DRAFTFutur eModels for Mind-Machines

Marvin L MinskyMassachusettsInstituteof Technology

http://www.media.mit.edu/people/minsky/

Abstract

“Seeknot to follow in the footstepsof menof old; seekwhat theysought.” – Matsuo Basho

In recentyearssomepolitical leadersof severalcountrieshaveexpressedconcernthatin futureyearstheircountrieswillnot have enoughyoungpeopleto supportthe largeproportionof old ones. So, incredibly, they proposeto take stepsto increasetheir reproductionrates. Insteadwe embarkon programsto develop intelligent robotsthat could increaseproductivity in thefieldswhereshortagesmayappear. Then,eachworkinghumancouldeasilysupportmany moreotherones– with lessdamageto ourenvironment.However, therehasnotbeenmuchprogressin recentyearstowardmakingmachinesthat areableto do mostmundanejobs that peopledo. I think this is becausemostAI researchershave notusedadequatelarge-scalemodelsfor designingsystemsthatcouldhave enough“commonsense”or “resourcefulness.”

1 Intr oduction

Humanity hasalways facednew technologicalfrontiers– but rarely did it appreciatethosewonderfulopportuni-ties. However, thepastthreecenturieshasbeendifferent,I think – andover thepastfifty years,we’veseenthemostimmenseprogressin history. For examplePhysics,As-tronomy, andCosmologyhave progressedperhapsmorein thepasthalf-centurythanthey did sinceGalileo’s time.Biology hasmovedevenmorequickly; thefield of molec-ularBiology wasvirtually bornjustfifty yearsago.Today,I think, we areenteringasimilar phaseof Psychology.

To build reliable,humanlikerobots,we’ll needwaystomake themunderstandtheproblemsthatwe wantthemtosolve. Onewayto dothiswould to enablethemto think inwayslikeours.However, wedon’t yetknow how todothis– becausewe still know too little aboutour own minds.Our mindsareworking all the time, but we rarely thinkaboutwhatmindsare. Whataremindsmadeof andhowthey work? How do mindsbuild new ideas?Why couldour scientistsdiscover so much aboutatomsandoceansandplanetsandstars– yetsolittle aboutwhatour feelingsare? Our mindsareworking all the time – yet we knowalmostnothingaboutthem. We rarelydiscussthesesub-jectsin schools,or think aboutthemin our daily lives. Itis almostasthoughwe’ve imposeda tabooagainsttryingto think aboutsuchthings.

How doesImaginationwork? How do minds learnfrom experience? How do we recognizewhat we see?How do we choosewhich wordsto say?How do we un-derstandwhat they mean?How doescommonsenserea-soningwork? Eachof thesecommonabilitiesis basedonhugenetworks of processes.So, to answerthoseques-

tions, we’ll needto accumulatemore good ideasaboutwhatare thosenetworks,how they evolved,andhow theirresourceshave managedto merge– to form theconstruc-tions we call our minds. In this essayI will startby re-viewing someideasaboutminds– eachof which hasjustenoughpartsto answercertainkinds of questions.ThenI will suggesthow thesesimplemodelscanbe expandedandcombinedto make bettertheoriesaboutour psychol-ogy. (Eachbrief sectionbelow will befurtherdiscussedinmy forthcomingbook,TheEmotionMachine.)

2 One-Part Modelsof Mind

Themostpopularconceptof ahumanmindenvisionseachpersonashaving a ‘Self” – which embodiesall thosefea-turesand traits that distinguishyou from everyoneelse.But whenwe askwhatSelvesactuallydo, we’re likely tohearthis vacuousview:

Your Selfviews the world by usingyour senses,andchoosesall your desires and goals. Then it solvesall your problemsfor you, by exploiting your ‘intel-ligence’.It formulatesplansfor whatnext youshoulddo– andthenmakesthepertinentmusclescontractsothat yourbodyperformsyouracts.

Isn’t this a strangeidea?It saysthatyou make no de-cisionsyourselfbut justdelegatethemto somethingelse–to thatmythicalpersonyou call ‘your Self’? Clearly this‘theory’ can’t answerour questions– so why would ourmindsconcoctsucha fiction?

