耶鲁大学公开课

IntroductiontoPsychology:Lecture13TranscriptMarch7,2007<<backProfessorPaulBloom:Whatwe'vebeentalkingaboutsofarinthecoursearehumanuniversals,whateverybodyshares.So,we'vebeentalkingaboutlanguage,aboutrationality,aboutperception,abouttheemotions,aboutuniversalsofdevelopment,andwe'vebeentalkingaboutwhatpeopleshare.Buthonestly,whatalotofusareveryinterestediniswhywe'redifferentandthenatureofthesedifferencesandtheexplanationforthem.Andthat'swhatwe'llturntotoday.

Sofirst,we'lldiscusshowarepeopledifferent,differenttheoriesaboutwhatmakesyoudifferentinapsychologicalwayfromthepersonsittingnexttoyou,andthenwe'llreviewdifferenttheoriesaboutwhypeoplearedifferent.Andthisistheclasswhichisgoingtobotherthemostpeople.It'snotdualism.It'snotevolution.It'sthisbecausethescientificfindingsonhumanpsychologicaldifferencesare,tomanyofus,shockingandunbelievable.AndIwilljusttrytopersuadeyoutotakethemseriously.

Okay.So,howarepeopledifferent?Well,there'sallsortsofways.Yoursexualidentity--Itisatthecoreofyourbeingforalmostallofuswhetheryou'remaleorfemale.Howwerefertoyouinlanguage,whatpronounweuse,isindexedonhowwe--onyour--onhow--whetheryou'remaleorfemaleandrelatedtothatthoughimperfectlyisyoursexualorientation,whoyou'reattractedto.Thequestionofwhysomeofusthinkofourselvesasmalesandothersasfemales,andthequestionofwhysomeofuswouldideallywanttohavesexwithmales,otherswithfemales,otherswithboth,andthenafewotherswhohavehardertodefinedesires,issuchagoodquestionthatwe'regoingtotalkaboutitafterspringbreakwhileallthesexualdesirehasbeenspentandyoucouldfocuson[laughter]onascientificdiscussionofthis--notthatIrecommendyoudothatonspringbreak.

Howhappyareyou?Thisisalsosuchagoodtopicit'sgoingtogetitsownclass.Theverylastclassofthesemesterisdevotedtohappinessandthequestionofwhatmakespeoplehappy,whatmakespeopleunhappy,andwhatmakespeopledifferintheirhappiness.IfIaskedyoutorankhowhappyyouarefromascaleof1to10,thenumberswoulddifferacrossthisroom.Andthere'sdifferenttheoriesastowhy.Yoursuccessandfailureinlife--Thisissomewhatinterestingbecauseyoucouldstudythisinmoreorlessobjectiveways.Wedonthavetoaskpeople.Wecouldlookatyourrelationships,howtheybegin,howtheyend,yourjobsatisfaction.Wecouldlookatyourcriminalrecords.Someofyouaregoingtoseetime.Mostwillnot.Someofyouwillgetintolittletroublesallthroughyourlife.Someofyoualreadyhaveseentheinsideofapolicestation,possiblyalineup.Otherscouldn'tgonearsuchathing.Whatdeterminesthat?

Andattherootofallhumandifferencesaretwomainfactors.Andso,Iwanttotalkaboutthetwomaininterestingfactors.Oneispersonality.Theotherisintelligence.Andthisiswhat--ThesearethedifferencesI'lltalkabouttodayfirstfromthestandpointofhowdowecharacterizethem,howdoweexplainthem,andthenfromthestandpointofwhythesedifferencesexistinthefirstplace.

Onewaytocharacterizepersonalityisintermsofpeople'sstylewithdealingwith--indealingwiththeworldandparticularlytheirstylewithdealing--indealingwithotherpeople.So,youtakeasimplecharacteryouknowofandyoucouldtalkaboutthatperson'spersonality.Youcouldtalkaboutitintermsofbeingimpulsive,irresponsible,sometimeslazy,good-hearted.Youcouldcomparethatperson'spersonalitywithotherpeople'spersonalitiessuchasmycolleaguewhogaveatalklastclass.He'swonderful.He'sresponsibleandreliableandverykind[laughter]anddifferentfromHomer.Andso,thisdifferenceisadifferenceinpersonality.

