Why We Evolved to Size Up Angry Faces

Most of our daily lives hum along effortlessly. We automatically rise when we wake, speak when we wish to communicate, and eat when our empty bellies grumble. These behaviors helped our ancestors survive and reproduce. But we also need to size up situations and people that might threaten us. How well do we do this?

In one recent investigation, researchers from Australia and the United States argued that angry faces tell a specific story that takes little effort to understand. Rather than being a simple threat signal, angry faces gives us information about people’s physical strength, which is the crucial element in determining their fighting ability. Using some cool facial morphing software, the researchers showed participants faces and then manipulated the seven primary facial muscles involved in an angry facial expression. Some faces flexed all seven angry facial muscles; others flexed fewer than seven.

The more angry muscles the faces flexed, the more participants rated the person as being physically strong. The key is that participants did not need to take a course on the biology of human emotion to make their ratings. They didn’t need to know the seven facial muscles that comprise an angry facial expression. Participants automatically knew the strongest and angriest face when they saw it.

So, the next time you get a twinge of terror when you see an angry face, don’t sweat it. Your mind is automatically telling you something aimed at keeping you safe and sound.