Specifically, the scent of a man can impact the stress response in rodents used in science experiments. So, if there's a male researcher around the lab rats or mice, the animals have an elevated corticosterone response. In other words, they get stressed out.

Some scientists had hypothesized that researchers could impact the brain chemistry of mice, so McGill University decided to test the hypothesis. As it turns out, it's true.

Researchers discovered that mice that work with men initially have a higher pain tolerance, because of the stress hormone released. After about 30-40 minutes, the effects abated. 

The effects were nonexistent with females, and when there was both male and female scent. Researchers aren't 100 percent sure why this happens, but according to Dr. Jeffrey Mogil, a neuroscientist from McGill who helped run the study, it has to do with the rodents' responses to another male mammals in the area. He says that they're anticipating having to possibly fight or flee. 

What should scientists do going forward? Mogil thinks that they should include in a paper's method whether male or female researchers were involved in the project.

As to how many studies have been impacted or might have to change because of the findings? Mogil's unsure, but he's reviewed some of the studies that he's worked on and there's been an impact.