Not everyone has the same muscles for pulling faces.

Katharine Sanderson


Maybe we're not all the same under our skin, after all — at least where our faces are concerned. Next time you look at that special someone, it's worth reflecting that their alluring smile could well be down to their uniquely wonky facial muscles.

A team of international researchers has studied the facial muscles of 18 Caucasian cadavers, and found some striking similarities in the faces — but also some interesting differences. All had the same set of five muscles that control the six facial expressions common to all humans: anger, happiness, surprise, fear, sadness and disgust.

But there are 11 more facial muscles that people have in different numbers, and different sizes, on the two supposedly symmetrical sides of the face. Some of the faces studied had some of these extra muscles on one side of the face but not the other, although the five basic muscles were always symmetrical.

Friendly faces

The individual musculature make-up allows idiosyncrasies to develop so that individuals can be identified by close friends, says lead author Bridget Waller of Portsmouth University. The regularity of muscles controlling the basic expressions, however, means that these general emotions can be communicated to anyone.

“We can all do these 'loud', important signals like smiling,” Waller explains, “but you might be able to have a slightly different smile.”

So although people's facial muscles differ, it doesn't necessarily mean that they can't pull the same face — just that they might use different muscles to do it, Waller suggests. People often subconsciously mimic the expressions of others as an emotional response, for example.

The study's results can be explained evolutionarily, Waller says. Humans have been selected to have very clear facial signals — the same basic muscles communicate the same principal emotions in everyone. But Waller suggests that the combination of up to 11 other facial muscles shows that individual facial 'signatures' are important for creating relationships within social groups.

“We have this biological basis for facial expression, but we also have room for cultural variation and individual variation,” says Waller.