New research from the University of Western Australia explores why those with eating disorders (and those without) may perceive their body as bigger or smaller than it really is. According to the study “Past visual experiences weigh in on body size estimation,” our body perception is likely a distortion rooted in past observations of ourselves as well as others, which prove to have harrowing effects.

The team of researchers from UWA’s School of psychological Science, headed by Dr. Jason Bell, worked with the Pisa Vision group in Italy to discover evidence of this inherent bias called serial dependence: an effect of our brain averaging data over time. “The data show body size judgments are biased towards prior experience. As a person’s weight increases above the average, so too does the likelihood that their prior experience involves smaller bodies. Because the brain combines our past and present experiences, it creates an illusion whereby we appear thinner than we actually are,” Dr. Bell explained.

To reach these findings, the researchers studied 103 female participants. First, these participants were shown a series of images, which depicted a range of female bodies: underweight, normal-weight, overweight, and obese. Then, they were tasked with judging the size of the body by marking a visual analogue scale called the body-line. Upon evaluation of the participants’ judgments, the researchers found evidence of sequential bias in perceived body size—with judgments guided by the previously viewed body.

Dr. Bell further explains the implications of the team’s findings: “The research demonstrates human observers are often poor at estimating their own body size and the size of others. Crucially, body size judgments are not always accurate and can be biased by various factors. Sometimes it’s influenced just by the people we stand next to. These findings have important implications for weight loss approaches, including our chances of dieting successfully. What makes this particularly interesting from a health perspective is that misperceiving body size is a common symptom of eating disorders or obesity.”

Harmful eating disorders include anorexia nervosa and bulimia, which come with serious risks and symptoms: Individuals with anorexia—an illness characterized by extreme weight loss or lack of appropriate weight gain—oftentimes experience dizziness, lack of concentration, weakness, and distorted body image; and those with bulimia—a disorder defined by excessive overeating and purging—commonly experience weight fluctuations, dehydration, and distorted body image.

The common denominator in the above disorders, as well as those that go unmentioned? A skewed perception of one’s body. This is a particularly troubling cause and effect of many body issues in the world today—a dynamic Dr. Bell hopes to change: “Ideally, we’d like to correct these illusions, so people are able to make an accurate assessment of their weight and whether it has changed for better or worse.”

Sources:
University of Western Australia (2018, January 10). Our Brains Can Trick Us Into Thinking We Are Thinner Than We Are. NeuroscienceNews. Retrieved January 10, 2018 from http://neurosciencenews.com/thinner-illusion-brain-8293/

Alexi, J., Cleary, D., Dommisse, K., Palermo, R., Kloth, N., Burr, D. & Bell, J. (2018, January 9). Past visual experiences weigh in on body size estimation. Scientific Reports. Retrieved on January 10, 2018 from https://www.nature.com/articles/s41598-017-18418-3