The detectability, discriminability, and perceived magnitude of painful electrical shock

Abstract

Thresholds for sensation, pain, and tolerance were obtained from 20 male and 20 female observers who received trains of electrical pulses applied to the volar forearm. Also determined were estimates of sensory magnitude for a series of stimuli that spanned the pain sensitivity range (PSR) between pain threshold and tolerance, as well as Weber fractions for the discrimination of stimuli at the midpoint of the PSR. There were great individual differences in all dependent variables. Females had significantly lower values for all thresholds but did not differ from males in the growth of sensory magnitude or in discriminatory capacity. Power functions, with a median exponent of 1.74 and a mean of 2.39, fit the scaling data well. The results are analyzed for a suggested negative correlation between exponent and stimulus range. The presence of such an effect indicates that electrocutaneous stimulation provides a powerful technique for the analysis of individual differences and the evaluation of psychophysical theories.Electrical stimulation of the skin provides a useful induction method for laboratory studies of pain (Procacci, Della Corte, et al., 1974;Rollman, 1983a; Smith & Andrew, 1970): it is readily graded in intensity, can be turned on and off instantaneously, and produces no lasting physical damage.Past research has typically demonstrated that the subjective magnitudes of the sensations produced by electrical pulses can be related to their current or voltage by a power function with an exponent greater than unity, indicating that the perceived intensity grows at a rate faster than the physical one. The reported value of the exponent of the power function has varied considerably, from near 1.0 to beyond 3.0 (e.g., Algom, Raphaeli, & Cohen- Raz, 1986; Babkoff, 1976 Babkoff, , 1978 Beck & Rosner, 1968;Bevan, 1966;Bromm & Treede, 1980; Bujas, Szabo, Kovacic, & Rohacek, 1975; Ekman, Frankenhaeuser, Levander, & Mellis, 1964Hawkes, 1960; McCallum & Goldberg, 1975;Sachs, Miller, & Grant, 1980;Sternbach & Tursky, 1964;Stevens, Carton, & Shickman, 1958;Tashiro & Higashiyama, 1981). These differences can be ascribed, in part, to the effects of stimulus parameters and correction of the power function for threshold (Rollman, 1974), to the nature and scaling of the physical stimulus (Myers, 1982), to the painfulness of the presentations (Jones, 1980), and to regression and range effects (Cross, Tursky, & Lodge, 1975).Although electrical shocks can be painful, most of the studies cited above determined power functions at levels that were weak enough for the sensation to be described as being tactile rather than nociceptive. Although there This research was supported by Grant AO-392 from the Natural Sciences and Engineering Research Council of Canada to the senior author. Requests for reprints should be sent to Gary B. Rollman, Department of Psychology, University of Western Ontario, London, Ontario N6A 5C2, Canada.have been attempts to obtain psychophysical functions for intense stimuli in several modalities (e.g

Psychophysics in the field: Perception and memory for labor pain

“…This variation is hardly surprising. Although we lack both an objective yardstick against which to measure individual differences (Algom & Marks, 1984) and studies of measured endogenous pain for a comparison, a threefold to sixfold range of exponents is what is usually reported for experimentally induced pain, and, in fact, for some other sensory continua as well (see Rollman, 1992;Rollman & Harris, 1987, for recent reviews).…”

“…The first method, and the one utilized most often, is to present the same set of stimuli to all observers (e. g., Algom, Raphaeli, & CohenRaz, 1986, 1987. The second method is an attempt to tailor the stimulus set to each individual's range (e.g., Rollman & Harris, 1987), thereby acknowledging individual differences explicitly. In the present study, experimental homogenization of stimulus range was, of course, neither possible nor necessary.…”

Magnitude estimates for electrical pulses: Evidence for two neural mechanisms

“…The subjects in the previous studies were often exposed to current pulses detennined arbitrarily by the experimenter. In this case, the sensory qualities induced by the particular pulses are usually different for each subject, because individual differences in absolute threshold for electrical pulses are great and its dynamic range is very narrow (Higashiyama & Tashiro, 1987;Rollman & Harris, 1987). Unfortunately, however, since most studies did not report stimulus current relative to threshold current, it may be difficult to guess the sensory qualities induced by the stimulus current.…”

“…Previous studies on electrical stimulation have reported diverse slopes of the power functions fitted to magnitude estimates: Bujas, Szabo, Kovacic, and Rohacek (1975) S. S. Stevens (1960), and S. S. Stevens, Carton, and Shickman (1958) obtained high slopes of 3.5 or more; Babkoff (1976Babkoff ( , 1978 and Tashiro and Higashiyama (1981) obtained low slopes of.9 to 1.2; Cross, Tursky, and Lodge (1975), Rollman and Harris (1987), and Sachs, Miller, and Grant (1980) obtained moderate slopes of 1.7 to 2.5. Moreover, Rollman and Harris (1987) noted considerable individual differences in the slope of the power function for electrical shock.…”

“…Moreover, Rollman and Harris (1987) noted considerable individual differences in the slope of the power function for electrical shock.…”