We all know that we shouldn’t judge people by their appearance – but we do. “In every ancient culture, one can find beliefs that the face is the window to a person’s true nature,” says Alexander Todorov, a psychology professor at Princeton University.

Even as relatively recently as the 19th century, many people believed in physiognomy: the ‘art’ of judging someone’s personality by their facial characteristics. From the 20th century onwards, most people came to understand that our characters aren’t determined by the way we look – but we still make countless assumptions about people based on their appearance.

These impressions are often influenced by our own unwitting biases. It’s been found that most people react more positively to faces that resemble their own, and view more ‘typical’ faces as more trustworthy. So even if you consider yourself a distinctly non-judgemental person, sorry – you definitely are.

“We form these immediate impressions of people – we just can’t help it,” Todorov tells Business Insider.

In his research, Todorov uses computer-generated faces to discover what personality traits people associate with particular physical attributes, from trustworthiness to competence, intelligence to naivety.

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These assumptions, he warns, are highly inaccurate – but knowing what they are can help us to resist them.

Here, we’ve picked out some of the most interesting findings from Todorov’s research and others.

Better-looking people are seen as better people, period

From a young age, most of us are taught that beauty is only skin-deep; that a good face doesn’t necessarily equate to a good heart. However, according to one study, most people assume that attractive individuals will also rank highly for other positive traits. In particular, very good-looking people are generally viewed as being more competent, intelligent and sociable than your average Joe. 

Older people are viewed as being more intelligent and determined

In another piece of research cited by Todorov, the positive traits of being “distinguished, intelligent and determined” were associated with faces like Susan Sarandon’s: an older appearance, thinner lips, and wrinkles at the corners of the eyes. 

Competence is associated with darker skin, masculine features and attractiveness

In an experiment conducted at the Todorov Lab at Princeton, people were presented with computer-generated images of faces and asked to rate how competent they thought the faces looked.

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As the faces gradually became more masculine, more attractive and darker-skinned, their perceived competence also increased, according to Business Insider.

Smiley women are seen as being most trustworthy

In a similar experiment, Todorov and his colleagues also used computer-generated faces to find out which features are most associated with trustworthiness, Business Insider reports. They discovered that the more feminine and smiley a face is – think Game of Thrones’ ever-beaming Emilia Clarke – the more likely people are to trust them. 

People have a lot of feelings about baby faces

Baby faces (characterised by large eyes, a round face, full lips and a small nose bridge, like Selena Gomez)  can be both a blessing and a curse, and psychological research has found that they elicit a mixed range of responses. They're perceived as being physically weak, naïve and submissive – but also as honest, kind and warm.

Images: Rex Features