Scent of Male Scientists Triggers Stress Response in Rodents; Study Finds

Scientists have found that scent of male scientists causes stress in lab rodents. The research explains why men find it harder than women to replicate scientific studies using animal models.

The study, conducted by researchers at McGill University in Montreal, found that a rodent in the presence of a male scientist would experience high levels of anxiety. The stress response would be equivalent to that caused by confining rodents in a tube for 15 minutes or forcing them to swim for three minutes.

The stress reaction also made rodents less sensitive to pain, meaning that results of behavioral experiment could be skewed by the presence of men in the lab.

Researchers found that the presence of women created no such stress response.

"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," said Jeffrey Mogil, a psychology professor at McGill and senior author of the paper.

For the study, researchers placed cotton T shirts near the test mice. The shirts were worn the previous night by male or female researchers.

Researchers found that the stress was caused due to chemosignals, or pheromones secreted by the experimenters' armpits. Males produce higher concentrations of this chemical signal than females.

The presence of the pheromone in large amounts warns the rodents of a nearby male, which leads to the stress response. "A lone male is up to no good - either hunting or defending his territory," Mogil told The Verge.

Lab-rodents also had increased body temperature and elevated levels of stress hormone corticosterone, The Verge reported.

What was surprising is that lab animals exposed to both men and women's T shirts were calmer than rodents exposed to only men's shirts, according to IB Times.

The study doesn't mean that men should be barred from conducting research on rodents. Simple changes in research methodology could account for the difference in rodent behavior. The effect of the pheromones diminishes over time, meaning that males can reduce the discrepancies in the research by staying with the rodents before the start of the test. Also, publications could include the gender of the researcher conducting the behavioral experiments, according to Mogil

"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," said Robert Sorge, a psychology professor at the University of Alabama, Birmingham. Sorge led the study as a postdoctoral fellow at McGill.