EMPATHIC RAT: In a new study, rats surprised scientists with altruistic behaviors by busting their friends out of jail and sharing a snack of chocolate chips.
Image: AlexK100, Wikimedia Commons
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The English language is not especially kind to rats. We say we "smell a rat" when something doesn't feel right, refer to stressful competition as the "rat race," and scorn traitors who "rat on" friends. But rats don't deserve their bad rap. According to a new study in the December 9 issue of Science, rats are surprisingly selfless, consistently breaking friends out of cages—even if freeing their buddies means having to share coveted chocolate. It seems that empathy and self-sacrifice have a greater evolutionary legacy than anyone expected.
In 2007 neuroscientist Peggy Mason of the University of Chicago wrote about the neurobiology of empathy for Scientific American. Inbal Ben-Ami Bartal, a new PhD student in integrative neuroscience who worked across the street from Mason in a different lab, saw the article and proposed a collaboration. "Scientific American really brought us together," Mason says.
In the new study, Mason, Bartal and University of Chicago colleague Jean Decety placed pairs of rats in Plexiglass pens. One rat was trapped in a cage in the middle of the pen, whereas the other rat was free to run around. Most free rats circled their imprisoned peer, gnawing at the cage and sticking their paws, noses and whiskers through any openings. After a week of trial and error, 23 of the 30 rats in the experiment learned to open the cage and free their peers by head-butting the cage door or leaning their full weight against the door until it tipped over. (The door could only be opened from the outside.) At first the rats were startled by the noise of the toppling door. Eventually, however, they stopped showing surprise, which suggests that they fully intended to push the door aside. Further, the rodents showed no interest in opening empty cages or in those containing toy rats, indicating that a break out was their genuine goal.
In this first set of experiments, most rats seemed quite willing to help their peers, but Mason wanted to give them a tougher test. She placed rats in a Plexiglass pen with two cages: in one was another rat, in the other was a pile of five milk chocolate chips—a favorite snack of these particular rodents. The unrestricted rats could easily have eaten the chocolate themselves before freeing their peers or been so distracted by the sweets that they would neglect their imprisoned friends. Instead, most of the rats opened both cages and shared in the chocolate chip feast.
"In our lab we called it the 'chocolate versus pal' experiment," Mason says. "The rat could have put his butt in the opening of the cage containing chocolate to block the other guy, but he didn't. They were sharing food with their pals. In rat land, that is big—I was shocked." Mason says that free rats typically took the chocolate out of the cage before eating it and that sometimes the free rats placed the chocolate chips in front of or very near their recently sprung peers, "as if delivering it."
Mason's new study is one of the most recent in a series of experiments changing how scientists think about empathy and altruism in the animal kingdom. At first, most people agreed that true altruism was a uniquely human characteristic requiring an awareness of one's actions as selfless. Now it seems that many animals have evolved instincts to help others, even at a cost to themselves, and that we inherited these same instincts. "The bottom line is that helping an individual in distress is part of our biology," Mason says. "It's not something that develops or doesn't develop because of culture."
In earlier work, McGill University psychologist Jeffrey Mogil and his colleagues showed that mice recognize their peers' pain—what researchers call "emotional contagion"—and spend more time with suffering cage mates. His team also developed a scale to measure pain expressed on the faces of mice.
Mogil was impressed with Mason's study, but had some questions about the findings. "This is surprising because it's not clear what the motivation for the prosocial behavior is, although the prosocial behavior is clearly there," says Mogil. Both Mogil and Mason point out that because trapped rats squeak out alarm calls now and then, which stress out any fellows that hear them, the rats opening the doors might be trying to silence their peers. Mason thinks the alarm calls aren't frequent enough to motivate the rats, but Mogil is not so sure.
In future research, Mason wants to investigate why some male rats never learned to break open their friends' cages. All six female rats in the first set of experiments figured out how to liberate their peers, but only 17 out of 24 male rats obliged. Mason's best guess is that some rats are paralyzed by alarm calls. Recognizing distress in another is not enough; the rats need to suppress their own panic before they can help. Mason cites research suggesting that females are generally more empathic than males as a possible explanation, but the findings are controversial.
Mogil says he plans to follow up the research as well. For starters, he is interested in whether another common lab animal—the mouse—can learn to spring its peers, too. And he wants to perform the experiments with rodents that are strangers to one another, rather than ones that have been raised together.
In the last couple decades research on empathy and helping behaviors in animals has become more prevalent. "At first people were scared away from this research because they didn't want to be derided as anthropomorphic," Mogil says. "More and more evidence is coming along that all mammals can do this sort of thing. I think fear over the word anthropomorphism is starting to subside."
If anything, recent science shows us that we are not as guilty of endowing animals with uniquely human qualities as we are of failing to understand just how many qualities animals and people share.
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7 Comments
Add CommentMaybe females are naturally more empathetic. Or they are simply lazy. I own two pet rats and often hide their food in a taped cardboard box. The male never tries to get to the food; it's the girl who works her butt off lol.
Reply | Report Abuse | Link to thisIt would have been interesting to know how well the rats knew each other before the experiment. From other rat owners I know that there are ratties that bond very closely, and other who just don't click and barely tolerate each other.
I meant that maybe MALE rats are lazy ;).
Reply | Report Abuse | Link to thisI guess that must mean that those of us humans who claim to know what empathy is, and therefore who must be making a choice when we don't show it in our interactions with others, must be evolutionarily more advanced than rats......? :)
Reply | Report Abuse | Link to thisAnd the same question regarding the related concept altruism. :)
Reply | Report Abuse | Link to thisI remember a study about vampire bats regurgitating blood they had fed upon so that others who failed to acquire food would be able to eat.
Reply | Report Abuse | Link to thisCall it altruism, empathy, or whatever, I think this is just a case of a species doing what it has to to survive. Survival of the species. In evolutionary terms, it guarantees the maximum amount of genetic difference in a species while attempting to ensure future generations. The first instinct may be self-preservation, but somewhere there is another instinct that acts as a survival of your species and goes far beyond offspring.
Very interesting re the vampire bats. So, again the same question seems to apply. Does the capacity to be able to override by choice this "other instinct" (which instinct helps to ensure species survival at the expense potentially of individual survival) represent "advancement" in terms of evolution? ;) One can envision instances in which it would seem to be so--instances where such "self-sacrifice" would provide no benefit for either species or individual survival, and having the capacity to evaluate the pros and cons of the sacrifice would therefore have species survival value. However, if the capacity to choose is taken to the extreme, one can see where it could turn into "every individual for him/herself," which would seem to be a total disaster for the survival of a social organism such as humans.
Reply | Report Abuse | Link to thisI feel that unselfishness in the animal kingdom is closely related to motherhood. Mothers of all species must be unselfish to care for their young, and in turn, it builds a bond with the young animals who in turn share respect and unselfishness to their mother later on in life.
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