Dichotic and dichhaptic techniques

Auditory and tactual asymmetries frequently demonstrate right side advantages for verbal stimuli and the opposite effects for nonverbal stimuli. Such asymmetries may, however, reflect the perceived position of events in space, rather than the role of anatomical afferent pathways with suppression of ipsilateral by contralateral routes. Consequently, despite popular tradition, simultaneous competitive stimulation (dichotic or dichhaptic) may be unnecessary. We review the reliability and the relatively low validity of such techniques for predicting hemispheric specialization in various clinical and normal populations. We discuss the role of stimulus factors, the various indices and measures, the effect of order and mode of report, division of attention, task difficulty and memory factors.