Showing papers on "Summation published in 1974"

The roles of vibration amplitude and static force

Abstract: Previous work (Verrillo, 1963, 1968) has shown that when measured as a change in absolute threshold, spatial summation occurs only at vibration frequencies above 40 Hz. The present study measured vibrotactile spatial summation at suprathreshold amplitudes. A matching task was used to investigate the effect of varying contactor size on sensory magnitude at three different vibration frequencies. Unlike the threshold data, increasing contactor size resulted in increases in sensory magnitude at 25 and 40 Hz as well as at 160 Hz. The amount of summation varied directly with amplitude for the two lower frequencies. In a second experiment, the effect of increasing static force, independent of contactor size, was investigated. The results indicated that the spatial summation effects noted in the first experiment may be due to increases in static force and not contactor area. The implications of these results for the concept of spatial summation and for the duplex mechanoreceptor hypothesis are discussed.

Simple form of the auditory running‐average hypothesis: application to the temporal summation of loudness and to the delayed perception of the offset of brief stimuli

Abstract: A simple form of the auditory running‐average hypothesis is presented, and is applied to two phenomena: the temporal summation of loudness and the delayed perception of the offset of brief stimuli. For both phenomena, the predictions of the hypothesis describe the data well.

Spatial summation in the warmth sense

Abstract: The warmth sense is characterized by generous spatial summation: perceived strength of warmth sensation increases with increasing areal extent of stimulation as well as with increasing stimulus intensity. When intensity is low, area exerts its greatest effect, in that warmth depends on the product of stimulus area and intensity - i.e., on total power in watts. Response to integrated heat input at low intensity enables the warmth sense to help maintain constant body temperature. As stimulus intensity increases, area’s relative influence on warmth diminishes until the pain threshold is reached, whereupon spatial summation vanishes. Lack of summation at high intensity enables the warmth sense to help protect the skin from potentially damaging heat. The level-dependence of spatial summation is reflected in the way stimulus size influences the psychophysical power functions that relate warmth sensation to stimulus intensity: the larger the areal extent of the stimulus, the smaller the exponent of the power function.

Vibrotactile spatial summation: effects of vibration amplitude and static force

Abstract: Vibrotactile spatial summation was investigated at suprathreshold amplitudes using a matching task. Previous work [R. T. Verrillo, J. Acoust. Soc. Am. 35, 1962–1966 (1963)] at threshold amplitudes has shown that spatial summation occurred only at frequencies greater than 60 Hz. Three frequencies, 25, 40, and 160 Hz, were tested at several intensity levels above threshold. The change in perceived magnitude between two contactor sizes (static pressure on the contactors held constant) was measured to determine if summation would occur at vibration frequencies below 60 Hz. The results showed that spatial summation occurred at 25 and 40 Hz in amounts which varied directly with vibration amplitude. At 160 Hz, spatial summation was present but independent of amplitude. The data are consistent with the hypothesis that spatial summation is mediated by deep‐lying receptors which are more sensitive to high frequencies but which can be stimulated by strong, low‐frequency signals. A second experiment investigated an earlier finding by Craig and Sherrick [Percept. Psychophys. 6, 97–101 (1969)] that static force rather than static pressure, penetration, or contactor area was the mechanical coupling factor most responsible for spatial summation effects. Changes in sensory magnitude comparable to those found in the first experiment were found in the second experiment when static force rather than contactor area was varied. The results suggest that changes in static force which accompanied changes in contactor area in the first experiment may have been responsible for the summation effect. [This research was supported by an NIH grant.]