Therapist: “That simplistic legend makes life seemmore pleasant. It keepsus from seeinghow muchof our soulare controlled by unconscious,detestable

goals.”

Pragmatist: “It alsohelpsto make usefficient! Morecomplex ideasmightjust slowusdown.It wouldtaketoo longfor our hardworkingmindsto understoodev-erythingall thetime.”

Thetroublewith that“Self” ideais thatit doesnotex-plain what’s insidea mind. It’s a theorythatdoesn’t haveenoughpartswe can useto build explanations. If youask abouthow your mind makesdecisions,the Central-Self modeljust avoidsthatquestion,by ascribingall yourabilities to anothermind inside your mind. (Before thedawn of moderngenetics,a similar theorywasprevalent:it proclaimedthat every spermalreadycontaineda per-fectly formed little personage.)The notion of a CentralSelf can’t helpusto understandourselves.

Many otherpopulartheoriestry toderiveall thevirtuesof mindsfrom onesinglesourceor principle:

Survivalinstinct: All our goalsstemfromtheinstincttosurvive.

PleasurePrinciple: All our drivesare basedon seekingpleasure

Aversion Principle: We’re driven by needsto escapefrompain.

Conflict Resolution:All our actionsare directedat re-solvingconflicts.

Urge to control: Our resourcesevolvedto control ourenvironment.

ReinforcementandAssociation:Themindgrowsby ac-cumulatingvariouskindsof correlations.

Eachof these‘unified theoriesof mind’ hasvirtuesanddeficiencies.For example,the Survival-Instincthypothe-sishelpstop describea wide rangeof behaviors – but it’sbasedonawonderfullywrongidea.Overthecourseof ourevolution, our brainsassembleda greathostof systems–eachof which servedin a separateway to protectusfromcertainkindsof harm. Theresultof theprocesswasthata brain is a ‘suitcase’of systemswith similar functions;however, thosesystemshavenocommonstructure– sotounderstandhow thosesystemswork, we’d have to exam-inethemoneby one.That‘survival instinct’ is justanillu-sion.Whenyou look atmindasasinglething– insteadofa grandarchitecturalscheme– you’ll seelittle morethana featurelessblur, insteadof the marvelousstructureyouare.

3 Two-Part “Dumb-Bell” Models ofMind

Many popularmentalmodelsare basedon “dumb-bell”distinctionsthattry to divide theentiremind into just twocomplementaryportions, such as Left-Brain vs. Right-Brain, Rationalvs. Intuitive; Intellectualvs. Emotional,or Consciousvs. Unconscious. Thesecanbe betterthanSingle-Selfmodels.However, they too oftensupportold

superstitionsthat make it hard to develop more usefulideas. For example,whenneurologistsdiscoveredsomedifferencesbetweenthe brain’s two hemispheres,this re-vivedmany views of our mindswhich were,in our moreancienttimes,expressedin termsof oppositeslike Dev-ils vs. Angels, Sinnersvs. Saints,andYins vs. Yangs.Sothispseudoscientificschemerevivednearlyeverydeadideaof how to seethementalworld asa battlegroundfortwo equalandoppositepowers.

Why aredumbbelltheoriessopopular?I suspectthatthis is because– just like thoseold myths– they providejust enoughparts to tell storiesof conflicts. Insteadofbelieving suchstory-like myths, we should try to maketheoriesof why they enchantus.

4 Thr ee-partModels of Mind

Three-parttheories,althoughstill too simplistic, arerichenoughto suggestbetterideas.Herearea few of my fa-voritesuchframeworks:

Paul MacLean’s “Triunebrain” hypothesis[TheTriuneBrain in Evolution] triesto explainhow mindsbehavein termsof machinerythat evolved in threestages–namely, when our ancestorsbecameReptiles, thenMammal, and finally, Primates. He identifiesthosehypothetical‘layers’ with stagesof our evolutionaryhistory – as well as with different aspectsof think-ing. However theevolution of our ‘lower’ brainsys-temsdid notsuddenlyceasewhenthose‘higher’ onescame.They all continuedto co-evolve,sothateachofourbehavioral functionsis basedoncomponentsfromeverystage.

