大腦如何辨美丑 中英互譯

It’s1878.SirFrancisGaltongivesaremarkabletalk.He’sspeakingtotheanthropologicinstituteofGreatBritainandIreland.Knownforhispioneeringworkinhumanintelligence,Galtonisabrilliantpolymath.He’sanexplorer,ananthropologist,asociologist,apsychologistandastatistician.He’salsoaeugenist.Inthistalk,hepresentsanewtechniquebywhichhecancombinephotographsandproducecompositeportraits.Thistechniquecouldbeusedtocharacterizedifferenttypesofpeople.

Galtonthinksthatifhecombinesphotographsofviolentcriminals,hewilldiscoverthefaceofcriminality.Buttohissurprise,thecompositeportraitthatheproducesisbeautiful.

Galton’ssurprisingfindingraisesdeepquestions:

Whatisbeauty?

Whydocertainconfigurationsoflineandcolorandformexciteusso?Formostofhumanhistory,thesequestionshavebeenapproachedusinglogicandspeculation.Butinthelastfewdecades,scientistshaveaddressedthequestionofbeautyusingideasfromevolutionarypsychologyandtoolsofneuroscience.We’rebeginningtoglimpse

thewhyandthehowofbeauty,atleastintermsofwhatitmeansforthehumanfaceandform.Andintheprocess,we’restumblinguponsomesurprises.

Whenitcomestoseeingbeautyineachother,whilethisdecisioniscertainlysubjectivefortheindividual,it’ssculptedbyfactorsthatcontributetothesurvivalofthegroup.Manyexperimentshaveshownthat

afewbasicparameterscontributetowhatmakesafaceattractive.

Theseinclude

averaging,symmetryandtheeffectsofhormones.

Let’stakeeachoneoftheseinturn.

Galton’sfindingthat

compositeoraveragefacesaretypicallymoreattractivethaneachindividualfacethatcontributestotheaverage

hasbeenreplicatedmanytimes.Thislaboratoryfindingfitswithmanypeople’sintuitions.Averagefacesrepresentthecentraltendenciesofagroup.Peoplewithmixedfeaturesrepresentdifferentpopulations,andpresumablyharborgreatergeneticdiversityandadaptabilitytotheenvironment.Manypeoplefindmixed-raceindividualsattractiveandinbredfamilieslessso.

Thesecondfactorthatcontributestobeautyissymmetry.

Peoplegenerallyfindsymmetricfacesmoreattractivethanasymmetricones.Developmentalabnormalitiesareoftenassociatedwithasymmetries.Andinplants,animalsandhumans,asymmetriesoftenarisefromparasiticinfections.Symmetry,itturnsout,isalsoanindicatorofhealth.Inthe1930s,amannamedMaksymilianFaktorowiczrecognizedtheimportanceofsymmetryforbeautywhenhedesignedthebeautymicrometer.Withthisdevice,hecouldmeasureminorasymmetricflawswhichhecouldthenmakeupforwithproductshesoldfromhiscompany,namedbrilliantlyafterhimself,MaxFactor,which,asyouknow,isoneoftheworld’smostfamousbrandsfor“makeup.”

Thethirdfactorthatcontributestofacialattractivenessistheeffectofhormones.

Andhere,Ineedtoapologizeforconfiningmycommentstoheterosexualnorms.Butestrogenandtestosteroneplayimportantrolesinshapingfeaturesthatwefindattractive.Estrogenproducesfeaturesthatsignalfertility.Mentypicallyfindwomenattractivewhohaveelementsofbothyouthandmaturity.Afacethat’stoobaby–likemightmeanthatthegirlisnotyetfertile,somenfindwomenattractivewhohavelargeeyes,fulllipsandnarrowchinsasindicatorsofyouth,andhighcheekbonesasanindicatorofmaturity.

Testosteroneproducesfeaturesthatweregardastypicallymasculine.Theseincludeheavierbrows,thinnercheeksandbigger,squared-offjaws.Buthere’safascinatingirony.Inmanyspecies,ifanything,testosteronesuppressestheimmunesystem.Sotheideathattestosterone-infusedfeaturesareafitnessindicatordoesn’treallymakeawholelotofsense.Here,thelogicisturnedonitshead.Insteadofafitnessindicator,scientistsinvokeahandicapprinciple.

Themostcommonlycitedexampleofahandicapisthepeacock’stail.Thisbeautifulbutcumbersometaildoesn’texactlyhelpthepeacockavoidpredatorsandapproachpeahens.Whyshouldsuchanextravagantappendageevolve?EvenCharlesDarwin,inan1860lettertoAsaGraywrotethatthesightofthepeacock’stailmadehimphysicallyill.Hecouldn’texplainitwithhistheoryofnaturalselection,andoutofthisfrustration,hedevelopedthetheoryofsexualselection.

