“It took the researchers two years to examine the data, with the review looking at more than 1,000 different studies. Their findings are detailed but the basic summary is that emotions are expressed in a huge variety of ways, which makes it hard to reliably infer how someone feels from a simple set of facial movements. “People, on average, the data show, scowl less than 30 percent of the time when they’re angry,” says Barrett. “So scowls are not the expression of anger; they’re an expression of anger — one among many. That means that more than 70 percent of the time, people do not scowl when they’re angry. And on top of that, they scowl often when they’re not angry.”