Mind Association
Wide Computationalism
Author(s): Robert A. Wilson
Source: Mind, New Series, Vol. 103, No. 411 (Jul., 1994), pp. 351-372
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WideComputationalism
ROBERTA. WILSON
1. Introduction
It has often been thoughtthatindividualismin psychology, the view thatpsychological states must be taxonomized so as to superveneon the intrinsic,physical
propertiesof individuals,l receives supportsfrom the computationaltheory of
mind, a view taken by many philosophersand cognitive scientists to be a foundationalassumptionof contemporaryresearchin cognitive science.2The computationaltheoryof mind,or computationalism,can be summarizedas the view that
psychological processesandmentalstatesareessentially computational.It makes
an empiricalclaim aboutthe natureof cognitive processingand suggests to many
a methodological claim about how cognitive psychology, or cognitive science
more generally,ought to proceed.
This paperoffers a challenge to those who have either arguedfrom computationalism to individualismor thoughtsuch an inference plausible by identifying
a possibility that has either been overlooked or not treatedseriously by proponents of this family of arguments.The possibility is that of wide computationalism, and I shall defend both the possibility and the plausibility of wide
computationalismin partsof cognitive psychology.
To get a clearer fix both on the type of argumentfor individualismI have in
mind and the natureof the objection I shall pose to it, consider the following
explicit argument,which I shall referto as the computationalargumentfor individualism:
I Following Stich (1983), I employ a supervenienceformulationof individuals,rather
than Fodor's (1981) "methodologicalsolipsism" formulation,which says that the taxonomy of an individual'spsychological states should not presupposeany essential reference
to that individual's environment.I am not concerned here with differences between the
two formulationsand shall use both in my discussion. Individualismcharacterizedin either way is not a view specifically or only about mentalrepresentationor mentalcontent.
(Hence thereareindividualists,such as Stich (1983, Ch. 8), who are sceptical aboutmental
representation.)
2 Those who have seen computationalismas offering supportfor forms of individualism in psychology include Devitt (1990, 1991), Egan (1992), Fodor (1981, 1987), and
Segal ( 1989, 1991). The papersby Egan and Segal offer the most explicit argumentsfrom
computationalismto some form of individualism.
Mind, Vol. 103 . 411 . July 1994
?) Oxford University Press 1994
352 RobertA. Wilson
(1) Cognitive psychology taxonomically individuates mental states and
processes only qua computationalstates and processes.
(2) The computationalstates and processes that an individual instantiates
superveneon the intrinsic,physical states of that individual.
Therefore,
(3) Cognitive psychology individuatesonly states and processes that supervene on the intrinsic,physical states of the individual who instantiates
those states and processes.
While the "only"in (1) gives this argumentthe necessarystrengthfor its conclusion, this will make (1) seem implausiblystrongto many who adopta more pluralistic view of psychological taxonomy.Although I think that individualismin
psychology as it has been articulatedand defendedby some of its leading proponents is adequatelyexpressedby (3) above, and so any argumentfrom computationalism to individualismso conceived requiresa strong, exclusionarypremise
such as (1), I do not wish to defend this claim here. In fact, make (1) (and so (3))
as weak or as qualifiedas you like. Still, the computationalargumentfor individualism should be rejectedbecause its perhapsinnocent-soundingsecond premise
is false, and it is false because of the possibility of wide computationalismin psychology.
2. Thepossibility of wide computationalism
Suppose that cognitive processing is computational,at least from the point of
view of those seeking systematic, scientific, psychological explanations. The
states (and the processes which are the transitions between such states) over
which a computationalpsychology quantifiesneed not be individualisticbecause
the cognitive system to which they belong could be partof a wide computational
system. That is, the correspondingcomputational system could transcendthe
boundaryof the individualand include partsof that individual'senvironment.If
this were so, then the computationalstates of such a cognitive system would not
superveneon the intrinsic,physical states of the individual;likewise, the resulting computationalpsychology would involve essential referenceto the environment beyond the individual.The states and processes of a wide computational
system are not taxonomizedindividualistically.
In this section I will concentrateon explaining the coherence of the idea of
wide computationalism,i.e., with defendingthe possibility of wide computationalism. I consolidatethis defence by consideringtwo objectionsto wide computationalism in ?4, going on in ?5 to identify examples of existing research in
computational psychology that can be plausibly understood in terms of wide
computationalism.
