It's something almost all of us do every day – making judgments about someone based purely on their face.
Do you look competent? Do you look trustworthy? Others decide that about you in less than a second.
But is it accurate, and what can we do about what experts call the new 'ism' – face-ism?
There are 14 bones in the face and 42 muscles twitching to tell a tale about you and everyone you meet.
American researcher Prof Christopher Olivola has published a paper about what our face says about us, like our competence.
"People associate facial competence with being more facially mature as supposed to being baby-faced," he says.
Prof Olivola his team took hundreds of computer-generated faces with neutral expressions and had men and women rate them on how trustworthy and competent they appeared.
"This research tells nothing about how actually competent men or women are; all this is telling us is that we have this collective stereotype," says Prof Olivola.
If these perceptions aren't accurate, why does face-ism occur? Experts say we use faces to predict the behaviour of others.
"No it's not reliable but it's better than guessing," says University of Auckland emotion researcher Nathan Consedine. "On average a person who has a particular kind of face is going to behave in a particular kind of way."
Face-ism often occurs where we don't know much about the other person, such as when we meet strangers, or even when we vote.
"It's voters who are less knowledgeable about the elections and who have high exposure to the candidates that you might see on TV," says Prof Olivola. "They're the ones whose votes are most likely to be related to how competent a politician looks."
To test this we took the faces of five Kiwi politicians to London and showed them to people who wouldn't know anything else about them, asking who was the most and least trustworthy.
Watch the video for the full Story report.