Some Comparisons between Touch and Hearing

The skin can be used for sound localization with accuracy nearly as good as that for hearing. However, auditory sound localization is based on the utilization of both intensive-difference and temporal-difference cues while cutaneous sound localization is based almost entirely on the utilization of only intensive-difference cues. Furthermore, the time interval necessary for resolving two temporally separated pulses was found to be 2.0 ms for binaural and monaural stimulation and, at best, 10 ms for stimulation of the skin. The superior temporal acuity of the ears over the skin was again demonstrated by the finding that pairs of auditory pulses separated by less than 30 ms were perceived as more separated in time than pairs of cutaneous stimuli separated by the same time interval. A series of experiments was conducted to measure inhibitory interaction between touch and hearing. When absolute thresholds were measured by a tracking method in which the subject was free to vary his judgment criterion, auditory stimulation by a click was found to increase tactile thresholds for mechanical pulses by as much as 5.0 dB. Intense tactile pulses slightly increased the auditory click threshold. Subsequent experiments using signal-detection methodology revealed that auditory-tactile masking is caused by a slight reduction in stimulus detectability accompanied by a corresponding increase in the subject's criterion.