connectionism and the commitments of folk psychology

8/12/2019 Connectionism and the Commitments of Folk Psychology

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Philosophical erspectives,, AI, Connectionism,ndPhilosophical sychology,995

CONNECTIONISM AND THE COMMITMENTSOF FOLK PSYCHOLOGYTerenceHorgan ndJohn iensonTheUniversityfMemphis

Manyphilosopherselievethat onnectionisms incompatible ithfolkpsychology,ndhence hat he uccess fconnectionismould upportlimina-tivistonclusionsbout ropositionalttitudes.omephilosophersctuallyrguethat certain rands f)connectionismassuch liminativistmplications.nthispaperwe examinewosuch rguments,uetoRamsey, tich, ndGaron1990;hereafter,SG). Theirprincipal rgumententers rounda feature f thepropositionalttitudeshey allfunctionaliscreteness.SG's second rgumentcentersnthequestionwhetherhepredicatesf commonensepsychologyreprojectable.We conclude hat heir rgumentsrenotsuccessful. ommon ensepsy-chology, roperlynderstood,s not ncompatibleith onnectionism,roperlyunderstood-at eastnotin thewaythatRSG allege.But we arenotsimplyconcernedorefutenotherliminativistrgument,ven hough SG's paperhasbeenquite nfluential.'SG's argumentsrea useful ehicle or ettinglearerabout he ssuesonwhich heirrgumentsurn, oncerningoth olk sychologyandconnectionism.1. The FunctionalDiscretenessArgument.

RSG's main rguments that ommonensepsychologyascommitmentsthat renot atisfiedyanimportantlassofconnectionistodels.Thus, fthecorrectmodels of human cognition ie withinthat class, commonsensepsychology illbe shown obe seriouslynerror.In thisSectionwe layoutRSG's argumentn four teps: hecommitmentofcommon ensepsychologyofunctionaliscreteness,classofconnectionistmodels hat reheld olackfunctionaliscreteness,n example fa modelfromthat lass,andtheexplicit rgumenthat uchmodels ackfunctionaliscrete-ness. In Section2 we look at common ensefunctionaliscretenessn moredetail.Weargue hat ommonense scommittednly ocertainaradigmasesof functional iscreteness,nd that connectionist odelsof the class RSGidentifyoexhibit iscretenessfthat ind.We alsopoint ut hat onnectionistmodelsnthis lasscanexhibitther inds ffunctionaliscretenesshich om-


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128 / TerenceHorgan ndJohn iensonmonsenserecognizess possible, ut o which t is not committed.1.1A Commitmentf Common ense Psychology.RSG base theirmain argumentn three ommitmentsf common ensepsychologyconcerning ropositional ttitudes: ropositional ttitudes resemanticallynterpretable;heyhave a causal role; and they refunctionallydiscrete. SG call this luster f featuresropositionalmodularity504). Thefirst wo are familiar. ropositionalttitudesre the orts f things hat an betrue r false, atisfiedr unsatisfied,ndthe ike; n the urrenterm f art, heyhavecontent. ndpropositionalttitudesnfluenceehavior, elief ixation,tc.inwaysthat re appropriateo their ontent. o say that ropositionalttitudesarefunctionallyiscretes to saythat hey anhaveeffectsinglyor n content-based structures,s whena conclusion s drawn rom wo premises,withnootherropositionslaying role).RSGhold hat istributedonnectionistodelsdonot atisfyhe ommonensedemand or unctionallyiscretetates ecausein suchmodels ll informations encodedholistically-hencenseparably-throughouthenetwork.Theymention wodifferent ays n which ommon ense propositionalattitudesrefunctionallyiscrete. irst, hey anbe acquired r ost ndividually(nearly nough).Forexample, Henry...hadompletely orgottenhat he carkeyswerehiddenn therefrigerator,"504-5) although e had forgottenothingelse.And fyouare told hat hekeys re ntherefrigerator,ouwillacquiresmall cluster fnewbeliefs, utmostof yourbeliefswill be notbe altered.The secondkind of functional iscretenesss more importantn theargument.ometimes person as a total etof beliefs nd desires hat rovidemore han ne reasonforperformingn action,A. And sometimest happensthat heperson oesA for ne ofthose easons,with heother ossiblereasonnotfiguringn the tiology fthe ction t all.Likewise,ometimes person asseveral etsof beliefs hat ould ead her o infer particularewbelief, , andshe nfers from ne of those ets,with heothers otfiguringn her hinkingat all. Thus, ccordingo commonensepsychology,t s a determinateuestionwhichpotential easonsforan actionor change n beliefwere the actual oroperativeeasons.Accordingocommon ense sychology,hen,he ame tatessemanticallyevaluable nd hasa content-appropriate,unctionallyiscrete,ausalrole. Suchstates avewhatRSG callpropositionalodularity.unctionaliscretenesssthefeature n which he rgumenturns. ince semanticvaluabilitynd somekindof causal roleare taken orgrantedor hemostpart,we willusually peakoffunctionaliscreteness,eservingpropositionalodularity'or ontextsnwhichsemanticvaluabilityorcausalrole) might e an issue.


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Connectionismnd theCommitmentsf Folk Psychology 1291.2 A Class of Connectionistodels.

RSG claim that distributedonnectionismmust deny propositionalmodularity.hey haracterizeclassofconnectionistodels,which, hey laim,are incompatible ithpropositional odularity,n particular ithfunctionaldiscretenessf semanticallyvaluablestates.The models in this class arecharacterizedythree roperties:i. Their ncoding f nformationn the onnectioneights nd n thebiasesonunits s highly istributedatherhan ocalist.ii. Individualhiddenunits in the networkhave no comfortable

symbolicnterpretation;hey re subsymbolic....iii. Themodels re ntendeds cognitive,otmerelys implementa-tions f cognitivemodels. p. 508)Featuresi) and ii) aremeanto nsurehat t snotpossible o associate pecificinformationith articularocal parts f themodel.Connectionsnd nodes renot obe semanticallyvaluablendividuallyr n small ets. nformationn themodel sencoded olisticallyhroughouthenetworkr hroughoutarge ortionsof the network. urthermore,ach node contributeso representing anydifferentropositions,nd each connection eight ontributeso storingmanydifferentropositions.hus, nformations containedn thenetworkolisticallyand globally, ot ocally.Andthismeans,RSG argue, hat ll ofthe nformationin thenetworks involvedn all of itsprocessing,o that t is notpossible osingle utcertainits f nformations operative-and therss inoperative-ina token rocess, s folkpsychologyequires.As RSG note, eatureiii) is not bout henetworks such,but bouthowit s tobe interpreted.he dea sthathemodel s supposed o tellus somethingabouthow themindworks,not how it mightbe embodied.Consider, orinstance,classicalparser-a classical omputerrogram hich s meant o takenaturalanguage entencess inputndyield tructuralescriptionsfthe nputsentencess output. ucha programan be considered hypothesisbout hecognitiverocesses, nowledgetructures,nd so forth,nvolved nrecognizingthe grammaticaltructuref sentences. he program an be run on manydifferentomputers, ith different achine anguages; hehypothesisboutcognitions the ame n each case.The machineanguage f thecomputerhattheprogram appens o be runningn is irrelevanto thecognitive toryheprogramroposes.

One couldattempto usea connectionistetworko implementheopera-tion f such classicalprogram.hiswouldbe toattemptouse thenetworksanimplementationf the lassicalmodel-as analternative,northodoxind fmachine anguage.Therewould stillbe no differencen thehypothesesutforwardbout ognition. his s thekindof construalf connectionistodelsthatiii) rulesout.


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130 / TerenceHorgan ndJohn iensonBut a connectionist odel-for instance, parsingmodelsuch as Berg(1992)-can alsobe construeds offeringnalternativetory bout he ognitive

processesnvolvednrecognizinghegrammaticaltructuref sentences,storythat s in competition ith heclassicalmodel.Thiswould be to construehemodel s a cognitivemodel, s required y iii). Whenunderstoodn thisway,RSG hold, distributedonnectionistmodels are incompatiblewith thepropositional odularityf folk-psychologicaltates.1.3An Example.

