Flutterby™! : Feelin' no pain 'cause of the scent of a guy

Science Magazine: Male Scent May Compromise Biomedical Research:

Jeffrey Mogil’s students suspected there was something fishy going on with their experiments. They were injecting an irritant into the feet of mice to test their pain response, but the rodents didn’t seem to feel anything. “We thought there was something wrong with the injection,” says Mogil, a neuroscientist at McGill University in Montreal, Canada. The real culprit was far more surprising: The mice that didn’t feel pain had been handled by male students. Mogil’s group discovered that this gender distinction alone was enough to throw off their whole experiment—and likely influences the work of other researchers as well.

The paper is Nature Methods: Olfactory exposure to males, including men, causes stress and related analgesia in rodents.

We found that exposure of mice and rats to male but not female experimenters produces pain inhibition. Male-related stimuli induced a robust physiological stress response that results in stress-induced analgesia. This effect could be replicated with T-shirts worn by men, bedding material from gonadally intact and unfamiliar male mammals, and presentation of compounds secreted from the human axilla. Experimenter sex can thus affect apparent baseline responses in behavioral testing.

Via MeFi, in which Etrigan observes:

So... men are literally biologically worse at science.