Rodents are the workhorses of biomedical labs. So it’s important to know if they’re stressed out, which could affect results. Now we know that lab rodents may be regularly exposed to a big stressor: men.
Researchers noticed that mice showed a lower pain response—a sign of stress—when a human was present. So they put mice and rats into clear cubicles, where their faces were visible, and injected them with an irritant. The rodents expressed pain through grimacing when no humans were nearby. But when confronted with a male researcher, or even just his odoriferous T-shirt, the animals grimaced less.
