A research team in China bred male mice whose brains lacked the ability to respond to the neurotransmitter serotonin as part of a recent study. Serotonin is a chemical that is also produced by humans. It contributes to good feelings, and its production is often a component of antidepressants. Without it, the male mice were more likely to exhibit sexual attraction (mounting, mating calls, you know, your basic late-night antics) when around only other male mice. When in a mixed group, they showed no particular preference for males or females. It's the first time that a neurotransmitter was shown to relate to mammalian sexuality, according to the BBC, but scientists caution against using this study to draw conclusions about humans. For one thing, mice respond primarily to odor when it comes to sexual attraction, unlike people. (Sorry Axe Deodorant Body Spray.) And humans on serotonin-affecting drugs, of which there are many in the marketplace, generally don't display any change in sexuality.
Still, science does appear to have solved one thing with this study: that pesky mouse addiction to carbs.