Wide computational systems are computational systems that are not fully
instantiatedin any individual.Since they literallyextend beyond the boundaryof
the individual,not all of the states they containcan be taxonomizedindividualis-
WideComputationalism 353
tically. Within a wide computationalsystem much of the processing that takes
place may well be instantiatedfully within the boundaryof the individual, but
what makes it a wide system is that not all of the computationalprocesses that
make up the system are so instantiated. If there are computational (formal)
descriptionsof both an organism'senvironmentand its mental states, and causal
transitionsfrom the formerto the latterthat can be thoughtof as computations,
thereis a processbeginningin the environmentandending in the organismwhich
can be viewed as a computation,a wide computation.
To some, the coherence of wide computationalism,its mere possibility, will
seem unproblematic.For example, in responding to MartinDavies' claim that
"cognitive psychology treats information processing systems (modules) and
whole creaturesqua embeddedin particularlargersystems and ultimatelyparticularenvironments"(Davies 1991, p. 482) GabrielSegal says
the superveniencebase of a representation'scontent is some largersystem in which the representationis embedded.This could be: the whole
creatureplus its environment,the whole creature,the largestmodule in
which the representationoccurs, a sub-processorof that module, a subsub-processorof thatmodule, a sub-sub-sub.... Individualismis the thesis thatthe representationalstates of a system are determinedby intrinsic properties of that system. It seems likely that whole subjects (or
whole brains)make up large, integrated,computationalsystems. Whole
subjectsplus embeddingenvironmentsdo not make up integrated,computationalsystems. That is one reason why individualistsdraw the line
where they do: the whole subjectis the largestacceptablecandidatefor
the superveniencebase because it is the largestintegratedsystem available. (1991, p. 492 ellipsis in original)3
Here Segal seems to be conceding the coherence of wide computationalism,
claiming that,as a matterof fact, we don't find computational,cognitive systems
largerthanthe individual.This passage identifiesprecisely where a proponentof
wide computationalismdisagrees with the propQnentof the computationalargument:she rejectsthe claim thatthe "whole subject",the individual,is, as a matter
of fact, "thelargestintegratedphysical system available"for computational,psychological explanation.
Given the coherence of wide computationalismimplicit in this passage, it is
not surprisingthat in Segal's surroundingdiscussion he notes that the disagreement here is properlyresolved by an examinationof empiricalresearchin computationalpsychology. Segal himself thinks that the crucial claim that "whole
subjectsplus embeddingenvironmentsdo not make up integrated,computational
systems, can be defended on a posteriorigrounds. One would expect, then, an
individualistof Segal's persuasionalso to consider(2) in the computationalargument to have an a posteriorijustification,one which while allowing for the mere
3 Segal characterizesindividualismhere as a thesis about mental representation,although individualistshave typically defendeda view aboutpsychological states in general
(see footnote 1). Individualistsalso adopta more specific view of the natureof the subvenient base than Segal suggests: it is constitutedby the intrinsic,physical propertiesof the
individual.As we will see, one cannotsimply equateindividualandcomputationalsystem,
or assume thatthe latterwill be partof the former.
354 RobertA. Wilson
possibility of wide computationalsystems shows why our computational,cognitive systems are individualistic.
Not all individualistsadoptthis view of (2). For example,FrancesEgan (1992)
has argued that computational taxonomies are individualistic of their nature:
thereis somethinggeneralabouttaxonomyin computationalpsychology, or perhaps about computationaltheory more generally still, which entails that cognitive, computationalstates and processes are individualistic.If Egan is right,then
wide computationalismis inconsistent with some more general featureof computationalpsychology or computationaltheory,and (2) is not something which
simply happens to be true of the computational systems that we instantiate;
rather,it says something true about computationalsystems per se, and can be
defended on a priorigrounds.4
To bringout the contrastbetween these two types of defence of (2), and to see
why the more a prioridefence is problematicin this context, consider the details
of Egan's argument.It begins with the claim thatthe goal of computationaltheories of cognition is "to characterizethe mechanismsunderlyingour variouscognitive capacities" (pp. 444-445).5 And such theories "construe cognitive
processes as formal operationsdefinedover symbol structures"(p. 446). Now,
Symbols arejust functionallycharacterizedobjects whose individuation
conditionsare specified by a realizationfunction fR which maps equivalence classes of physical features of a system to what we might call
"symbolic"features. Formal operations are just those physical operations that are differentiallysensitive to the aspects of symbolic expressions that under the realization function fR are specified as symbolic
features. The mapping fR allows a causal sequence of physical state
transitionsto be interpretedas a computation.
