Animalthinking.

Foralongtime,scientistsdidn'tstudyanimalthinking.Mostofthemdidn'tbelievethatanimalscouldthink.Theythoughthumansweretheonlythinkinganimals.Nowmorescientistsarestudyingthissubject.Butit'sveryhardtoprovethingsthatnoonecanseeormeasure.Sosomescientistsdecidedtotakealookatbrains.Isbiggerbetter?No.Cowbrainsarebiggerthandogbrains,butthatdoesn'tmakecowssmarterthandogs.Andsquirrelshavesomeofthebiggestbrainsofallfortheirbodysize.Butsquirrelsaren'tevenclosetobeingthesmartestanimalsintheworld.Sothesizeofabrainmaygivesomecluesaboutbrainpower,butitdoesn'tproveanything.Otherscientistsstudythinkingbywatchinghowanimalssolveproblems,whowatchanimalsinthewildorsetupthinkingtestsinalab.Forexample,ascientistmightputsomefoodjustoutofananimal'sreach.Onekindofanimalmaygrabastickanduseittoslidethefoodover.Anotherkindmightnotbeabletofigureoutawaytogetthefood.Somescientiststhinkanimalsthathavelotsofproblemstosolvemustbesmarterthananimalswithsimplelives.Scientistsalsostudycertainkindsofbehaviourforcluesaboutthinking.Theywatchforthreethings:whetheranimalsusetools,howtheyactwitheachother,andhowtheycommunicate.

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1Forthebodysize,dodogshavesmallerbrainsthansquirrels?2Whathavescientistslearntfromtakingalookatthesizeofanimals'brains?3Howdootherscientistsstudyanimalthinking?4Whataresomecertainkindsofbehaviourforcluesaboutthinkingthatscientistsstudy?5Putthesentence"butit'sveryhardtoprovethingsthatnooneseeormeasure."intoChinese.