January 27, 2012

Rodents choose not to rat each other out

The most maligned creature in the animal kingdom might just get a public relations makeover, thanks to a recent University study.

A team of University researchers have confirmed the existence of something akin to human empathy in rats, after months of laboratory testing. Professor of Neurobiology Peggy Mason presented the experiment, whose results were published in Science December 9, over lunch at the Biological Sciences Learning Center on Monday afternoon.

In the experiment, one rat was trapped in a restrainer device—a plastic tube with a door that could only be opened from the outside. The second rat was left to roam in the cage around the restrainer, presented with the possibility of freeing the trapped rat by nudging open its door.

According to Mason, the presence of the trapped rat drastically altered the rats’ behavior.

“The rats acted normally when the restrainer was empty or contained a plastic rat, but behavior changed drastically when a live rat was trapped,” she said. “The free rats overcame their natural anxiety and tendency to stay near the edges of the cage and were drawn to the center of the cage to liberate their cage-mates.”

The rats in the study took about six days to discover how to free their cage-mates, after which they acted intentionally and efficiently to open the restrainer.

“Once they get the restrainer open, they instinctively freeze for a second, then have a period of celebration and playing with their freed cage-mate,” said Mason, who co-authored the study with psychology professor Jean Decety and Inbal Ben-Ami Bartal, a graduate student in psychology.

The researchers ruled out other motivations the rats might have for their actions by tweaking the experiment in various ways, with each trial confirming that empathy motivated the rodents’ behavior.

Even when presented with the option of two restrainers, one containing a trapped cage-mate and the other containing chocolate chips—a favorite rat snack—the rodents predictably liberated their cage-mates, then left their trapped friend some of the chocolate chips.

“That was what really shocked me,” Mason said. “This told us that helping a cage-mate is on a par with chocolate. He could eat all the chocolate if he wanted to, and he does not.”