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Biomedical subjects

H J Crawford

Publications and source records attributed to H J Crawford.

18 recordsLinked to original sources
PubMed1995

Visual field asymmetry in facial affect perception: moderating effects of hypnosis, hypnotic susceptibility level, absorption, and sustained attentional abilities.

Effects of hypnotic level, affect valence and cerebral asymmetry on reaction time (RT) in the discrimination of Ekman and Friesen's (1978) stimuli of angry and happy faces were studied in counterbalanced conditions of waking and hypnosis. Assessed previously on two hypnotic susceptibility scales [Harvard Group Scale of Hypnotic Susceptibility; Stanford Hypnotic Susceptibility Scale, Form C (SHSSC)], non-depressed subjects were 16 low (0-4 SHSSC) and 17 highly (10-12 SHSSC) hypnotizable, right-handed college students. Subjects were required to identify affects of faces, presented tachistoscopically to left (LVF) or right (RVF) visual fields, by using a forced-choice RT paradigm. Highs were significantly faster than lows in angry and happy affect recognition. Hypnosis had no significant effects. For highs only, angry emotional valence was identified faster when presented to the right hemisphere (LVF), but there were no significant hemispheric effects for happy emotional valence. For lows there were no hemispheric differences. Gender was a nonsignificant factor. Significant correlations showed that faster reaction times to angry and happy stimuli, in both LVF and RVF in waking and hypnosis, were obtained by subjects who reported more deeply absorbed and extremely focused and sustained attention on the Tellegen (1982) Absorption Scale and a subscale of the Differential Attentional Processes Inventory (Grumbles & Crawford, 1981). Vividness of Visual Imagery Questionnaire (Marks, 1973) and Affect Intensity Measure (Larsen, 1985), in general, did not correlate with RTs. The potential role of the fronto-limbic attentional system in the recognition of external visual sensory affect is discussed.

Adult↗
PubMed1994

Brain dynamics and hypnosis: attentional and disattentional processes.

This article reviews recent research findings, expanding an evolving neuropsychophysiological model of hypnosis (Crawford, 1989; Crawford & Gruzelier, 1992), that support the view that highly hypnotizable persons (highs) possess stronger attentional filtering abilities than do low hypnotizable persons, and that these differences are reflected in underlying brain dynamics. Behavioral, cognitive, and neurophysiological evidence is reviewed that suggests that highs can both better focus and sustain their attention as well as better ignore irrelevant stimuli in the environment. It is proposed that hypnosis is a state of enhanced attention that activates an interplay between cortical and subcortical brain dynamics during hypnotic phenomena, such as both attentional and disattentional processes, among others, are important in the experiencing of hypnosis and hypnotic phenomena. Findings from studies of electrocortical activity, event-related potentials, and regional cerebral blood flow during waking and hypnosis are presented to suggest that these attentional differences are reflected in underlying neurophysiological differences in the far fronto-limbic attentional system.

Attention↗
PubMed1993

Effects of hypnosis on regional cerebral blood flow during ischemic pain with and without suggested hypnotic analgesia.

Using 133Xe regional cerebral blood flow (CBF) imaging, two male groups having high and low hypnotic susceptibility were compared in waking and after hypnotic induction, while at rest and while experiencing ischemic pain to both arms under two conditions: attend to pain and suggested analgesia. Differences between low and highly-hypnotizable persons were observed during all hypnosis conditions: only highly-hypnotizable persons showed a significant increase in overall CBF, suggesting that hypnosis requires cognitive effort. As anticipated, ischemic pain produced CBF increases in the somatosensory region. Of major theoretical interest is a highly-significant bilateral CBF activation of the orbito-frontal cortex in the highly-hypnotizable group only during hypnotic analgesia. During hypnotic analgesia, highly-hypnotizable persons showed CBF increase over the somatosensory cortex, while low-hypnotizable persons showed decreases. Research is supportive of a neuropsychophysiological model of hypnosis (Crawford, 1991; Crawford and Gruzelier, 1992) and suggests that hypnotic analgesia involves the supervisory, attentional control system of the far-frontal cortex in a topographically specific inhibitory feedback circuit that cooperates in the regulation of thalamocortical activities.

Adult↗
PubMed1993

Sustained attentional and disattentional abilities: differences between low and highly hypnotizable persons.

Relations between sustained attentional and disattentional abilities and hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility: Form A; Stanford Hypnotic Susceptibility Scale: Form C) were examined in 38 low (0-3) and 39 highly (10-12) hypnotizable college students. Highs showed greater sustained attention on Necker cube and autokinetic movement tasks and self-reported greater absorption (Tellegen Absorption Scale) and extremely focused attentional (Differential Attentional Processes Inventory) styles. Hypnotizability was unrelated to dichotic selective attention (A. Karlin, 1979) and random number generation (C. Graham & F. J. Evans, 1977) tasks. Discriminant analysis correctly classified 74% of the lows and 69% of the highs. Results support H. J. Crawford and J. H. Gruzelier's (1992) neuropsychophysiological model of hypnosis that proposes that highly hypnotizable persons have a more efficient far frontolimbic sustained attentional and disattentional system.

