Female Lab Rats Are the Victims of Gender Bias, Too

Sexism in the workplace isn’t limited to humans. Because neuroscientists presumed that hormonal fluctuations in female lab rats would affect their test results, they have mainly stuck to studying male lab rats. But they may not be getting the whole story, reports Bethany Brookshire at Science News.

Female lab rats do indeed have hormonal surges that affect their behavior—but so do males. Previous research has shown that females consume more cocaine when in heat (in other words, with higher estrogen levels) than at other times. But males with low or high testosterone performed poorly on memory tests.

It’s not just the hormones and their effects that differ between the sexes—it’s also the timeframe for hormonal surges. Behavioral neuroendocrinologist Irving Zucker, who detailed these differences in a 2017 study [PDF] in Biology of Sex Differences, tells Science News that females’ hormones vary more over a few days, while males’ vary more over the course of a single day.

There are also differences between the sexes that have nothing to do with hormones at all. In a 2015 study in eLife, Rebecca Shansky, a neuroscientist at Northeastern University, showed female and male rats a tone or light followed by a (harmless) shock to the feet. While all of the rats first learned to freeze after the signal, fearing the shock, some of the females responded to subsequent signals by racing around the cage—for no obvious hormonal reason. Shansky concluded that female rats may learn to process fear differently than males, suggesting that equality of the sexes among lab rats (at least in terms of studying them) can lead to more insightful results.

Plus, if male and female rats behave differently in a given situation, it’s possible that male and female humans would, too. (Perhaps unsurprisingly, human females have also frequently been excluded from clinical trials, including several important long-running studies on aging and other issues.)

And if you’re starting to feel like rats deserve more credit than you’ve previously given them, check out these other impressive rat facts.