Nonverbal hand movements serve self-related functions in blind individuals

OBJECTIVE: Blind individuals suffer from visual (i.e., sensory) deprivation. So-called "blindisms" (or "nervous" movements) have been described as the nonverbal consequence of such deprivation. However, the neuropsychological functions of such behaviours of blind individuals have not been investigated yet. We therefore analyzed the nonverbal hand movement and gestural behaviour of blind individuals with the hypothesis that their nonverbal expressions rather serve their own mental state than the nonverbal (/gestural) depiction of (mental) images.

METHODS: The (entire) nonverbal hand movement and gestural behaviour of right-handed healthy blind, (matched) sighted, and (matched) sighted/blindfolded individuals was analyzed during a standardized interview situation (about emotions and actions) by four independent (certified) raters employing the Neuropsychological Gesture (NEUROGES) Coding System.

RESULTS: The results show no difference of the overall hand movement activity between blind, sighted, and sighted/blindfolded individuals. Increased position shifts and on body focused hand movements were found in blind individuals when compared to sighted and sighted/blindfolded individuals. Sighted but neither blind nor sighted/blindfolded individuals increase egocentric deictic and pantomime gestures during the re-narration of an audio story.

DISCUSSION: Blind individuals seem to desynchronize during conversation (shifts), increase self-stimulation behaviour due to sensory deprivation (on body), but reduce the nonverbal transfer of mental images via hand gestures. We therefore conclude that nonverbal hand movements of blind individuals rather serve their own mental state but not for the transfer of mental images.