Abstract
Distance is a critical factor determining the perceptual quality of visual objects. The closer they are, the better we see. Our visual experience, however, does not entirely depend on physical aspects of objects. In fact, the distinction between far and close distance is quite subjective. We often see distant objects with greater acuity as if they were near us. The present study investigated effects of motor capability on visual analysis in the space distant from the body (extrapersonal space). Since the vision has its critical role in guiding the action, we hypothesized that if a person is able to perform an action by using a tool, visual representations of the extrapersonal space might be altered. Using a keyboard, participants manipulated a ball on the screen at a distance they could not reach by hands. Each participant's contrast threshold was measured before and after the manipulation task. As results, participants who were able to control the ball showed improved visual sensitivity relative to those who passively watched the ball moving (Experiment 1). Furthermore, when participants could move the ball in a certain area of the screen but not in the other, improved visual sensitivity was observed only in the area where motor capability was experienced (Experiment 2A). The effect of motor capability, however, was not significant in the peripersonal space (Experiment 2B). Overall, our results demonstrate that visual analysis of distant space can be improved by motor capability, which was temporarily induced by tool-use. It further suggests the tight link between action and vision.