RSG describe simple hree-layered,eedforwardonnectionistetwork,which hey escribes "a connectionistodel fmemory."henetwork,alledNetwork , hassixteennput odes, ne output ode, nd a hiddenayer f fournodes. nput onsists fencodings f sixteen ropositions,or xample,

Dogs have fur.Catshave fur.Dogs havegills.Fish havegills.Eight nputnodes are usedto encodethe subject f the proposition,ight oencode hepredicate.Network was trained p so that tsoutput ode is on (> .9) when heinput ropositions true,ndoff < .1) when he nput ropositions false.Thus,thenetwork as memorizedheanswers o a true/falseest.The networkscapableofgeneralizing;t respondedorrectlyo encodingsf cats have egs'and Catshavescales,'whichwerenot n the raininget.1.4 TheArgument

RSG observe hat[t]henformationncodednNetwork is storedolisticallynddistributedthroughouthenetwork.henevernformations extractedrom etwork,bygivingtaninput tringnd eeingwhethertcomputeshigh ra lowvaluefor he utputnit,manyonnectiontrengths,any iases ndmanyhidden nits lay rolenthe omputation.nd ny articulareightrunitorbiaswillhelp ncodenformationboutmanyifferentropositions.513)

This s certainlycorrectescriptionftheworkingsfthenetwork.Wheneverthe ruthr falsehoodfa propositioni.e.,high r owoutput odeactivation)is computed romn input roposition,ll ofthehidden nits ndmany ftheweightsare involvedin the computation. SG argue thatthis holisticcomputations incompatibletheyay, radicallyncongruent")with he ropo-


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Connectionismnd theCommitmentsfFolkPsychology 131sitionalmodularityf common ensepsychology."

For s we aw nSection,commonense sychologyeemsopresupposehattheres generallysic] ome nswero the uestionf whetherparticularbelief rmemorylayed causal ole n a specificognitivepisode. ut fbelief ndmemoryre ubservedya connectionistetworkikeours, uchquestionseem ohavenoclearmeaning.513)2. Critiqueof theFunctionalDiscretenessArgument.

The overall tructuref ourcritiques as follows.We distinguishhreedifferentaysthatntentional ental ropertiesstate-types)anbe possessedbya cognitiveystemsection .1). Onthebasisofthis ripartiteistinctionedistinguisheveraldifferentossibleforms ffunctionaliscreteness;e thenargue hat ommon ensepsychologys committedoonlyoneof theseformsof functionaliscreteness,nd that ommonensepsychologyeaves t an openempirical uestionwhetherr notanyof theother orms remanifestedypropositional ttitudesn humans section2.2). With this discussionasbackground, e press hree eparate eplies o RSG's argument.First, onnectionistodels,ncluding SG's Network , typicallyxhibittheonlykindof functionaliscretenessowhich ommonensepsychologyscommitted.hus,even f connectionismoes precludeome or all oftheotherkinds,this fact wouldnot generaten incompatibilityithcommon ensepsychology;ather,twouldmeanthat onnectionismnswersn thenegativecertain mpirical uestions bout functionaliscretenesshatcommon ensepsychologytself eaves open section .3).Second, ven fcommon ensepsychology ere ommittedo those therkinds ffunctionaliscreteness,nd even fhuman ognitionailed o exhibitthem,hesefactswouldonly howthat ommonensepsychologys somewhatmistaken boutpropositionalttitudes;heywouldnotshowthat ropositionalattitudeson't exist section .4).Third, e argue hat onnectionismoesnot eally recludeny f he therkinds f functionaliscretenessnyway.nprinciple,nyorall of them ouldbe manifestedn a connectionistystemn which nformations embodiedholisticallynd distributedlynweightsnd nactivationatternscrossnodes.Such functional iscreteness ormallywould not involvedistinct hysicalcomponentsf thenetwork's ausalevolution;nsteadt wouldbe discernibleonly t a more bstract, athematical,evelofdescriptionn which henetworkis characterizeds a high-dimensionaldynamicalystem"section .5).2.1 Psychological tates:Occurrent,ispositional,ndMorphological.

There rethree ifferentays n which ntentionalontentr intentionalstate-typesanbe possessedbyhumansndother ognizers. hefirst woare


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132 / TerenceHorgan ndJohn iensonstandardly entionednthe iteraturef philosophyf mind; hethird s not.First, person an possessthe ntentionalropertyccurrently.his means, tleastroughly,hat token f therelevant sychologicaltate-typeccurs s aconcretevent r tatewithinhe erson. n connectionistodels, epresentationsare certain atternsf activation-those atternshat re nterpreteds havingintentionalontent. atternsfactual, ccurrentctivationn thenetworkre heconcretetates hat onstitutets oken epresentations,nd hat hus lay he ole(in themodel) of occurrent ental tates.Second, person an possess he ntentionaltate-typeispositionally.hismeans, t east oughly,hat he ognitiveystemsdisposed o generate tokenof that ype under ppropriateircumstances, tokenwhichwill thenhavesuitably ontent-appropriateffects n the system's ognitive rocessing ndbehavior.n connectionist odels,dispositionalntentionaltate-typeshus rea matterf a network'sweights eing et to produce ) tendencyo generateoccurrentepresentationsnder ppropriateircumstances.Third, person anpossess ntentionalontent orphologicallyas wewillput t). Morphological ossession f intentionalontentM is a matterf thecognitive ystem's eing isposed, yvirtue f tspersistingtructureatherhanbyvirtue fanyoccurrenttates hat re okens fM,to undergotate ransitionsthat resystematicallyppropriateo content -and to do so, at eastmuch fthe time,without enerating token fM duringheprocess.Morphologicalcontent iffers rom ccurrentepresentationalontente.g., occurrent elief)because it involvesthe cognitive ystem'spersistingtructure,ather hanoccurrentokeningfM.Morphologicalontent iffersrom ispositionalepre-sentationalontente.g.,dispositional elief) s standardlynderstoodand ascharacterizedn he recedingaragraph)ecause he elevant ispositionsssoci-atedwithmorphologicalontentnvolve endenciesther han hetendencyogenerateoken epresentationsith hat ontent.Consider, or xample, cognitive ystemwhich reats ll members f acertain lass, R, ofrepresentationsimilarly.ttends o make he amekinds finferencesrom epresentationsn R. When tacquires newrepresentationntheway it acquired he members fR, it tends o makethe samekinds ofinferences ith hatnew representation.ut it has other epresentationsromwhich tdoesnotmakesimilar nferences.he systemhus reatsmembersfR as representationsfthe ame ype;neffect,ttreatshekinds epresentedythe members fR as speciesofthesamegenus.But thesystemmayhave norepresentationor hegenus tself. hus, he ystemannot epresenthefact hat(thekindsrepresentedy) two members fR arespeciesofthe samegenus,thoughttreatshem s such. We can sayR is a classofrepresentations;hesystem annot.) his s thekind fthinghatwould ount s (inthis asepurely)morphologicalontent.In connectionistodels,morphologicalossession f ntentionalontentsa matter f informationeingembodied in theweights." The tendencyogenerateccurrent ental tateswhen ppropriates,ofcourse, lso something


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Connectionismnd theCommitmentsfFolkPsychology 133that's intheweights." o dispositionalntentionaltates an beseen s a specialcase of morphologicalontent.)

Common ense sychologyttributesoth ccurrentnddispositional odesof possession or hevarious inds f state-typest posits, ncluding eliefs nddesires. ispositional eliefs, esires, tc., s such, re unconscioustates; nyconsciousmental tate s an occurrenttate.On theother and, ommon ensepsychologyoes leave opentheconceptual ossibilityf occurrenteliefs nddesires hat re unconscious. here s no apparenteasonwhyan intentionalpsychologicalheoryouldnotpositmorphologicalontent,naddition o occur-rent nd dispositionaltate ypes.As far s we can see, morphologicalontentis consistent ith ommon ensepsychology,utcommon ensepsychologysnot committedo morphologicalontent.22.2 Types fFunctionalDiscretenes,nd their tatuswithin ommon ensePsychology.

