 So we know that body size is an important marker for physical and mental health but what this research tells us is that when it comes to judging body size you simply can't believe your own eyes and that's because we can all experience a type of visual illusion where we can misperceive our own body size and that of others around us and what basically occurs is that the brain is averaging information across time and what this means in the context of body size and body estimation is that if our weight grows to be above average so too does the likelihood that the bodies we've seen previously are smaller than that and because our brain blends together the past and the present this causes a distortion or an illusion in which we can experience or perceive ourselves as being thinner than we actually are. So the research is conducted on a computerized paradigm in which we display images of females in a rapid presentation and participants simply judge the size of the female they see using a visual analogue scale they just mark a line with a mouse where they think the body belongs and what we find is that the judgment that people give to a body size is actually heavily related to the images that they've seen previously in the sequence and this allows us to estimate and also measure the exact amount of body size illusion that the individual is perceiving. If we take this in the context of obesity recognizing when we're overweight or obese is an important step towards therapy including weight loss programs and dieting if we look at the other end of the extreme anorexia and bulimia for instance then we're going to see the opposite type of illusion for these individuals they're going to perceive themselves as being larger than they physically are and this means that they're actually going to have an unhealthy opinion of their own body weight and shape where they're physically severely underweight they'll perceive themselves to be larger than they are by having people more aware of the difference between what they see and what they physically are we can move forward in their dieting success.