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Rats might not be such rats after all, say scientists

The gap between human and animal behavior narrows as rats cement their position on the list of species shown to help others with no personal gain.

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    A researcher in Sao Paulo, Brazil, holds a lab rat in 2008.
    Andre Penner/AP
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Are animals more human than we thought? Or is it humans who are more animal-like?

Scientists are moving toward a startling conclusion: humans can no longer claim that they are the only ones with an elevated sense of morality. For instance, studies have found that chimpanzees will give food to one another when given the opportunitySo will dogs.

Scientists are learning that prosocial behavior, that is helping others with no direct personal benefit for oneself, is far more common than previously imagined in the animal kingdom. Now, we can include another animal in the growing club of creatures that appear to be motivated by morality: rats.

New research work by Cristina Márquez and Marta Moita at the Champalimaud Centre for the Unknown in Lisbon studies the prosocial behavior of rats. Their research, which appears this week in Cell Press, adds to the growing field of research on animal morality.

In order to measure rats' prosocial inclinations, Dr. Márquez and Dr. Moita sought to answer a question. If given the opportunity, would a rat give food to another rat, with no cost or benefit to itself?

To find out, the researchers created a double T-maze with two rats inside. One rat was assigned to be the “helper” and the other the “partner.” The helper had to decide whether or not to help the partner get food.

By tapping the "nose port" on one door, the helper would get a food pellet for itself. By tapping a port on another door, a pellet would be dispensed to both the helper and the partner. Automation allowed the researchers to ensure findings with minimal human interference.

The researchers found that, 70 percent of the time, the helper would tap the second door, dispensing food to both rats. Only one out of the 15 rats studied would consistently make selfish choices, said Márquez.

Altruism is a sub-category of prosocial behavior, but is distinguishable from it as altruism requires a cost or sacrifice on the part of the altruistic animal. Prosocial behavior comes at no cost to the animal lending aid. While altruistic behavior has been largely studied by scientists, prosocial behavior has not gained as much exposure in the scientific community.

In past experiments, the prosocial inclinations of rats were measured only when the animals were in stressful conditions. For instance, a study published in May found that most rats will tend to act to save another rat from drowning. In this most recent experiment, however, the rats were not placed under stress.

Additionally, the scientists found that a display of food-seeking behavior by the “partner” rat was necessary to drive the “helper” rat to make prosocial decisions. This is consistent with similar findings including in studies with primates conducted in 2007 and 2009.

So why are humans and rats more similar than we thought? “Prosociality is beneficial in many situations, for both humans and rats,” said Moita in a press release.

The findings point to a growing sense that humans inherited – as opposed to invented – morality. If that's true, then moral behavior may be an ancient practice, one possibly carried out by rodents' and humans' common ancestor, which is believed to have lived some 75 million years ago.

“It is possible that the stories we construct about the motives to our social actions could also be explained by biological mechanisms that have evolved to keep a group of individuals cohesive,” says Moita.

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