The shape of the vibrotactile loudness function: The effect of stimulus repetition and skin-contactor coupling

Abstract

In the psychophysical literature describing the relationships between physical and psychological magnitudes, as physical intensity increases, perceived intensity often grows much faster near threshold than at higher levels. In this laboratory, however, the loudness curve for sinusoidal vibrotactile stimuli was best fit by a single-limbed function rather than by the expected two-limbed function. In the present study, we measured the growth ofvibrotactile loudness of250-Hz sinusoidal stimuli by the method of absolute magnitude estimation to explore the source of the one-versus two-limbed discrepancy. The number of times that the stimulus was presented was varied, as well as whether the stimulator contacted the skin with constant force or constant penetration. Neither of these manipulations affected the shape ofthe loudness function consistently. Number of repetitions influenced the shapes of the magnitude estimation functions, but only for a few individuals. Skin-contactor coupling did not affect the shapes of the functions, although the absolute level (vibrotactile loudness) was consistently greater for constant indentation.

Neural coding in the Non-Pacinian I tactile channel: A psychophysical and simulation study of magnitude estimation

“…Furthermore, we found that the power-function exponent increased with a larger contactor size in the P channel, consistent with the results obtained with large contactor sizes in earlier studies (Verrillo et al 1969;Collins and Cholewiak 1994;Verrillo and Bolanowski 2003). This is probably due to spatial summation in the P channel.…”

“…Our results, therefore, are comparable to the lower and steeper limb of the power functions reported in the literature. Collins and Cholewiak (1994) did not observe two-limbed functions either, even with a larger stimulus intensity range.…”

“…Since the HSs had never performed magnitude estimation before, they were first trained for judging line lengths visually (Zwislocki and Goodman 1980;Collins and Cholewiak 1994). The HSs assigned numbers to line lengths without using a standard or a modulus.…”

“…The magnitude estimates obtained from human subjects were fitted by power functions and the differences in the functions were presented for the NP I and the P channels, including the confounding effect of contactor size. Although magnitude estimates have been previously reported for tactile sensation by many researchers (Stevens 1959(Stevens , 1968Verrillo et al 1969;Fucci et al 1984;Collins and Cholewiak 1994;Hollins and Roy 1996;Verrillo et al 2002), the NP I channel has not been directly tested in isolation before. This is not an easy task, because the NP I channel can only be selectively stimulated in a small dynamic range (520 dB) without activating additional channels.…”

Conveying Looming with a Localized Tactile Cue

“…Furthermore, the observer received three exposures of the pair, separated by 10 s, before a judgment was required. Repetition of stimuli in this manner is common in the psychophysical literature (e.g., Collins and Cholewiak, 1994), allowing subjects a sufficient number of exposures to be confident of their judgments without presenting so many repetitions as to cause undue fatigue or boredom.…”