With hesedistinctionsnmind,et us reconsiderommon ensepsychol-ogy's commitmento functional iscreteness.onsider, or nstance, SG'sexample fClouseau.Clouseauhas heard hat hehotel s closedfor he easonand that he rain s outof service. he Butler ays hat e spent henight t thehotel nd tookthetrain ackto town n themorning. ommon ensereckonsthat louseaumight ave nferredhat hebutlers lying rom is belief hat hehotel s closedfor he eason, r from is belief hat hemorningrain as beentaken ut ofservice,r from oth. rom heperspectivef commonense hereis-often-a determinatenswero the uestionwhichtwas.RSG believe hatno determinatenswer o this uestions possiblefhuman ognitiveystemsrerelevantlyike theirNetwork .Whydoes common ensereckon his a determinateuestion?The firstthoughtfthe ommon ensepsychologists thattdepends ponwhich elevantbeliefs onsciouslyccurred o Clouseau andwhichogical onnectionse wasaware f). fheconsciouslyhoughtf hehotel losing ndconsciouslyealizedthattsbeing losedmeanthat heButler ouldn't ave pend he veningn thehotel, utdidn't ememberhe rain t all atthe ime,well-its obviouswhichonewas operative.Consider lsoRSG's example fAlicetheE-mailer. licehad tworeasonstogoto her ffice.he wanted o talk o her esearchssistant,ndbelieved hathe wouldbeattheoffice. nd shewantedo send omeE-mailmessages,whichshe believed he coulddo fromheoffice. Common ensepsychologyssumesthatAlice's goingto herofficemight avebeen causedby either ne ofthebelief/desireairs,or by both, nd thatdetermininghich of theseoptionsobtains s an empiricalmatter."p. 505) In RSG's rendition,lice's desire osendsomeE-mailmessageswas causallynert.Whymight hat e? Themostnaturalxplanations thatt didnot onsciouslyccur o her ntherelevantimeframewhileherdesire o talkto herresearchssistant id. The relevantime


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134 / TerenceHorgan nd John iensonframes not, f course,ust theperiod mmediatelyreceding erdepartureorthe office. he might ave had a thoughtarlyn themorning hich he couldhave expressed ut oudby saying, Oh, 've gotto talk o Fred oday bout...."She might hen avetaken areof somehouseholdhores, ead hepaper, ottenready o go to theoffice nd departed, ithout red ever again entering erconsciousness.Thus, the paradigmaticases of propositional odularityecognized ycommon ensepsychologyre cases n which he ausally ctivementaltate soccurrentnd conscious,whereas he causally ormantmental tate s disposi-tionalbutnotoccurrent.hat s, the type f functional iscretenesso whichcommon ensepsychologys clearly ommitteds thefollowing.

1. SI is occurrent;2 is dispositionalutnot occurrent.(Subcase:SI conscious/S2 nconscious)(Hereandbelow, I is the tate hat s causally ctive; 2 is a state hatcould have ed to the ame action r thought utdid not do so inthiscase.)We will call this ubcaseoftype1 functionaliscretenessaradigmaticunc-tionaldiscreteness.

Common ense lsorecognizeshat ne mightmakeuse of nformationhatdoes not rise to consciousness, r arrive t a conclusionwithout onsciousinference,speciallynrapidphysical ctivity.3hus we should dd a secondsubcase otype1 functionaliscreteness:nconscious/unconscious.It is not contraryo common enseto consider ossiblecomplicationsfparadigmaticunctionaliscreteness,speciallyn thecase of explanationfactions, ecisions,hoices, tc.Perhaps lice smore eeplynterestedn her -mail conversationshan he cares o admit o herself. o her real" reasonforgoing o theoffice s to send ome E-mailmessages, ut she "tellsherself'aswemight ay)that he s going otheoffice o talk o Fred.Her desire o sendE-mail messageswas occurrentnd causally fficacious,utshe suppressedawarenessf ts fficacy,ndperhapsfthedesire tself. his eems o be a caseinwhichbothdesires retokened, ut nwhich nlyone,the one that s notconsciously onsidered,s the actual cause. Thus, common sense clearlyrecognizeshepossibilityfa second ype f functionaliscreteness.

2. S1 is occurrentnd S2 is occurrent.(Conscious/conscious;onscious/unconscious;nconscious/conscious;unconscious/unconscious.)All four ubcases re onceptuallyossible lthoughhefirstsperhapsuestion-able from hepointof viewof common ense. t seems odd to suppose hatClouseauthoughtfthehotelclosing, houghtf thetrain eingtaken ut ofservice, nderstoodhat achwas incompatible ith omethingheButler ad


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Connectionismnd theCommitmentsfFolkPsychology 135said, nd nferredhat heButlerwas lying rom neofthese eliefs utnot heother.

Dispositionalossession f an intentionaltate-typeoesnotmake directcausalcontributiono an outcomehe tate-typeould ause;rather,ispositionalstates nter hecausalfray ndirectlyiathe xercise f thedisposition,.e., viathe occurrenceuring rocessingf anoccurrentoken f that tate-type.ase1 involves situation here hedispositiono produce token f S2 doesnotgetexercised uring rocessing,o it s, in a sense, degenerateype f func-tionaldiscreteness.t needs o be stated ecause t s theonecase of functionaldiscretenesso which ommonense s clearlyommitted.iven hat ntentionalstate-typeshatremainmerely ispositionalo notplay a causal role,threefurtherases areworth istinguishing.3. SI is occurrent;2 ismorphological.(Conscious/unconscious;nconscious/unconscious.)4. SI ismorphological;2 is occurrent.(Unconscious/conscious;nconscious/unconscious.)5. SI is morphological;2 is morphological.

Common ense allowsfor he conceptual ossibilityf each of Cases 3through,becauseone canmake ntelligible,rom hepoint fviewof commonsense, he dea that here s morphologicalontenthathas a causal role.Forinstance, ere s the ranscriptf an actual onversation:

J: The Parkers re at their lace;thered flag s up on theirmailbox.N: Yeah,I saw their olden retrieverog] lastnight.J: Oh, yeah;youtoldme that. forgot.Clearly,J nferredheParkers' resence rom heflag,notfrom hedog. Theflag s thethinghe thoughtf. Had he rememberedhedog,he might averealized hathe did not have to tellN aboutthe Parkers. o far, hisstoryillustrates ype1 functionaliscreteness.But t llustratesomething ore.To infer hat heParkers erehomefromtheraised lagon theirmailbox,Jmust ely nsomethingike F) theflag s upon theParkersmailbox nlywhen hey re here oraise t.Likewise,whenNinferredhatthe Parkerswerehome,she reliedon somethingike (D) theParkers' olden shere nlywhen hey rehere.Thus,we have nstances f F)and D) exhibitingunctionallyiscrete ausalroles.

But t s quiteunlikelyhat itherF) or D) consciouslyccurredoeitherJorN.And,wesubmit,t squite ntelligibleromhepoint fviewofcommonsenseto suppose hatneitherF) nor D) was tokened ubconsciouslyither;indeed,hat either as tokenedubconsciouslyeemsmoreikelyo us than ot.If it was not, his s nota case ofType1 or ofType2 functionaliscreteness.If the informationF) thatplayeda role in J's inference as not tokened


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136 / TerenceHorgan nd John iensonconsciously r unconsciously,hen twas morphologicalatherhan ccurrentrmerely ispositional.4his seems, hen, o be construabley common ense sa case of Type5 functionaliscreteness.o common ense videntlyoespermitthepossibility f morphologicalontentndType5 functionaliscreteness.InSection5 we offer n example onstruables Type 4 functional iscreteness,plus variants f RSG's Clouseau example or ach of Types2-5.)Butourmainpointn this ection s that ommon ense s only ommittedto theparadigm ase of functionaliscreteness,ype1 functionaliscretenesswhere hecausally ctivestate s conscious.The other ases we have distin-guished re recognized y common ense as possibilities,ome as thequiteserious ossibilities.

InSection .5 below,we argue hat ll five ypes f functionaliscretenessarepossible n models hat allwithin he lassofmodels haracterizedyRSG.2.3. First Reply: Folk Psychology nd DistributedConnectionism reCompatible.

The most mmediateeply oRSG's functionaliscretenessrguments nowquite traightforward.heonlykind ffunctionaliscretenesso which ommonsensepsychologys committeds paradigmaticunctionaliscreteness.onnec-tionistmodelshave no trouble t all manifestinghisdegenerate indof func-tionaldiscreteness.or, on one hand, heoccurrenteliefs f common ensepsychologyorrespond ostnaturallyo certainokened ctivation atternsn aconnectionistetwork;nd ctivation atternsave causal nfluencenproces-sing.Processingna connectionistetworks spreadingctivation. nthe therhand, hedispositionaleliefs f common ensepsychology orrespond ostnaturallyo a connectionistetwork's ispositionso generateheactivationpatternshat unctionn thesystems representation-tokens;ndwhen uch adispositionemains ormant,o that herelevantctivationatternoes notgettokenedduringprocessing,henthe pattern oes not affect he system'sprocessingsince t s not there). hus,paradigmaticunctionaliscretenessseasilyaccommodated ithin he relevant lass of connectionist odels: anactivationatternan occur hat onstitutestoken epresentationhat ausesacertainubsequentutcome, hile tthe ame ime he ystemas a dispositionalrepresentationhichwouldbringbout he ameoutcomewere tactivatedndyetremains ormant n thisparticularccasion.Therefore,he connectionistmodelsconsideredyRSG do notprecludehekindof functionaliscretenessto which ommon ensepsychologys committed.

