Brain regions responsible for understanding feelings and emotions show little activity in men when facing anger, which explains their stoic silence in stressful situations.
The study by USC researchers revealed that in contrast, stressed women show increased brain coordination when looking at angry faces.
"These are the first findings to indicate that sex differences in the effects of stress on social behaviour extend to one of the most basic social transactions - processing someone else's facial expression," said Mara Mather, director of the Emotion and Cognition Lab at USC.
In the study, the researchers present a series of tests indicating that, under acute stress, men had less brain response to facial expressions, in particular, fear and anger.
In both men and women, looking at pictures of faces caused activity in the part of the brain used in basic visual processing (the "fusiform face area") and in parts of the brain used for interpreting and understanding facial expressions.
However, men under acute stress showed decreased activity not only in the fusiform face area but also decreased coordination among parts of the brain that help us interpret what emotions these faces are conveying.