First impressions are long-lasting but often times these snap judgments are very biased. For instance, a new study suggests that people make value-based judgments about a stranger’s personality based only on their bodies. A slimmer body is associated with active or positive personality traits (self-confident and enthusiastic), whereas a plumper body shape was associated with more passive or negative traits (lazy and careless).

“Our research shows that people infer a wide range of personality traits just by looking at the physical features of a particular body,” Ying Hu, a psychologist at the University of Texas at Dallas and first author of the new study, said in a statement. “Stereotypes based on body shape can contribute to how we judge and interact with new acquaintances and strangers. Understanding these biases is important for considering how we form first impressions.”

Hu and colleagues digitally created 140 realistic-looking body models (70 female and 70 male) based on laser scans of actual human bodies. The 3-D renderings were generated using random values for 10 different body dimensions, so the psychologists had precise physical measurements of each type of body.

The renderings were shown to 76 undergrad students from two angles, who had to indicate which of 30 trait words appearing on the screen applied to that body. The words reflect dimensions of the ‘Big Five’ personality traits, which are openness, conscientiousness, extraversion, agreeableness, and neuroticism. Some of these trait words can be classed as positive (‘enthusiastic’, ‘extraverted’, ‘dominant’) or negative (‘quiet’, ‘reserved’, ‘shy’).

When the researchers linked the results to the body shapes, they identified a trend whereby heavier bodies were associated with more negative traits and lighter bodies were linked to more positive traits. What’s more, male and female body shapes that fit stereotypical dimensions for attractiveness (broad shoulders for men and pear-shape for women) were associated with more active personality traits (quarrelsome or extraverted), whereas male and female body shapes that leaned towards rectangular shapes were associated with more passive traits (trustworthy, warm, dependable).

The researchers were even able to predict personality trait judgments based on various combinations of body shape features, they reported in Psychological Science. 

First impressions are highly influential, despite the well-worn admonition not to judge a book by its cover. One study showed that we form a judgement about the character of a person – whether that person is caring, trustworthy, aggressive, extrovert, competent and so on — within a tenth of a second of seeing an unfamiliar face. Once this snap judgment has been made, it’s surprisingly difficult to budge.

This is only the most recent study in a body of evidence that suggests appearance has great influence on social interactions and personality development. Another study, for instance, found that people use facial features to infer a stranger’s personality traits. The idea that a person’s character can be glimpsed in their face, a type of pseudoscience known as physiognomy, has, of course, no scientific basis to it, but that doesn’t stop most of us when it comes to forming first impressions.

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