Nerds have hormones too, you know

The researchers found that volunteers crossed the bridge faster when a virtual woman was present, as compared with a virtual man or no virtual person whatsoever. This proved true only if the scientist overseeing the experiment was also a woman and not a man, the researchers noted. The volunteers did not cross faster if the virtual witness was a woman but the scientist was a man, for instance, or if the scientist was a woman but the virtual witness a man.

These findings seem to support the idea that male risk-taking is aimed primarily at impressing females. Another possibility is that the attention from women in these experiments — both real and virtual — made the volunteers feel better about themselves, enabling them to cross the bridge faster with less fear. Yet another alternative is that volunteer speed increased when they had two females watching them as opposed to just one.