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Even rats will lend a helping paw: study

Dec. 8, 2011
Courtesy of Science,
Washington State University
and World Science staff

Rats will free dis­tressed cage­mates from a trap, even when there’s no ev­i­dent re­ward for the help—and even when it might cost them a lit­tle food, a study has found.

Sci­en­tists say the phe­nom­e­non is an un­usu­al find­ing of em­pa­thy in an­i­mals oth­er than pri­mates—hu­mans and their ev­o­lu­tion­ary rel­a­tives, the apes and mon­keys.

Em­pa­thy has of­ten been con­sid­ered un­ique to pri­ma­tes, though a re­lat­ed phe­nom­e­non dubbed “e­mo­tional con­ta­gion” has been iden­ti­fied among a wid­er va­ri­e­ty of spe­cies. In that ef­fect, an an­i­mal ex­pe­ri­ences the emo­tions of oth­ers.

Al­though em­pa­thy does over­lap some­what with emo­tion­al con­ta­gion, the dif­fer­ence is that an em­pa­thet­ic an­i­mal can “put it­self in anoth­er’s shoes” while main­tain­ing its own per­spec­tive and emo­tion­al separa­t­ion.

In the stu­dy, In­bal Ben-Ami Bar­tal and col­leagues at the Uni­vers­ity of Chi­ca­go re­ported that af­ter sev­er­al train­ing ses­sions, most rats learn­ed to quickly open a con­tain­er hold­ing a fel­low cage­mate. That they did so showed they rec­og­nized the dis­tress of the oth­er rat, but could stay calm enough to open the cage—show­ing emo­tion­al con­ta­gion was­n’t at work, the in­ves­ti­ga­tors said.

The an­i­mals, they added, did­n’t open con­tain­ers that were emp­ty or that con­tained oth­er ob­jects. But the oft-mal­igned ro­dents did free oth­er rats even when they weren’t al­lowed to so­cial­ize with them af­terwards, which is a well-es­tab­lished re­ward. Fur­ther, when the free rats had ac­cess to a hand­ful of choc­o­late chips, which they could have eat­en by them­selves, they still freed their trapped cage­mates and shared the choc­o­late with them. 

The scientists said more fe­male than male rats be­came door-o­peners, con­sist­ent with sug­ges­tions that fe­males are more em­pa­thet­ic than ma­les. 

The find­ings ap­pear in the Dec. 9 is­sue of the re­search jour­nal Sci­ence.

“Sim­pli­fied mod­els of em­pa­thy, as in mice and rats, of­fer new in­roads for un­der­stand­ing our own social-e­mo­tion­al na­ture and nur­ture,” wrote Wash­ing­ton State Uni­vers­ity neu­ro­sci­ent­ist Jaak Pansepp in an ac­com­pa­nying com­men­tary. “Such knowl­edge may eventually help us pro­mote nur­tu­rant be­hav­iors in hu­mans,” added Pansepp, who was­n’t in­volved with the stu­dy.

“There is no ques­tion that all oth­er an­i­mals have emo­tion­al feel­ings,” he said in a lat­er in­ter­view. “The sci­ence is strong for that. And all our strongest bas­ic emo­tion­al feel­ings come from brain net­works all mam­mals share. Un­for­tu­nate­ly, cur­rently we can’t sci­en­tif­ic­ally com­pare the in­tens­ity or great­ness of feel­ings across spe­cies.”

“How­ever, be­cause we have a great­er ca­pacity to think than most, we can do more with our emo­tions than oth­er an­i­mals. We can write mu­sic. Cre­ate po­et­ry. And be­cause of our high­er men­tal abil­i­ties, we al­so have great­er ca­pa­ci­ties for both em­pa­thy among strangers and cru­el­ty. There are hints that across mod­ern his­to­ry em­pa­thy has been win­ning out over cru­el­ty. But then one looks at the 20th cen­tu­ry and won­ders.”


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Rats will free distressed cagemates from a trap, even when there’s no evident reward for the help—and even when it might cost them a little food, a study has found. Scientists say the phenomenon is an unusual finding of empathy in animals other than primates—humans and their evolutionary relatives, the apes and monkeys. Empathy has often been considered unique to primates, though a related phenomenon dubbed “emotional contagion” has been identified among a wider variety of species. In that effect, an animal experiences the emotions of others. Although empathy does overlap somewhat with emotional contagion, the difference is that an empathetic animal can “put itself in another’s shoes” while maintaining its own perspective and emotional separation. In the study, Inbal Ben-Ami Bartal and colleagues at the University of Chicago reported that after several training sessions, most rats learned to quickly open a container holding a fellow cagemate. That they did so showed they recognized the distress of the other rat, but could stay calm enough to open the cage—showing emotional contagion wasn’t at work, the investigators said. The animals, they added, didn’t open containers that were empty or that contained other objects. But they did free other rats even when they weren’t allowed to socialize with them afterwards, which is a well-established reward. Further, when the free rats had access to a handful of chocolate chips, which they could have eaten by themselves, they still freed their trapped cagemates and shared the chocolate with them. The authors note that a greater portion of female than male rats became door-openers, which is consistent with suggestions that females are more empathetic than males. The findings appear in the Dec. 9 issue of the research journal Science. “Simplified models of empathy, as in mice and rats, offer new inroads for understanding our own social-emotional nature and nurture,” wrote Washington State University neuroscientist Jaak Pansepp in an accompanying commentary. “Such knowledge may eventually help us promote nurturant behaviors in humans,” added Pansepp, who wasn’t involved with the study. “There is no question that all other animals have emotional feelings,” he said in a later interview. “The science is strong for that. And all our strongest basic emotional feelings come from brain networks all mammals share. Unfortunately, currently we can’t scientifically compare the intensity or greatness of feelings across species.” “However, because we have a greater capacity to think than most, we can do more with our emotions than other animals. We can write music. Create poetry. And because of our higher mental abilities, we also have greater capacities for both empathy among strangers and cruelty. There are hints that across modern history empathy has been winning out over cruelty. But then one looks at the 20th century and wonders.”