Given this method of individuatingcomputationalstates, two systems
performing the same operations over the same symbol structuresare
computationallyindistinguishable.(p. 446).
From this, claims Egan, it follows that "if two systems are molecularduplicates
then they are computationalduplicates.Computationaldescriptionsare individualistic: they type-individuatestates without referenceto the subject's environment or social context"(p. 446).
Egan's final conclusion here does not follow, unless one equates computational systems with subjects, i.e., with individuals.Yet doing so would beg the
4 Two points aboutcalling this position Egan's:(a) as we will see, there are strandsto
Egan's discussion which suggest that she accepts a view of the relationshipbetween computationalismand individualismcloser to Segal's; (b) the position is one which I think
many individualistfind appealing.My concern here is to identify an individualisticposition alternativeto Segal's; I returnto discuss Segal's view in ?5 below.
5 Egan continues:"this goal is best served by theories which taxonomize states individualistically"(p. 445). This may suggest that she sees computationalpsychology as individualistic for instrumentalor pragmaticreasons ratherthan because of the natureof
computationalindividuation.But, as I hope will be clear from what follows, her actualargument does not appeal at all to whetherindividualisticor wide taxonomies "best serve"
the goal she has identified;rather,it claims that individualismis strictly implied by the
methodby which computationalstates are individuated,
WideComputationalism 355
question against the wide computationalist, for the wide computationalist
endorses precisely the claim that there can be computational systems which
extend beyond the boundaryof the individual.There is nothing in the method of
computationalindividuationitself to which Egan points which implies that the
class of physical featuresmappedby a realizationfunction cannot include members that are partof the environmentof the individual.This being so, Egan has
not provideda sound argumentfor why individualism(aboutcomputationalpsychology) follows from the very natureof computationalpsychology, and so her
view does not point to some internalincoherence in the idea of wide computationalism.
Wide computationalismis analogousto wide functionalism, the view that the
conceptual role defining mental states extends into the world (Harman 1987,
1988; Kitcher 1991). Yet wide computationalismis both more modest and more
radicalthanwide functionalism,and providesthe basis for a strongercase against
individualism.It is more modest in that it concedes that individualismis true of
at least some mental processes and rejectsonly its all-encompassingnature;it is
more radicalbecause it denies somethingaboutthe notion of a formal or computationalsystem-that it be instantiatedin an individual-which is almost without
exception taken for grantedby individualists,and so underminesthe computational argumentfor individualismin a fundamentalway.And it is a more decisive
objection to individualism, supposing the "radical"claim to be established,
because it not only removes computationalismas one of the major supportsof
individualismwithoutrejectingcomputationalismbut also providesthe basis for
arguingfrom computationalismto a distinctly non-individualisticview of computationalpsychology itself.
The challenge to the computationalargumentis not posed by directlydefending the claim that psychological states requirea broad construalbut, rather,by
arguing that the formal or computational systems in which they are instantiated
or of which they are a partextend beyond the individual.The distinctionbetween
an individualand a cognitive, computationalsystem is centralto an understanding of wide computationalism.Even if one thinksthat many computational,cognitive systems are fully instantiatedin the individual,wide computationalismis
a possibility because the boundariesof the individualand those of the computational, cognitive system need not be identical.
An example of a possible wide computationalprocess is the familiarprocess
of multiplication.6 Typically, apart from multiplication problems that are
included in one's "times table",one multiplies numbersby storing intermediate
solutions in some writtenform, usually on paper,and then solving the next componentof the problem,storingthe resulton paper,and so on. The actual process
thatone goes throughin multiplyingnumberstogethertypically involves the storage of symbols on paper. The problemsolving activity itself need not and does
not take place solely in one's head; it involves, rather,the use of symbols (and
conventions) which are not stored exclusively in the head. A descriptionof the
6 Thanksto Sydney Shoemakerhere;see also Clark(1989, Chs. 4,
7, and 1993, Ch. 6).