Eric Berne’s “TransactionalAnalysis” hypothesisisbasedon the idea that every personevolves sub-personalitiesbasedon modelsof thechild, adult,andparent. [Eric Berne,TransactionalAnalysisin Psy-chotherapy] This is quite different from MacLean’sscheme,andmoresuitablefor describingthe devel-opmentof socialbehaviors.

SigmundFreud’s “Psychoanalysis”theory was basedon a psychologicaltriad of interactionsbetweena“Id” or collectionof Instinctive urges,a “Superego”thatembodiesourhigh-levelsocializedgoalsandpro-hibitions, and an “Ego” that resolves or suppressesthe conflictsbetweenthem. I especiallylike Freud’s‘sandwich-like’ architecture,first becauseit is non-hierarchical,andsecondbecauseit emphasizes‘neg-ative knowledge’– thatis, knowing which thingsoneshouldnotdo. Competencerequiresbothpositiveandnegative knowledge– andI suspectthat asmuchashalf of ourcommonsenseknowledgemayhaveof thisnegative character. [SeeMarvin Minsky, “NegativeExpertise”]

Figure1

5 Viewing the Mind as a “Cloud ofResources”

Thehumanbrainhashundredsof partsthathavedifferentfunctions– soany comprehensivemodelof mindmustin-cludedescriptionsof all thoseresources.By “resources”I meanto includebothbodiesof knowledgeandprogram-like processes– suchasperceptualschemesfor makingdescriptions,for forming goalsandfor makingdecisions,or methodsfor solvingdifficult problems.Especially, thebrainneedsresourcesto assesswhatotherresourcesdo –e.g., to decidewhich onesare making goodprogressorwastingour time, or to recognizeconflictsandtry to re-solve them. This suggeststhat we think of the brain asa cloudof variedresources,whereeachcanuseothersincertainways.[Figure1]

Holistic Philosopher: That whole idea seemswrongto me. By dividing themindinto smallerparts,aren’t youlikely to missthewholepoint? Unlessyoulook at a thingasa whole, you’ll missits mostvital aspects.Surely youneeda more holistic view.

Every representationwe use is boundto miss someimportantaspects,for which we must switch to anotherview or a different type of representation.So to under-standanythingwell, we’ll usuallyneedto useseveralsuchviews, and someways to interconnectthem. Certainly,this must includesome“high level” views that try to de-scribetheentirething. However, ‘holistic thinkers’ don’talwaysrecognizethatvaguesummarieshave their limits,too. Like cartoons,they give us illusions of “seeingthewholething at once.” However, thesetendto beoversim-plified views thatcannotexplain anything in detail – justasmapsdisplayonly a few striking features,while sup-pressingdetailsof theactualregions.

Thisideaof amindasacloudof resourcesmightseemtoovagueto havemuchuse,but it helpsusto escapefromthosedumbtwo-partmodels.For considerthe followingtypeof phenomenon:Onemomentyour babyseemsper-fectly well, but thencomesomerestlessmotionsof limbs.Next you seea few catchesof breath– andin just a fewmomentstheair fills with screams.TheSingle-Selfmodelhas no way to explain what could possibly causesuchchanges– but this is easierto explain if we assumethat

Figure 2

ananimal’s braincontainsseveralalmost-separatesetsofresources– whereeachset evolved to serve somevitalneedlike procreation,nutrition, or defense.This model,developedby NikolaasTinbergenandKonradLorenz,isdescribedin Tinbergen ‘s book “The Study of Instinct”(OxfordUniversityPress,1951).It doesnotexplainmuchabouthumanthoughtbut hasturnedout to besurprisinglygoodat accountingfor muchof whatanimalsdo.

