Here's a fun study about how men find it more difficult to judge women's emotions than men's emotions and how different parts of their brains light up in the two cases. The study has photographs of eyes only, twenty-two men looking at them and a humongous amount of statistical manipulation to produce the results. It is summarized here.
I'm not saying that the results are wrong. I can't tell, actually, given that the raw data isn't there, and I'm too tired to try to sleuth through the statistics. But with 22 cases it should have been possible to post the success rates of each individual man. This is important, because a few outliers could seriously affect the findings.
The discussion of the results is fascinating, too. The authors mostly address the possibility that these men are better at getting emotions expressed by men's eyes right, because, roughly, they learn them by looking at the mirror in the morning. Or, rather, we are better at deciphering people most like ourselves.
But then at the very end of the report they give a nod to evolutionary psychology:
The finding that men are superior in recognizing emotions/mental states of other men, as compared to women, might be surprising. From an evolutionary point of view, accurate interpretations of other men’s rather than women’s thoughts and intentions, especially threatening cues (also related to amygdala responsiveness [40]), may have been a factor contributing to survival in ancient times. As men were more involved in hunting and territory fights, it would have been important for them to be able to predict and foresee the intentions and actions of their male rivals.
Perhaps. But note that usually evolutionary psychology is all about the necessity to pass one's genes on, and the prelude to that requires to find someone of the opposite sex to mate with. Suddenly understanding that opposite sex (women) matters not a whit but male aggression does.
I guess I have trouble with articles which are all about brain imaging and technical language and suddenly the discussion adds a few hypotheses that nobody can ever confirm, based on the assumption that men were more involved in hunting and territory fights and that those fights were so crucial for survival that they created an adaptation which made men better at reading emotions in other men than in women. What about all that need to find women to mate with?
There are alternative explanations, including the theory that one is best at interpreting emotions in people who are most similar to oneself, but also the fact that even in today's society it is more important to understand the emotional cues given by more powerful people. Because they matter more.