In a recent Dove ad, an FBI forensic artist sketched a series of women based purely on the way they described themselves and again as others described them. The artist could only hear their voices, not see their faces.

A video about the experiment, which has been viewed on YouTube more than 22 million times and counting, revealed stark difference between the way the women saw themselves and the way others saw them. Across the board, the self-described portraits were the least attractive -- suggesting, according to the Dove marketing team, that we are all more beautiful than we think we are.

So, why can’t we see ourselves as we really are?

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Over the course of our lives, experts said, our sense of self-image develops through a complicated interplay between cultural ideals, life experiences and accumulated comments by others. The result is, inevitably, a distortion of reality.

“You could look at a photograph and you would always be able to pick yourself out because we all have internal representations of what we look like,” said David Schlundt, a psychologist at Vanderbilt University in Nashville.

“But all of your experiences, all the teasing you went through as a child, all the self-consciousness you had as a teenager, and all the worrying about whether you would be accepted as good enough or attractive enough are called forth in” how people think of themselves, Schlundt said. “It’s not a perceptual thing. It’s a combination of emotion, meaning and experience that builds up over our lifetime and gets packaged into a self-schema.”

The bulk of research on self-perception has focused not on facial features but on body image, but the two are related. And research suggests that culture plays a major role in what we consider beautiful and how we think we stack up to others, said Rachel Salk, a doctoral student in clinical psychology at the University of Wisconsin, Madison.

Salk studies “fat talk” among women, the practice of criticizing the size and shape of their bodies together with their friends. Fat talk is a widespread phenomenon, especially among certain demographics. In one of her studies, published in 2011 in the journal Psychology of Women Quarterly, 93 percent of women at a Midwestern University disparaged themselves in social situations, often by denying that their friends were fat while claiming to be fat themselves.

Hearing fat talk made women more likely to engage in it, Salk and her colleague Renee Engeln found in another study. And the more that women engaged in this kind of talk, the more dissatisfied they were with their bodies, even though women who did the most fat talk did not weigh the most, and most of the women in the study were of average weight.