Self-attributed body-shadows modulate tactile attention

Our body-shadows are special stimuli in the visual world. They often have anatomical resemblance with our own body-parts and move as our body moves, with spatio-temporal correlation. Here, we show that self-attributed body-shadows cue attention to the body-part they refer to, rather than the location they occupy. Using speeded spatial discrimination for tactile or visual targets at the hands, or for visual targets delivered near the hand-shadows, we demonstrate that mere viewing of task-irrelevant shadows can selectively facilitate tactile discrimination at the body-part casting the shadow (Experiment 1). In addition, such facilitation only develops through time for cast-shadows that have no resemblance with the body-part, but move in spatio-temporal correlation with it (Experiment 2). Conversely, facilitation fades away rapidly for shadow-like images that resemble the stimulated body-part, but are in fact static pictures (Experiment 3). Thus, recognising oneself as the owner of a shadow affects distribution of tactile attention.