Hypnotically induced limb anesthesia and adaptation to displacing prisms: A failure to confirm.

Abstract

Three groups of subjects were tested for accuracy of pointing at a visual target before and after wearing displacing prisms. One group consisted of 10 highly susceptible subjects given a hypnotic suggestion for limb anesthesia following the pretest, and a second group included 10 low susceptible subjects instructed to fake limb anesthesia. A control group (n = 10) unselected on susceptibility received no special instructions. The high susceptibles reported significantly greater felt anesthesia than subjects in the other two treatments (p < .05). Nevertheless, subjects in all three groups showed very large displacement errors (i.e., errors in pointing) following prism removal. Our results failed to confirm previous reports that placement errors were eliminated by hypnotic suggestion in highly susceptible subjects. Theoretical implications are discussed.

Prism adaptation with hypnotically induced limb anesthesia: The critical roles of head position and prism type

“…A portion of their adaptation magnitude may have been artifactual. Spanos et al (1981Spanos et al ( , 1983) also confirmed (and statistically so) the fmding first reported by our laboratory that the presence of hypnotic anesthesia is related to a failure to perform the nose-touch task in a veridical manner. Unlike the reports of Spanos et al, all of whose anesthetized subjects failed to accurately fmd their noses, we find either what Spanos et al reported or that subjects do find their noses but that it takes them longer to do so when their limbs are anesthetized than when they are not.…”

“…We have argued that such anesthesia disrupts proprioceptive feedback from the arm and, as a result, adaptation does not occur (e.g., Wallace & Fisher, 1979). Spanos et al (1981) failed to replicate our effect; that is, they reported that adaptation to prism displacement occurs regardless of whether subjects are asked to perform a task with hypnotic anesthesia in the adapting limb or without it. However, as we have previously argued (Wallace & Fisher, 1982), Spanos et al (1981) introduced a situation during prism exposure that overrode the effect of the hypnotic anesthesia.…”

“…Spanos et al (1981) failed to replicate our effect; that is, they reported that adaptation to prism displacement occurs regardless of whether subjects are asked to perform a task with hypnotic anesthesia in the adapting limb or without it. However, as we have previously argued (Wallace & Fisher, 1982), Spanos et al (1981) introduced a situation during prism exposure that overrode the effect of the hypnotic anesthesia. If a visual target is present to which subjects point during prism exposure, this provides individuals a reference point.…”

“…However, it is equally as important that critical procedures be maintained in seeking confirmation. We believe Spanos et al (1981Spanos et al ( , 1983 failed to do this.…”

“…Recently, Spanos and his colleagues (Spanos, Dubreuil, Saad, & Gorassini, 1983;Spanos, Gorassini, & Petrusic, 1981) reported two failures to replicate a phenomenon involving hypnotic anesthesia which has been reported by our laboratory and by that of others (Wallace & Fisher, 1979;Wallace & Garrett, 1973,1975Welch & Snyder, cited in Welch, 1978, p. 27). The phenomenon involves adapting to prism displacement when hypnotic anesthesia is present in an adapting limb.…”