Hassociallivingshrunkourbrains?Ourbrainshaveshrunkinthepast20,000years.InTheDomesticatedBrain,BruceHoodarguesthatit'saresultoflivingtogetherinsocietiesTWENTYthousandyearsago,theaveragehumanbrainwas10percentlargerthanitistoday.Somepeople,suchasDavidGeary,apsychologistattheUniversityofMissouriinColumbia,claimthatthedipincranialcapacitymarksourdwindlingintelligence.Others,likeJohnHawks,ananthropologistattheUniversityofWisconsin-Madison,attributeittoimprovedbrainefficiency.ButforBruceHood,theauthorofTheDomesticatedBrainandapsychologistattheUniversityofBristol,UK,theshrinkageisbestexplainedbychangesinsociety."Wehavebeenself-domesticatingthroughtheinventionofcultureandpracticesthatensurethatwecanlivetogether,"hewrites.Ourbrains,hebelieves,aregettingdownsizedbydomesticity.Domesticationtendstohavethateffect.AccordingtoHood,everyspeciesthathasbeendomesticatedbyhumanshaslostbraincapacityasaresult.Bredforpassivity,theirtestosteronedecreases,reducingthesizeofallorgans.Dogsareagoodexampleandtheeffectontheirbehaviouristelling:wherewolveswilltrytosolveaproblemthroughcunning,dogsareadeptatsolicitinghelpfromtheirmasters.Drawingonhisresearchindevelopmentalpsychology,Hoodoftenenlistsparallelsbetweendogsandchildrentosupportthenotionofhumandomestication.Likedogs,kidsarehighlyskilledatenlistingassistance.Eveninfantshavetheknack,gettingparentstofetchanout-of-reachobjectwithaglance.Alsolikedogs,theyaregreatreadersofsocialcues:onlydogsandhumansknowtofollowapointedfingertoanobject.Ofcourse,humancultureismoresophisticatedthanthedomesticationofdogs,andHoodishighlyattentivetodifferencesbetweenhumansandothercreatures.Imitationisoneinterestingareaofdistinction.Chimpsandpre-schoolchildrenbothmimictheactionsofothersinordertolearnanewskill.Butachimpwillimitateonlythemotionsnecessarytoachievethegoal,whereasachildalsomimicsstepsclearlyunrelatedtothetask."Whywouldchildrenover-imitateapointlessaction?"asksHood.Becausetheyaremoreinterestedinfittinginthaninlearninghowbesttosolvethetask,hesays.Hoodargue...