356 RobertA. Wilson
process of multiplicationmust include a descriptionof mathematicalsymbols,
and for most humanbeings such a descriptionpresupposesa referenceto something externalto the individualorganism.A crucial partof the process of multiplication, namely, the storage of mathematical symbols, extends beyond the
boundaryof the individual.Consideredas multipliers,we are partof wide computationalsystems.
To show the coherence of wide computationalism,this need only be taken as
an account of a possible computational,cognitive process, perhapsnot one that
we instantiate. Yet I have described the example in terms of our cognitive
processingbecause I thinkthathumanmathematicalproblemsolving, as well as
much problem solving more generally, involves (indeed, essentially involves)
the exploitationof representationsin one's environment.The more complex the
computational process we engage in-for example, non-trivial mathematical
proofs-the more plausiblethis strongerclaim is. Proofs of complex theoremsin
quantificationallogic are rarelycarriedout entirely in one's head: at least some
of the symbols are storedexternally.What are storedarepointers to the symbols
thatone uses, and while such pointersmay be storedinside the head, the symbols
to which they point are not storedinternallyat all: thatis why one needs a blackboard,pen and paper,or even a calculator.
Not only can a case be made for conceiving of mathematicaland logical processes as wide computationalprocesses:the same is trueof perceptualand behavioural processes. Wide computationalismis appropriatein cases in which the
interactionbetween an individualand something externalto that individualis a
crucialpartof the computationalprocess being describedas an explanansin psychology. In the case of perception,it is an intrinsicpartof that process that the
system accept input from the environmentand process it so that furthermental
processing can proceed.The perceptualprocess involves an interactionbetween
an individualandher environment.This is in no way incompatiblewith providing
a computationalaccountof perception(see ?5 below).
Since perceptionis a process which begins with environmentalinputs, inputs
which themselves may have a formal descriptionand so be accessible to a computational,cognitive system, all components of the perceptualprocess can be
described as part of a wide computationalsystem. An individualistmay object
that this characterizationof the process of perceptionsimply begs the question.
The relevantobjects of perceptionare not externalbut internalto an individual;
for example they are 2-D retinal images, not some type of environmentalinput.
A wide computationalaccount of perceptionpresupposesa view of perception
which an individualistshould reject.
This objection in effect concedes a weak or negative point I want to make in
this section, namely,thatthe formalor computationalnatureof mentalprocessing
itself doesn't entail individualism:one also needs to make a substantialclaim
about, for example, the objects of perception in order to derive individualism
from computationalism. The same is true for any area of cognition which is
Wide Computationalism
357
claimed to be computational.The formality of cognition itself does not entail
individualism.
Insofaras this points to a gap between computationalismand individualismin
psychology, it allows for thepossibility of wide computationalism.But a stronger
claim about wide computationalismcan be formulatedand, I think, ultimately
defended.Psychological states are computationalonly insofaras they are partof
an implementedformal system. (For those who find this controversial, see my
discussion in the next section.) But the formal systems of which at least some
psychological states are a partare not fully instantiatedin any naturalindividual,
i.e., in an organism.So, qua computationalstates, such psychological states are
not instantiatedin any individual.Statedin this way, the argumentallows one to
draw not only the conclusion that a wide computationalpsychology is possible,
but, assumingthe truthof computationalism,the conclusionthat,for at least some
psychological states, such a psychology is necessary.
Thus far I have said little about the central notion of formality; to further
demystify wide computationalismI turnto discuss this notion more explicitly.
3. The notion offormality
Computationalismis sometimes expressed as the view that, since cognition is
formal, cognitive psychology should be restrictedto positing and quantifying
over the formalpropertiesof mentalstates.This expressionof computationalism,
whatFodor(1981, pp. 226-228) has called theformalitycondition,may make the
argumentfrom computationalismto individualismin psychology appearcompelling, for the formal propertiesthat mental states have are often thought of as
intrinsic propertiesof mental symbols, such as their shape and size.7 This conception of computationalismallows one to thinkof formalpropertiesas a particularspecies of mentalcausal powers, propertieswhich superveneon the intrinsic,
physical propertiesof the individual,andmakes it temptingto view computationalism as providing a general theoretical framework for further specifying the
natureof such powers. The task of a cognitive psychology which presupposes
computationalism,on this conception of formality, is to discover the intrinsic
propertiesof tokens in the language of thought. In senses that I shall explain
below, such propertiesare both non-semanticand non-physical.8
It shouldbe emphasizedfirst,however,thatthe formalityconditionis an interpretation of computationalism,or a claim about what the acceptanceof compuI As Fodor says, "formaloperationsapply in terms of the, as it were, shapes of the objects in their domains"(1981, p. 227, footnote omitted). It is unclearhow literally Fodor
intendsthis suggestion,thoughhe relies on it in many places, includingmorerecentwork;
for example, see his 1987, p. 18.
