Nothing about GK’s performance would suggest that the special abilities associated with the right hemisphere offer any particular advantage, so far as hypnosis is concerned. At the same time, however special, GK was only one subject. Accordingly, we followed our study of GK with a pilot study of patients who had suffered unilateral brain damage as a result of a stroke.
The subjects in this study were 16 right-handed patients, 8 men and 8 women, averaging 56 years of age (SD = 16.40), members of a stroke survivor support group at a large university medical center who volunteered for a study of hypnosis. All signed a written informed consent to participate that was approved by the local institutional review board for the use of human subjects in research. All subjects were in the chronic stage of stroke: a minimum of six months had passed since the onset of their lesion.
Nine of these subjects (5 men, 4 women) had damage due to strokes affecting the left cerebral hemisphere (LH), and seven (3 men, 4 women) had damage due to strokes affecting the right hemisphere (RH). All exhibited behavioral evidence of unilateral stroke, including contralateral hemiparesis or sensory impairment and/or speech and language dysfunction characteristic of LH stroke. None of the subjects exhibited frank unilateral spatial neglect or anosognosia and none had comprehension deficits that precluded understanding instructions. Clinically obtained neuroradiological images were available for the majority of subjects: they confirmed the presence of a unilateral stroke in 7/9 subjects with LH injury and in 4/7 subjects with RH injury. shows the distribution of the lesions in the two groups. Most had lesions in the frontal, temporal, or parietal regions.
Radiological Findings in Stroke Patients
The patients’ average score on the Mini-Mental Status Exam (MMSE; Folstein et al., 1975
) was 25.75 (SD
= 3.97), indicating essentially intact cognitive abilities. There was no difference in MMSE performance between the LH and RH groups (t
< 1). In return for their participation, the patients received an honorarium of $25 plus reimbursement of their travel expenses for a single experimental session lasting 75 minutes.
Following informed consent, each patient received an individual administration of the Arizona Motor Scale of Hypnotizability (AMSH), which consists of an induction of hypnosis accompanied by suggestions for 16 representative hypnotic experiences. The AMSH itself was derived from existing standardized tests of hypnotizability, such as SHSS:A and C and HGSHS:A. It is so named because it focuses mainly on ideomotor suggestions of two types: direct and challenge, with less emphasis on cognitive items. Each of the 16 test suggestions (including one for eye closure administered during the hypnotic induction procedure itself) is scored dichotomously (pass/fail) on the basis of objective behavioral criteria, yielding scores that can range from 0 to 16 points. Normative information based on 100 college-student subjects, and the AMSH script, is available as an internet resource (Kihlstrom, 2011a
). The AMSH was originally constructed to address a question concerning the multidimensional structure of hypnotizability: whether the direct and challenge suggestions constituted separate factors. It was employed in the present study because of the availability of contemporaneous norms, derived from the sample of 100 students described earlier.
Many of the AMSH suggestions are lateralized, targeting either the left or the right arm or hand: as with GK, these suggestions were modified to take account of the patients’ hemiplegia. As before, three suggestions involving bilateral movements were eliminated entirely: for purposes of comparison; scores on these items, and occasional missing data, were estimated by regression based on the combined set of patient and student data.
The AMSH was first scored according to the standard criteria established in the published scales from which it was derived. shows the number of items passed, according to these standard criteria. Despite differences in age, not to mention neurological status, the average AMSH score for the stroke patients was only slightly lower than that of the normative group of college students (t < 1).
Hypnotizability Scale Performance -- Standard Scoring
It is conventional to classify hypnotic suggestions into two major categories: “Ideomotor” suggestions, as their name implies, involve suggestions for bodily movements (e.g., the subject’s head is falling forward); “cognitive” suggestions focus on changes in perception and memory (e.g., for age regression) -- which, of course, may also have consequences for behavior (Kihlstrom, 2008
). Ideomotor suggestions, in turn, come in two major types: “direct” suggestions facilitate motor activity, as when it is suggested that the subject’s outstretched hand is growing heavy and falling; “challenge” suggestions inhibit motor activity, as when it is suggested that the subject’s arm is rigid, and he cannot bend it. Excluding the direct suggestion for eye closure, which is administered during the hypnotic induction procedure itself (pass rate: 89% for students, 94% for patients), AMSH contains six direct suggestions, six challenge suggestions, and three cognitive suggestions. also shows mean scores on these subscales. There were no significant differences between the patients and the students on any of these subscales: Direct, t
(114) = 1.01, n.s.; Challenge and Cognitive, both t
also shows that the two groups of stroke patients did not differ significantly from each other, in terms of total scale score (t < 1), or any of the three types of items: Direct, t(14) = 1.81, p < .10; Challenge, t < 1.; Cognitive, t < 1. Contrary to the laterality hypothesis, there was again a tendency for subjects with RH lesions to score higher than those with LH lesions.
3.4. Alternative Scoring
Compared to direct suggestions, challenge suggestions are more complex, with a ternary structure: there is first a suggestion of an ideomotor effect (e.g. “Your arm is getting stiff”), then a suggestion of an inhibition of control (e.g. “You cannot bend it”); and finally a challenge to the of inhibition (e.g. “Go ahead, try to bend it”). Accordingly, as a rule, challenge suggestions are more difficult than direct suggestions; for different reasons, cognitive suggestions also tend to be more difficult than direct suggestions. In order to take account of differences in item difficulty, the AMSH items were rescored by adjusting the criteria for passing until the direct suggestion, challenge, and cognitive suggestions were of roughly equal difficulty, in terms of mean scores in the normative sample of college students. This had the effect of making the direct suggestions somewhat harder, and the challenge and cognitive suggestions somewhat easier. For example, the pass rate for the Eye Closure item in the student sample dropped from 89% under the standard scoring to 56%; for the patients, it fell from 94% to 69% (for details, see the normative study posted online).
shows the mean scores on the overall scale, and on each of the subscales, rescored according to this alternative scoring method. The patients again scored slightly lower than the students, but the overall difference was not statistically significant: t(114) = 1.19, n.s.). Interestingly, however, the difference was statistically significant for the direct suggestions: t(114) = 3.53); corresponding differences for the challenge and cognitive suggestions were not significant (both ts < 1).
Hypnotizability Scale Performance -- Alternative Scoring
Within the patient group, there was again a tendency for subjects in the RH group to score somewhat higher on the direct suggestions than those in the LH group (t(14) = 1.78, p < .10); the differences in total score, and on the challenge and cognitive suggestions, did not approach statistical significance (all t < 1).