Unit-8-Nature-and-Nurture新编大学英语第二版第三册课文翻译

Unit 8 Nature and NurtureTwins, Genes, and EnvironmentHeredity or environment: which is stronger? Th

文档仅供参考，不能作为科学依据，请勿模仿；如有不当之处，请联系网站或本人删除。 Unit8NatureandNurture Twins,Genes,andEnvironment Heredityorenvironment:whichisstronger?Thepotentialswhicha personisbornwithdetermineinsomewaywhathewilldoinlife.Therefore heredityisfate,akindofpredestination.However,genesdonotworkina vacuum;assoonaswebeginconsideringtherolethattheyplayinthe developmentoftheindividual,weseethattherecanbenodevelopment withouttheinteractingenvironment.Nocharacteristiciscausedexclusivelyby eitherenvironmentorgenes. Therelativeeffectsofheredityandenvironmentaremostclearly observableinidenticaltwins.Mostidenticaltwinsareraisedtogetherandare remarkablyalikeinbothappearanceandbehavior.Thesecasesdemonstrate thatindividualswiththesamegenes,whenraisedinthesameenvironment, willrespondtoitinmuchthesameway.Theydonotindicatewhatwould happeniftheseidenticalindividualswereraisedseparately. Anumberofstudieshavebeenmadeofidenticaltwinsraisedapart.The twinswhowerethesubjectsofthesestudieslivedinAmerica,wereraisedin muchthesamephysicalenvironments,andexperiencedmuchthesame nutritionalhistories.Therefore,asonemightexpect,theymaintainedthe closestresemblancetoeachotherinphysicalappearance,height,andweight. Exceptionsoccurredwhenonetwinhaddevelopedarathersevereillnessand theotherhadnot;butonthewholeeveryoneisimpressedbythegreat psychologicalandphysicallikenessesthatexistbetweenidenticaltwins,even thosewhohavebeenseparatedfrominfancy. Inastudyofnineteensetsoftwinswhohadbeenseparatedfrombirth, investigatorsfoundthatinapproximatelytwothirdsofthesetstherewere nomoresignificantdifferencesthanexistedamongunseparatedpairsof twins.Thisstronglysuggeststhepowerofthegenesandthelimitationof theeffectofenvironment.However,itmustberememberedthat,although theidenticaltwinswhowerestudiedlivedindifferentfamiliesfarremoved fromeachother,theenvironmentsinthosefamilieswerenot,onthewhole, substantiallydifferent.Usuallyeveryeffortwouldbemadetoputeachchild inahomewithabackgroundsimilartothatofitsownfamily,andtherefore itshouldnotbesurprisingtofindthatthetwinsdevelopedsimilarly.Butin