8 I thankRobertStalnakerfor emphasizingthis point in discussion.The formalityconditionfocuses on only the firstof these contrasts,the contrastbetween formaland semantic
properties.
358 RobertA. Wilson
tationalismentails or involves, not simply a statementof computationalismitself.
While the notionof formalityis often used in computationaltheory,talkof formal
propertiesas intrinsicproperties of the individualcomponentsof computational
systems is, in certainrespects, misleading. The conception of formalityused in
logic, mathematicsand computerscience, the disciplines which provide the ultimate foundationsfor computationalismin psychology, is quite distinct from that
expressedby the formalitycondition.In these disciplines the focus is on the properties and behaviourof formal systems. A formal system consists of primitives,
formation rules, formulae, axioms, and rules of inference. The foundations of
logic is concerned,in part,with the relationshipbetween the notions of a formal
system, an effective procedure,an algorithm,a computation,and the set of recursive functions.On this conceptionof formality,whatI shall call the systemicconception offormality, a given formal system could be expressed in alternative
notationsand, in principle,could be realizedby a nationof people relatedto each
other as the rules of the system specify (cf. Block 1990, Searle 1981). In this
sense, the intrinsic,physical propertiesof symbols in a formal system are arbitrary.9
On the systemic conceptionof formality,thereis little talk of the formalproperties thatparticular symbols have. The sorts of "formalproperties"which are
primarilydiscussed, propertiessuch as being closed undermodus ponens, being
transitive,being compact,andbeing soundandcomplete,arepropertiesof formal
systems or, derivatively, propertiesof symbols as elements of formal systems.
Computationalprocesses, operationsand instructionsare often thoughtof as formal, but this is to say only that they can be adequatelydescribedas the result of
the applicationof rules or algorithmswhich constitutethe system to which they
belong. Insofaras particularsymbols in a formal system have formal properties,
it is not clear whethersuch propertiesare intrinsicor extrinsic propertiesof the
symbols themselves. For example, an instanceof the symbol "A" will lead to an
instanceof the symbol "B" and do so in virtue of its "shape"in a formal system
containingonly the rule "A = B". But since this formalproperty,having thatparticularshape, has thateffect only in a formal system with a rule of thattype, one
shouldbe wary of identifyingsuch formalpropertieswith intrinsiccausal powers
that symbols possess. In any case, what is clear is that such propertieshave the
causal significance that they do only insofar as the symbols to which they are
attributedare partof a formal system.
The systemic conception of formality,which I shall rely on in the remainder
of the paper,makes it naturalto express computationalismas the view that cognitive psychology ought to be pitched at a computationallevel of description.I
said above thatthe formalpropertiesof mentalstatesare supposedto be bothnonsemanticand non-physical,and I want to explain what these two contrastsimply
9 Interestingly,Rollins (1989) and Devitt (1990, 1991) both draw something like the
distinction I am drawing here between the formalitycondition and the systemic conception of formality,althoughneitherseems to thinkthe formalityconditionmisleadingin the
way in which I am claiming it is.
WideComputationalism 359
about the (narrow)computationalist'sconception of cognition by looking at the
two differentconditionsthat a computationallevel of descriptionof psychological states and processes must satisfy.
In contrastto the physical level of description,the computationallevel is distinct from and irreducible to the levels of description which characterize the
physical realizationsof a particularformal system. The same computationalprogram, the same formal system, can be instantiatedin many physically distinct
ways. Given computationalism,this is the sense in which psychology is autonomous of the physical sciences. It is this autonomy,and so the contrastbetween
the formaland the physical, which, I think,underliesthe firstpremiseof the computationalargument.
