Summary of Chapter two and methodological considerations for the thesis.

This chapter has illustrated some of the complex themes relating to the definition and measurement of hypnotizability, dissociation, and restraint, in addition to providing a basic introduction to the socio-cultural model in which such concepts may fit. The problems of terminology are rife within the areas examined, and there are confusions that occur based on the differential use o f terms, and the implication of such usage. Overall, two general hypotlieses emerge from consideration o f the literature in chapter one and chapter two The first is that h)^notizability may act as an index of suggestibility relevant for a socio-hypnotic hypothesis o f restrained eating concerns. The second is that dissociation may be related to disinhibition and bingeing phenomena, possible as a defence mechanisms, and/or possibly as a pre-disposition to dissociate that leaves individuals open to lack of higher level control over behaviours and general openness to external suggestion.

As few studies have examined these issues within the non-clinical literature, a good place to start would be by examining if tlie hypothesised relationships exist between measures of restraint, hypnotizability, dissociation and disinhibition. Investigation o f such relationships can help reveal future directions for establishing causal relationships. A primary tool in such a research endeavour is the use of correlational and regression tecluiiques (Multiple Regression and Correlation: MRC, Cohen & Cohen, 1983), which allow the assessment o f degree o f relationships and consideration of overlapping variance in relation to dependent variables of interest.

Before moving onto the first empirical chapter, an overview o f the main measures used throughout this tliesis is appropriate. This section acts as a brief outline o f the scales formats and basic statistics.

2.5.2. Measures of Hypnotizability.

Harvard Group Scale o f Hypnotic Susceptibility: Form A (HGSHS:A, Shor & Ome, 1962). Amongst tlie number o f hypnotizability scales available, the HGSHS:A is one of the most widely used and has been specially developed for group administration. The scale usually consists o f a ten minute induction containing suggestions for progressive relaxation and eye closure, preceded by a non-hypnotic suggestion for the head falling forward, and followed by a further 11 test suggestions. As already mentioned in eailier sections the test suggestions are roughly defined within three different categories, ideo- motor, challenge items, and cognitive items, and are listed below (table 2.3) in order of presentation.

The hypnotic amnesia suggestion is assessed by asking participants to recall after de-induction of hypnosis as much as possible o f what they were asked to do in the test (i.e. the test suggestions) in 3 minutes. Failure to recall at least three test suggestions is scored as a successful amnesia. The amnesia is revered using the phrase ‘Now you can remember everything’ which is a trigger phrase given as part of the anmesia suggestion allowing recall o f test items. Participants tiying to recall anything they had previously forgotten in a fiirther 2 minutes. The remaining test suggestions are self-scored in a standard response booklet as either passed or failed. Issues concerning the factor structure of the HGSHS:A have been addressed in an earlier section, and so will not be covered here.

The total score for the HGSHS:A is derived summing the number o f passed responses, and ranges from 0 to 12. Shor and Orne (1963) found an initial mean o f 7.39 using the HGSHS:A with an internal consistency (Cronbach’s a ) of 0.80. Subsequent large scale studies have found means ranging from 5.45 (SD 2.95) in a Autsralian sample (Sheenan & McConkey, 1979, n = 1944) to 6.51 (SD 2.43) in German sample (Bongartz, 1985, n = 374).

Table 2.2.

Hypnotic suggestions used in the HGSHS:A

Suggestion Type Description

1 Head Sway

TNDUCnON

Ideo-motor Non-hypnotic, pre-induction item with

suggestions of head falling forward

Eye focus on specific spot on hand, progressive relaxation.

2 Eye Closure’ Ideo-motor Suggestion of heavy eyelids, closing eyes.

Part o f induction.

3 Hand lowering Ideo-motor Heaviness in outstretched hand pulling

hand down.

4 Arm Immobilisation Challenge Inability to lift up arm from lap.

5 Finger Lock Challenge Inability to unclasp fingers.

6 Arm Rigidity Challenge Inability to bend outstretched arm.

7 Magnetic Hands Ideo-motor Hands drawn together.

8 Communication inhibition Challenge Inability to nod head.

9 Fly Hallucination Cognitive Hallucinating a fiy buzzing around head.

10 Eye Catalepsy Challenge Inability to open eyelids.

11 Amnesia Cognitive Inability to remember test suggestions.

12 Post-Hypnotic suggestion Cognitive Scratch left ear when hearing a tapping

noise.

