Rats more social than previously believed: Study

Rats are much more social than previously believed, according to a study which suggests they can use their fellow rodents as danger antennas, by being sensitive to the emotions of the rats around them.

The researchers from the Netherlands Institute for Neuroscience put two rats face to face, and then startled one of them -- the demonstrator -- with a brief electrical stimulation of the paws.

The study, published in the journal PLOS Biology, noted that the bystander rat suddenly looked scared on witnessing its electrically stimulated neighbour jump.

"The bystander catches the fear of the demonstrator," explained study co-author Rune Bruls.

According to Bruls, the reaction of the bystander also influences how the stimulated rat feels about the shock. The researchers said bystanders that were less scared reduced the fear in their demonstrators.

"Fear just jumps from one rat to another. That way a rat can prepare for danger before they even see it," Bruls said. The researchers tried understanding the brain region involved in empathy in rats.

In humans, they said, witnessing the pain of others activated a region between the two hemispheres which is also active when we feel pain in our own body. To see if this region is the same in rats, they injected a drug to temporarily lower the activity of this area.

"What we observed, was striking: without the region that humans use to empathize, the rats were no longer sensitive to the distress of a fellow rat. Our sensitivity to the emotions of others is thus perhaps more similar to that of the rat than many may have thought," said Christian Keysers, the lead author of the study.

The researchers also said the empathy found between the rats were independent of whether the rats knew each other before the study. For rats that had never met each other, the emotions of its pair in the study was as contagious as for rats that had shared the same home for 5 weeks.

"This really challenges our notions of the origin of empathy," said Valeria Gazzola, a senior author of the study. "What our data suggest, is that an observer shares the emotions of others because it enables the observer to prepare for danger. It''s not about helping the victim, but about avoiding to become a victim yourself," Gazzola explained.