Adult↗
PubMed1992

Transient positive and negative experiences accompanying stage hypnosis.

Frequency of positive and negative experiences accompanying stage hypnosis was assessed in follow-up interviews with 22 participants of university-sponsored performances. Most subjects described their experience positively (relaxing, interesting, exciting, satisfying, illuminating, and pleasurable), but some described it negatively (confusing, silly, annoying, and frightening). Five subjects (22.7%) reported partial or complete amnesia; all were highly responsive to the stage hypnosis suggestions. One subject was completely unable to breach amnesia and felt annoyed and frightened. Five subjects (22.7%) believed the hypnotist had control over their behavior. Participants (n = 15) tested subsequently on the Stanford Hypnotic Susceptibility Scale, Form C (Weitzenhoffer & Hilgard, 1962) were mostly moderately to highly hypnotizable (M = 7.07), and the scores correlated significantly (r = .68) with the percentage of passed stage hypnosis suggestions.

Adolescent↗
PubMed1992

Individual differences in afterimage persistence: relationships to hypnotic susceptibility and visuospatial skills.

To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images.

Adult↗
PubMed1990

EEG correlates of hypnotic susceptibility and hypnotic trance: spectral analysis and coherence.

EEG was recorded monopolarly at frontal (F3, F4), central (C3, C4) and occipital (O1, O2) derivations during A-B-A conditions of waking rest, hypnosis (rest, arm immobilization, mosquito hallucination, hypnotic dream), and waking rest. Stringently screened on several measures of hypnotic susceptibility, 12 very low hypnotizable and 12 very highly hypnotizable, right-handed undergraduate, subjects participated in one session. Evaluations were Fast-Fourier spectral analysis, EEG coherence between selected derivations and maximum spectral power within EEG bands. In eyes open and closed conditions in waking and hypnosis, highly hypnotizable subjects generated substantially more mean theta power than did low hypnotizable subjects at all occipital, central and frontal locations in almost all conditions of waking and hypnosis, with a larger difference in frontal locations. Both low and high hypnotizables showed increased mean theta power in hypnosis, suggesting an intensification of attentional processes and imagery enhancement. Mean alpha power was never a predictor of hypnotic susceptibility. Interactions with hypnotic susceptibility showed that highly susceptible subjects had more beta activity in the left than right hemispheres, while low susceptible subjects showed only weak asymmetry. No main effects for or interactions between waking/hypnosis and hypnotic level were found for coherence between derivations or maximum spectral power within theta, alpha and beta EEG bands.

Alpha Rhythm↗
PubMed1989

The effects of hypnosis upon cognitive responses to persuasive communication.

Several writers have suggested that hypnotic responsiveness is directly related to the content of S's covert self-statements. To test this notion, low and high hypnotizable Ss in either hypnosis or waking conditions were exposed to a recorded message advocating that college seniors be required to pass a comprehensive exam in order to graduate. Following message presentation, Ss listed all of the thoughts which occurred to them while listening to the message; these thoughts were later coded as counterarguments, favorable thoughts, or neutral thoughts. Hypnotized Ss generated significantly fewer counterarguments and agreed more with the message than waking Ss. In addition, high hypnotizable Ss (in both waking and hypnosis conditions) produced significantly more favorable thoughts and agreed more with the message than low hypnotizable Ss. Results, therefore, provided a demonstration of the differential impact of context (induction) and trait (hypnotizability level) upon different cognitive phenomena. Implications for the occurrence of hypersuggestible behavior are discussed.

Adult↗
PubMed1986

Eidetic-like imagery in hypnosis: rare but there.

The production of eidetic-like imagery during hypnosis in subjects with high but not low hypnotizability was supported in three separate experiments using nonfakable stereograms (Julesz, 1971; Gummerman, Gray, & Wilson, 1972). In Experiment 1, 6 (25%) of 24 stringently chosen, high hypnotizables were able to perceive one of the superimposed stereograms (presented monocularly) during conditions of standard hypnosis or hypnotic age regression, or under both conditions, but not during waking. In Experiments 2 and 3, low and high hypnotizables were presented stereograms in an alternating, monocular fashion (one-half to each eye). In Experiment 2, 10% of the high hypnotizables perceived one or more stereograms in hypnosis or age regression, but not during waking. In Experiment 3, none of the 17 low hypnotizables reported correct stereograms, but 6 of the 23 high hypnotizables (26%) did. Relationships between imagery performance and visuo-spatial abilities were investigated. Results support the general hypothesis that hypnosis enhances imaginal processing of information to be remembered that is a literal or untransformed representation.

