Men and women have evolved differently when it comes to detecting expressions of emotion on people's faces.

In a study, scientists showed participants sets of photographs of human faces. In some cases four photographs, and in other cases, eight. All but one face in each set was neutral. The participants were told what facial expression to look for in a particular set, and in each case the face very obviously exhibited that emotion. Women were consistently faster at picking up on facial expressions of happiness, sadness, surprise and disgust, but men were faster at picking up on anger.

Are men looking for trouble?

In a way, yes. Neither men's nor women's ability to detect an angry male face was affected by the number of photographs, but they were slower to identify an angry female face in a set of eight faces than in a set of four. Scientists explain that evolutionarily speaking, men pose more of a physical threat than women, and so it makes sense for both men and women to be quicker at picking up on a man's anger.

A man's speed at detecting anger in other men makes evolutionary sense too, insofar as men's abilities to quickly detect another man's anger probably more seriously affected their survival.