Now,whenwetalkaboutpersonalitywe'retalkingaboutsomethingelseaswell.We'retalkingaboutastabletraitacrosssituationsandtime.So,ifallofasuddenthepersonnexttoyoukindofsmacksyouinthehead,youmightbeangrybutwewouldn'tcallthat"personality"becausethat'ssomethingthat'saresultofasituation.We'dallfeelthatwayinthatsituation.It's"personality"ifyouwalkaroundallthetimeangry.That'dbeastabletrait.That'dbesomethingyoucarryaroundwithyouandthat'swhatwemeanbypersonality.

Now,howdowescientificallycharacterizedifferencesinpersonality?Andit'sadeepquestion.There'sbeenalotofattemptstodoso.Anyassessmenthas--Anygoodassessmenthastosatisfytwoconditions.Andthesearetermswhicharegoingtoshowupalloverpsychologicalresearchbutit'sparticularlyrelevantforthissortofmeasure.Oneis"reliability."Reliabilitymeansthereisnotmeasurementerror.Andonecrudewaytothinkaboutreliabilityis,atestisreliableifyoutestthesamepersonatdifferenttimesandyougetthesameresult.MybathroomscaleisreliableifwheneverIstandonit,itgivesmemoreorlessthesamenumber.It'snotreliableifit'soffbytenpoundsinthecourseofaday.Similarly,ifIgiveyouapersonalitytestnowanditsaysthatyou,reanxiousanddefensive,well--andthengiveittoyoutomorrowanditsaysyou'recalmandopenminded,it'snotareliabletest.So,reliableissomethingyoucouldtrustovertime.

"Validity"issomethingdifferent.Validityisthatyourtestmeasureswhatit'ssupposedtomeasure.So,validitymeansit'ssortofagoodtest.Forgetabouthowreliableitis.Doesittapwhatyou'reinterestedin?So,forexample,supposeIdetermineyourintelligencebythedateofyourbirth.IfigureoutwhatdayyouwerebornandIhaveatheorythat,fromthat,predictshowsmartyouare.That'smyintelligencetest,thedateofyourbirth.MaybepeopleborninJanuaryarethedumbest,peopleborninDecemberarethesmartest.Isthat--IwasbornonChristmasEve.[laughter]Isthatareliabletest?Yes,it'sawonderfullyreliabletest.I'lltestyoutoday;I'lltestyoutomorrow;I'lltestyounextyear;I'lltestyouthedayyoudie;I'llgetthesameIQscore.Isitavalidtest?It'sajoke.It'sabsolutelynotavalidtest.Ithasnothingtodowithintelligence.Butyounoticedthesearetwodifferentthings.Somethingcanbereliablebutnotvalidandsomethingcanbevalidandnotreliable.

Now,therearenoshortageofpersonalitytests.Youcouldgetthemallovertheplaceincludingontheweb.So,Itookonerecently.Itook"whichsuperheroareyou?"[laughter]Andit'saseriesofquestionsdeterminingwhatsuperheroyouare.Youcouldtakethisyourselfifyouwantto.Thesamewebpage,bytheway,offersyouatestinwhetheryou're"hot"ornot.We'lldiscussthatlater.AndwhenIdidthis[laughter]ittoldmeIwasBatman[laughter]and"youaredark,lovegadgets,andhavevowedtohelptheinnocentnotsufferthepainyouhaveendured."Now,thehonest--[laughter]Now,tobehonestthough,it'sneitherreliablenorvalid.WhenIfirstdidthetestIcameupas"TheIncredibleHulk."Ithenchangedmyanswersabitandwas"WonderWoman."[laughter]Andfinally,outoffrustration,IcarefullytailoredmyanswerssoIwouldbeBatman.ButthefactthatIcandothat,well,raisesquestionsaboutboththereliabilityofthismeasureanditsvalidity.

Hereisanexample金火arealworldexample.Thisis,inblackandwhiteform,aversionoftheRorschachtest,theRorschachinkblottest.HowmanypeoplehaveheardoftheRorschachtest?Okay.Isthereanybodyherewhohasactually,inanysortofsituation,takenaRorschachtest?Somepeoplescatteredintheroomhavetakenthem.Itwasoriginallyusedonlyforpsychiatriccasesbutthenbecameextremelycommon.AbouteightypercentofclinicalpsychologistsclaimtouseitandmostgraduateprogramsintheAmericanPsychologicalAssociationwhoareaccreditedteachit.Catholicseminariesuseitforpeoplewhowanttojointheseminary.

