ASA 124th Meeting New Orleans 1992 October

4pPPa22. The effect of vibrotactile noise on the growth of sensation magnitude and on the intensity DL.

Inst. for Sensory Res., Syracuse Univ., Syracuse, NY 13244-5290

In this study, the hypothesis that the DL for vibrotactile amplitude discrimination is independent of the slope of the sensation magnitude function was tested. The slope of the sensation magnitude function was varied by requiring subjects to make amplitude discrimination judgments in the presence of or in the absence of vibrotactile noise. The slopes of the sensation magnitude functions were determined through a matching technique in which the subject adjusted stimulus amplitudes of a 250-Hz stimulus presented alone and a 250-Hz stimulus presented with a masking noise so that their sensation magnitudes were equated. The slope of the matching function was found to increase as a function of the intensity of the masking stimulus. In the second phase of the experiment, the intensity DL was measured by the gated-pedestal method for test stimuli presented under the stimulus conditions used in the matching procedure. For all but the weakest stimuli, the DL was found to be independent of the masking condition. This finding supports the hypothesis that the DL is the same when sensation magnitude is held constant and is independent of the slope of the sensation magnitude function. [Work supported by P0 1 DC-00380.]