The Industrial Revolution was a dizzying time. People were moving from small outposts to big cities; they were crossing borders and settling far from their roots. Society had been so much simpler for the past couple of million years, when everyone for the most part lived in tribal groups. These were essentially extended families in which you either knew or knew of anyone you could possibly encounter, and so you could easily discern their demeanor and intentions. Now, though, we have to quickly and reliably tell friend from foe, at a time when so many people look so different from you.

Hence the 19th century was the golden age of a pseudoscience known as physiognomy. “The physiognomists promised an easy way to solve the problem of understanding other people,” writes Alexander Todorov, a psychology professor at Princeton, through “knowing them from their faces.” Physiognomists proposed and promoted rules about how facial features and structures revealed character traits and abilities.

Impressive

Professor Todorov’s new book, Face Value: The Irresistible Influence of First Impressions, is about much more than 19th-century pseudoscience. It’s about first impressions more generally. We all form them instantly—within 30 to 40 milliseconds, before we can consciously register even seeing a face. And we start exceptionally early on, probably at around seven months of age. We also seem to agree on these impressions, which makes the physiognomists’ promise so appealing.

Yet this agreement does not make our first impressions any more accurate than the physiognomists’ claims. (They, obviously, found the features of European faces to epitomize intelligence and moral fiber.) The thing about an impression, then, is that, by definition, it cannot be an inherent property of any subject in isolation. It needs an object. It is the mark made when one thing is impressed upon another, like that made when a coin is pressed into a piece of clay and then removed. Other people’s faces are thus more akin to mirrors reflecting our own biases than to windows revealing their owners' inner lives; the first impressions we make of other people based on their faces say more about us than about them.

According to Todorov, the way we evaluate faces is by placing them on a grid with two axes: goodness and power. Faces with more goodness are perceived to be trustworthy, and those with more power are perceived as dominant. In Face Value, he finds that faces ranked as trustworthy also happen to be happy faces, as opposed to angry faces. So we judge people’s fundamental (trust)worthiness based on their emotional state, which is by nature (a) fleeting and (b) universal, in that happiness is experienced by everyone from time to time.

Our trust in happy faces may not be surprising, and it may even be prudent for the immediate future. But it is hardly fair, and it is certainly not accurate over time. And it bodes exceptionally ill for people with "resting bitch face."

Bad impressions

Happiness is not the only factor that makes a positive first impression. Familiarity matters, too. “We tend to distrust atypical faces,” writes Todorov. “We trust those who look like members of our own tribe.”

But what makes a face atypical is often only our lack of exposure to faces like it. Our familiarity with only certain (types of) faces has another consequence, too: our familiarity lets us discern things about the inner states of people who are close to us from their faces. Unfortunately, this makes us think that we can discern things about strangers from their faces. But we cannot. It is our familiarity with those we love, not something in their faces, that gives us this ability.

Face Value is a fun, quick, easy read, full of interesting tidbits. Here are a few: Francis Galton, Charles Darwin’s cousin, coined the phrase “nature versus nurture.” A heightened contrast between the eyes and mouth and the rest of the face makes a face look more feminine, which is why women wear make-up. The Mona Lisa smile appears when we look at her eyes, when her mouth is in our peripheral vision.

The book is also full of great pictures, like the composite image of the faces of Ronald Reagan and Leonid Brezhnev, as well as a picture that meshes the top of Justin Bieber’s face with the bottom of Beyoncé’s. Todorov’s findings, and his research methodology, make for fascinating reading.

Todorov also mentions that, in our uncertain times, new physiognomists now claim to be able to divine a person’s religion, politics, and sexuality from objective measures like the facial width-to-height ratio (that’s the ratio of the distance between the right and left cheekbones to the distance between the eyebrows and upper lip). The appeal of their claims is no less tempting now than it was 150 years ago. And their claims are no truer now than they were then.