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Laboratory rats are often used to study diseases and new drugs. In a new study, however, researchers used lab rats in a very different way. The research team set out to find an explanation for the old stereotype that women tend to be more afraid of mice than men are. They discovered that mice tend to be bolder in the presence of women and more stressed in the presence of men.

"Scientists whisper to each other at conferences that their rodent research subjects appear to be aware of their presence, and that this might affect the results of experiments, but this has never been directly demonstrated until now," researcher and psychology professor, Jeffrey Mogil, said reported by the Dailymail.

For this study, the research team from McGill University in Montreal, Canada, examined how lab mice reacted to male and female experimenters. The researchers had exposed the mice to men and women by placing a previously worn T-shirt near the mice. They discovered that when men released pheromones, these high concentrations triggered a stress response in the mice. The researchers stated that the mice's stress levels are equivalent to the stress response seen in mice that are restrained for 15 minutes in a tube or forced to swim continuously for three minutes.

When the mice were around women, however, they were less stressed and bolder. The researchers believe that since women release lower concentrations of pheromones, the mice are not as intimidated and are more likely to show themselves in public. The researchers added that these findings question study results that use lab mice. If mice react differently based on the gender of the experimenter, some of the results could be skewed.

"Our findings suggest that one major reason for lack of replication of animal studies is the gender of the experimenter - a factor that's not currently stated in the methods sections of published papers. The problem is easily solved by simple changes to experimental procedures," study leader Professor Robert Sorge said. "For example, since the effect of males' presence diminishes over time, the male experimenter can stay in the room with the animals before starting testing."

The study was published in Nature Methods.