The Somatic Rubber Hand Illusion does not modulate perceived hand position in children with severe visual impairments

In the Somatic Rubber Hand Illusion (SRHI), synchronous brushing of a participant’s hidden hand and a dummy hand induces proprioceptive drift, a shift in perceived position of the hand towards the dummy hand, along with the sensation of brushing one’s own hand. While sighted individuals experience proprioceptive drift since childhood, blind adults are immune. Here, we tested Severely Visually Impaired (SVI, n = 13) children and sighted controls (n = 44) with the SRHI. Surprisingly, both groups subjectively reported illusory self-touch. We posit that children with severe visual impairment tentatively infer a common cause when experiencing synchronous stroking of both a dummy hand and their own hand – just like sighted children do. However, unlike sighted children, their perceived hand position is not updated accordingly. Contrary to our hypothesis, we found that only in the SVI group proprioceptive precision predicts drift values, as well as illusory self-touch, with higher precision leading to larger drifts and a stronger illusion. We suggest that higher proprioceptive competence is required for SVI children to develop sighted-like responses to the illusion and overcome difficulty in re-mapping body position onto external space based on multisensory stimulation.