Intensity difference limens for lingual vibrotactile stimuli

Abstract

Lingual differential sensitivity for intensity was measured by determining difference limens (DLs) at three different frequencies and five sensation levels. DLs were obtained from five normal adult subjects. The results indicated a relationship between the DL values (expressed as a Weber fraction: AliI) and frequency. Overall, the data obtained indicate that the lingual sensory system can provide DL functions that are compatible with those of other tactile sensory systems, as well as those derived from other sensory modalities, such as audition.The measurement of differential sensitivity of both the auditory and tactile sensory systems has previously been examined in order to determine each system's ability to resolve slight differences between perceived stimuli differing in intensity. The difference limen (DL) is the unit typically employed as an index to express the differential sensitivity of a sensory system. Harris (1963) and Riesz (1928) examined the differential sensitivity of the human auditory system and determined that the DL or "just noticeable difference" Gnd) for intensity is approximately .50 dB. The results of these investigations also showed that the ability of the auditory system to detect .50-dB changes in intensity appears to be relatively independent of both sensation level and frequency, except for sensation levels near threshold.Differential sensitivity for intensity of the tactile sensory system yields somewhat more varied results than those found for the auditory sensory system. The size of the DL (at moderate to high intensities) as measured by various investigators has ranged from .30 (Sherrick, 1950), to .11 (Schiller, 1953), to .05 (Knudsen, 1928. These values were obtained by using the Weber fraction (M/I). Craig (1972) suggests that the discrepancies in the reported DL values for tactile sensitivity at moderate to high intensities may be due to differences in the various experimental methodolOgies. Even though these DL variations exist, Craig (1972) indicates that two generalizations can be made in relation to the factors affecting tactile DLs. First, at low intensities, M/I is large and decreases as intensity increases. Second, DLs for the sense of touch appear to be independent of frequency.The existing tactile DL information has been obtained primarily from the hand and index fmger. The purpose of the present study was to examine the differential vibrotactile sensitivity of the human tongue in order toThe authors would like to acknowledge the contributions of Neal Sloane to the development of this study.

Frequency and amplitude discrimination along the kinesthetic-cutaneous continuum in the presence of masking stimuli

“…The amplitude discrimination thresholds in the higherfrequency region did not change with amplitude in the present study. Several earlier studies have also reported that amplitude discrimination thresholds remained constant at amplitude levels above about 15 dB SL for mid-and highfrequency reference signals ͑Craig, 1972; Fucci et al, 1982;Gescheider et al, 1990;Knudsen, 1928;LaMotte and Mountcastle, 1975͒. Although overall trends in the data were similar across participants, individual differences in threshold values were noted, particular for the masked conditions ͑C2-C4͒. For frequency discrimination, no one subject stands out as consistently exhibiting the highest values of WF ͓e.g., see panel ͑d͒ of Fig.…”

Vibrotactile intensity discrimination measured by three methods

“…Knudson (1928) reported the lowest value (0.05), a value corresponding to a 0.4-dB increase in amplitude, and Sherrick (1950) reported the highest value (0.3 as cited by Craig, 1972), corresponding to a 2.3-dB increase in amplitude. Weber constants between these extremes have been reported by Craig ( 1972Craig ( , 1974, Fucci et aT. (1982), and Schiller (1953).…”

“…The subject was required to indicate which of two vibratory bursts of equal duration separated by a time interval was more intense. This method has been used more than others in recent studies of vibrotactile intensity discrimination (e.g., Craig, 1972Craig, , 1974Fucci et aT., 1982) and in recent studies of auditory intensity discrimination (Florentine and Buus, 1981;Jesteadt et al, 1977;Penner et al, 1974). In the continuous-pedestal method, the subject was required to detect an increment in a pedestal of ongoing vibration by indicating which of' two observation intervals contained an increment in the amplitude of continuous stimulation.…”

Constructing and Evaluating Vibration Magnitude Models for Visualization

“…For amplitude Difference Thresholds, the smallest one (0.4 dB) was reported by Knudson, and the highest one (2.3 dB) was reported by Sherrick [28]. Other vibration studies have published JND values between these two extremes [5,9]. Their conditions and methods varied a lot, so it is difficult to directly compare the results.…”