The Creative Imagination Scale (CIS: Barber & Wilson, 1978/1979): The CIS is also used as a test o f hypnotic suggestibility, when applied with an hypnotic induction. The main purpose of the CIS was to create a scale that was more permissive and less authoritarian, especially in relation to challenge suggestions, than the standard hypnotizability scales such as the HGSHS:A and the SHSS: C. However, the CIS can also be used more as a test of waking suggestibility, as can the Harvard and Stanford scales, when no hypnotic induction is used. The CIS is more cognitively and imagery orientated and based on a set of 1 0 imagined scenarios, usually preceded with

motivational ‘think with’ instructions designed to orient participants towards an active engagement in the process o f imagery construction. After the suggestions participants rate the subjective reality of their imagined experiences, in relation to potentially real

experiences, on a scale ranging from ‘0’ or not at all the same [as a real experience] to

‘4 ’ [almost exactly the same as a real experience]. Overall scores are obtained by summing over items to give a possible score between 0 (lowest level of waking

suggestibility) to 40 (highest score of waking suggestibility).

The original mean for the CIS (Barber & Wilson, 1978/1979, based on Kiddoo (1977-unpublished conference paper) using no preliminary think with’ instructions, was 20.8 (SD 8.6) for n = 217. A number o f studies have used the CIS reporting various

means close to the original value (e.g. Sheenan, McConkey, & Law, 1978: n = 305, mean = 20.60, SD 6.90; Suita, 1987: n = 111, mean = 20.69, SD 7.56; Laidlow & Large, 1997: n = 38, mean = 20.81, SD 10.7). However, use o f ‘think with’ instructions have been suggested as raise CIS score above these means by increasing the impact of suggestion (Wilson & Barber, 1978; Hilgard, Sheehan, Moneteriro, & MacDonald, 1981), though this has been recent challenged (Laidlow & Large, 1997).

Initial reliabilities for the CIS found reasonable split-half reliability of r = 0.89 (Barber & Wilson, 1978/79, n = 217). Factor analysis o f the CIS indicated the scale items load on one factor (McConkey, Sheehan, Law, & White, 1977; Barber & Wilson, 1978/79), conceptualised as hypnotic-like susceptibility. Given the earlier discussions about the nature o f hypnotic susceptibility, this factor may best be interpreted as imagery related waking' suggestibility.

2. 5. 3. Measures of Dissociation.

As mentioned previously, two scales are used throughout this thesis as measures of dissociation, the DES 11 and the PAS. They have been mentioned numerous times throughout these initial chapters, but a brief summary; is provided here for ease of access.

Ùissociative Experiences Scale II (DES II). The DBS 11 (a revision of the rating format from a visual analogue to a percentage scale: Bernstein & Putnam, 1993) consists of 28 items, each referring to a potential dissociative experience (e.g. “Some people have the experience of driving or riding in a car or bus or subway and suddenly realising that they don’t remember what has happened during all or part of the trip”). Participants rate

the frequency o f each experience on a percentage scale with responses broken down into increments o f 1 0%

The scale items were derived from clinical interviews with people diagnosed under tlie DSM HI dissociative disorder category, in addition to consultation with clinical and diagnostic experts. The initial aim o f the scale was to capture a continuum o f dissociative experiences, ranging from everyday non-pathological dissociation to pathological dissociative phenomena. Such phenomena include experiences related to memory, identity, awareness, and cognition. It is important to note that tlie DES was original constructed for use in clinical populations, though it has been widely adopted in non-clinical studies.

Means for the original DES, in non-clinical samples (as reviewed by Carlson & Putnam, 1993), vaiy from 3.7, (Goldner et al, 1991; control group for eating disorders) to 7.8 (quoted as unpublished data in Carlson & Putnam, 1993). A relatively high mean score o f 21.8, SD 12.8 was found in a student sample by Frischholz, et al. (1992). Median values have ranged from 4.4 (Bernstein & Putnam, 1986, original development paper) to 6.4 (Deinitrak et al., 1990; non-clinical control group for eating disordered patients). However, in a large non-clinical population sample examination of the DES (n = 1,055) by Ross, Joshi, and Currie (1990, conducted as part of a population survey in Winnipeg, Canada) the mean level was found to be 15.6 (SD 12.1) for women and 15.2 (SD 12.7) for men with ages ranging 18-29. As age increased the mean level of dissociative experiences decreased, with a mean DES score in the age cohort 30-39 o f 10.3 (SD 8.9) for women and 11.9 (SD 10.2) for men. The mean for the entire sample was 10.8 (SD 10.2). It also appears that general dissociation scale scores are particularly skewed in both clinical and non-clinical populations (Bernstien & Putnam, 1986).