In the emainderf his ubsection e willamplifyhis eply, ydiscussing(i) theNetworkA described yRSG andtheir emarks bout t, ii) RSG'sreplies o certain bjectionshey hemselvesonsider,nd iii) recent emarksaboutRSG's modularityrgumentyStich nd Warfieldforthcoming).There retwo kindsofrepresentationsnNetwork . The inputayer sinterpreteds representinguestions oncerninghe truth rfalsityf certain


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138/TerenceHorgan ndJohn iensonimplausible,"ecause"in common ensepsychologyeliefs ndpropositionalmemoriesre typicallyfsubstantialuration;nd they rethesorts fthingsthat ognitivegents enerallyave otsof evenwhen hey renotusing hem"(p. 518). Butthe ppropriateounterreplys straightforward:t s only ccurrentbeliefsthatare appropriatelyegarded,withinconnectionistmodeling, sactivationatterns.RSG also discussthe suggestionhat"long standing eliefsmightbeidentifiedotwith ctivationatterns,utwith ispositionsoproduce ctivationpatterns,"ndtherelateduggestionhat thefamiliarhilosophicalistinctionbetween ispositionalnd occurrenteliefsmight e captured,nconnectionistmodels, sthedistinctionetween ispositionsoproducectivationatternsndactivation atternshemselves"pp. 518-9). They reply hatdispositionsoproduce ctivationatternsarenotthediscrete,ndependentlyausally ctivestates hatfolkpsychologyequires"p. 519). Once againthecounterreplysstraightforward:olk sychologyecognizes distinctionetweenccurrentnddispositionalelief,nd s not ommittedothefunctionaliscretenessfdispo-sitional eliefs uadispositional;t sonly ommittedo paradigmaticunctionaldiscreteness.Dispositionsore-createeliefs,memories,tc. re ntheweightsholistically.utthe recreatable)ctivationatterns not ntheweightswhenit snot ctive. t is nowhere. hus, here eally s noquestion f thefunctionaldiscretenessfdispositionaleliefs.t isnot hat ll ofthedispositionaleliefsaredirectlymplicatednprocessing; oneofthem re.7)So connectionistepresentationsave,byand large, unctionallyiscretecausalroles.Thoserepresentationshat etactivatedna process laya causalrole nthat rocess; hosenot ctivated o not.Andthe pecific ausalrolesoftheones that etactivated epend ponpatternsfspreadingctivation.8Stich ndWarfieldforthcoming)eply o a similar bservationyAndyClark 1990). Clark uggestshatt s only "belief-in-action"as opposed oalong-standingelief,whichmaybe just a dispositionoproduce n occurrentbelief-in-action)hat eeds o becapableoffunctionallyiscreteausalpotency(p. 96). Stich nd Warfield's elevantrguments that heproposals tooweak,

for n henterpretationfpropositionalodularity...,odeterministicystemhatstoresropositionalnformationould ail o atisfyropositionalodularity.f hisisright,heres nothingtallwecouldearn boutheworkingsf uch systemthatwould how hattviolatesmodularitynd hus oesnot eally avebeliefs.(Section.2)Wetake and thus' n the ast ineto mean andfor his lackofpropositionalmodularity]eason'.Otherdeep commitmentsf common ensepsychologymight e violated ven fpropositional odularitys not.Thus,the operative omplaintn thispassage is that, n theproposedinterpretationfpropositionalodularitywhich equires iscreteausalpotencyonlyfor okened epresentations),o systemouldfail o satisfyropositional


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Connectionismnd theCommitmentsfFolk Psychology 139modularity,nparticular,osystemould ail oexhibitunctionaliscreteness.Our eplysfourfold.irst, etwork is a model f single,mmediatecognitivetep-in thiscase,roterecall.There re no representation-levelintermediaries.iven hathe nputndoutputfsuch one-steprocessre(interpreteds) representations,ndthat epresentationsre enteredingly,nothingould how hathe ystemacksType1 functionaliscreteness.heoccurrentepresentationn the nputayer s causally ctive.Dispositionalrepresentations-oneshat ouldbe in the nputayer utarenot-arenotcausallyctive.But econd,hiss surelyothingocomplainbout. ny ognitiverocesswhichs mmediateor system,9ndwhicheceivesnly ne elevantnputta timemust, bviously,xhibitype functionaliscreteness.Itdoesnot vendependuponthe system eingdeterministic.)his ust means hatthecommitmentf common ense psychologyo functionaliscretenessfpropositionalttitudess a very eak ommitment.However,hird,t s easy o maginetherortsf onnectionistodelshatmightot xhibitunctionaliscretenessor okenedepresentations.modelof ome ask hatnvolves ultipleimultaneousoft onstraintatisfaction,orinstance,ust llowmany epresentationso be activet once. tmight ften,perhapsven ypically,e impossibleo determinehichepresentationserecausallyesponsibleor he olutiono a problem,speciallyf he epresenta-tions rewidely istributed.urthermore,ome ystemsith istributedepre-sentationsnwhich achnode ontributesomany ifferentepresentationsanhavemany epresentationsctivetonce y uperpositionfrepresentations,nwhich ase tmay e-thoughtneed ot e cf. ection.5 below)-impossibleto eparatehe ausal ontributionfdistinctepresentations.hus,here ay emodels f hese inds, ith ensibleepresentationevel nterpretationshat onot xhibitype functionaliscreteness.Finally,ourth,ommonense sychologys notcommittedo Type2functionaliscretenessnyway.he nly ind f unctionaliscretenessowhichit s actuallyommitteds triviallyatisfiable.2.4 SecondReply:Ontologicallyonservativeheory hange.

Suppose, or he akeofargument,hatwe arewrongnclaiminghatcommonense sychologysonly ommittedothe ind ffunctionaliscrete-ness hatnvolvesconsciousccurrenteliefnd non-activatedispositionalbelief,nd thatt is actuallyommittedo someorall of theother indsdelineatedn ection.1 above. upposeoo althoughewill rguegainsthisin he extubsection)hat istributedonnectionistodelsf he ort ketchedbyRSGare ncompatibleith hefurtherinds f functionalodularity.otheseuppositionsanctionSG'skey laim, iz., Ifconnectionistypothesesofthe ortwewill ketchurnut o beright,o toowill liminativismboutpropositionalttitudes"p. 500)?


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140/Terence organndJohn iensonSurely ot.RSGthemselvesraw distinctionetweenontologicallyon-servative"heoryhangeswhich reservehe ey heoreticalntitiesositedy

of n originalheory hile lteringrreplacinghat heory'slaimsboutthoseentities),nd ontologicallyadical"heoryhangesinwhichhe ntitiesositedby the ld theoryrerepudiateds well).Even f commonense sychologyhappensobe committedoone rmore indsffunctionaliscretenessfType2 throughype , alteringhe heoryydroppinghis ommitmentould e aratheronservativehange-especiallyince heserenot aradigmaticases ffunctionaliscreteness.uch change ould ot ven pproachntailinghattherereno beliefs.'02.5 ThirdReply: trong ormsofFunctional iscreteness re Not Precluded.Distributedonnectionistodelsmbodynformationolistically,atherthanontainingiscretetemsfpropositionalnformationnphysicallyiscreteinternaltates,tructures,rprocesses.nformationhats not ccurrentlyepre-sented s distributedhroughouthenetwork,ndeachpart fthenetworkcontributesostoring uchr ll of ts nformation.o it ppearslausiblehatdistributedonnectionistodelsre ncompatibleith unctionaliscretenessfTypes -5.This ppearanceotivatesSG'sargument.ut he ppearancesmisleading,s wenow rieflyxplain.Webegin ydescribingway f hinkingaboutmorphologicalontentn connectionism.e then iscuss commonphenomenonhats plausiblyegardeds involvingype functionaliscrete-ness-that s, a situationn whichmorphologicalontentrumpsccurrentcontent.henwe revisit louseaund he utler.Thenatural athematicalrameworkor escribingonnectionistetworksis the ody fmathematicaloncepts,echniques,nd esultsnownsdynami-calsystemsheory.o describenetworks a dynamicalystemstospecifyin certainay ts emporalvolution,othctualndhypothetical.achnodeinthenetworks assignedseparateimension,raxis, na high-dimensionalhyper-space;he ossiblectivationalueshe ode an ake re ointslonghataxis. achpossibleotal tate f he ystems thusepresentedy unique ointinthe ystem'sstatepace"inthe aseof onnectionistetworks,ftenalled"activationpace").Thedynamicalystem,s such, s essentiallyhe fullcollectionftemporalrajectorieshenetworkould ollowhroughts tatespace-with trajectorymanatingromach ointt an ccupyn tatepace.Thedynamicalystemanbethoughtf s a high-dimensionaleometri-cal/topologicalbject. usefuleometricaletaphoror ynamicalystemssthenotionf a landscape inthe ase ofnetworks,nactivationandscape).Think f thenetwork's-dimensionalctivationpaceas a contoured-dimensionalurface,rientedhorizontally"n n+1)-dimensionalpace. or achpoint ,the emporalrajectoryhathe etworktself ould ollowhroughtsactivationpace f t were o evolvewithouterturbation)rom is thepath"downhill"long he andscapehat ballwould ollowfpositionedtp and


