Visual context and practice change the distribution of attention in touch.

It has often been shown that people experience difficulty restricting their tactile attention to one hand when both hands are touched simultaneously, especially if the hands are in close spatial proximity. Taken in conjunction with a growing body of evidence that the sensations arising from stimulation of the skin are referred to locations in external space rather than their positions on the body, these tactile attention findings provide evidence for the spatial distribution of attention in touch. However, the effect of spatial distance between the arms on the distribution of attention has been shown in only a limited number of studies and in single testing sessions. In a set of experiments we examined the stability of the arm separation effect by measuring performance over two sessions and with varying visual information about arm location. Tactile selection was more efficient when the stimulated hands were placed far apart compared with when they were adjacent but the effect was short lived (session 1 only) and only occurred when participants were tested with their eyes open. These findings suggest that somatosensory attention is a flexible, dynamic process, based on coordinates that can vary over time.