The reason that women are more "emotional" i.e. expressive than men is that hyper-expressiveness makes it more difficult for other people to detect your deceit.

For those not familiar with the distinction between signal and noise, imagine that you're in a large room with a machine that's generating a constant tone at a somewhat low, say a musical note. This is the signal, what you're trying to hear.

When the room is empty, hearing the signal is easy. Now imagine that the room starts filling up with people. As they move around, talk to each other, call over the waitress for more cocktails and hors d'oeuvres, they generate noise. As the room gets noisier, the signal gets harder and harder to hear. Eventually you can't hear it at all.

The obviously fake and exaggerated emotion that women constant practice on each other is noise. Eventually they are so habitually expressive that when they're genuinely emotional about something, they can act it out without worrying about somebody picking up on what they're actually feeling. In other words, because the baseline style of expression for women is highly exaggerated, strong feeling is harder to detect by comparison.

Women, since they are the ones playing this game, are usually better at reading other women. Men are at a serious disadvantage because the male style of communication, which tends to be more stoic and reserved, exists to promote high-trust communication between men. If a man gets genuinely worked up about something, then it's relatively easy to tell how he's feeling. When dealing with other men this is not a problem, because men are naturally inclined to settle disagreements with authority and hierarchy rather than manipulation and deceit. Women exploit this. They know that their own feelings will be difficult for the average man to read and they're so practiced from their dealings with other women that reading him will be easy for them.

Obviously there are exceptions, but I think this is the general rule. Any thoughts? I'm familiar with signaling theory in biology but I'm wondering if anybody knows of some rigorous literature on this specific topic.