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Connectionismnd theCommitmentsf FolkPsychology 141then llowedo "roll."Eachpoint n he ctivationandscapeorrespondso total ctivationtateof henetwork.ertainf hese ointsre epresentation-realizingoints: henthenetworks inthe otal ctivationtate orrespondingothe iven oint,neormore epresentationsre okeneds activationatterns.n general,epresen-tationsre multiplyealizablen connectionistodels.Representationsreidentifiedith ctivationectors,ypicallyith ctivationectorshatpecifyactivationalues or nly relativelymall ortionf he odes f he etwork.Such vectorhus pecifiesalues or ome, ut ot ll dimensionsf ctivationspace.All pointshatatisfyhese alueswill ealize he iven epresentation."Also, everalistinctepresentationsan, ngeneral,erealized y singleointin activationpace:the point'scoordinatesimultaneouslyatisfyinghecoordinate-specificationsf everal ifferentectors,ach fwhichsidentifiedwith distinctepresentation.'2From he ynamicalystemsoint fview,ognitive-leveltateransitionsin a connectionistetworkre rajectorieslong he ctivationandscaperomone epresentation-realizingointo nother.hese ransitionsependointlyntwo nterrelatedactors:i) the elativeositionsn the ctivationandscapefthe epresentation-realizingoints,nd ii) the opographyf he andscapetself.Landscapeopographys determinedy he onnectionsmonghe odesnd heweightsnthose odes. Trainingp"a network,yprogressivelylteringtsweightsnaccordance ith ome earninglgorithme.g.,backpropagationferror),mountso the rogressiveoldingf he ctivationandscapen a waythatesultsnsystematicallyontent-appropriaterajectoriesromnerepresen-tation-realizingointoanother.'3earninghusnvolvesmodificationftheexistingctivationandscape,n way hatccommodatesew nformationhileleavingntacthe nformationo which hat s learneds irrelevant.Learningo make certainlassofinferences,or nstance,roducesslope r nclinenthe ctivationandscape.rom very ointealizing(possi-bly omplex) epresentationf certainind,he ystems inclinedoproceedto a pointealizingcorrespondingepresentationf differentind. he and-scape lsohas thernclines,ubservingotentiallyonflictingnferencesnehaslearnedomake.Andmany thernclinesoo, ubservingariousotentiallyconflictingendencieso evolve rom nerepresentationalointo anothernvarious on-inferentialontent-appropriateays. o the ctivationandscapesavery igh imensional,ubtlyontoured,pacewithnclinesponnclinesponinclines.Think fthedisorientationnd ontortionfearliereologicaltratabyrisingew and.)Thus, eingnclinedo make n nferenceoesnotmeanthat newillmake he nference.In any particularognitiverajectorylongthe activationandscape,informationhatspartf he ontentf epresentation-realizingointslonghattrajectorys the informationhatbecomes ccurrent-i.e.,etsexplicitlyrepresented-duringhe ognitiverocessorrespondingo thatrajectory.nthe therand,nformationhatsaccommodatedy he rajectoryithouteing


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142/Terence organndJohniensonpart f he ontentf ny epresentation-realizingoint n t s relativeothattrajectory,nyway) orphologicallymbodiedatherhan xplicitlyepresented.The ocaltopographicaleaturesf the andscape-i.e.,hevarious ifferent,superimposednclinesresentn he mmediateicinityf given epresentation-realizingoint-arewhat eterminehe ontent-appropriaterajectoryromnysuch ointo anotherne.Onespecial aseof nclinesnactivationpace omes p fairlyftennconnectionistiscussions.epresentationsre houghtfas attractorointsrregionsn ctivationpace, nd ne peaks f he asinof he ttractor-viz,hesetof all pointsn activationpacefrom hich he ystem illevolve otheattractor.basins, ofcourse,n nclinell ndividuallopes fwhichead othe ame lace.For differentind fexample f an incline,onsidersystemhat aslearnedo make class fHumeannferences.henevertencountersn A, itexpectsB. But thasneverccurrentlyepresentedhe ropositionhat 's areB's, and t is notcurrentlyisposedo do so. Perhapsf t is sophisticatedenough,t ould ome ooccurrentlyelievehat 's areB's by eflectingn tsown nferentialendencies.ut thasnot eflectedn thatway.In such case, he nformationhat 's areB's is containednthe ystemmorphologicallybutnotdispositionallyr occurrently).hat s, theres aninclinen ts ctivationpace onnecting-realizingointsoB-realizingoints,but heres nopointn ts urrentctivationpace hat ealizes hebelief hatA's areB's.Considerow he henomenonfprejudice. persons stronglynclinedtocome o ertainindsfjudgments,, boutnyoneor nything)e lassifiesas being f a certainype, .14Onoccasion efeels need o explainne ofthoseudgments,ometimesromxternalrodding,ometimesot.On theseoccasionse comes pwithnexplanationf he articularudgmenthat oesnot eferotype . And ypically,he xplanationsegives re atherifferentin differentases.Theprejudiceonsistsn an nclinen that erson'sctivationpace rompointsealizingepresentationsf ndividualssbeingfkind topointsealiz-ingJjudgmentsbouthosendividuals.heperson ay aveittle rno nclin-ation o (occurrently)elieve hegeneralizationonnectingtoJ. Beinghuman eing, ehas, fcourse,he apacityoentertainhat eneralization.)Often henJjudgmentsmade,t sprecededy noccurrentepresenta-tion, ,that he ersonuts orward-toimselfrothers-ashe eason or isJjudgmentn a particularccasion.ut nfact, iscausallynert. heresnopathn ctivationpace romointsealizingbut ot ealizingrepresentationof n individuals ofkind to theJ udgment.tthenetworkevel, heresnospreadingfactivationrom toJ.The nclinein ctivationpace),.e.,morphologicalontent,laysn ctualcausal ole nbringingbout heJ udgment;he ccurrentepresentation,,doesnot.Thus,wehavehere conceptuallyossibleaseofType functional


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Connectionismnd theCommitmentsfFolk Psychology 143discreteness.epresentationmight e a complexepresentationhat ullyjustifies-in the asiest ase, hepremisesfa valid rgumentorJ. YetKleads to J only n conjunctionith he mis)informationorphologicallyembodiedn he nclinerom -realizingointsoJ-realizingoints;ndK leadstoJ nthatasewhetherrnot he nferentialrajectoryommencesromnR-realizingoint. urthermore,he ersoneed ot onsciouslyepresenthe actthat he ndividuals ofkindK for isprejudiceoncerning's to comentoplay. It san nterestingmpiricaluestionhetheruch representationustbe occurrentt all,even nconsciously.)Consider,n ight f he oregoingiscussion,SG'sexamplefClouseau.Supposehat louseau'snternaletworksata point inactivationpace hatrealizes he tate-type:(B) believinghat he utleraidhe penthe ighttthe illage otel,and hat esaidhe arrivedack n themorningrain.Supposehat louseau'sctivationandscapeasdistinct,eterminate,nclineswithint hat espectivelyubserverajectoriesppropriateo belief-typesandT,respectively:

(H) believinghathe illage otels closed or he eason.(T) believinghat hemorningrain asbeen aken ut fservice.(Wewill all hesenclinesheH-inclinend heT-incline,espectively.)ntheimmediateicinityf thepoint on Clouseau'sctivationandscapehat iscognitiveystemurrentlyccupies,he ocal opographysa complexontour-ing onsistingf he uperpositionfvariousifferentnclines,ncludingheH-inclinend he -incline.upposehat tpoint ,the -inclinend ertaintherinclinesnot ncludingheH-incline)ffectivelycancel achotherut"; .e.,when uperimposedogether,he -inclinend hese thernclinesointly akeno net ontributionothe ocal opographyn he icinityfp.Finally,upposethat he ominantet ffect,ocallytpoint , s contributedy heH-incline.So an nferentialrajectoryommences,manatingrom and erminatingtapoint 'whichealizes he tate-type:

(L) believinghat he utlers lying.This s a scenarionwhich louseau elieveshat he illage otels closed orthe eason, e alsobelieveshat hemorningrain asbeen ake ut f ervice,andhe nfershat hebutlers lyingn the asis fthe irst elief utnot hesecond.This cenarioanbe furtherlaboratedn several ays, orrespondingoType throughype functionaliscreteness.fthe ontentfboth eliefandbelief is only mbodied orphologicallyn theH-inclinendT-incline


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144/Terence organndJohniensonrespectively,ut eitherontentets ccurrentlyepresenteduringlouseau'sinferentialrocess,hen egetmorphological/morphologicalunctionaliscrete-ness:Type .But herere hreetherariantsr he cenario,herehe ontentofoneorboth eliefslsobecomesccurrent,.e., s partf he epresentationalcontentf point , or of someother oint long he nferentialrajectorycommencingrom : H andT both ccurrentType ); H occurrentutnotT(Type ); T occurrentutnotH (Type ).So the pshotf his ubsectionsthatll fourf hese indsffunctionaldiscretenessre pen onceptualossibilities,nderistributedonnectionism.RSGaremistakeno supposehatunctionaliscretenessf ognitivetatesanonlyoccur fthecontentfthose tatess embodied,n weightsnd/ornactivationatterns,n a physicallyiscreteay.'53. The ProjectablePredicatesArgument.

RSG brieflyffer second rgumentor heradicalncompatibilityfconnectionismnd common ensepsychology. etworkA learned hetruthvaluesofsixteen ropositions.SG describe secondmodel,Network, whichlearnedhe ruth alues f hose ixteenropositionslusonemore. heweights,biases, ndinternalctivationalues n processingrenotsimilarn NetworksA and B, andthedifferencesetweenhem onot orrelatenanywaywith hedifferencen what heyhave"learned". othofthesenetworksepresenthepropositionhat ogshavefur,mong thers. here re ndefinitelyany therconnectionistetworkshatepresenthe nformationhat ogshave ur, hichdiffern ndefinitelyany ays rom etworksandB.Fromhese bservations,SGargues follows.

...commonense sychologyreatsredicatesxpressinghe emanticropertiesfpropositionalttitudess projectable.hus believes hatdogshave fur'or'remembershat ogshavefur'willbe projectableredicatesn commonensepsychology....But]houghherere ndefinitelyanyonnectionistetworkshatrepresenthenformationhat ogshave urust s well sNetworkdoes, hesenetworksaveno projectableeaturesn commonhat re describablenthelanguagefconnectionistheory.514)Thus, we takeit,the conclusions that ommon ensepsychologyreats sprojectablehuge lass fpredicateshat onnectionismenderson-projectable.(Projectableredicates,ayRSG,are the ort fpredicateshatre ppropriatelyused in nomological or law-like generalizations"p. 504).) Hence, ifconnectionismurnsut o becorrect,here illbe no states fthekind hatthese ommon-sensesychologicalredicatesurporto ascribe.'6RSG professnot to find "featuresn common hatare describablenconnectionistheory"nNetworks andB. We suppose hat hey rethinking


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ConnectionismndtheCommitmentsf FolkPsychology 145ofconnectionistheorys the heoryfnetworks:ctivationevels ndtheequationshat eterminehem, eights,iases,nd earninglgorithms.hereareindeed o projectableredicatesere hat orrespondotheprojectablepredicatesfcommonense sychology.But he rojectableredicatesf ommonense sychologyre predicatesexpressinghesemanticropertiesfpropositionalttitudes."onnectionisttheorylsohaspredicatesxpressinghe emanticropertiesf epresentations-e.g., thepredicate,representationhatdogshavefur.'A largepartofconnectionistheorizingonsistsf alkbout epresentations.ead he escrip-tion f ny onnectionistodel eadRSG'sdescriptionfNetwork Promin-entnthe escriptionf ny onnectionistodelsanaccountf he epresen-tationsnthemodel ndofhow heyrerealizednthenetwork.heconnec-tionist odelsnwhich SG'sargumententersre, heynsist,obeconstruedas cognitiveodels. urely,f model s construeds a cognitive odel,henrepresentationsillbe a centralart fthe heoryf hatmodel.Thus,Network andNetwork do have featurencommonhatsdescribablenthe anguage fconnectionistheory:hey oth epresenthepropositionhat ogshavefur. nd, fcourse,heyhare his eatureith llthose therctualndpotentialonnectionistodelshat ave representationofthe ropositionhat ogshavefur.

Furthermore,onnectionistepresentationredicatesre rojectable.or nyreasonablyuccessfulonnectionistodel hat as representationf he ropo-sitionhat ogshave ur,representationhatogshave ur'willbea projectablepredicate.fthe lleged epresentationsfa model renot rojectableelativeto thecognitiveaskbeingmodeled,hemodeldoesn'twork. xactly owrepresentationredicatesre rojectableelativeo modelwilldepend pon hecognitiveask eingmodeled.ut hats whatnewouldxpect,ince ognitivemodels endobeaimed tmodelingsingleognitiveask r mall lusterftasks,nd he ausal ole fa representationelativeo onecognitiveaskwillbedifferentromts ausal ole elativeo differentognitiveasks.'7When he amenetworks trainedponthe ame askmorehan nce,therere ifferencesnweights,iases,nd ctivationevels fhiddenodes,utgeneralizationsnvolvingepresentation-levelonnectionistredicatesre ypi-cally rojectableromne rainedpnetworkothe ther. epresentation-levelgeneralizationsre imilarlyrojectablehen istinctetworksre mplementa-tions f he ame ognitiveodel,ndwhen imilar etworksre rainedpondifferentut imilarasksaswereRSG's Network andNetwork).Generalizationsnvolvingepresentation-levelonnectionistredicatesrenot,ngeneral,rojectableromneconnectionistodel oothers evotedodifferentognitiveasks; he erms fsuch generalizationreoften ot venapplicableo theothermodel. utthat s a result f thenaturefcognitivemodeling.nany ase, t s not differenceromommonense. romhe ointofview f ommonense sychology,he egreefprojectabilityfgeneraliza-tionsnvolvingropositionalttituderedicateso otherognizersnd other


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146 / TerenceHorgan nd John iensonkinds fcognizerss quitevariablend context ependent.hus, onnectionismhas projectablepredicates-predicatesssigning epresentationso networkmodels-that ineup quite nicelywith heprojectable redicatesf commonsensepsychology.WhenRSG say"thesenetworksaveno projectableeaturesn common"(ouremphasis), heres a sense n whichwhat hey ay s true. henetworksssuch have no projectable eaturesn common.The models-the networksinterpreteds performing cognitive ask-do have projectable eatures ncommon.Cognitive cience s a branch f scientific heory hatspans andinterconnectseveral evels ofdescription.Within lassical,pre-connectionist,cognitive cience, he canonical rticulationf themulti-level ature f theenterpriseas givenby DavidMarr,whowrote:Atone xtreme,he op evel,s the bstractomputationalheoryf he evice,nwhich he erformancef he evice scharacterizeds a mappingromnekindofinformationo another,heabstractropertiesfthismappingre definedprecisely,nd ts ppropriatenessnd dequacyor he askre emonstrated.n hecenters the hoice frepresentationor he nput ndoutputndalgorithmotransformneinto heother. t theotherxtremere thedetails f howthealgorithmnd representationre realized hysically-theetailed omputerarchitecture,o tospeak. 1982, 4-25)Thus,Marrdentifieshree heoreticallyignificantevels fdescription.he toplevel, he evel ofthemental ua mental, pecifies cognitiveunction:transi-tion-functionhat airs ognitivetateswith he ppropriateognitiveuccessor-states.'8The middle evel specifies he algorithmy whichthatfunctionscomputed.And the lowest evel specifies he physicaldevice in which thealgorithms implemented.'9An algorithm,r program,s a mathematicalbject, set of rulesformanipulatingymbolsor data-structuresurelyon the basis of theirfor-mal/structuralroperties,ndependentf ny ntentionalontentheymight ave.Symbols nddata-structures,o described,re also mathematicalbjects.Thus,themiddle evel nMarr's ypologysa mathematicaleveloforganization.hislevel of organizationmediatesbetween ntentionalmental tatesand theirphysical ealization.ntentional entaltates nd tate-transitionsrerealized ycertainmathematicaltates ndstate-transitions,hich nturn rerealizedbycertain hysical tates nd state-transitions.20he mathematicalevel is theappropriatenefor haracterizinghe bstractystemffunctional/organizationalfeatureshat onstitutesature's ngineeringesign orhuman ognition.