ItwasinventedbyaguynamedHermanRorschach.Hedevotedhisentirelifetotheinkblottest.Hisnicknamewhenhewasateenage嗽❷Iamnotkiddingyou致❷was"Inkblot."[laughter]Andtheideaisbylookingattheseinkblotsandthenseeingwhatsomebodysaysyougetgreatinsightsintothenatureoftheirpersonality,intowhattheyare.Anybodywanttotryit?Comeon.Yes.Whatdoyousee?

Student:Iseetwopeopleholdinghandspressedtogether.

ProfessorPaulBloom:Twopeopleholdinghandspressedtogether.Verygood.Anybodyhaveadifferentreading?Yes,inback.Yes.Yes.

Student:Dancingbears.

ProfessorPaulBloom:Dancingbears.Okay.Good.[laughter]Good.Okay.Igottowriteyournamedown--[laughs][laughter]reportyoutohealth-No.Dancingbears,verygood.Anybodyelse?Oneother.Yes.

Student:Amaninaskimask.

ProfessorPaulBloom:Amaninaskimask.Well,itturnsoutthattherearerightanswersandwronganswerstotheRorschachtest.Accordingtothetest,andthisisfromarealRorschachtest,"itisimportanttoseetheblotastwohumanfigures,usuallyfemalesorclowns."Goodworkoverthere."Ifyoudon't,it'sseenasasignyouhaveproblemsrelatingtopeople."[laughter]Ifyouwanttogofor"acaveentrance"or"butterfly"or"vagina,"that'salsookay.[laughter]Now,theRorschachtestistranscendentlyuseless.Ithasbeenstudiedandexploredanditisasuselessasthrowingdice.Itisasuselessastealeaves.Nonetheless,peopleloveitandit'susedallovertheplace.Itisusedforexampleinchildcustodycases.Ifyouhavebrokenupwithyourpartnerandyouguysarequarrelingoverwhogetstokeepthekids,youmightfindyourselfinashrink'sofficelookingatthis.Andinfact,thisiswhytheyendupontheweb.Thereareservices.Therearepeoplewhohavebeenkindenoughtoputonthewebtheseinkblots,includingtherightanswerstothem.Buttheyareworthlessaspsychologicalmeasures.

Canwedobetter?Well,weprobablycan.GordonAllportdidastudywherehewentthroughthedictionaryandtookallofthetraitsthathebelievedtoberelatedtopersonalityandhegoteighteenthousandofthem.Butwhatwasinterestingwastheyweren'tnecessarilyindependenttraits.So,thetraitslike"friendly,sociable,welcoming,warm-hearted"seemedtoalltapthesamething.So,Cattellandmanyotherstriedtonarrowitdown,triedtoaskthequestion,"Inhowmanywaysarepeople'spersonalitiesdifferentfromoneanother?"Howmanyparametersofdifferencedoyouneed?HowmanynumberscanIgiveyouthatwouldnarrowyouinandsaywhatpersonalityyouare?

OneapproachwasfromEysenck,whoclaimedtherewerejusttwo.Youcouldbesomewhereonthescaleofintroverted-extroverted,andsomewhereonthescaleofneuroticandstable.Andsincethere'sbasicallytwotypesoftraitswithtwosettingsforeach,therearebasicallyfourtypesofpeople.Lateronheaddedanothertraitwhichhedescribedas"psychoticismversusnon-psychoticism"thatcrudelymeantwhetheryou'reaggressiveorempathetic.Andthenyouhavethreetraitswithtwosettingseachgivingyoueighttypesofpeople.LateronCattelldroppeditdownintosixteenfactors.So,thesesixteenpersonalityfactorsaresixteenwayspeoplewoulddiffer.Andso,ifIaskedyoutodescribeyourroommatealongthesesixteendimensions,youshouldbeabletodoso.

