Apparently, a 2009 study showed "that heterosexual men's (but not heterosexual women's) cognitive performance is impaired after an interaction with someone of the opposite sex (Karremans et al., 2009)."
By the way, I love how they were careful to include 'but not women.'
Researchers at the Behavioural Science Institue in The Netherlands, took it one step further. They tested men who hadn't even met the girl yet. Just the mere possibility of interaction with a woman reduced men's mental processes.
When I told my husband about this study, his response was the following:
"Well, yeah. Then, when they actually meet her it's ten times worse. Add a rival to the mix, and the stupidity becomes exponential."
Ladies, the next time a guy does something stupid to "impress" you just remember that, apparently, they can't help it.