ABSTRACT
The vibrotactile laboratory at the Institute for Sensory Research was a direct outgrowth of ongoing auditory research at that institution. The equipment required only that a mechanical shaker replace the earphone , auditory thresholds were available for comparison , equal-loudness contours had been determined for hearing but not for vibrotaction , and the systematic study of subjective magnitude by ratio scaling was already in full swing in auditory labs throughout the world. Although the investigation of touch still receives comparatively little support, we have made significant progress since Frank Geldard (1970) voiced the hope that " we are not forever committed to documenting perceptual mediocrity" (p. 15). We now have accepted methods for determining detection thresholds, contours
18. VIBROTACTILE SENSATION MAGNITUDE 261
The first systematic experiment designed to describe the relationship between subjective intensity and the amplitude of vibration on the skin was performed by Stevens (1957). He used the method of magnitude estimation , using a designated standard, and found that the power law adequately describes that relationship . Using the same methodology , Sherrick (1960) and Franzen (1966) obtained results that agreed with Stevens. With the exception of these three studies , the early investigations dealing with suprathreshold vibrotactile sensation were focused primarily on attempts to better understand auditory phenomena (Bekesy , 1960) and attempts to develop cutaneous communication systems (Geldard, 1961) . Motivated by both of these goals , there also were early attempts to generate "equalloudness" functions for the skin , analogous to the well-established auditory curves. Goff (1967) published two contours of equal subjective intensity in her study of vibrotactile frequency discrimination, and Stevens (1968) , using a matching procedure, constructed a series of equal-sensation contours across five frequencies at seven levels of intensity. Although he had not used ratio scaling, the curves published by Stevens were the most complete set of data available at the time .