totheconclusionthattwoorthreeis

Morerecently,peoplehavecometoofew,butsixteenmightbetoomany.Andthere'sapsychologicalconsensusonwhat'sbeenknownas"TheBigFive."And"TheBigFive"personalityfactorsarethese,andwhatthismeansiswhenwetalkabouteachotheranduseadjectives,theclaimiswecoulddosointhousandsofdifferentways,butdeepdownwe'retalkingaboutoneofthesefivedimensions.Thismeansthatwhenapsychologicaltestmeasuressomethingaboutsomebody,abouttheirpersonality,ifit'sagoodtestit'smeasuringoneofthesefivethings.Anditmeansthat,aspeopleinteractingwithoneanotherintheworld,thesearethefivethingsthatwe'reinterestedin.So,oneofthemis"neuroticversusstable."Issomebodysortofnuttyandworryingoraretheycalm?"Extrovertversusintrovert.""Opentoexperienceversusclosedtoexperience.""Agreeable,"whichiscourteous,friendlyversusnonagreeable,rude,selfish.And"conscientiousversusnotconscientious,"carefulversuscareless,reliableversusundependable.Agoodwaytothinkaboutthesethingsisintermsoftheword"ocean,"o-c-e-a-n.Thefirstlettercapturesopenness,conscientiousness,extroversion,agreeableness,andneuroticism.Andtheclaimisthosearethefour--thefivefundamentalwaysinwhichpeopledifferfromoneanother.

Well,whyshouldwebelievethis?Whyshouldwetakethistheoryseriously?

Well,there'sactuallysomeevidenceforit.Itseemstohavesomereliabilityinthatit'sstableovertime.So,ifyoutestpeopleoveryears--IfItestyourpersonalitynowonthefivetraitsandtestyoufiveyearsfromnow,itwillnothavechangedmuch.Andonceyoupasstheageofthirty,it'sverystableindeed.IfyouthinkaboutyourparentsandthengiveMomandDadamentaltestonwheretheystandoneachofthefivetraits,tenyearsfromnowMomandDadwillstillbethere.Italsoseemstogetagreementacrossmultipleobservers.So,ifIaskforeachoftheirfivetraits--IfIaskyourroommatewhatheorshethinksofyou,thenIaskyourprofessorwhatheorshethinksofyouandyourmomwhatheor--whatshethinksofyou,[laughter]howwould--backtogender--Howwouldtheymatchup?Theytendtooverlapalot.Youwalkaroundandyouleave--andyourpersonalityleavesatrailinthemindsofpeoplearoundyou.Andthistrailischaracterizedintermsofthesefivedimensions.

Finally,itseemstobe--predictreal-worldbehavior.Ifthisdidn'thaveanythingtodowiththerealworld,youwouldn'tbeveryhappycallingitvalid,youwouldn'ttakeitseriouslyasatest,butitdoes.So,conscientiousness--howyouscoreonaconscientiousscale,relatestohowfaithfulyouaretoyourspouse.Howopenness--openyouareonapsychologicalpersonalitytestrelatestohowlikelyyouaretochangeyourjob."Extroverts"lookpeopleintheeyemoreandhavemoresexualpartnersbecausethey'reextroverts.So,thesearerealscales.The"Batman,Hulk,WonderWoman"doesn'tcorrespondtoanythingintherealworld,butwhereyoustandoneachofthesefivedimensionsdoesseemtocaptureit.

Asanexampleoftheagreement,bytheway,somebodydidastudyofseveralofthecharactersonthetelevisionshow"TheSimpsons"becausetheywantedtofindcharacterswhicheverybodyknew.AndtheyhadthirteensubjectsjudgetheseSimpsoncharactersoneachofthefivedimensions.Theseis"openness,neuroticism,conscientiousness,andextroversion"andtheyfoundconsiderableagreement.Andthisisn'tactually--WhatI'vecoveredup[ontheslide]isthe"agreeableness."So,forthoseofyouwhohaveneverseenthetelevisionshow,thisisallgoingtobeconfusing,butthoseofyouwhohave,canyouguesswhichcharacterswouldbeparticularlyagreeable?Anybodyguess.Yeah.

Student:FlandersProfessorPaulBloom:Flanders.Youareright.ThemostagreeablepeopleareFlandersandMarge.Whowouldnotsoagreeable?