In contrastto the semanticor representationallevel of description,the computationallevel specifies the propertiesof mentalsymbols andthe rules constituting
the formal system of which those mental tokens are a part without referenceto
what, if anything,those symbols represent.The proponentof the computational
argumentfor individualism claims that, perhaps unlike the semantic level of
description,the computationallevel specifies propertieswhich aredeterminedby
10 This
the intrinsic,physical statesof the organismin which they are instantiated.
featureof the propertiesspecifiedat the formallevel of descriptionmakesthe second premiseof the computationalargumentintuitivelyplausible.
4. Twoobjections to wide computationalism
One primafacie strengthof wide computationalismis that it is fairly non-committal regardingthe precise computationalcharacterof cognition. For example,
it would seem to be compatiblewith both "classical"and connectionistconceptions of computationalismin psychology.Yetthis potentialstrengthof wide computationalismmay be seen as its Achilles' heel by someone pressingthe issue of
the degree to which wide computationalismis a realist view of computational
psychology: to what extent does the plausibilityor even the possibility of wide
computationalismturnon a view of computationalismthat is committedto little
more than the utility of the computationalmetaphor in psychology? To put it
slightly differently:does wide computationalismpresupposethat computational
explanationsin psychology only model the phenomenathey purportto explain,
in the same way that there are computationalmodels of other phenomena,such
as the motions of planetarysystems? If so, then wide computationalismwill be a
view of little significancefor computationalpsychology. Centralto the computa'0 This contrastbetween computationaland intentionaltaxonomies is clear in Egan
(1992), where a defence of individualismabout computationalpsychology is combined
with a defence of wide intentionalcontent. One could, I suppose, hold just the reverse of
this: thatcomputationaltaxonomiesmay be wide but intentionaltaxonomies must be narrow. Exploringthis option should be of interestto those who accept wide computationalism but wish to defend an individualisticview of intentionality.
360 RobertA. Wilson
tional paradigmin psychology is the idea that an individual'smind is not simply
describedor modelled by a computerprogram;cognition is rule-guided,not simply regular (Bennett 1989). Wide computationalismis possible only if one relies
on a weak readingof the computationalmetaphor,a reading which does not do
justice to computationalistcommitmentsin contemporarycognitive psychology.
To understandhow a wide computationalsystem could producerule-guided
behaviour, consider how a narrow computational system could do so. Since
standardpersonal computersare paradigmcases of narrowcomputationalsystems, we can make our discussion more concrete by asking how they produce
behaviourby actuallyfollowing rules. Computersfollow rules by instantiatingor
implementingprogramsconstitutedby such rules. So what is it to implementa
program?For a physical device to be capable of implementinga given program
is for it to have its physical states configured in such a way that transitions
betweenthose statesare isomorphicto transitionsbetween statesthatthe program
specifies, i.e., there is a mappingfrom equivalence classes of physical states to
the symbolic states thatconstitutethe program.Since implementationalpower is
characterizedin termsof the mathematicalnotionof isomorphism,thereis a large
numberof actual programsand an infinite numberof possible programswhich
any given physical device can implement.One closes the gap between the power
to implement and actual implementationby identifying the appropriatecausal
interaction between the physical storehouse for the program (e.g., a physical
disk) and the computeritself. So, in responseto the grandepistemological, scepticism-mongeringquestion,"Of the infinitenumberof programsthat a computer
could be implementing,how do you know thatit is implementingthis program?",
we say: "It implementsthis one because it is this one that is encoded on the disk
we inserted."(And since a physical disk is simply one type of storehousefor a
program,we could replace referenceto a physical disk here by referenceto anything else a programis storedon.)
This view of implementationmay make it sound as thoughthe programis epiphenomenalto the physical operationof the computer,raisingdoubts about it as
an accountof rule-guidedbehaviour:in what sense is the behaviourthatthe computergeneratesanythingmore than regular behaviour,behaviourthat appearsto
be rule-governedbut, in fact, is not? I should make it clear that I think that the
programdoes play a causal role in the behaviourof the physical device, and that
the behaviourit producesis thus rule-governedand not merely regular.But while
we may wish to say that the machinebehaves in the way it does because of how
it was programmed(i.e., because of the programit instantiates),we should be
sure to distinguish this sort of "downward"causation from that which exists
between the physical states themselves. Unless there is massive causal pre-emption "fromabove", symbolic states can't be viewed as the direct causal antecedents (the efficient causes) of later physical states. In general, to understandthe
causal role that higher-level states play in the productionof behaviour,we need
a broaderconception of the notion of a causal role thanis typically assumed(see
Wilson 1993, 1994, in press).
