Perceptual learning following a long-lasting tactile reversal.

Crossing 2 adjacent fingers produces a distorted perception when 2 tactile stimuli are touched to the crossed fingertips. This is because a given pair of fingers has a functional range of action within which spatial perception is correct (uncrossed fingers) and beyond which perceived location of tactile stimuli is wrong (crossed fingers). The present study tested the possibility that this range of action could be modified following a long-lasting crossing. Therefore, the functional range of action of the 2nd and 3rd fingers was tested every month in 6 volunteers who maintained the finger crossing for as long as 6 months. The results show that after a variable period of time the range of action was enlarged such that spatial perception was correct with crossed fingers as well. The perceptual organization of the human hand therefore depends on experience and is not rigidly determined on a genetic basis.