Student:KrustyProfessorPaulBloom:Krustyisactually--Krustyisacomplicatedcase[laughter]butMr.Burns--butalso--Whereishe?Oh,he'snot--Nelson,where'sNelson?Anyway,there'sNelson.YougetstrongconsensusthatNedFlandersandMargeSimpsonarehighlyagreeablepeople,6.27and5.46,whileMr.BurnsandNelsonareverylow.Nelson'sthelittlekidthatwhentroublehappenshegoes,"Haha."Andthat'sapsychologicalsignforlowagreeability.[laughter]Okay.That'sallIwanttosayatthispointaboutpersonalityandhowwemeasureitand,again,we'regoingtogetbacktoitlaterwhenwetalkaboutdifferencesinpersonality.Now,Iwanttodealwiththesecondbigdifference.Thesecondbigdifferenceisintelligence.Now,howdoyoudefineintelligence?There'snoeasydefinition.Likepersonality,it'skindofdifficulttogetyourfingersonwhatwe'retalkingabouthere.Inonesurveytheyasked1,000expertstodefineintelligence.Andsomeanswersshowedupoverandoveragain.So,justabouteverybodysaidintelligenceinvolvesabstractreasoning,problemsolving,andthecapacitytoacquireknowledge.That'satthecoreofbeingsmart.Otherpeoplementionedthingslikememory,mentalspeed,language,math,mentalspeedagain,knowledge,andcreativityalsoashallmarksforintelligence.Andagain,itmightbedifficulttodefineitbutyouhaveagutfeelingaboutwhatitis.

So,youknowHomerisactually--andthisispartoftheshow--isactuallyoflimitedintelligence.Mycolleagueisofveryhighintelligence,awonderfulfellow,[laughter]buthe'sprobablynotassmartasthatguy[pointingtoapictureofEinstein]whoisreally,reallysmart.Andthisguy,RalphWiggum,isparticularlystupid.[laughter]Andsoyouhavearange.Andit'simportanttofigureouthowtocharacterizeit;thisiswhatresearchdoes,butthere'sagutfeelingthattherearesomepeoplewhoaresmartandotherpeoplewhoareverysmartandsomepeoplewhoaredumbandotherswhoareverydumb.Whatyouwanttodo,fromascientificstandpoint,ischaracterizethisinamorerobustandinterestingfashion.Andthetextbookhasanicereviewofthehistoryofattemptstodefineandmeasureintelligence,butthereisacoupleofideasIwanttofocuson.

OneisanideadevelopedbySpearman,whichisthere'stwotypesofintelligence.Thereis"G"andthereis"S.""S"isyourabilityonspecifictests.So,ifthereistenteststhatyou'regivenaspartofanIQtest,tensubtests,you'llgetadifferentscoreoneachofthesubtests.There'llbeamathtestandareadingtestandaspatialtestandyou'llgetdifferentscores."G"referstoageneralintelligence.Andthegeneralintelligenceissomethingyoubringtoeachofthetestsincommon.So,thisisdiagrammedhere.Youhavethesesixtests.Foreachofthemthereisan"S"andthenabovethatthereisa"G."Now,"G"isaveryimportantnotion.Theterm"G"isusedbypsychologistsalotevenincasualconversation.Peoplesay,"So,whatdoyouthinkofhim?""Ithinkheishigh'G.'"Andwhatyoumeanishe'sasmartguy.Whydoyouneed"G?"Well,youwouldn'tneed"G"ifyourperformanceoneachofthesetestshadnothingtodowitheachother.Ifthetestsweregenuinelyseparate,there'dbenogeneralintelligence.Butwhatpeoplefindoverandoveragainisthatwhenitcomestoexplainingpeople'sperformanceonmultipleintellectualtasks,there'stwothingsgoingon.There'showgoodthereis--theyareonthespecifictask,butthenthere'salsoasortofgeneralcorrelationthatpeoplebringtothetasks.

AndIcouldexpressthiswithanathleticanalogy.ImagineImrunningagymandwehaveallofthesedifferentathletictests.So,wehavearunningtest,wehaveabasketballshootingtest,aswimmingtest,fencing,alistoftenofthem.Now,eachofyougothrougheachofthetestsandthenyou'lleachgettenscores.Butwhatwe'lldiscoveristhatthescoresarenotindependentofoneanother.Peoplewhoaregoodatoneathleticthingtendtobegoodatanother.Ifthere'ssomebodywho'sreallygoodatrunningandswimming,oddsarethey'reprobablyprettygoodatclimbing.AndthesamethingholdsforIQ,whichisaboveandbeyondhowgoodpeopleareatspecificthingsthereseemstobeafactorastohowwelltheyareingeneral.Andthisfactorisknownas"G."Now,there's,again,anextensivehistoryofmodernintelligencetestsandwhat'sreallyinterestingisthetestsnow.Whatyouneedtoknowaboutthemoderntests,theWechslertestforbothadultsandchildren,ishowthey'rescored.Thewaytheyarescoredisthat100isaverage.So,it'sjustautomatic.Whatevertheaverageisis100.It'sasifIdidtheMidterm--gradedtheMidterm,computedtheaverage,gaveeverybodywhogottheaverage100,saidyourscoreis100.It'sjusttheaverage.Itworksonthenormalcurveandwhatthismeansisthatitworkssothatthemajority,68%,getbetween85and115ontheirIQtest.Thevastmajority,95%,getbetween70and130.Ifyouare,say,above145IQ,whichIimaginesomepeopleintheroomare,youbelongto0.13%ofthepopulation.That'sthewayIQtestswork.

