> "My experience is that girls seem to have an easier time with emotional expression from a much earlier age."

I think the main reason for this, is that girls are usually allowed emotions, while boys are taught to repress their emotions ("Don't cry", "Man up!", "Don't be a wuss", etc.).

That's why women are - on average - more connected to their emotions, and more aware of them. OTOH men are usually out of touch with their feelings, unaware of their real emotions, and therefore cannot empathize with others.

This difference is not innate, is mostly cultural.