Vibrotactile intensity discrimination measured by three methods

Abstract

The difference threshold for the detection of changes in vibration amplitude was measured as a function of the intensity and frequency of stimuli delivered through a 2.9-cm2 contactor to the thenar eminence. Stimuli were either 25- or 250-Hz sinusoids, narrow-band noise centered at 250 Hz, or wideband noise. Thresholds were measured by two-interval, forced-choice tracking under three methods of stimulus presentation. In the gated-pedestal method, subjects had to judge which of two 700-ms bursts of vibration separated by 100 ms was more intense. In the continuous-pedestal method, subjects had to detect a 700-ms increment in the amplitude of an ongoing pedestal of vibration. In the two-burst-continuous-pedestal method with 1500-ms pedestals, the subject had to detect which of two successively presented pedestals contained a 500-ms amplitude increment. Thresholds were consistently lower for detecting increments in the amplitude of a continuous pedestal of vibration than for detecting amplitude differences between briefly presented successive pedestals or amplitude increments in successive pedestals. A "near miss" to Weber's law was found both for sinusoidal and for noise stimuli. The difference threshold was not affected by stimulus frequency condition.

Discrimination of vibrotactile frequencies in a delayed pair comparison task

“…However, vibrotactile masking and adaptation phenomena bear marked similarities to presentation-order effects. In vibrotactile masking, a prior stimulus may substantially raise the detection threshold of a target vibration occurring up to 200 msec later (Gescheider, Bolanowski & Verrillo, 1989;Gescheider, Bolanowski, Verrillo, Arpajian, & Ryan, 1990;Gescheider, Verrillo, & Van Doren, 1982;Hamer, Verrillo, & Zwislocki, 1983;Kirman, 1986;Verrillo & Gescheider, 1977;Verrillo, Gescheider, Calman, & Van Doren, 1983). However, masking effects completely dissipate 500 msec after stimulation, the shortest delay period used in the present study, whereas observed discrimination order effects persisted for 30-sec delays.…”

Difference thresholds for intensity perception of whole-body vertical vibration: Effect of frequency and magnitude

“…At both frequencies, the relative difference threshold decreased (by about 2 %) when the stimulus magnitude was increased from 0.1 to 0.5 ms -2 r.m.s. A similar phenomenon has been observed in some studies of difference thresholds at the thenar eminence where vibration intensity discrimination at 25 and 250 Hz is enhanced as intensity increases (Gescheider et al, 1990). Discrimination sensitivity at 20 and 100 Hz has been found to be U-shaped or V-shaped, with a maximum enhancement at about 20 dB sensation level (Delemos and Hollins, 1996), which results in a "near miss" to Weber's Law.…”

Weber's Law in Decision Making: Integrating Behavioral Data in Humans with a Neurophysiological Model

“…This is not a trivial prediction, given that contrary to most other demonstrations, here Weber's law is predicted in a domain different from stimulus intensity, namely vibrotactile frequency. The results of previous research (in humans and monkeys) are somehow mixed with respect to whether vibrotactile frequency discrimination does or does not abide by Weber's law (Goff, 1967;Mountcastle et al, 1972;Gescheider et al, 1990;Mahns et al, 2006). This is especially relevant given that such attempts have not always considered the important physiological differences between the sensory pathways encoding vibrotactile stimuli in the flutter range and those encoding higher frequency vibrations.…”

“…Indeed, previous attempts to establish Weber's law for vibrotactile frequency have provided mixed results. For instance, Gescheider et al (1990) reported that intensity difference thresholds on the finger in humans did not vary as a function of frequency (25 vs 250 Hz). Similarly, Tommerdahl et al (2005) reported that the Weber fraction (the ratio between difference threshold and absolute stimulus frequency), which should remain relatively constant across frequencies if Weber's law were to hold, varied considerably from 25 to 200 Hz base frequencies.…”