Now,thisisaboutIQtests.Wecouldnowaskabouttheirreliabilityandtheirvalidity.Whatdotheymean?Well,thishasturnedouttobeamatterofextremedebate.This[slide]justreiterateswhatIjustsaid.AlotofthedebatewasspawnedbythebookbyHerrnsteinandMurrayabout--calledTheBellCurve.AndinTheBellCurvetheseauthorsmadetheargumentthatIQmattersimmenselyforeverydaylifeandthatpeople'sstatusinsocietyMhowrichtheyareandhowsuccessfultheyar敝

followsfromtheirIQasmeasuredinstandardIQtests.Now,thisbookmadealotofclaimsanditsprobablybeforemanyofyou--manyofyourtime,butspawnedhugecontroversy.Andasaresultofthiscontroversysomeinterestingpaperscameout.

OneresponsetotheHerrnsteinandMurraybookwasbytheAmericanPsychologicalAssociation,whichputtogetheragroupoffiftyleadingresearchersinintelligencetowriteareportonwhattheythoughtaboutintelligence--whattheythoughtabout,"DoesIQmatter?HowdoesIQrelatetointelligence?Howdoes--what'sthedifferent--whyarepeopledifferentinintelligence?Whydodifferenthumangroupsdifferinintelligence?"andsoon.Atthesametime,therewasalsoanothergroupofIQresearchers,notquitethesameasthefirstgroup,gottogetherandwroteanotherreport.Andifyou'reinterestedinthis,thelinkstothereportsareonthePowerPointslide.

Well,whatdidtheyconclude?Theconclusionswereslightlydifferentbuthere'sthebroadconsensusbytheexpertsregardingtheimportanceofIQtests.AndtheclaimisIQisstronglyrelatedmoreso--probablymoresothananyothersinglemeasurablehumantraittomanyimportanteducational,occupational,economic,andsocialoutcomes.Insomecases,thecorrelationisverystrongsuchassuccessinschoolandsuccessinmilitarytraining.Inothercases,it'smoderatebutrobustsuchas"socialcompetence."Andinothercasesit'ssmallerbutconsistent,"lawabidingness,"andtheyconcludewhateverIQtestmeasureitisofgreatpracticalandsocialimportance.

So,IQmatters.Moreparticularly,IQmattersfor"socialachievement,"for"prestigiouspositions,"andfor"onthejobperformance"andotherwork-relatedvariables.IfIknowyourIQscore,Iknowsomethingaboutyouthatmatters.It'snotirrelevantjustasifIknowyourscoreonapersonalitytestofTheBigFiveIwouldknowsomethingaboutyouthatactuallywouldtellmesomethinginterestingaboutyouintherealworld.

Ontheotherhand,there'salotofcontroversyaboutwhythisconnectionexists.So,tosomeextent,peoplehaveworriedthattheeffectivenessofIQisaself-fulfillingprophecy.Andhereiswhy.IfsocietytakesIQtestsimportant--seriously,theybecomeimportant.So,it'struethatyourIQisveryrelatedtoyoursuccessingettingintoagoodschoollikeYale.Butthereasonforthis,inlargeextent,isbecausetogettoYaletheygiveyouanIQtest,theSAT.So,thesameforgraduateschool.ThereistheGRE,whichisyetanotherIQtest.So,tosomeextent,it'saself-fulfillingprophecy.Icouldmake--Societycouldchoosetomakehowtallyouareextremelyimportantforeducationalsuccess.TheycouldsaynobodyundersixfeettallgetsintoYale.Andthensomepsychprofessorwouldstandupandsay,"Ofcourse,heightisprofoundlyrelatedtoeducationalaccomplishment,"anditwouldbebecausepeoplemadeitso.