The internal consistency o f the overall DES has been reported to be good to excellent including split half (Bernstein & Putnam, 1986; n = 73, r = 0.83, Pitblado & Sanders, 1991 : n = 43, r = 0.93) and Cronbachs Alpha (Frischholz et al, 1990: n = 321, whole scale Alpha = 0.95; Fischer & Elnitsky, 1990: Alpha for their DES single 21 item factor = 0.90; Dubester & Braun, 1995: whole scale alpha = 0.96 and 0.97).

The DES has also been used to identify sub-groupings o f items that relate t o . principle factors relating to absorption, de-personalisation/de-realisation, and amnesia,

and different types o f dissociation based on normal or chronic pathology. Though mentioned in previous sections, a brief suimnary o f tlie findings from factor analysis studies follows.

In clinical samples a three factor solution has been readily replicated, with small degrees of variation on the specific item loading (e.g. Carlson, et al. 1991), with amnesia being the principle factor, followed by absorption/imaginative involvement, and finally depersonalisation/de-realisation. Frischholz, Braim, Sachs, Schwartz, Lewis, Shaeffer, Westergaard, and Pasquuotto (1991) examined the so-called tri-dimensional structure of the DES, interpreting a non-patliological absorption like dimension, and two pathological dimensions based on amnesia and depersonalisation/de-realisation. They foimd that the three dimensions were present in both clinical and non-clinical samples, and held a good level of internal consistency (alphas ranging from 0.77 to 0.90). However, the tliree factor solution lias only been found in ceitain non-clinical studies (e.g. Carlson et al, 1991; Ross, Joshi, & Currie, 1991) with absorption and changeability as a principle factor, followed by depersonalisation/de-realisation, then an amnesia factor. Waller (1993) has suggested that excessive item skew in the DBS may create spurious factors, and demonstrated that correcting for skew produced only a one factor solution, similar to Fischer and Elnistky (1990).

An alternative interpretation, and therefore use of the DES is based on more recent work suggesting a more taxonomic aspect o f the DES (Waller, Putnam, & Carlson, 1996; Waller & Ross, 1997). This perspective identifies two aspects of the DES, a latent pathological taxon representing possible chronic dissociative pathology, and a more non-pathological factor representing imaginative-absorption type dimensional responses. Tliis re-classification may be more appropriate in elucidating the role of different types o f dissociation in relation to features o f research interest. This is especially useful as sub-scales derived from taxonomic pathological and non- pathological dissociation can be generated from the original DES and DES II (Waller & Ross, 1997).

Perceptual Alteration Scale (PAS: Sanders, 1986):T\\q PAS is another scale used for measuring dissociation, and it is used in tliis tliesis primarily because, like the DES H it has been used before in the investigation non-clinical eating problems (e.g. Rosen and Petty, 1994). Much less work has been done on the psychometric properties o f the PAS.

Sanders (1986) initially reported means o f 90.2 (SD 16.24) for non-bingeing college students using the full 60 item version. The original reliability for the overall PAS has been recorded at 0.95 for the original 60 item scale, however, subsequent studies have used the 27-item version based on Sander’s original paper (e.g. Fischer & Elnitsky, 1990; Rosen & Petty, 1994). A reduced 21-item scale based on the factors extracted from the 27 item scales (Fischer & Elnitsky, 1990) scored a reliability o f 0.85. Sanders identified three PAS sub-scales relating to modification o f affect (Cronbach’s a = 0.88), modification o f control (Cronbach’s a = 0.88), and modification o f cognition Cronbach’s a = 0.70). Each o f these sub-scales is assumed to examine some alteration in normal everyday functioning. However, tlie extent to which these factors are replicable has been questioned (Fischer & Elnitsky, 1990), and use o f such sub-scales may require restricting to explorative methods.

2.5.4. Measures of dietary restraint and disinhibition.

Two principle scales are used throughout this thesis as measures of dietary restraint, the cognitive restraint scale of the Tliree Factor Eating Questiomiaire (Stunkard & Messick, 1986: TFEQ cognitive restraint) and the Concern for Dieting sub-scale o f the Revised Restraint Scale (Herman & Polivy, 1980: RRS concern for dieting), which cover related but different facets o f the restraint construct. The TFEQ also contains two sub-scale relating the disinliibition of eating (TFEQ disinliibition) and susceptibility to hunger (TFEQ susceptibility to hunger or hunger scale) which are detailed briefly below. Again these scales are used as they are the principle scales developed within the dietary restraint literature, and have been used to explore relations between dietary restraint, hypnotic-like suggestibility, and dissociation in previous studies (e.g. Frasquilho & Oakley, 1997). An excellent review of these and other restraint scales can be found in Gorman & Allison (1995).

