived distances of the targets are measured. There is large initial under-responding. Feedback rapidly makes responses almost accurate. Throw training transfers completely to walking. Walk training produces a small effect on throwing. Under instructions to respond to perceived distances, under-responding recurs. The phenomena are well described by a model in which the relation between target distance and response distance is determined by a sequence of a perceptual, a cognitive, and a motor transform. Walk learning is primarily motor; throw learning is cognitive.


Conclusion/Results

This study confirms that in a dark or lighted virtual environment, subjects walk and throw short of the target. It shows that, if they are given error feedback, subjects quickly correct the trained response to be near the target distance on average. Transfer tests show that throw training acts to produce near accurate throwing and walking. Walk training produces near accurate walking and improves throwing slightly. When, after the training and transfer test, subjects are instructed to respond to the perceived positions, some throw-trained subjects revert to their initial stage 1 responses and some show no reversion. Overall, walk-trained subjects show partial reversion, consistent with partial nulling the cognitive transform, but not the walk transform. Within a stage, responses are stable, except for stage 2, in which responses change rapidly in the first session. The results are accounted for by models in which different sets of a perceptual, a cognitive, and a motor transform are applied to determine the response functions in each condition. The effect of error feedback is to change one or both of these transforms.


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