Guardia et al. (2012) Dissociation in Anorexia Nervosa (Edexcel A-Level Psychology): Revision Notes
Guardia et al. (2012) Dissociation in Anorexia Nervosa
Participants
The study involved two groups:
- Anorexia nervosa group: 25 female patients from an eating disorders clinic in Lille, France, all meeting DSM IV criteria for anorexia nervosa. Within this group, 12 had restricting type and 13 had binge/purge type.
- Control group: 25 healthy female students.
Both groups were matched for age (mean approximately 24 years) and education level (around 13 years of education after primary school). The table below shows the actual body measurements of both groups:
| Group | BMI (mean kg/m²) | Shoulder width (mean cm) |
|---|---|---|
| Anorexia nervosa group | 15.6 | 37.7 |
| Control group | 22.1 | 41.5 |
The groups were carefully matched for age and educational background to control for confounding variables. This matching ensures that any differences observed in body size perception are more likely due to anorexia nervosa itself rather than demographic factors.
Aim
This study aimed to build upon earlier research by the same team, which had found that patients with anorexia nervosa struggled to estimate their own body size accurately and misjudged whether they could fit through a door opening that was clearly wide enough for them. The current study investigated whether this perceptual problem extended beyond judgements about their own body to include judgements about other people's body size when performing the same task.
Research Question: Do patients with anorexia nervosa misjudge only their own body size, or does this perceptual distortion extend to judging other people's bodies as well?
Procedure
Researchers projected a door-frame shape onto a wall to create the illusion of an opening that participants could potentially walk through. In total, 51 different width shapes were projected, ranging from 30 cm to 80 cm wide. These projections were presented in random order, with each width shown four times to each participant.
Participants were tested individually and asked to make two types of judgements:
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First-person perspective: Each participant predicted whether they could walk through each door frame at normal speed without turning to the side.
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Third-person perspective: Participants judged whether a female researcher standing in the room could fit through the frame. The researcher's BMI and shoulder width were similar to those of the control group.
Task Setup
Imagine a participant sitting in a room while a door frame image is projected on the wall. The frame might appear as 40 cm wide in one trial, then 65 cm in the next (random order).
For each frame, the participant answers:
- "Could I walk through this without turning sideways?" (first-person)
- "Could the researcher walk through this without turning?" (third-person)
This process is repeated 204 times per participant (51 widths × 4 presentations).
Findings
The results confirmed previous findings and revealed an important distinction:
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The anorexia nervosa group showed substantial overestimation of their own body size, judging that they would be unable to fit through door frames that were considerably larger than their actual body size.
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However, patients with anorexia nervosa were much more accurate when predicting whether the researcher could pass through the frames. Their judgements about the 'other person' were comparable to those of the control group.
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The control group demonstrated no substantial difference in their ability to accurately predict the passability of either themselves or the other person.
Key Finding: AN patients showed a dissociation in body size perception - they misjudged their OWN body size but accurately judged OTHERS' body size.
Interestingly, researchers identified a correlation between the passability judgements made by the anorexia nervosa group and their pre-illness body weight and size. Patients who had lost more weight in the six months before the study showed a greater difference between their judgements of their own passability and their judgements of the other person's passability.
Conclusion
Evidence from this study suggests that patients with anorexia nervosa have not adapted their internal body image to reflect their current body size after developing the disorder. The brain appears to still perceive the body at a larger size despite visual information that would contradict this perception.
The researchers discovered that patients who had recently lost weight showed a greater discrepancy between their own and other person judgements. This finding suggests that when people with anorexia lose weight, their central nervous system (CNS) cannot update the body image schema quickly enough to provide an accurate representation of current body size.
Neurological Lag Explanation
This neurological lag might explain why patients with anorexia continue to perceive themselves as larger than they are and persist in attempting to lose weight, even when their brain does not accurately perceive their current size. The brain maintains an outdated "map" of the body despite actual physical changes.
Evaluation: Strengths
Reliable methodology: The researchers measured body size perception using highly standardised methods and equipment, which enhances the reliability of the findings. The use of precise door-frame projections with multiple trials (each width presented four times) increases confidence in the measurements.
Adequate sample sizes: The sample sizes were quite substantial throughout all stages of the study (25 participants per group), providing a reasonable amount of validity to the conclusions drawn.
While 25 participants per group may seem modest, this is actually considered a reasonable sample size for experimental psychology research, particularly when studying a specific clinical population like anorexia nervosa patients.
Builds on previous research: This study continues a line of investigation by the same research team, adding to the developing body of research that helps understand the origins of anorexia nervosa from a biological perspective. Much of the older research focused on sociocultural factors, so this represents a valuable shift towards scientific understanding of the disorder.
Appropriate sample characteristics: Although most patients with anorexia nervosa are female, an increasing number of males are diagnosed. However, the majority of sufferers are young females, so using an all-female sample is appropriate for representing a large portion of the target population.
Evaluation: Weaknesses
Limited generalisability: The sample used in this study faces several limitations. Only 25 participants were studied in each group, all of whom were female. This provides limited data from which to generalise to the entire target population, especially as males are not represented at all in this research.
Geographical and demographic restrictions: The evidence came from only 25 patients attending one clinic in Lille, France, which is unlikely to represent all patients suffering from anorexia nervosa, as they were all from the same geographical area and were all relatively young. Older patients or patients from different cultural groups may be seriously under-represented, limiting the extent to which findings can be applied more broadly.
Generalisability Concerns
The homogeneous sample (similar age, all female, one location) reduces confounding variables but also restricts how widely the findings can be applied. Different age groups, males, or patients from diverse cultural backgrounds might show different patterns of body image dissociation.
Methodological concerns with third-person condition: The experimenter used in the third-person perspective condition had a body size that more closely matched the control group than the patient group. This may have meant that the control group had an advantage at estimating her ability to pass through the frame projected on the wall. The researchers acknowledged that obtaining a third person with a similar body size to the anorexia nervosa patients might involve asking patients with the disorder to judge the body size of another person with body image-related issues, raising ethical concerns.
Ecological Validity Issue
The study may lack validity in the sense that making a visual judgement of a person's ability to pass through a virtual door frame is different from actually attempting to walk through the projected shape. A more ecologically valid test might involve projecting the frame onto the wall and then observing the participant's approach to the opening, noting whether they walk as if they can fit through it or begin to turn or slow down as if they will be unable to pass through. This would provide a more realistic measure of the body image the participant holds in their mind.
Unknown mechanisms: A possible problem with research of this nature is that very little is actually known about the actions of many genes. Therefore, although a relationship has been seemingly uncovered in related research, the explanation for how genetic factors are implicated in anorexia nervosa is still not fully understood.
Remember!
Key Points to Remember:
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Guardia et al. (2012) found that patients with anorexia nervosa overestimate their own body size but can accurately judge other people's body size, suggesting a dissociation in body image perception.
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The study used a door-frame projection task with 51 different widths (30-80 cm) to test both first-person and third-person perspective judgements.
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Patients who had lost more weight in the six months before the study showed a greater difference between self and other judgements, suggesting the central nervous system cannot update body image schemas quickly enough.
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Strengths: Reliable standardised methods, adequate sample sizes (n=25 per group), and appropriate demographic characteristics for the target population.
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Weaknesses: Limited generalisability due to small sample size, geographical restrictions (one clinic in France), lack of male participants, and potential ecological validity concerns with using visual judgements rather than actual behaviour.
Mnemonic - "OWN vs OTHER": AN patients misjudge their OWN body but not OTHER bodies!