Three Factor Eatin2 Questionnaire (TFEQ): Developed by Stunkard and Messick as an

alternative measure o f restraint related behaviours to tlie RRS, the cognitive restraint sub-scale deliberately avoids mention o f disinhibited eating, but rather relies and the disinhibition of eating scale of the TFEQ to provide such information.

TFEQ Cognitive restraint: As mentioned in previous sections, the cognitive restraint scale appears to measure both the conscious intention to monitor and regulate eating in

terms o f reducing food intake, and a behavioural component related to successful restraint o f eating. A number of studies have provided means for the TFEQ_cognitive restraint scale, and for women means vary from higher values of 10.2 (SD 5.6: USA college students sample, n = 617; Gorman & Allison 1995) and 13.1 (SD 4.3: German females in weight reduction program, n = 46,132; Westenhoffer, 1991) to lower values o f 6.5 (SD 4.7: German women, n = 62; Laessle et al, 1989). There are wide differences in means dependent on nationality, and sample type, so caution is advised in selecting restrainers and non-restrainers based on population norms. Westenhoffer’s findings are potentially related to a sample selection bias in that women on weight loss programme will generally be high in restraint concerns and behaviours.

Gorman and Allison (1995) report suggestions for guidelines o f 0-10 as low to average restraint, 11-13 as high restraint, and 14 plus as a potential clinical range. Median splits are used in this thesis when restrainers/non-restrainer groupings are sought, but otherwise it appears more sensible to adopt a non-dichotomous approach to the measure and use correlational and regression based analyses.

Overall reliabilities in terms o f internal consistency (Cronbachs Alpha) for the cognitive restraint factor for normal weight women are veiy good to excellent, ranging from .80 (18-30 year old German college women, n = 60; Laessle et al, 1989) to 0.91 (New York college students, n = 823: Allison, et al., 1992).

TFEQ Disinhibition o f eating (loss o f control over eating) and TFEQ Susceptibility to hunger. Few studies have looked specifically at tlie means and reliabilities of tliese factors The original (Stunkard & Messick, 1985) mean o f the TFEQ disinhibition factor was 10.0 (SD 5.9), with a Cronbach’s alpha of 0.91; and for the TFEQ susceptibility to hunger factor original mean was 7.1 (SD 4.1), with a Cronbach's Alpha ofO.85.

Revised Restraint Scale, concern for dietins sub-scale (RRS concern for dieting).

Developed earlier than the TFEQ, the RRS (Hennan & Polivy, 1980) was originally intended as an overall measure o f chronic unsuccessful restraint However, as mentioned above in the review of dietary restraint measures, two potentially separate sub-scales have been identified, and concern for dieting sub-scale and a weight fluctuation sub-scale. In tliis thesis tlie RRS concern for dieting sub-scale is used

primarily, in order to measure features o f chronic concern over the monitoring and regulation of food intake.

Little research has examined the separate psychometric properties of the RRS concern for dieting sub-scale, and tlie principle studies examining its validity (e.g. Laessle, et al, 1989) tend not to report means and reliabilities. However, some means have been reported ranging from 7.8, SD 3.0 (Wardle & Beales, 1987) to 9.3, SD 4.0 (Gorman & Allison, 1995).

Body Mass Index (BMP: This provides a general measures of adipose fat tissue, and has been widely used in obesity research, and is calculated for each study in this thesis. BMT consists o f weight (in Kg) divided by Height (in metres)^, with a general value of 30 plus as an indicator o f obesity. BMI o f 30 and over is used as an exclusion criterion in this thesis, to prevent data from obese participants entering final analyses, as this thesis is primarily concerned witli non-obese individuals. Williams et al. (1995) also identified a moderating role of BMT in terms o f relationships between restraint and disinhibition, where higher BMI indicates a better correlation between restraint and disinhibition, whilst lower BMI leads to lower correlations between restraint and disinliibition.

2.5.5. Other measures and final issues o f importance.

Throughout this thesis other measures are used related to restraint, loss of control over eating, and more general factors such as social desirability. These measuies are introduced within their respective chapters, and details o f reliabilities and means are given there.

As a final issue, the guidelines for multivariate data analysis suggested by Tabacluiick and Fidell (1996) are adopted tlirougliout tlie empirical chapters. Tliese guidelines include examination o f data distributions for excessive skew, kurtosis, and outliers, and the treatment o f these problems. Missing data are dealt with, where appropriate, using Cohen and Cohen's (1983) excellent treatment on the issue, and througliout statistics are conducted on variables with and witliout missing data replacement.

Ethical Approval.

All studies adhered to the Ethical Guidelines relating to informed consent and proper conduct in relation to experimental procedures involving human paiticipants as published by the University College London Ethics Committee, and were submitted for ethical approval by that committee.