Onthisaccount,thedisplayofthepeacock’stailisaboutsexualenticement,andthisenticementmeansit’smorelikelythepeacockwillmateandhaveoffspring.Now,themoderntwistonthisdisplayargumentisthatthepeacockisalsoadvertisingitshealthtothepeahen.Onlyespeciallyfitorganismscanaffordtodivertresourcestomaintainingsuchanextravagantappendage.Onlyespeciallyfitmencanaffordthepricethattestosteroneleviesontheirimmunesystem.Andbyanalogy,thinkofthefactthatonlyveryrichmencanaffordtopaymorethan$10,000forawatchasadisplayoftheirfinancialfitness.

Now,manypeoplehearthesekindsofevolutionaryclaimsandthinktheymeanthatwesomehowareunconsciouslyseekingmateswhoarehealthy.AndIthinkthisideaisprobablynotright.Teenagersandyoungadultsarenotexactlyknownformakingdecisionsthatarepredicatedonhealthconcerns.Buttheydon’thavetobe,andletmeexplainwhy.

Imagineapopulationinwhichpeoplehavethreedifferentkindsofpreferences:forgreen,fororangeandforred.Fromtheirpointofview,thesepreferenceshavenothingtodowithhealth;theyjustlikewhattheylike.Butifitwerealsothecasethatthesepreferencesareassociatedwiththedifferentlikelihoodofproducingoffspring—let’ssayinaratioof3:2:1—theninthefirstgeneration,therewouldbe3greensto2orangesto1red,andineachsubsequentgeneration,theproportionofgreensincrease,sothatin10generations,98percentofthispopulationhasagreenpreference.Now,ascientistcominginandsamplingthispopulationdiscoversthatgreenpreferencesareuniversal.Sothepointaboutthislittleabstractexampleisthatwhilepreferencesforspecificphysicalfeaturescanbearbitraryfortheindividual,ifthosefeaturesareheritableandtheyareassociatedwithareproductiveadvantage,overtime,theybecomeuniversalforthegroup.

Sowhathappensinthebrainwhenweseebeautifulpeople?Attractivefacesactivatepartsofourvisualcortexinthebackofthebrain,anareacalledthefusiformgyrus,thatisespeciallytunedtoprocessingfaces,andanadjacentareacalledthelateraloccipitalcomplex,thatisespeciallyattunedtoprocessingobjects.Inaddition,attractivefacesactivatepartsofourrewardandpleasurecentersinthefrontanddeepinthebrain,andtheseincludeareasthathavecomplicatednames,liketheventralstriatum,theorbitofrontalcortexandtheventromedialprefrontalcortex.Ourvisualbrainthatistunedtoprocessingfacesinteractswithourpleasurecenterstounderpintheexperienceofbeauty.

Amazingly,whileweallengagewithbeauty,withoutourknowledge,beautyalsoengagesus.Ourbrainsrespondtoattractivefacesevenwhenwe’renotthinkingaboutbeauty.Weconductedanexperimentinwhichpeoplesawaseriesoffaces,andinonecondition,theyhadtodecideifapairoffaceswerethesameoradifferentperson.Eveninthiscondition,attractivefacesdroveneuralactivityrobustlyintheirvisualcortex,despitethefactthattheywerethinkingaboutaperson’sidentityandnottheirbeauty.Anothergroupsimilarlyfoundautomaticresponsestobeautywithinourpleasurecenters.Takentogether,thesestudiessuggestthatourbrainautomaticallyrespondstobeautybylinkingvisionandpleasure.Thesebeautydetectors,itseems,pingeverytimeweseebeauty,regardlessofwhateverelsewemightbethinking.

Wealsohavea“beautyisgood”stereotypeembeddedinthebrain.Withintheorbitofrontalcortex,there’soverlappingneuralactivityinresponsetobeautyandtogoodness,andthishappensevenwhenpeoplearen’texplicitlythinkingaboutbeautyorgoodness.Ourbrainsseemtoreflexivelyassociatebeautyandgood.Andthisreflexiveassociationmaybethebiologictriggerforthemanysocialeffectsofbeauty.Attractivepeoplereceiveallkindsofadvantagesinlife.They’reregardedasmoreintelligent,moretrustworthy,they’regivenhigherpayandlesserpunishments,evenwhensuchjudgmentsarenotwarranted.

Thesekindsofobservationsrevealbeauty’suglyside.Inmylab,werecentlyfoundthatpeoplewithminorfacialanomaliesanddisfigurementsareregardedaslessgood,lesskind,lessintelligent,lesscompetentandlesshardworking.Unfortunately,wealsohavea“disfiguredisbad”stereotype.Thisstereotypeisprobablyexploitedandmagnifiedbyimagesinpopularmedia,inwhichfacialdisfigurementisoftenusedasashorthandtodepictsomeoneofvillainouscharacter.Weneedtounderstandthesekindsofimplicitbiasesifwearetoovercomethemandaimforasocietyinwhichwetreatpeoplefairly,basedontheir