However, he discretemathematicsf algorithmss notcommon o allapproachesocognition. s discussednSection .5, thenaturalmathematicalframeworkor onnectionisms the heoryfdynamicalystems. nd fcogni-tive ransitionsrenotdeterminedy algorithmsver ymbols,hen t neednotbe assumed hat hepotentialognitiveransitionsfa cognitiveystemonsti-


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Connectionismnd theCommitmentsfFolkPsychology 147tute tractablyomputable unction.Marr'stri-level ypology orcognitivescience anthusbe seenas a speciesof a moregenericri-levelypology:

Cognitive tate-Transitions.he levelof themental ua mental.MathematicalState-Transitions.he level offunctionalrganization.Physical mplementation. he level ofthephysical ua physical.Connectionistognitivemodels re notherpecies f his enericypology, iththemathematicsfdynamicalystemss thenaturalmathematicalrameworktthemiddle level of description,nd withconnectionistetworksoften ssimulatedn conventionalomputers)s theprototypicalevicesforphysicalimplementation.2"In bothclassical and connectionistognitive cience,then, heorizinginvolves hecognitive,hemathematical,ndthephysicalevelsofdescriptionandthe nterconnectionsmong hem. nboth lassical ndconnectionistogni-tive cience, redicatest each evelofdescriptionreprojectable,ven houghthe state-typeshey express are multiplyrealizable at lower levels ofdescription.22o claim, s RSG do,that onnectionistodels hat iffernthemanner f theirNetworkA andNetwork "haveno projectable eaturesncommon hat re describablen thelanguage f connectionistheory,"s toignorethe factthatconnectionistognitive cienceincludestwo levels ofdescriptionbovethe evelof thephysical ua physical.4. Conclusion.

RSG argue hat ommon ensepsychologys incompatible ith certainbrand fconnectionismecause ommonensepsychologys committedo thefunctionaliscretenessfpropositionalttitudes,hile thatbrand f connec-tionism recludesunctionaliscreteness. edistinguishedhreeways nwhicha cognitiveystemmaypossess ntentionalontent:ccurrently,ispositionally,ormorphologically.ixing ndmatchingheseways fpossessingontenteadsto several onceptuallyossible ypes ffunctionaliscreteness. eargued hatcommon ensepsychologys committedo onlythe most nnocuous indoffunctional iscreteness-Type functionaliscreteness,n which occurrentrepresentationsake causalcontributionndmerely ispositionalnesdo not.Virtuallyny systemhathas representations,ncludinghesystemsfRSG'sbrand fconnectionism,illexhibit ype1 functionaliscreteness.Common ensealso recognizeshepossibilityf the other ypes f func-tionaldiscretenesshatwe distinguish,ndsome of thesepossibilitiesuggestinterestingaysto think boutcognition.We suggestedin Section2.5) thatthese therypes ffunctionaliscretenessouldbe foundndistributedonnec-tionistmodels. Thus, even if common sense psychology s more deeplycommittedo functional iscretenesshanwe believe,RSG wouldnothaveshown that common sense psychology s incompatiblewith distributed


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148 / TerenceHorgan nd John iensonconnectionism.We alsoargued Section ), contraryoRSG,that onnectionistheoryoeshaveprojectable redicatesomparableo thepropositionalttituderedicatesfcommon ensepsychology.Even if we have succeeded n showing hatRSG's argumentsre notsuccessful,his onstitutesnly limited efense f he ompatibilityf connec-tionism nd common ensepsychology. here re other rgumentsfoote.g.,Davies 1991) that urporto demonstraten incompatibilityetween onnec-tionism nd common ense." Butaddressinguch rgumentsndthe ssues heyraise s a taskfor nother ccasion.Notes1. The paperhas been anthologizedt least four imes see the entry or t in thebibliography),ndhas beenwidely iscussedntherecent hilosophicaliterature.2. We leave open the questionof what sortsof conditionsmustbe met bymorphologicalontentn order or tto count s themorphologicalossession fabelief or of someother tate-typef common ensepsychology). ere is oneplausible-lookingequirement:norderobe a belief,he tate-typeust e onethatcan become noccurenthought ithinhe ognitiveystem. orphologicalontentonlycounts s a belief fthat ontents also possesseddispositionally.3. Whetherrrivingt a conclusionwithout onscious nferences properly alledinferencet all fromhepoint fviewofcommonense s not lear.But tdoes notmatter orpresent urposes.4. This sort f thing-non-tokenednformationlayingn essential ole ncognitiveprocessing-appearso beubiquitous.f treally oesoccur, s the henomenologyofconscious xperienceuggests,hen ny dequate heory fcognition eeds o beable to account or t.5. This arguments stated s clearly allacious.t has the ame ogicalforms: sincethere renon-cowsnthepasture, here re no cows nthepasture.Since networkA has states hat mbody ropositionalnformationndiscretely,t acks tates hat

embody ropositionalnformationiscretely.)utwhatRSGobviouslymean sthatthepropositionalnformationmbodiedn the ystem's eightss not mbodied yfunctionallyiscreteubstructuresf weightedonnections.6. O'Brien saysherethat he nformations encoded n the network'sonnectivitymatrix,ndthis s not n uncommon ay o speak.Wewould hoose,however, otto saythat heweights hemselvesncode nformation,hough heymaybe saidtoembodyRSG's word) nformation.nformations notrepresentedn theweights;it's representednthe representations.he weights o notconstitute code.7. Intraditional,re-connectionist,odels fmemoryncognitivecience,memoriesare full-fledgedepresentations;hey eside n a mental filecabinet,"nthe ameform swhen hey ecome ccurrentybeing etched ack nto he ystem'sentralprocessingnit. utthe deaof toredin-the-head,r n-the-soul) emoriessnotpresupposedy ommon ense sychologyeven houghf tmighteem otosomephilosophers ducatedin classical cognitive cience). Commonsense is notcommittedo any particulariewabout heontology fmemory; ence t is notcontraryo common ense osaythat eliefs nd memories reno wherewhennot


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ConnectionismndtheCommitmentsfFolkPsychology 149active.Cf.Locke:"Memory,ignifieso morebut his, hat heMindhasa Power,in many asesto revivePerceptions...And n thisSense t s, that ur deas aresaidto be inourMemories, henndeed,heyreactually owhere, ut nly hereis an abilityn theMind,when twill,torevive hem gain.... (Essay, I.X.ii.)8. There aremanyways nwhich ctivated epresentationsight e involved n aprocess.Some might, orexample,be falsestarts hat re overruled yfurtherinformationr processing. ut nsuchcasesit s often ossible, y followingutpathsof spreadingctivation,o determine hich ctiverepresentationsadeapositive asual contributionn bringingbouttheend result, nd which ctiverepresentationsot overruled.9. Aparticularype f ognitiveransition ighte traversedn everal ognitivetepsbyoneconnectionistystemut eapt n a single ound yanother.f.Lloyd1991.

