A study by Judith Mergen and colleagues shows that women with Anorexia Nervosa and healthy controls are pretty much similar in their ability to accurately localize a tactile stimulus on the skin: body overestimation is more likely due to cognitive-affective aspects than to perceptual deficits. 

Anorexia Nervosa is a severe mental disorder characterized by a significant low body weight, an intense fear of gaining weight and a body image disturbance. Within this context, body perception is often discussed simply in terms of (overestimation) of body size and shape. One aspect of body perception that has been overlooked in women with anorexia is tactile localization, which refers to the ability to indicate where a tactile stimulus was applied on the skin. The fact that touch receptors are covering the entire surface of the body underline the important role of the sense of touch in informing the individual of its body size.

In a novel adaptation of a localization paradigm, participants were asked to localize stimuli - applied to their back or to their abdomen - on a screen showing a live image of the touched body part. The results are described in Psychiatry Research (Vol. 267, pp 446–454), and were published together with Anouk Keizer (University of Utrecht), Katja Kölkebeck (Münster University Hospital (UKM), Dept. of Psychiatry and Psychotherapy), and Heiko Wagner and Maarten van den Heuvel (Dept. of Movement Science).

Use the Elsevier Share Link to access the article for free. Simply click and read (available until August 18th, 2018).

Women with anorexia and healthy controls did not differ in their ability to localize the stimulus. Neither were there any group differences between localization performance for stimuli applied the back and the abdomen. One explanation we offer is that focusing on the localization instead of on a body size or (tactile) distance estimation minimizes the (possibly conscious) influence of cognitive-affective factors. Indeed, the women with anorexia did have a significantly worse cognitive-affective body image compared to healthy controls, yet this was not reflected in a difference in their localization performance.

The results of this study support the idea that body overestimation in women with anorexia, as it was found in previous studies, is more likely to be due to cognitive-affective aspects (such as body dissatisfaction) rather than to perceptual deficits.

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Mergen J, Keizer A, Koelkebeck K, van den Heuvel MRC, Wagner H. Women with Anorexia Nervosa do not show altered tactile localization compared to healthy controls. Psychiatry Research 267: 446–454, 2018.