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DD has noted that the ONE constant in her research observations of human subjects in pairs programming is that the male paired subjects tend to be OVER-confident, and the female ones UNDER confident. If anything, their data suggests that the female teams are less error-prone and work faster when they work as a cohesive team.

This is actually a pretty well-known phenomenon. Men overrate their abilities, intelligence, skill at driving, attractiveness, etc while women underrate themselves, even when, as a group, they test as more competent.