Visual experience is required to develop a flexible sense of position.

In the somatic Rubber Hand Illusion, a blindfolded participant is guided in brushing a dummy hand, while the experimenter synchronously brushes the participant’s hand. This can induce proprioceptive drift (PD), i.e., a shift in perceived position of one’s own hand. One population that is immune to PD are blind adults, a fact often attributed to their hypothesized superior proprioceptive precision. To explore the role of visual experience on PD and if a lack of vision causes different developmental trajectories, we recruited Severely Visually Impaired (SVI) children (6-11 y.o.; n=14) and compared their PD to that of sighted-age-matched controls (n=51). As hypothesized, SVI children failed to show PD across the age span, unlike sighted children, whose PD increased as a function of age. We then tested whether I) proprioceptive precision and II) distance between the initially perceived position of their own hand and the placement of the dummy hand predicted PD in sighted children. I) did not predict PD in sighted children, nor were there any differences between groups in this parameter. Instead, II) was significant (i.e., the farther the two, the larger the shift) and not modulated by age. We speculate that sighted children show PD as a reaction to the conflict between inter-hand distance (proprioceptive information) and coherence between the stimulation performed (which is actually on the dummy hand) and the one received (tactile and kinesthetic feedbacks). Thus, an intermediate position, where the stimulated hand would be if participants were stroking their own hand, becomes an attractor. The perceptual system of SVI children, instead, fails to react to this conflict and continues to compute the position of the hand irrespectively of any additional contextual information. Visual experience is therefore necessary to remap the body in external space and achieve a reduction in intersensory conflict.