Somatoperceptual asymmetry for cognitive stimuli: support from experimental and clinical observations

Two studies, one experimental with intact-brain subjects (Study I), and one clinical with left or right hemisphere-damaged and non-neurological general medical patients (Study II), were conducted to examine somatolateral asymmetry in the recognition of verbal (letter) and visuospatial (nonsense shapes) stimuli. Blindfolded subjects were required to explore two stimuli dichhaptically, and were instructed to haptically identify the target stimulus in a set of test stimuli. The findings of Study I indicated that fewer trials were required to recognise nonsense shapes when they were presented to the left hand, whereas fewer trials were required for letters when they were presented to the right hand. The findings of Study II indicated that performance of the hand ipsilateral to the damaged left hemisphere was better for nonsense shapes than for letters, and performance of the hand ipsilateral to the damaged right hemisphere was better for letters than for nonsense shapes.