Angry men stand out in a crowd.

By comparing how quickly human facial expressions of different types are detected in a crowd of neutral faces, researchers have demonstrated that male angry faces are a priority for visual processing – particularly for male observers. The findings are reported by Mark Williams of the Massachusetts Institute of Technology and Jason Mattingley of the University of Melbourne, Australia, and appear in the June 6th issue of Current Biology.

In evolutionary terms, it makes sense that our attention is attracted by threat in the environment. It has long been hypothesized that facial expressions that signal potential threat, such as anger, may capture attention and therefore "stand out" in a crowd. In fact, there are specific brain regions that are dedicated to processing threatening facial expressions. Given the many differences between males and females, with males being larger and more physically aggressive than females, one might also suspect differences in the way in which threat is detected from individuals of different genders.

In the new work, Williams and Mattingley show that angry male faces are found more rapidly than angry female faces by both men and women. In addition, men find angry faces of both genders faster than women, whereas women find socially relevant expressions (for example, happy or sad) more rapidly. The work suggests that although males are biased toward detecting threatening faces, and females are more attuned to socially relevant expressions, both sexes prioritize the detection of angry male faces; in short, angry men get noticed. The advantage for detecting angry male faces is consistent with the notion that human perceptual processes have been shaped by evolutionary pressures arising from the social environment.

Angry males are a greater potential threat than angry females. So it makes sense that natural selection would favor a wiring of human brains that make them more easily recognized.

There's a security angle here: Secret Service and other professional bodyguard outfits that need to recognize angry male would-be assassins might do that job better with male agents. However, do assassins look and feel angry? Or are some feeling thrills at what they are about to do? If assassins express other kinds of emotions when preparing to kill then maybe women would be better at recognizing them.

What I wonder: Just how many distinct adaptations and abilities has natural selection wired into human brains? How many of those abilities are trade-offs with other abilities? For example, in the case above while males have an advantage recognizing angry faces females have an advantage in decoding the meaning of other facial expressions.

Also, once scientists identify which genetic variations make those abilities more or less pronounced which abilities will people choose to give their offspring? I think the question of how people will genetically engineer their offspring is one of the most important questions we face for the future.