So,tosomeextent,thesocietythatdrawshighlyonIQtestsregardingpromotionandeducationalachievementandmilitarystatusandsoon--it'sjustgoingtofollowthatIQthenbecomesimportant.Atthesametime,however,theroleofIQisprettyclearlynotentirelyasocialconstruction.ThereissomeevidencethatyourIQscorerelatestointelligenceinaninterestingsenseincludingdomainslikementalspeedandmemoryspan.So,yourscoreonanIQtest,forinstance,istosomeextentrelatedtohowfastyoucouldthinkandyourmemoryabilities.

Now,Iwanttoshifttothesecondhalfoftheclassandtalkaboutwhy.So,wetalkedabouttwodifferences,onein"personality",one"intelligence."IwanttotalkaboutwhypeopledifferbutbeforeIdo,dopeoplehaveanyquestions?Yes.

Student:Aboutpersonality--ThismorningItookatest--Thewaythetestwas,theyaskedyou100questionsand[inaudible]ProfessorPaulBloom:It'sagoodquestion.Thequestionisthisyoungmantook--justtookapersonalitytest.HewasacceptedintoSlytherin,whichisaHogwartsreference.I'mhiptothat[laughter]and--butthequestionisagoodone.You'reacleverman,high"G,"andyouwantedtobeinSlytherin.Howdoweknowyoudidn'tworkthetest?You'regoingtogetthesepersonalitytestsallthetimeandthepersonalitytests--You'reapplyingforabusinessandoneofthetestssays"Iliketostealfrommybosses."Well,Idon'tthinkso.No.That'salittleIQtestrightthere.So,thequestionishowdoyouavoidthatproblem?Thetestconstructorshavedonesoincertaincleverways.Forinstance,thereareoftencatchquestionsdesignedtocatchaliar.Someofthesequestionsposeveryunrealisticphenomenasoyoumighthaveaquestionintheresaying"IhaveneverdoneanythingIamashamedof."Now,somepeoplewillsay,"Yes,that'strueofme,"buttheytendtobeliars.Andso,unrealisticquestionstendtocatchliars.

Also,yougetthesamequestionaskedindifferentwaysacrosstheonehundreditemsandtheycouldusethecorrelationstofigurethesethingsout.Again,theproofissortofinthepudding.Thereliabilityandvalidityofatestisdetermined,inpart,byjusthowwellitdoesatpredictingyourfutureperformanceonthetestandyourrealworldperformance.Andatestthatiseasilyfooled--easilytrickedbysmartpeoplewouldn'tsurvivelongasapersonalitytest.So,weknowthetestyougotisaprettygoodtestbecauseitseemstoworkformostpeople.Yes.

Student:[inaudible]ProfessorPaulBloom:It'sagoodquestion.Thequestionwasabout"EmotionalIQ,"whichissomethingI'mactuallygoingtotouchuponalittlebitlaterinthecourse,butpeoplehavetalkedaboutdifferentformsofintelligence.Andemotionalintelligence,socialintelligence,isarguablyacandidateforsuccessacrossdifferentdomains.TheevidenceforitspredictivepowerisnotasstrongasforregularIQtestssoyoumightberight.Itmightturnouttobeamuchbetterpredictorbutone,it'snotclearthatweknowthatyet.PeterSaloveyhasactuallydonesomeveryinterestingresearchonthisandiscontinuingworkalongthoselines.Thesecondthingisemotionalintelligenceisactuallyrelatedtogood,old-fashionedintelligence.Theykindofpulltogetheralot.So,it'snotentirelyseparatebutthat'sagoodpointandI'dliketoreturntoitalittlebitlateroninthecourse.Yes.

Student:[inaudible]ProfessorPaulBloom:Goodquestion.Howdoyoudeterminewhen—whatagoodtestis?Andagain,it'sarealartgoingthroughthedetailsofhowtodothatbutthebroadanswersinvolvereliabilityandvalidity.It'sagoodtestifItestyoutodayandItestyoutomorrowandIgetthesamescore.It'sareallygoodtestifyourscoreonthattestpredictsyourgradesor,ifit'sapersonalitytest,predictshowmanygirlfriendsyouhaveorpredictswhetherpeoplethinkyou'reaniceguy.So,youhavetoseeboththereplicabilityofthetestovertimebutalsoitsrelationshiptorealworldphenomena.Andthat'simportant,again.WhydoweknowtheBatman,WonderWoman,Hulktestisabadone?Well,oneanswerisbecausewhatI--howIscoreonthattestisn'tgoingtotellyouanythingaboutme.It'snotgoingtorelatetomygrades.It'snotgoingtorelatetohowwellI'mliked.HowdoweknowtheSATisuseful?Well,itactuallycorrespondswithotherthingslikegrades.Yes,inback.