WideComputationalism 361
Although I have stated this view of how computers produce rule-guided
behaviourin termsof familiarnarrowcomputationalsystems, the narrownessof
the system plays no significantrole in the view; much the same story can be told
of a wide computationalsystem. The accountof implementationalpower is precisely the same: the wide computationalsystem has the power to implementjust
those programsfor which thereis an isomorphismbetween the system's physical
states andthe symbolic statesthe programspecifies. The accountof actualimplementationis a generalizationof thatin the case of narrowcomputationalsystems:
a wide computationalsystem implementsthe "program"physically storedin the
environmentwith which it causally interacts.Determiningthe propersymbolic
description of aspects of an organism's environment is an a posteriori matter,
much as doing so with respectto an organism'sinternal structureis.
"Program"occurs in scare-quoteshere because of two importantdifferences
between the programsthat run on standardcomputersand those that (narrowor
wide) computationalistsclaim runon us: (i) unlike the programsthat we encode
on physical disks, precisely what symbolic interpretationscan be given either to
aspects of an organism's environmentor to its internal structure(or both) are
things that must be discovered; (ii) these interpretationsmay not turn out to be
elaborate enough themselves to warrantthe label "program".Significantly, (i)
and (ii) distinguishwhat we know (and love?) as actual computersfrom organisms. We simply are not in the appropriateepistemological position to claim
eitherthatour brainsor our brainsplus our environmentsinstantiateprogramsin
precisely the sense that computersdo. And in light of the similaritiesand differences between us and computersthatemerge from empiricalresearch,we will be
able to decide whether"programs"or "internallanguages"are appropriatecategories with which to develop psychological explanations.None of this involves
adopting a weak understandingof the computationalmetaphorin psychology,
only some epistemic cautionthat should be adoptedwhetherone defends narrow
or wide computationalism.
The idea that by going wide one gives up on somethingcrucial aboutcomputationalismreflects a deeply Cartesianview of the mind, a vestige of thinkingof
the mind and body as distinct substances,which survives within contemporary
materialistand naturalisticviews of the mind. This vestige is the idea that there
is somethingspecial aboutthe mind, aboutwhat is "in the head",thatjustifies the
ascription of computationalstates to it, which is not shared with extra-cranial
reality;there is a bifurcationbetween mind and mere matterwhich makes only
narrowcomputationalisma serious option within psychology (cf. Segal 1991, p.
492, quoted above). I shall refer to this idea as Cartesiancomputationalismand
will say more aboutit in my conclusion.
Let me turnto a second objectionto wide computationalism,one which introduces broadly empirical grounds for doubting that we are wide computational
systems. As Egan (1992, pp. 446,457) notes, citing examples of researchin early
vision and in syntacticand morphologicalanalysis in linguistics, the psychological processes for which thereare the most satisfying computationalaccountsare
362 RobertA. Wilson
modular:they are domain-specificand informationallyencapsulated.11That is,
we have had our greatest empirical successes in computationalpsychology in
explainingthe characterof psychological processes which function with relative
independencefrom even much of the internalworkingsof the cognitive system,
let alone the external environment of the individual. If empirical success has
come within computationalpsychology only or even predominantlywith the correctnessof the presumptionof modularity,then thatshould cast doubton the idea
of developing an empiricallyadequatewide computationalpsychology.
Fodor (1983) makes this point aboutthe relationshipbetween modularityand
computationalpsychology more poignantlyby arguingthat "global systems are
per se bad domains for computationalmodels" (p. 128). Specifically, what he
calls central processes, such as problemsolving and belief-fixation,are unlikely
to have computationalmodels precisely because they are, in his view, non-modular. The non-modularityof central processes gives one reason to be sceptical
aboutthe real (versusmere) possibility of an adequatecomputationalpsychology
explaining them. And what is true of central processes, processes which have
access to a variety of representationalinputs, is also true of wide computational
processes, processes which access representationsthatare outside the individual.