Eidetic Imagery↗
PubMed1983

Hypnosis and lateral cerebral function as assessed by dichotic listening.

In a replication of Frumkin et al. we investigated the hypothesis that hypnosis may facilitate a shift in brain hemispheric dominance, as assessed by right-ear dominance shifts in a dichotic listening paradigm. Eight low, 13 medium, and 8 high hypnotizables, as assessed by the Stanford Hypnotic Susceptibility Scale, Form C, were given the Berlin et al. dichotic tape during two waking conditions and following an alert hypnotic induction. Results contradicted Frumkin et al. In contrast, low hypnotizables showed a significant reduction in right-ear dominance, suggestive of greater participation of the right cerebral hemisphere following hypnotic induction. Highs and mediums did not change. Discussion centers around procedural differences between the two studies (particularly type of hypnotic induction and instructions to attend to one or both ears) and the possible influence of relaxation/anxiety levels upon lateral shifts in cerebral function.

Adult↗
PubMed1982

Hypnotizability, daydreaming styles, imagery vividness, and absorption: a multidimensional study.

In 25 male and 31 female university student and staff volunteers, the interrelationships between the following measures were studied: hypnotic susceptibility (Stanford Hypnotic Susceptibility Scale, Forms A and C), imagery vividness (Vividness of Visual Imagery Questionnaire; VVIQ), involvement in everyday activities (Tellegen Absorption Scale; TAS), and daydreaming styles (28 scales of Singer & Antrobus's Imaginal Processes Inventory). Factor analysis produced a factor characterized as a positively vivid and absorptive imagination style. Hypnotic susceptibility, VVIQ, TAS, and positive-affect daydreaming styles all loaded on this factor. Two other factors were a dysphoric daydreaming style and a lack-of-attentional-control style. Stepwise multiple regressions suggested that males and females, at least within this sample, exhibit different relationships between hypnotic susceptibility and predictor variables. Similar differences were found for the VVIQ and the TAS and their daydreaming-scale predictor variables.

Adolescent↗
PubMed1981

Hypnotic susceptibility as related to gestalt closure tasks.

The investigation was concerned primarily with the relationship of gestalt closure tasks to hypnotizability on a test of the hypothesis that the more highly hypnotizable do better on a task of holistic visuospatial functioning than those less responsive to hypnosis. Several other cognitive tasks were included: visualization, disembedding of hidden figures, and syllogistic reasoning. Sex differences were inconsistent in the four studies reported. In Study 1 (22 male and 20 female university students), high hypnotizables scored significantly higher than low hypnotizables on the gestalt closure tasks, but there were no significant correlations between hypnotizability and the other cognitive tasks. In Study 2 (25 male and 25 female university students) and Study 3 (41 male and 37 female university students), females showed significant correlations between hypnotic susceptibility and gestalt closure scores. In Study 4 (37 male and 27 female high school students), a significant correlation between hypnotic susceptibility and gestalt closure was found for males. The results are consistent with studies of different types of cognitive functioning (hemispheric preference, creativity, attentional distribution, imaginative involvement, and absorption), all indicating differences in cognitive abilities associated with high hypnotizability.

Adolescent↗
PubMed1979

Hypnotic deafness: a psychophysical study of responses to tone intensity as modified by hypnosis.

Hypnotic deafness was suggested for 1000 Hz tones presented in random orders at seven intensities between 17 and 70 db. Subjects were 70 college students stratified into four levels of hypnotic susceptibility, ranging from low to high. Four conditions were presented within a single session. Two conditions tested normal hearing, one in waking and one in hypnosis; two tested reported loudness of the tones as reduced by hypnotic suggestion. The method of magnitude estimation was employed. Hearing reduction was found to correlate .59 with hypnotic susceptibility in the total sample. Few high hypnotizables reduced their hearing to zero; their mean residual hearing during the deafness conditions was 55% of normal. Power functions for the relationship between tone intensity and magnitude estimates for conditions of normal hearing and deafness were found to be relatively parallel and orderly, differing primarily in intercept value. Order effect anomalies are discussed. The "hidden observer" method showed that for 4 of the 70 subjects the covert hearing was found to be at least 20% greater than that reported overtly within hypnotic deafness and approached normal hearing. As in our previous hypnotic analgesia research, not all subjects who reduced their hearing significantly gave subsequent covert reports which differed from reported overt hearing. Discussion is given for evidence of two levels of information processing during hypnotically suggested perceptual distortions.

Audiometry↗