"Soft hair indicates cowardice and coarse hair courage," they wrote. Impudence, the treatise says, was evident in "bright, wise-open eyes with heavy blood-shot lids"; a broad nose, meanwhile, was a sign of laziness, like in cattle.

The Ancient Greeks believed wide, flaring nostrils suggested a person could be lazy 

 

Consider the face’s bone structure – whether it is relatively short and wide or long and thin. Lefevre has found that people with higher levels of testosterone tend to be wider-faced with bigger cheekbones, and they are also more likely to have more assertive, and sometimes aggressive, personalities.

 

The link between face shape and dominance is surprisingly widespread, from capuchin monkeys – the wider the face, the more likely they are to hold a higher rank in the group’s hierarchy – to professional football players. Examining the 2010 World Cup, Keith Welker at the University of Boulder, Colorado, recently showed that the ratio of the width and height of the footballers’ faces predicted both the number of fouls among midfielders, and the number of goals scored by the forwards.

 

How could the plumpness of your cheeks say so much about you? Benedict Jones at the University of Glasgow thinks a new understanding of fat’s role in the body may help explain it. “How healthy you are isn’t so much about how much fat you have, but where you have that fat,” he says. Pear-shaped people, with more weight around the hips and bottom but slimmer torsos, tend to be healthier than “apples” with a spare tyre around the midriff, since the adipose tissue around the chest is thought to release inflammatory molecules that can damage the core organs. Perhaps the fullness of your face reflects the fatty deposits in the more harmful areas, Jones says. Or it could be that facial fat is itself dangerous for some reason.

 

Besides these more overt cues, very subtle differences in skin colour can also reveal your health secrets. Jones and Lefevre emphasise this has nothing to do with the tones associated with ethnicity, but barely-noticeable tints that may reflect differences in lifestyle. You appear to be in more robust health, for instance, if your skin has a slightly yellowish, golden tone. The pigments in question are called carotenoids, which, as the name suggest, can be found in orange and red fruit and veg. Carotenoids help build a healthy immune system, says Lefevre. “But when we’ve eaten enough, they layer in the skin and dye it yellow. We exhibit them, because we haven’t used them to battle illness.” The glow of health, in turn, contributes significantly to your physical attraction – more so, in fact, than the more overt tones that might accompany a trip to the tanning salon.

 

Looking smart

But now the discipline is gaining credibility, we may find that there are many more surprises hiding in your selfies. Intriguingly, we seem to be able to predict intelligence from someone’s face with modest accuracy – though it’s not yet clear what specific cues make someone look smart. (Needless to say, it is not as simple as whether or not they wear glasses.) Others are examining the “gaydar”. We often can guess someone’s sexual orientation within a split-second, even when there are no stereotypical clues, but it’s still a mystery as to what we’re actually reading. Further research might explain exactly how we make these snap judgements.

 

It will also be interesting to see how the link between personality, lifestyle and appearance changes across the lifetime. One study managed to examine records of personality and appearance, following subjects from the 1930s to the 1990s. The scientists found that although baby-faced men tended to be less dominant in their youth, they grew to be more assertive as the years wore on – perhaps because they learnt to compensate for the expectations brought about by their puppyish appearance.

 

Our faces aren’t just the product of our biology. We can’t change our genes or our hormones – but by cultivating our personality and sense of self-worth, they may begin to mirror something far more important.