What your cheekbones say about you: Study shows brains make snap judgments on whether to trust a face ‘in a matter of milliseconds’

Scientists have discovered that our brains make snap judgments about strangers’ faces before we have even consciously registered them – giving a whole new meaning to the sense of a good “first impression”.

It has long been thought that high cheekbones and eyebrows signal trustworthiness, large eyes indicate attractiveness and a broad smile suggests approachability – but little was known about how or why our brains are wired to think this.

Now a study from a team of psychologists at New York University has revealed that such impressions are formed in “a matter of milliseconds” in the brain’s amygdala, a structure that is important for human social and emotional behaviour.

Scientists came up with a set of real and computer-generated faces that conformed to a certain set of preconceptions about which previous studies have been done.

They were shown to a group of test subjects and, as with previous studies, people strongly agreed on the level of trustworthiness conveyed by each face.

Afterwards a new group were shown the same images – but for just three hundredths of a second – 33 milliseconds – at a time.

This is not enough time for the conscious part of the brain to register what is going on – but brain scanner readings showed it was enough for the amygdala to respond – and in the same specific regions as with the first group.

“Our findings suggest that the brain automatically responds to a face’s trustworthiness before it is even consciously perceived,” explained Jonathan Freeman, an assistant professor at NYU’s Department of Psychology and the study’s senior author.

“The results are consistent with an extensive body of research suggesting that we form spontaneous judgments of other people that can be largely outside awareness.”

Freeman said the experiments they carried out gave further credence to the power of our hard-wiring to think that higher inner eyebrows and pronounced cheekbones are seen as trustworthy and lower inner eyebrows and shallower cheekbones are seen as untrustworthy.

And a University of York study last month provided further evidence that similar principles can be applied to other characteristics. Breaking down faces to their key constituent parts and shapes, they found that subjects nearly always identified large smiles with approachability.

Youthfulness and attractiveness were governed by the size and shape of our eyes and eyebrows, while the way the brain registered “dominance” was closely aligned with masculine facial structures.

Like others, though that study showed that there is really no correlation between these features and a person’s actual personality. And that’s perhaps not surprising, given just how quickly these judgments are made.

Freeman's study was published last night in the Journal of Neuroscience.