Misandry in Mice: Is sexism among rodents destroying science?

"This is a nightmare. It isn't real. It isn't... DON'T TOUCH ME!"

In world-breaking cute news, it turns out that mice are scared of men. Robert Sorge and colleagues decided freak some mice out by seeing whether the gender of the researcher could affect the behavior of mice, and they discovered that mice experienced greater stress in the presence of men compared to women.

Besides being funny to imagine a mouse atop a chair shrieking as a man approaches him and trying to bat him away with a mini broom, it does have some serious implications for not only how we should conduct future research but also in how much confidence we should attribute to past research that hasn't controlled for this factor.

SHRIEKING MICE

Before discussing the complications this research raises, we'll first look at what the study did and exactly what they found. One of the main measures used in the study was the "mouse grimace scale", which adorably looks like this:

and presumably the judgement of where a mouse fell on the scale simply involved a group of researchers huddled around a mouse cooing: "Who's a grumpy mouse? You are! Yes, you're a grumpy mouse!". The pain response (or 'grimace') was used as a proxy for stress and this was associated with an observed "stress induced analgesia" (SIA). SIA simply means that when an individual is stressed, any pain it experiences is effectively numbed - like when an athlete injures themselves during a game but doesn't realise they are in pain until after the game has ended.

I'd love to be able to say that the researchers also used a handful of other semi-anthropomorphic measures, like a tiny mouse-sized Freudian couch where it talks about its feelings, but unfortunately they just looked at body temperature and corticosterone. However, these proxies for stress did support the conclusions reached based on the grimace metric.

So the main findings here were that mice demonstrated SIA in response to the presence of males, this occurred in both male and female mice although to a greater degree in females, and this effect continued even when they used male-scented T-shirts in place of an actual man. Interestingly, the effect could be abolished when there is a female-scented T-shirt in the room, and although the effect of the male-scented T-shirt faded after 30-60min, the effect persisted when tested again on following days (or, as the authors describe it, the male subject was faced with the same level of grimacing).

The explanation for why this might occur was speculated on by the authors but no definite explanations were proposed. The most plausible explanation suggested that it wasn't simply a reaction to potential predators but rather some olfactory chemical that is common to mammals alerts them to male competition, which is particularly relevant to territorial species like mice. There were some evopsych suggestions but I was too busy imaging little cavemen mice engaging in evolutionarily advantageous behaviors to fully appreciate the explanations put forward.

WHY IS THIS IMPORTANT?

One of the most obvious complications this research highlights is the effect that this could have on behavioral research. Specifically, we know that stress can affect aspects of behavior, like food interest and general preferences, and so if we are inadvertently stressing out some of our subjects in an entirely uncontrolled way then we will have difficulty comparing data between subjects, within subjects, across days, across conditions, etc. 

To illustrate the problem in a simpler way, imagine I was interested in testing your reaction time in a very basic task like clicking a button when a specific stimulus appears on a computer screen. Now suppose, unbeknownst to me, you had an extreme fear of snakes and spiders and, by sheer unfortunate luck for you, every now and then when you come in to the lab to participate in the experiment the lab is overrun with snakes and spiders. Because I'm working on the assumption that the presence of snakes and spiders isn't a relevant variable, I make no note of them being there on certain days, I don't observe your response in their presence, and I make no effort to standardise the lab environment to eliminate them as a confound.

Most likely what will happen is that I'll get a few aberrations in my data. For example, on Monday through to Thursday you performed quite well, with entirely normal reaction times that are well within the range for your specific demographic, and yet on Friday you barely completed any of the reaction time tasks, and the only data I have on your performance is the video recordings of you scratching at your arms yelling, "OH GOD, GET THEM OFF ME, GET THEM OFF MEEE!!" (but that information is discarded as being impertinent to the measures we're interested in).

In a lot of research this information will simply be ignored, or explained as an outlier and nothing more will come of it. The best case scenario is that the researcher will note in the Discussion section that the data seemed weird and recommend further research but likely nothing will come of it (especially if they don't even realise what variable might have been causing the odd data). 

With all that said, behavioral research isn't even the only area that is affected. A lot of purely biological work will also be affected, especially when it is directly stress-related but even when it is only indirectly affected in the sense that the release of stress hormones can cloud their results by interacting with a variable they're interested in. What this means is that if a researcher is looking at sex differences in male and female mice, and purely due to chance a male researcher handles more of one gender than a female researcher when performing the vital tests (or euthanising it before post-mortem tests are carried out) then we might notice a significant difference between male and female mice which is in actuality unrelated to the gender of the mice.

WHAT SHOULD WE DO ABOUT IT?

Perhaps the first step these researchers should take is to buy the domain: http://www.picturesofgrumpymice.com and try to kickstart the new cute animal meme - move over "lolcats"! Obviously that isn't a scientific issue, that's just good business.

In some interviews the authors have jokingly suggested that all male researchers should be fired or to be constantly chaperoned by a women but there are more realistic possibilities. Some suggestions have been for male researchers to sit in the animal room for an hour before approaching them, or for only women to be hired when stress is known to be a relevant factor to the issue being studied but even these options aren't overly practical. 

In my opinion, the simplest solution is for researchers to just be aware that this could be a confound. Record whether a man or woman handled the mice before specific tests, or on certain days, and when analysing your data you can see if there is a significant effect of researcher gender on your results. Alternatively, all male researchers will be armed with Maria Carey's latest perfume and told to generously apply it before entering the lab. Further research into Bugs Bunny cartoons will tell us if these researchers also need to apply clown-level makeup and wear ballgowns.