Oneform of a systemwith sucha descriptionmightresemblea humancommunity, wheredifferentpeopledodifferent jobs – as in Howard Gardner’s theoriesaboutMultiple Intelligences,which leadto goodmodelsfor rep-resentinga person’s largestscalebehavior. [See,for ex-ample,HowardGardner, Framesof Mind: TheTheoryofMultiple Intelligences.] However, eachmemberof a hu-man family, village, or corporationis alreadya compe-tentandautonomousperson– whereasinsideasingleper-son’s brain, eachresourceis far morespecialized;it cando only a certainfew things,anddependson the restforeverythingelse. So,whenwe envision an individual hu-manmind, it maybebetterto think of a largenetwork ofsmallermachines.Of coursethe resource-cloudview isnot quitewhatonewould call ‘a theory’ – becausewhileit saysthat thesystemhasparts,it doesnot specifywhatthosepartsare. It saysthey’re connected,but doesn’t sayhow. It suggestsno particulararchitecture.However, theveryvaguenessof theResource-Cloudideais whatmakesit a powerful tool for thought,just becauseit remindsusof thosedeficiencies.

In particular, it suggeststhat the brain must containenough“managers”to monitor, supervise,appraise,andcontrol the activities in particularsetsof otherresources.A typical resourceis connectedto severalothersandcanusethoseconnectionsin variousways,e.g., to exchangesomeinformationwith them,to exploit themfor variouspurposes.In particular, someresourceswill beespeciallyequippedto turn someother resourceson or off. Thus,from everymomentto thenext, only certainresourceswillbeactive– andthesewill determinewhatyour mind doesat any particularmomentof time. This suggestsa theoryof emotionsin whicheachemotionor ‘disposition’ resultsfrom somemoreor lesspersistentarrangementin whichcertainresourcesarehighly active, while othersaremore

Figure 3

quiescent:Anemotionalstateis whathappenswhenwe‘turn on’

a certainlargesetof resources.[Figure2]

6 A Lar ge-ScaleModel of ConsciousThought

How doesa brainemploy its resources?Oneway to startwould beto assume,ashasbeensuggestedby AaronSlo-man,thatour resourcesarearrangedin threeor morelev-els[Figure3]:– A “reactive” collection of resources“A” that includessystemsfor memory, perception,and other procedures,etc.– A “deliberative” collectionof resources“B” thatobserveandreactto theactivities in A.– A “self -reflective collectionof resourcesthat observeandreactto whathappensin “B,” etc.

No sucha complex systemcould work without moremachineryto control it. To seewhat that managementmight involve, let’s look at one fragmentof humanbe-havior.

Joan is part way across the street on the way topresenther finishedreport, and she’s thinking aboutwhat to sayat the meeting. Shehears a soundandturnsher headto seea quickly oncomingcar. Uncer-tain whetherto crossor to retreat, but uneasyaboutarriving late, she elects to sprint across the road.Later shereflectsabouther rather recklessdecision.“I couldhavebeenkilled if I’ d missedmystep– andthenwhatwouldmyfriendshavethoughtof me?”

Every minuteof every day, we experiencestreamsofeventslikethese.To someof them,wereactwithoutthink-ing. To othersweactmoredeliberately. Let’s try to imag-ine whatgoeson in Joan’s mind asshemakesherway tothatmeeting.Reactive Awareness: Shehears a soundand turns herheadin thatdirection.

WhenJoanturnedher headto look around,wassheconsciousof that sound,or wasthata ‘mindless’ re-action? Was sheaware of which musclessheusedto make herselfwalk acrossthat road? Not likely,becausemostof us don’t even know which muscleswe own. OtherresourcesinsideJoan’s brainmustbemoreinvolvedwith suchaffairs– but becausenopath-

ways communicatethis, Joanis not ‘aware’ of this.What is awareness,anyway? Whatdeterminesits fo-cus and range? What machinerydoesit usein thebrain?How many thingscanyoudoatonetime– andhow many canyoubeawareof? Presumably, thatwilldependon theextentto which they eachusedifferentresourcesfor them.But whenJoanperceivesthatap-proachingcar, this quickly takesthecenterstageandtakesholdof herfull attention.

Deliberative thinking: Sheis thinkingaboutwhatto sayat themeeting.

