Noninformative vision improves the spatial resolution of touch in humans

Research on sensory perception now often considers more than one sense at a time. This approach reflects real-world situations, such as when a visible object touches us. Indeed, vision and touch show great interdependence: th e sight of a body part can reduce tactile target detection times [1], visua l and tactile attentional systems are spatially linked [2], and the texture of surfaces that are actively touched with the fingertips is perceived usi ng both vision and touch [3]. However, these previous findings might be med iated by spatial attention [1, 2] or by improved guidance of movement [3] v ia visually enhanced body position sense [4-6]. Here, we investigate the di rect effects of viewing the body on passive touch. We measured tactile two- point discrimination thresholds [7] on the forearm while manipulating the v isibility of the arm but holding gaze direction constant. The spatial resol ution of touch was better when the arm was visible than when it was not. Ta ctile performance was further improved when the view of the arm was magnifi ed. In contrast, performance was not improved by viewing a neutral object a t the arm's location, ruling out improved spatial orienting as a possible a ccount. Controls confirmed that no information about the tactile stimulatio n was provided by visibility of the arm. This visual enhancement of touch m ay point to online reorganization of tactile receptive fields.