This is huge. The researchers were able to determine this by testing the pain threshold of the mice on something called the Mouse Grimace Scale (I am not making this up, and it would be, as Dave Barry would note, a great name for a band). In the grip of terror when in the presence of large males, the mice experienced lower levels of pain, similar to the way you don't notice that you have stubbed your toe as you flee in panic from a pursuing yeti. In response to female researchers, the mice felt no such stress.
The big takeaway: "Experimenter sex can thus affect apparent baseline responses in behavioral testing."
And we haven't been accounting for this at all. Jeffrey Mogil, the head author of the study, told the Verge, "I think that it may have confounded, to whatever degree, some very large subset of existing research."
Decades of science are going to be perhaps not voided but certainly called into question. "Did you in fact have a negative reaction to that makeup," scientists must now ask their cosmetics-testing mouse subjects, "or were you so terrified by the giant testosterone monster in the lab with you that you weren't able to form an opinion about it at all?"
And it wasn't just human males. Dogs, cats and guinea pigs were among other stressful male presences, the scientists found. Mice consider lone males a threat, and the only way to balance this out besides having female researchers join male researches every time the latter perform their studies is to have the male research assistant sit in the room for 45 minutes, establishing that he is not a threatening presence. And who has time for that?
There you have it. Women in science: They're not just a good idea. They're preferred by mice everywhere.