To do this shemustfirst considerhow several alter-nativesmight be received – andthencomparethoseimaginedreactions. This may require so many re-sourcesthatshehasto do this sequentially.

Reflective reasoning: Joan reflectsabout what shehasdone, andconcludesthatshemadea poordecision.

To what extent was she aware of what determinedherrisky decision?Reflectioninvolvesthinkingaboutwhatone’sbrain’shasrecentlydone.Thatkind of re-flectionrequiresresourcesto examinetherecordsthatotherresourceshavebeenkeeping.

Inter nal “Meta-Management”: but uneasyaboutarriv-ing late

Anotherfamily of resourcesis monitoringJoan’stem-poral progress,anddecidesthat whatever the meritsof whatsheis thinking,shecannotafford to delayherdecision.

Self-consciousReflection: “What wouldmyfriendshavethoughtof me?”

Joan thinks about how her friends might changetheir mentalrepresentationsof her. Reflectionslikethis have as their subject, a person’s private self-representations– the modelsor self-imagesthat weall constructto describeourselves.

Sothearchitectureof our mindsmustincludeat leastthesefivekindsof layers.This ideais furtherdevelopedinmy forthcomingbookTheEmotionMachine. Of course,a real brain is far morecomplex, andeachof thoselay-ersandarrowseventuallymustbereplacedby hundredsofsmallercomponents,interconnectedby thousandsof path-ways. (This schemeis partly inspiredby the researchofAaronSloman.)

7 Psychology Needs a Network ofLar geScaleModels

To understandthe humanmind, we’ll needto usesev-eral kinds of models. Somewill needonly a few parts– enoughto answerjustcertainquestions– but otherswillhave to be muchmorecomplex, to explain such‘highermental functions’ as reasoning,imagination, decision-making,andconsciousness.And,sincenoonesuchvision

canexplaineverythingthatwewantto explain,we’ll haveto keepswitchingbetweendifferentmodels.

Critic: That soundsvery disorderly. Why can’t yousimplycombinethemall, likethephysiciststry to do,intoasingleonethat combinesthevirtuesof all thosetheories?

That would result in sucha messthat no one couldhold it in mind all at once.We have to beableto usedif-ferentviews to highlight differentaspectsof things,andthat’swhy westill tendto speakaboutPhysics,Chemistry,andBiology – asthoughtheseweremoreor lessseparatesubjects.Someof thecontentsof eachof thosefieldscanbe deduced‘in principle’ from morebasicphysicalprin-ciples. The trouble is that we can’t do this “in practice”becauseno onecanactuallysolve thoseequations.(Andin Psychology, we can’t expect to have any suchset ofequations.)

The ‘large-scalemodels’thatwe’ve describedarenot‘hypotheses’to prove false or true. Instead, they aremorelike ‘pointsof view’ – particularwaysto think aboutthings,or to focusattentionon variousproblems.So it’snotaquestionof whichoneis ‘right’, but whereandwhento useeachview. Eachis a rougharchitecturalplan thatwill help us to understandcertainthings. However, be-causeeachof them has limitations, we’ll have to keepchangingour pointsof view, by shifting betweendiffer-ent Large-ScaleModel. Our own humanbrainsare toocomplex for us to envision all at once– so we’ll have tokeepchangingour representations.This shifting aroundmight at first seemdisturbing,but laterwe’ll seethat it’sworthwhile– becauseit will alsoenableusto describetheprocessthatactuallyhappensinsideourminds!

Using multiple modelsis not just a way to statethe-oriesaboutpsychology. It is part of psychology itself– becausewecanonly understandcomplex thingsbyswitching betweendifferent representations.This isthe basisof our mostpowerfulway to think: to keepinterweavingdifferentviewssofluentlythat weneversuspectthatwe’re doingit.

No systemascomplex asa humanmind canbe welldescribedby afew simplerules– becauseeachrulewouldhave many exceptions.This is becauseeachpartof suchasystemis likely to reflecttheparticularwaysthatit onceworked in the environmentin which it evolved(both outin the world andinsidethe brain). Thenwhenever somesubsystemfails to work, thosebrainswill tendto evolvea ‘patch’ – an ‘ad hoc’ way to help it to work. The re-sult is theaccumulationof multiple layersof patches,overhundredsof megayearsof evolution.