Student:[inaudible]ProfessorPaulBloom:Absolutely.Thequestionis--WhenI'mtalkingaboutpersonalityI'mdefiningitintermsofsomethingwhichisstableovertime.Andyourquestion,whichisagoodone,is,"Howdoweknowit'sstableovertime?"Can'titchange?Andtheansweris"yeah."Alotofpersonalitydoeschangeovertime.Apersonalitytestyougivetoaten-year-oldwillrelatebutnotsostronglywiththatindividualwhenhe'sfifty.Ontheotherhand,weknowthatthepsychologicalclaimthatthereexistssuchathingaspersonalityanditisstableovertime.Itssupportedbythefactthatifyou'reanextrovertnowyou'lllikelybeanextroverttwentyyearsfromnow.Notperfectly,soyou'reright.Youcouldchange.Youcouldbecomeanintrovert,youcouldbecomemoreofanextrovert,butwhereveryoustandnowissignificantlyrelatedtowhereyou'llbeinthefuture.Andthatjustifiestalkingaboutitasastabletrait.SamewithIQ.YourIQmightchange.Itmightgoup,itmightgodown,butitwon'tgoupandgodownthatmuchandthisiswhyitmakessensetotalkaboutintelligenceasamoreorlessstabletrait.

Okay.Whyarewedifferent?Well,you'redifferentbecauseoftwothings:Yourgenesandyourenvironment,yournatureandyournurture,yourheredityandyourexperience.Andthisdoesn'tsayanything.Thisisjustdefiningthequestion.Butthequestionoftheroleofgenesandtheroleofenvironmentinexplaininghumandifferencesisaninterestingoneanditcouldbeexploredindifferentways.

ButbeforetalkingaboutitIhavetoclearupacommonmisconception.I'mgoingtotalkabouttheeffectsofgenesandI'mgoingtotalkabouthereditybutIwanttobeclear.Iamtalkingabouttheroleofgenesandalsotheroleofenvironmentinexplaininghumandifferences,notinexplaininghumancharacteristics.So,thedistinctioniswe'reinterestedintheamountofvariationduetogeneticdifferences,nottheproportionofanindividual'straitthat'sduetogenes.

Soforinstance,youcouldpulltheseapart.Thequestionof--Whenweaskwhat'stheroleofgenes,what'stheroleofheredityinhowtallpeopleare,thequestionisnotaskingforyou--whatistheroleofyourgenesindetermininghowtallyouare?It'snotclearthat'sevenasensiblequestion.Thequestionisthere'saheightdifferencebetweenyouandmeandhimandher.Howdoweexplainthatdifference?AndIcouldillustratewhyhereditydoesn'tmeanthesamethingasthecontributionofthegenes.Heightisreasonablyheritable,meaningthedifferencesbetweenpeopleinthepopulationandhowtalltheyareisdueinlargepart,notentirely,butinlargeparttotheirgenes.

Whataboutthenumberoflegspeoplehave?Well,thenumberoflegspeoplehavefromzero,oneortwo,isactuallynotveryheritableatallbecausealmosteverybodyhastwolegsandpeoplewhohavefewerthantwolegstypicallyhavelostoneorbothlegsinanaccident.It'snotduetotheirgenes.So,ofcourse,whetherornotyouhavelegsisaverygeneticmatterbutthedifferencesinnumberoflegsisnotusuallygenetic.Andso,heredityisaclaimaboutdifferences,notaclaimabouttheoriginofanyspecifictrait.

Well,nowwe--Thatswhatheredity,whichisgenetic--Now,wecouldtalkaboutenvironment.Andwecouldbreakupenvironmentintotwosortsofenvironment.Oneissharedenvironment.Andsharedenvironmentistheextenttowhichthedifferencesarecausedbythings--byphenomenathatpeopleraisedinthesamehouseholdshare.Soifone--Supposesomeofyouareneurotic.Andsupposewewanttosaypartofthat'sduetoyourenvironment.Well,supposeyou'reneuroticbecauseyouhavelousyparents.Thatwouldbepart