The judgements are involuntary, unconscious and happen at frightening speed: some are made in as little as 33 thousandths of a second, which is barely enough time to register what you’re looking at. “In our studies people say ‘this is ridiculous, I barely saw that was a face’,” says Alexander Todorov, a psychologist from the Princeton University and leading expert in the subject.

These “thin slice” character judgements are based on the slimmest of clues. And yet they have far-reaching implications, from where you work to who you marry. Naturally, we expect CEOs and military personnel to look dominant, while those in caring professions should be baby-faced.

If you’re born with the right aesthetic, you’re more likely to be hired in the first place and may find it easier to rise through the ranks. On the other hand the wrong face – such as one that looks serious if you’re dating or stereotypically criminal in court – could blight your romantic prospects or even land you in jail.

But perhaps the most uneasy finding of all is how these snap judgements and prejudices shape politics. The science is not quite 40 years old, but the sheer weight of evidence is overwhelming. Though voters tend to have rational ideas about what makes a good leader – “The characteristic that always wins is competence,” says Todorov – the way these qualities are assessed is spectacularly reckless. In the end we discern it from the candidate’s face.