What doesit meanwhenyou say to yourself, “Thatwasa stupid thing to do,” or “I didn’t expect to succeedat that!” You’re alwayspraisingor blamingyourself,andholding yourself responsible.But whenever you changeyour emotionalstates,you’re using somedifferent pro-cessesandmemories– soyouareno longertheverysame‘you’. What givesus the sensethat we remainthe samewhile shuttling amongthosestates?Partly this mustbe

becausewe usethetermsfor describingourselves.Termslike ‘me’, ‘myself’ and ‘I’ help us to envision ourselvesaslike the‘eye’ of a cyclonethatstaysin oneplacewhileeverythingcirclesaroundit. In TheEmotionMachine I’ llarguethat the mind hasno singlewell-definedthing thatremainsthe samewhile controlling the rest. Insteadweeachhavearich collectionof personal,large-scalemodelsof ourselves.

Our ‘commonsense’ideas about ourselves have somany bad misconceptions.We all have grown up withcertaintraditionsthattacitly assume,for example,thatweeach‘hold’ a singlesetof beliefs. Thus,whensomeoneaskswhat you “really” believe – or what your ‘true’ in-tentionsare– or what you ‘really’ meantto say– thosephrasesmakesensein theSingle-Selfrealm.But a realis-tic view of your mind would show how it usesat varioustimes, different arrangementsof its resources– eachofwhich canmakeyouexhibit differentopinions,ideas,andconvictions.And despitewhateachof uslikesto think, noparticularoneof thosecliquesdeservesto becalled“whatI truly believe”.

8 Advice to Students

How shouldstudentselecta careerin thesefuture bur-geoningtechnicalfields? Oneapproachis to askwhat isthemostpopularfield now. Anotherapproachis theoppo-site: to chooseanunderpopulatedarea.Now, thepopularfields offer greatcurrentopportunities.(For example,ingenetics,eachof our hundredthousandgenesmaytake afew lifetimesto understand– for evolutionhasusedall thetricks thatthephysicalworld permits.)

However, a young,ambitiousstudentwho wishestomake a greatand fundamentalcontribution shouldcon-sider the idea of deliberatelyavoiding the most popularfields! For, considerthe arithmetic. Imaginethat in thenext tenyearstherewill betenmajordiscoveriesin a cer-tainfieldwherealreadytenthousandresearchersarework-ing. (This is thecaseatpresentin suchareas,for example,asNeuralNetworks, GeneticProgramming,SimpleMe-chanicalRobots,StatisticalLinguistics,andStatisticalIn-formationRetrieval.) Thenin eachdecade,eachof thoseresearcherswill haveperhapsonechancein 1,000to makea major discovery. Contrastthis with the situationin anequallyimportantfield thatcurrentlyemploysonly theor-derof a dozengoodresearchers– asin theareasof Rep-resentingCommonsenseKnowledge or Large-ScaleCog-nitive Architectures. Then you’ll have a thousandtimesbetterchanceto make animportantdiscovery! Many stu-dentshavecomplainedto methatit’seasierto geta job ina currentlypopularfield. However, if one looks for lessfaddishalternatives,onemayfind that the competitionisaccordinglyless.

References

Eric Berne,TransactionalAnalysisin Psychotherapy,GrovePress,New York, 1961

Howard Gardner, Frames of Mind: The Theory ofMultiple Intelligences, Basic Books, 1993, ISBN:0465025102.

Paul MacLeanTheTriune Brain in Evolution, PlenumPubCorp.,ISBN: 0306431688,New York, 1990

Marvin Minsky, Negative Expertise,Int. J. ExpertSys-tems, 7,1,pp. 13–19,1994orwww.media.mit.edu/people/minsky/

papers/NegExp.mss.txtNikolaasTinbergenTheStudyof Instinct,Oxford Uni-

versityPress,1951