Rats remember acts of kindness done by other rats, and are more helpful to individuals who previously helped them. It’s not clear if they do this because they are grateful or if they are trying to make sure that they will get helped in the future as well, but their behavior gives scientists a new understanding of animal social behavior.

Can rats develop friendships? This study sure seems to suggest that. Swiss researchers Vassilissa Dolivo and Michael Taborsky found that animals other than humans (namely rats) can reciprocate, helping each other based on how much help they’ve received in the past.

For this study, they fed female Norwegian rats two types of foods: bananas and carros. For rats, bananas are a favorite, while carrots – not so much. The twenty rats were put in a prisoner’s dilemma-type situation. Two people were responsible for delivering either bananas or carrots by pulling a stick. Eventually, the receiving rat would start to learn who of the helpers gives it bananas and who gives it carrots. Then, scientists switched the rats’ places, so the rats on the receiving end were now able to pull on a stick that would deliver cereal flakes to a certain helper. The rats recognized the handlers and were much more likely to give the banana handler cereal flakes; at the same time, the rats who received carrots were less likely to give out the food.

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But are the rats really helping out here, or is it simply random behavior?

“Two elements are involved: recognizing an individual, and responding to the quality of service,” Taborsky says.

The first element indicates a specific type of intelligence, but researchers were more interested in the second one – the ability to reciprocate. This might indicate that altruism, friendship and the desire to help others may actually not be as complex as previously thought – or that rats have more developed social skills than we gave them credit.

“The test rats showed a clear preference to pay back help to the partner that had provided them with the preferred food”, says Michael Taborsky. “They helped previous banana providers much quicker than previous carrot providers”.

Journal Reference:

  1. Vassilissa Dolivo, Michael Taborsky. Norway rats reciprocate help according to the quality of help they received. Biology Letters, 2015 DOI:10.1098/rsbl.2014.0959