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Therearetwofactorswhichdetermineanindividual'sintelligence．Thefirstisthesortofbrainheisbornwith．Humanbrainsdifferconsiderably,somebeingmorecapablethanothers．Butnomatterhowgoodabrainhehastobeginwith,anindividualwillhavealoworderofintelli-genceunlesshehasopportunitiestolearn．Sothesecondfactoriswhathappenstotheindividual--thesortofenvironmentinwhichheisbroughtup．Ifanindividualishandicappedenvironmentally,itislikelythathisbrainwillfailtodevelopandhewillneverattainthelevelofintelligenceofwhichheiscapable.
Theimportanceofenvironmentindetermininganindividual'sintelligencecanbedemonstrat-edbythecasehistoryoftheidenticaltwins,PeterandMark．Beingidentical,thetwinshadiden-ticalbrainsatbirth,andtheirgrowthprocesseswerethesame．Whenthetwinswerethreemonthsold,theirparentsdied,andtheywereplacedinseparatefosterhomes．Peterwasraisedbyparentsoflowintelligenceinanisolatedcommunitywithpooreducationalopportunities．Markwasreared
inthehomeofwell-to-doparentswhohadbeentocollege．Hewasreadtoasachild,senttogoodschools,andgiveneveryopportunitytobeStimulatedintellectually．Thisenvironmentaldifferencecontinueduntilthetwinswereintheirlateteens,whentheyweregiventeststomeasuretheirin-telligence．Mark'sI.Q．was125,twenty-fivepointshigherthantheaverageandfullyfortypointshigherthanhisidenticalbrother．Givenequalopportunities,thetwins,havingidenticalbrains,wouldhavetestedatroughlythesamelevel.
Thisselectioncanbestbetitled__________ A．MeasuringYourIntelligence
B．IntelligenceandEnvironment
C．TheCaseofPeterandMark
D．HowtheBrainInfluencesIntelligence
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