Samplings: October 2007

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Rat in foreground pulls stick attached to a tray (gray plate) that glides towards the cage, thereby providing partner rat in background with an oat flake. 

Res Schmid

"One good turn deserves another." Most people take that aphorism to heart—so much so, studies show, that after receiving help, we are more willing than before to help someone else, even a stranger. It might be tempting to think such virtue is unique to our species, but it turns out that the lowly rat is just as noble. To find out if grateful rats would lend a paw to perfect strangers, Claudia Rutte and Michael Taborsky of the University of Bern, Switzerland, trained rats to pull a lever that introduced food to a rat in a neighboring cage. On five consecutive days, trained test rats were caged either next to other helpful, trained rats or next to unhelpful, untrained rats. On the sixth day, Rutte and Taborsky discovered, test rats that had been paired with helpful neighbors were, on average, 21 percent more likely to pull a lever for a new neighbor they had never encountered than were test rats paired with unhelpful neighbors. What’s more, the rats could distinguish between strangers and former benefactors. In another experiment, test rats that encountered a rat that had given them food earlier were—not 21 percent—but 51 percent more likely to return the favor. Notably, Rutte and Taborsky studied only female rats. No word on whether males would be equally obliging. (PLoS Biology)