Most studies on sign lateralization provide inconclusive results about the role of the two hemispheres in sign language processing, whereas the cases reported in the clinical literature show sign language impairment only following left hemisphere damage, suggesting a similar neural organization to spoken languages. By discriminating different levels of processing, a tachistoscopic study found that in deaf subjects matches of sign language handshapes based on equivalence of meaning are processed faster in the right visual field, thus demonstrating a left hemisphere superiority.