10. Stich ndWarfieldforthcoming)ake ssentiallyhe amepointwithout,owever,distinguishingetween aradigmaticunctionaliscretenessndtheother inds).Needlessto say,this s a changeof position orStich.11. Amore amiliarource fmultipleealizabilitynconnectionistodels s that ftenmany ifferentectors-allvectorsmeetingome ondition-countsrealizinghesame representation..g., the representations considered ctivatedwhenallmembers f a certain et ofnodeshave activationevel> .85.12. Sometimes hen woor more istinctepresentationsre realized y single ointon the activationandscape, ach occurrentepresentationill correspondo aphysicallyiscreteub-patternf ctivation ithinhe verall ctivationtate f henetwork; ut ometimeshe otal omplex epresentationill nstead e a physicalsuperpositionf physical ub-patterns,ith ertain odes participatingimulta-neouslynseveral ub-patterns.In Bach's piano music, ften noteplayedon asingle ey elongs imultaneouslyo everal uperimposed,ontrapuntal,elodies.)13. Certain ophisticatedearningechniquesmploywhats calledthe movingarget"strategy, hich n effect rings bout a controlledo-evolutionfweights ndrepresentations;n dynamical ystems erms, hisamounts o the simultaneousmoldingfthe ctivationandscapendre-positioningfrepresentationaloints nthat andscape.We discuss pecificxamplesnHorganndTienson 1992a, 1993).14. Thetermprejudice'has negativessociations. uttherereprejudiceshatnclineonetomakepositiveudgments,s well as evaluatively eutraludgments.15. ForsterndSaidel (forthcoming)resent simplenetworkhat rguablyxhibitssomeofthekinds ffunctionaliscreteness e havebeendescribingand alsoillustratesome of theways thatfunctional iscretenesss relatedto variouscounterfactualonditionalsrue f the network's erformance).16. RSG state heallegedconnectionism/commonensecontrastn anotherway:

From he oint fviewofthe onnectionistodelbuilder,he lassofnetworksthatmightmodela cognitivegentwhobelievesthat ogshavefur s notagenuinekind t all, but simply chaotically isjunctiveet. Common ensepsychologyreats heclass of peoplewho believethatdogshave fur s apsychologicallyatural ind; onnectionismoesnot. 514-5)

Thissuggests rhetoricallytrongerliminativistonclusion:fconnectionismscorrect,hen ertain atural inds fcommonensepsychologyo not xistthoughitseemsoddtosaythat ommon ensepsychologyreatsheclassofpeoplewho


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150 / TerenceHorgan nd John iensonbelieve hat ogs ave ur,s opposedo he elieftself,s a naturalind).Wewilldiscuss he rgumentn terms f projectableredicates,lthough hatwe sayapplies qually o natural inds.17. Most any connectionistognitivemodel will exhibit ertain on-accidentalgeneralizationst he epresentationalevel fdescription.or nstance,nChapter1 ofRumelhartndMcClelland1986), nefinds he ollowingemarksboutmodel fmemoryetrievalhat mbodiesnformationbout hemembersftwogangs,he harksnd heJets:

Themodel...tendsoretrievehats commono hosememorieshichmatcha retrievaluewhichs toogeneralocaptureny nememory....n thiswaythemodel anretrievehe ypical alues hatmembersf heJets asoneachdimension-evenhougho oneJet asthese ypicalalues.p. 30)18. Marrabels he op evel the heoryf he omputation'.his eferso whats tobecomputed.ow t scomputeds to be determinedt themiddleevel.19. Ingeneral,he nterconnectionsetweenhesehreeevelsnvolvevariable umberof nterveningevels. low hartspecifyevels fdescriptionetweenhe op ndthemiddle-increasinglypecific eterminationsf the lgorithmywhich hecognitiveunctionscomputed.heremay e everalevels etweennAlprogramin a familiar rogramminganguage-Marr's iddle evel-and themachinelanguagefthe omputern which t s running-whichs notyet physical

implementation,ut rathers the abstractpecificationf the computationalprocesseshatiterallyet hysicallymplemented.he pecificationf network,including eightsnd ctivationquationsnd evels, ccupies similar ole nconnectionism.20. Multipleealizabilitys possible etweenach evel nd nebelow t.This ointscommonlyecognized ith especto thephysicalealizationfcomputationalprocesses,ut t sequallyrue or he omputationalealizationf ntentionaltate-transitions.orfurtherlaborationf his oint,eeHorgan1992, p.454-6)ndHorganndTienson1993,pp. 160).Onp. 162ofthe atter equote passagefrom arr1977) ndicatinghat e himselfvidentlyppreciatedhe oint uiteclearly.21. Thisgenericrameworknd hepossible irtuesf ts onnectionistpeciesrediscussedndetailnHorganndTienson1994, orthcoming).22. For a discussionfmultipleealizabilityfhigher-leveltatesndprocessesnconnectionistodels,eeBicklein preparation).23. Davies rguesi) thatommonense sychologyequireslanguagef hought,norder o accommodatehedistinctiveausal oles hat ommonense osits orsemanticonstituentsfpropositionalttitudes,ut ii) that onnectionismithdistributedepresentationss incompatibleith languagefthought. eagreewith avies hatyntaxsnecessaryosupporthe ind f ausal ole f emanticconstituentshat ommon ensepsychologymplies. utwe maintainhatconnectionismoesnot recludeitheryntactictructurenmentalepresentationsor structure-sensitiverocessing;ordoes t becomemeremplementationfclassicismy ncorporatinghese eatures.f.HorganndTienson1988,1989,1992a, 992b, orthcoming, forthcoming).


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Connectionismnd theCommitmentsfFolkPsychology 151ReferencesBerg,G. (1992). "A ConnectionistarserwithRecursive entence tructurendLexicalDisambiguation,"roceedingsftheAmerican ssociationorArtificialntelligence.Bickle,J. in preparation).Connectionism,eduction, nd MultipleRealizability."Clark,A. (1990). "Connectionist inds,"Proceedings f theAristotelianociety, 0.ReprintednC. andG. MacDonald eds.), The hilosophyfPsychologyBlackwell,forthcoming).Davies,M. (1991). "Concepts, onnectionism,nd the Languageof Thought," nW.Ramsey, . Stich, ndD. Rumelharteds.),Philosophy nd Connectionistheory,Earlbaum.Forster,M. and Saidel, E. (forthcoming).Connectionism nd the Fate of Folk

Psychology: ReplytoRamsey, tich, ndGaron," hilosophical sychology.Horgan, . (1992). "FromCognitive ciencetoFolk Psychology: omputation, entalRepresentation,nd Belief,"Philosophy ndPhenonemological esearch, 2.Horgan, . andTienson,J. 1988), "Settlingnto New Paradigm," outhern ournal fPhilosophy, 4, Supplement. eprintedn T. Horgan and J. Tienson (eds.),Connectionismnd thePhilosophy fMind Earlbaum, 991).Horgan, . andTienson, .1989)."Representationsithout ules," hilosophical opics,17.Horgan, . andTienson,J. 1992a). "Cognitive ystemss Dynamical ystems," opoi,11.Horgan,T. and Tienson,J. (1992b) "Structured epresentationsn ConnectionistSystems?"n S. Davis (ed.), Connectionism:heory ndPractice,Oxford.Horgan,T. and Tienson,J. 1993). "Levels ofDescriptionn NonclassicalCognitiveScience," nC.Hookway ndD. Petersoneds.),Philosophynd Cognitivecience,Cambridge.Horgan, . andTienson,J. forthcoming). "A Nonclassical ramework orCognitiveScience,"Synthese,ssueon connectionismndphilosophy.Horgan,T. and Tienson,J. forthcoming). Connectionismnd thePhilosophy fPsychology: epresentationalealismwithout ules.M.I.T.Lloyd,D. (1991). "Leapingto Conclusions:Connectionism,onsciousness,nd the

Computational ind," nT. Horgan nd J.Tienson eds.),ConnectionismndthePhilosophy f Mind,Earlbaum.Marr,D. (1977). "Artificialntelligence-APersonalView,"Artifcial ntelligence,.ReprintednJ.Haugeland ed.), MindDesign, M.I.T., 1981).Marr,D. (1988). Vision, reeman.O'Brien,G. 1991). "IsConnectionismommonsense?",hilosophical sychology,4.Ramsey,W., Stich,S., andGaron,J. 1990). "Connectionism,liminativismndtheFuture f Folk Psychology,"hilosophicalPerspectives, , ActionTheory ndPhilosophyfMind,1990,edited yJ.E. Tomberlin. eprintednW. Greenwood(ed.), TheFuture fFolkPsychologyCambridge,991); in W. Ramsey, . Stich,andD. Rumelharteds.),PhilosophyndConnectionistheoryEarlbaum,);nS.Christensennd D. Turnereds.), Folk Psychologynd thePhilosophy fMind(Earlbaum, 1993); and in C. and G. MacDonald (eds.), The PhilosophyofPsychologyBlackwell,forthcoming).


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152 / TerenceHorgan nd John iensonRumelhart,. andMcClelland,J. 1986). ParallelDistributedrocessing: xplorationsin theMicrostructuref Cognition.Volume : Foundations,M.I.T.Stich, . (1991). "CausalHolism nd Commonsensesychology: Reply o O'Brien,"Philosophical sychology,.Stich, . and Warfield, . (forthcoming).Do Connectionist indsHave Beliefs?-AReply o Clark ndSmolensky,"nC. and G. MacDonald eds.),ThePhilosophyfPsychology, lackwell.

connectionism and the commitments of folk psychology

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