ROLE OF SKIN COUPLING IN DETERMINATION OF VIBROTACTILE SPATIAL SUMMATION

A series of three experiments was carried out to determine the effects of variation of static force and contactor area on both absolute thresholds and the magnitude of vibrotactile stimuli at frequencies of 20, 80, and 250 Hz. The findings were: (a) If contactor penetration into the skin is constant, vibratory threshold amplitude falls off at the rate of 3 dB per doubling at 250 Hz, in agreement with previous studies, (b) There is no increase in vibrotactile magnitude with increase in area at constant amplitude, (c) Increasing static force on the contactor produces an increase in the vibrotactile magnitude. Also, changing contactor force can shift the exponent of the vibrotactile magnitude function. Some discussion is given of the questions raised by the present research, in particular the question of whether static conditions modify not only the mechanics of wave propagation, but also the excitability of neural systems in the tissues. © 1969 Psychonomic Society, Inc.