How First Impressions Form in a Fraction of a Second

You meet someone new and, almost before you’ve taken in their face, a quiet verdict has formed: friendly, serious, trustworthy, not sure. You didn’t choose to judge. It just happened.

How fast it happens

In a 2006 study at Princeton University, Janine Willis and Alexander Todorov showed people photographs of unfamiliar faces for just 100 milliseconds, a tenth of a second, and asked them to rate each person. Their ratings closely matched those of people who could look for as long as they liked.

This held for all five qualities tested: attractiveness, likeability, trustworthiness, competence and aggressiveness. Giving people more time did not change their judgements much. It mainly made them more confident in what they had already decided.

More time with a face mostly adds confidence, not accuracy.

What the brain is doing

Reading faces fast is useful. For most of human history, quickly deciding whether a stranger was a friend or a threat mattered a great deal. The brain appears to do this automatically, using whatever is visible:

• Facial expression. A hint of a smile reads as friendly and trustworthy. A slight frown reads as the opposite, even on a neutral, resting face.
• Face shape and features. People tend to agree with each other about which faces “look” competent or kind, even though these are only looks.
• Body language and voice. Posture, eye contact, energy and tone add to the picture within seconds.

Thin slices

Psychologists Nalini Ambady and Robert Rosenthal called these tiny samples of behaviour thin slices. In a 1993 study, people watched silent video clips of teachers lasting less than half a minute. Their ratings of the teachers predicted the ratings given at the end of term by students who had actually been taught by them.

That shows that manner and energy come across very quickly. It doesn’t show that a brief look reveals someone’s character.

How accurate are they?

This is where care is needed. First impressions are consistent: different people tend to reach similar snap judgements about the same face. But agreeing is not the same as being right.

A striking example comes from another Todorov study, published in 2005. People were shown pairs of faces of candidates in US Congress elections, people they didn’t recognise, for one second and asked who looked more competent. The candidate judged more competent had won in 68.8% of the 2004 Senate races.

That doesn’t mean faces show competence. It suggests that voters are influenced by appearance, which is a reason to be wary of our own snap judgements.

First impressions also colour everything that follows. Once we’ve decided someone is warm, we tend to read their later actions kindly. Psychologists call this the halo effect.

Judging people more fairly

You can’t switch first impressions off, but you can stop them deciding too much:

• Notice the verdict. Simply telling yourself “that’s a first impression, not a fact” weakens its hold.
• Look for evidence against it. Ask what you would expect to see if your first impression were wrong, then look for it.
• Use the same questions for everyone. In interviews, deciding the questions and what a good answer looks like in advance makes comparisons fairer.
• Give it time. Judge people on what they do over several meetings.

Making a good first impression

The same research points to simple things: arrive rested and on time, look at the person, smile when you greet them and give them your full attention. Small signals of warmth register fast. You don’t need to perform, and trying too hard tends to show.