Hand-eye correlation

Abstract

Repeated co-occurrence of a body movement and a sensation can lead to sensorimotor adaptation. An example is the adaptation to the distortions produced by wearing prism goggles (Stratton, 1897, Held, 1963), in which human subjects visually compensate, over time, for the spatial distortions produced by wearing the prisms as they move about in the environment. In studies of sensorimotor adaptation to date, the movement and the sensation have been naturally related to one another (e.g., eye movements and viewed color, Bompas & O'Regan, 2006). I first replicate the finding of Bompas & O'Regan (2006), but report the effect in meaningful perceptual units. Next I report for the first time a case of sensorimotor adaptation involving a completely arbitrary relationship between the movement and sensation. After repeated exposure to a pairing of leftward movements of a joystick with the appearance of a red spot, and rightward with green, observers judged a spot presented with leftward hand movements as greener than before exposure to the pairing. This change in judged hue, small but reliable across subjects, could be the result of a criterion shift (subjects categorizing red and green differently), or to an actual change in visual sensitivity dependent on the direction of hand movement. To address this issue, I measured Receiver Operating Characteristics (ROCs) for simple detection of green and red spots (not a color appearance judgment) while making rightward and leftward hand movements. I show that observers have compensated for the green spot with a decrease in sensitivity, only when making rightward hand movements, and for the red spot only when making leftward hand movements, while criteria remain stable. I conclude that the mechanism producing this adaptation is a general one that does not require a ""natural"" pairing. The brain can compensate for arbitrary sensorimotor contingencies, and thereby make visual sensitivity depend upon the direction of a hand movement.