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Crows found able to reason by “analogy”

Dec. 19, 2014
Courtesy of the University of Iowa
and World Science staff

Crows can rea­son by anal­o­gy, a study has found, show­ing an abil­ity to rec­og­nize how dif­fer­ent pairs of ob­jects have si­m­i­lar rela­t­ion­ships. 

That means crows join hu­mans, apes and mon­keys in show­ing ad­vanced “rela­t­ion­al” think­ing, ac­cord­ing to the re­search. The crows al­so passed their test with­out train­ing, except on a sim­i­lar-but-easier task, the re­search­ers said.

A hooded crow like the one studied in the ex­per­i­ments. (Cour­tesy Lo­mon­osov Mos­cow U.)


The crows’ feat is “phe­nom­e­nal,” said Ed Wasser­man, a Uni­vers­ity of Io­wa psy­chol­o­gist and co-author of a re­port on the find­ings, though “it’s been done be­fore with apes and mon­keys.” Wasser­man added that the crow brain is as “as spe­cial to birds as the brain of an ape is spe­cial to mam­mals.”

In the pa­per, pub­lished by Dec. 18 in the jour­nal Cur­rent Bi­ol­o­gy, Wasser­man and re­search­ers at Lo­m­on­o­sov Mos­cow State Uni­vers­ity describe how they in­i­tially trained two hood­ed crows to win treats by match­ing pic­tures.

Lat­er, they pre­sented the birds with two cups, one emp­ty and one with a treat. Each cup was cov­ered with a card show­ing two pic­tures. The task was to choose the card where the pic­tured ob­jects had the same rela­t­ion­ship as those shown on a third, “sam­ple” card. 

For ex­am­ple, if the sam­ple card dis­played two same-sized squares, the crows might have to choose the card with two same-sized cir­cles, rath­er than two dif­fer­ent-sized cir­cles.

The in­ves­ti­ga­tors said they were sur­prised to find that the crows could cor­rectly per­form this with­out spe­cif­ic train­ing. Their pre­vi­ous game had in­volved ex­actly match­ing pic­tures rath­er than analo­gies.

“Hon­estly, if it was only by bru­te force that the crows showed this learn­ing, then it would have been an im­pres­sive re­sult. But this feat was spon­ta­neous,” Wasser­man said, al­though some back­ground knowl­edge was pre­s­ent.

An­tho­ny Wright, a neuro­bi­ol­o­gist at the Uni­vers­ity of Texas-Houston Med­i­cal School, said the dis­cov­ery is on pa­r with demon­stra­t­ions of tool use by some birds, in­clud­ing crows.

“Ana­log­i­cal rea­soning, match­ing rela­t­ions to rela­t­ions, has been con­sid­ered to be among the more so-called ‘high­er or­der’ ab­stract rea­soning pro­cess­es,” he said. “For dec­ades such rea­soning has been thought to be lim­it­ed to hu­mans and some great apes. The appa­rent spon­tane­ity of this find­ing makes it all the more re­mark­able.”

Jo­el Fag­ot, di­rec­tor of re­search at the Uni­vers­ity of Aix-Marseille in France, agreed the re­sults shat­ter the no­tion that “soph­ist­icated forms of cog­ni­tion can only be found in our ‘s­mart’ hu­man spe­cies. Ac­cu­mu­lat­ed ev­i­dence sug­gests that an­i­mals can do more than ex­pect­ed.”

Wasser­man con­cedes there will be skep­tics and hopes the ex­pe­ri­ment will be re­peat­ed with more crows as well as oth­er spe­cies. He sus­pects re­search­ers will have more such sur­prises in store for sci­ence. “We have al­ways sold an­i­mals short,” he said. “That hu­man ar­ro­gance still per­me­ates con­tem­po­rary cog­ni­tive sci­ence.”


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Crows can reason by analogy, a study has found, showing an ability to recognize how different pairs of objects have similar relationships. That means crows join humans, apes and monkeys in exhibiting advanced “relational” thinking, according to the research. The crows also passed their test spontaneously—without specific training, although they had been trained on a simpler version of the task, the researchers said. The crows’ feat is “phenomenal,” said Ed Wasserman, a University of Iowa psychologist and co-author of a report on the findings, though “it’s been done before with apes and monkeys.” Wasserman added that the crow brain is as “as special to birds as the brain of an ape is special to mammals.” The paper, by Wasserman along with researchers at Lomonosov Moscow State University in Russia, was published by Dec. 18 in the research journal Current Biology. The experimenters initially trained two hooded crows to win treats by matching pictures to each other. Later, they presented the birds with two cups, one empty and one with a treat. Each cup was covered with a card showing two pictures. The task was to choose the card where the pictured objects had the same relationship as those shown on a third, “sample” card. For example, if the sample card displayed two same-sized squares, the crows might have to choose the card with two same-sized circles, rather than two different-sized circles. The investigators said they were surprised to find that the crows could correctly perform this without specific training. Their previous game had involved exactly matching pictures rather than analogies. “Honestly, if it was only by brute force that the crows showed this learning, then it would have been an impressive result. But this feat was spontaneous,” Wasserman said, although some background knowledge was present. Anthony Wright, a neurobiologist at the University of Texas-Houston Medical School, said the discovery is on par with demonstrations of tool use by some birds, including crows. “Analogical reasoning, matching relations to relations, has been considered to be among the more so-called ‘higher order’ abstract reasoning processes,” he said. “For decades such reasoning has been thought to be limited to humans and some great apes. The apparent spontaneity of this finding makes it all the more remarkable.” Joel Fagot, director of research at the University of Aix-Marseille in France, agrees the results shatter the notion that “sophisticated forms of cognition can only be found in our ‘smart’ human species. Accumulated evidence suggests that animals can do more than expected.” Wasserman concedes there will be skeptics and hopes the experiment will be repeated with more crows as well as other species. He suspects researchers will have more such surprises in store for science. “We have always sold animals short,” he said. “That human arrogance still permeates contemporary cognitive science.”