manyreasons.Thereisnoevidencethatrequiringchildrentomemorizenamesoflettersisthebestintroductiontoreading[R.L.Venezky,"Letternamingandlearningtoread"(theoreticalpaper31,WisconsinResearchandDevelopmentCenterforCognitiveLearning,Madison,WI,1971)].22.Thedevelopmentofpre-wordreadingskillsisreviewedbyE.J.GibsonandH.Levin[ThePsychologyofReading(MITPress,Cambridge,MA,1975),chap.8].23.J.Baron,inHandbookofLearningandCognitiveProcesses:LinguisticFunctionsinCognitiveTheory,W.K.Estes,Ed.(Erlbaum,Hillsdale,NJ,1978),vol.6.24.P.A.Kolers,Am.J.Psychol.79,357(1966).25.B.J.F.Meyer,TheOrganizationofProseandItsEffectsonMemory(North-Holland,Amsterdam,1975).26.D.E.Kieras,J.Verb.Learn.Verb.Behav.17,13(1978);A.M.Lesgold,S.F.Roth,M.E.Curtis,ibid.18,291(1979).27.P.FreebodyandR.C.Anderson,ReadingRes.Q.18,277(1983).28.N.E.SharkeyandD.C.Mitchell,J.Mem.Lang.24,253(1985).29.R.C.AndersonandP.D.Pearson,inHandbookofReadingResearch,P.D.Pearson,Ed.(Longman,NewYork,1984),p.255.30.R.C.SchankandR.P.Abelson,Scripts,Plans,Goals,andUnderstanding:AnInquiryIntoHumanKnowledgeStructures(Erlbaum,Hillsdale,NJ,1977).31.W.F.BrewerandD.A.Dupree,J.Exp.Psychol.Learn.Mem.Cognition9,117(1983).32.G.H.Bower,J.B.Black,T.J.Turner,CognitivePsychol.11,177(1979).33.A.L.Brown,B. 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B.ResnickandP.A.Weaver,Eds.(Erlbaum,Hillsdale,NJ,1979),vol.2;C.DeGoesandM.Martlew,inThePsychologyofWrittenLanguage:DevelopmentalandEducationalPerspectives,M.Martlew,Ed.(Wiley,NewYork,1983).39.D.LaBergeandS.J.Samuels,CognitivePsychol.6,293(1974).40.P.B.GoughandW.E.Tunmer,RemedialSpec.Educ.7,6(1986).41.J.Palmeretal.,J.Mem.Lang.24,59(1985).42.T.G.Sticht,inLanguageComprehensionandtheAcquisitionofKnowledge,R.FreedleandJ.Carroll,Eds.(Wiley,NewYork,1972),p.285.43.G.A.MillerandP.M.Gildea,Sci.Am.257,94(September1987).44.W.E.NagyandP.A.Herman,inTheNatureofVocabularyAcquisition,M.G.McKeownandM.E.Curtis,Eds.(Erlbaum,Hillsdale,NJ,1987).45.W.E.Nagy,R.C.Anderson,P.A.Herman,Am.Educ.Res. J.24,237(1987).46.Theproblemisgeneral:H.A.Simon[inMathematicalThinkingintheSocialSciences,P. F.Lazarsfeld,Ed.(ColumbiaUniv.Press,NewYork, 1954)]developeda"Berlitzmodel"todescribeit.LetthedifficultyofreadingDbeproportionaltothefractionofunfamiliarwords,andassumethatDdecreaseslogarithmicallywithhoursperdayspentreadingh,dD/dt=-aDh;thenif,atanygivenD,readingisfunforatimehandunpleasantafterthat,dh/dt=-b(h-h);thetimepathsofDandhcanbepredictedfromtheirinitialvalues.WhentheinitialvalueofDislargeandhissmallthestudentultimatelybecomesdiscouragedandquits;whenhissufficientlylarge,orDisrelativelylow,thestudentmovestowardskilledreading.47.L.M.TermanandM.A.Merrill,MeasuringIntelligence:AGuidetotheAdministrationoftheNewRevisedStanford-BinetTestsofIntelligence(HoughtonMifflin,Boston,MA,1937),p.302.48.E.D.Hirsch,Jr.,CulturalLiteracy:WhatEveryAmericanShouldKnow(HoughtonMifflin,Boston,MA,1987).49.A.S.PalincsarandA.L.Brown,inReadingEducation:FoundationsforaLiterateAmerica,J.Osborn,P.Wilson,R.C.Anderson,Eds.(LexingtonBooks,Lexing-ton,MA,1985).50.T.G.Sticht,W.B.Armstrong,D.T.Hickey,J.S.Caylor,Cast-OffYouth:PolicyandTrainingMethodsfromtheMilitaryExperience(Praeger,NewYork,1987).51.SupportedinpartbyagrantfromtheJamesS.McDonnellFoundationtoPrincetonUniversity.ComputationalNeuroscienceTERRENCEJ.SEJNOWSKI,CHRISTOFKOCH,PATRICIAS.CHURCHLANDTheultimateaimofcomputationalneuroscienceistoexplainhowelectricalandchemicalsignalsareusedinthebraintorepresentandprocessinformation.Thisgoalisnotnew,butmuchhaschangedinthelastdecade.Moreisknownnowaboutthebrainbecauseofadvancesinneuroscience,morecomputingpowerisavailableforperformingrealisticsimulationsofneuralsystems,andnewinsightsareavailablefromthestudyofsimplifyingmodelsoflargenetworksofneurons.Brainmodelsarebeingusedtoconnectthemicroscopiclevelaccessiblebymolecularandcellulartechniqueswiththesystemslevelaccessiblebythestudyofbehavior.UDNDERSTANDINGTHEBRAINISACHALLENGETHATISattractingagrowingnumberofscientistsfrommanydisciplines.Althoughtherehasbeenanexplosionofdiscoveriesoverthelastseveraldecadesconcerningthestructureofthebrainatthecellularandmolecularlevels,wedonotyetunderstandhowthenervoussystemenablesustoseeandhear,to9SEPTEMBERI988learnskillsandrememberevents,toplanactionsandmakechoices.Simplereflexsystemshaveservedasusefulpreparationsforstudyingthegenerationandmodificationofbehavioratthecellularlevel(1).Inmammals,however,therelationbetweenperceptionandtheactivityofsingleneuronsismoredifficulttostudybecausethesensorycapacitiesassessedwithpsychophysicaltechniquesaretheresultofactivityinmanyneuronsfrommanypartsofthebrain.Inhumans,thehigherbrainfunctionssuchasreasoningandlanguageareevenfurtherremovedfromthepropertiesofsingleneurons.Moreover,evenrelativelysimplebehaviors,suchasstereotypedeyemovements,involvecomplexinteractionsamonglargenumbersofneuronsdistributedinmanydifferentbrainareas(2-4).Explaininghigherfunctionsisdifficult,inpart,becausenervoussystemshavemanylevelsoforganizationbetweenthemolecularandsystemslevels,eachwithitsownimportantfunctions.Neuronsareorganizedinlocalcircuits,columns,laminae,andtopographicmapsforpurposesthatwearejustbeginningtounderstand(5-8).T.SejnowskiisintheDepartmentofBiophysicsattheJohnsHopkinsUniversity,Baltimore,MD21218.C.KochiswiththeComputationandNeuralSystemsProgramattheCaliforniaInstituteofTechnology,Pasadena,CA91125.P.S.ChurchlandisintheDepartmentofPhilosophyattheUniversityofCaliforniaatSanDiego,LaJolla,CA92093.ARTICLES1299.l on February 10, 2009 www.sciencemag.orgDownloaded
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