Suppose we agreethat,by and large,the empiricalsuccesses thatcognitive science has had thus far have involved highly modular systems, such as those
employed in visual perception and phoneme recognition. Perhapsthis is for a
deep reason, such as its only being highly modularsystems which are computational; alternatively,it could be due to a relatively shallow reason, such as its
being only highly modular computationalprocesses that theorists can readily
understandas computational.In either case, there is nothinghere that allows for
the applicationof a point about central processes to wide computationalprocesses since the latter can also be modular.As I hope the discussion in the next
section indicates,contemporaryresearchin cognitive psychology thatis properly
consideredas positing wide computationalsystems involves highly modularsystems.12
The implicit premise in the argument from modularity to individualism
sketched above- that modular systems are taxonomized individualistically-is
false because modularsystems may well encapsulateinformationthat is in the
" The notionof modularityat work here is thatarticulatedby Fodor(1983). While Fodor lists other features of modularsystems (e.g., they are fast and mandatory),domainspecificity and informationalencapsulationare the two most central.Although these notions themselves warrantsome conceptualelaboration(see Wilson, in press), let me here
simply providean intuitivegloss on each. A domain-specificsystem is one which operates
on some particulartype of information(a domain).An informationallyencapsulatedcognitive system acts as an input-outputfunctionon a specifiableand specific set of informational inputs and outputs: it encapsulates some kind or kinds of information, and is
insensitive to other information.
12 In fact, I thinkthatthereis no conceptualproblemin even centralprocesses, such as
inference, being modular:even they may be domain-specificand informationallyencapsulated.Dan Sperber(1994) has arguedfor this view, and I take the work of Cosmides and
Tooby in evolutionarypsychology to provide empirical supportfor it; see, for example,
Cosmides (1989) and Cosmides and Tooby (1987).
WideComputationalism 363
individual'senvironment,not elsewhere in the individual.Thus, the module may
be a partof a computationalsystem all right, but a wide computationalsystem.
Neitherof the chief two featuresof modularcognitive systems, theirdomain-specificity and informationalencapsulation, implies that such systems cannot be
properlyviewed as partsof wide computationalsystems. Being wide and being
modular are compatible propertiesfor a cognitive system to possess-and so
modularitydoes not entail individualism-because the location of the information with respect to which that system is encapsulateddoes not affect that system's domain-specificity.The real question to be answered is this: are narrow
computationalaccounts of given modularsystems always explanatorilyricher
thantheir wide rivals? It is only if the answerto this question is "Yes"that wide
computationalismcan be rejectedas less plausible in general than narrowcomputationalism.
5. Widecomputationalismin cognitivepsychology
Althoughthe possibility of wide computationalismsuffices to show thatthe second premise of the computationalargumentis false, for those antecedentlydisposed to think that wide computationalismis coherent the real interest in the
computationalargumentlies in the claim thatwe are plausiblyseen as wide computational systems. I think that wide computationalism is made plausible by
recent computationalresearch in both human and animal cognition. Showing
wide computationalismto be not only a coherentbut a plausibleview of our cognitive processing would both consolidate and broadenmy objection to the computational argument. I shall discuss two examples of research in cognitive
psychology which show wide computationalismin action.13
Sekulerand Blake (1990) devote a significantsection of their chapteron spatial vision and form perceptionto a discussion of an approachto form perception
pioneered in the work of Campbell and Robson (1968), an approachknown as
multiplespatial channels theory.The basic idea of the approachis that there are
specific stimuli which individual sets of neurons are sensitive to, these stimuli
being decomposableinto sinusoidalgratings. These gratingsare relatively simple, havingonly four relevantparameters:spatialfrequency,contrast,orientation,
and spatialphase.Any figurecomposed of these gratingsis definableformally in
termsof these four parameters.The bold and controversialclaim of this research
programis that any naturalscene in an organism'senvironmentcan be decomposed into its gratings,and this fact explains a greatdeal of humanform perception, includingits limitations.
On this conception of form perception,partof the task of the perceptualpsychologist is to identifyformalprimitivesthatadequatelydescribethe visual envi13 Thanksto both David Field and FrankKeil for useful discussion of the materialin
this section; they should not, however,be saddledwith the conclusions I draw here.
364 RobertA. Wilson
ronment,and to specify algorithmswhich apply to these primitivesto determine
complete visual scenes. To see what this means, take a case simplerthan human
vision, thatof a lens projectingan image of an object onto a piece of white paper.
Figure 1 shows the transferfunction for two lenses, which plots how contrastis
transferredthroughthe lens from object to image, and is definedover a range of
spatial frequencies.As input, it takes contrastin an object, producingas output
contrastin the image. We can likewise define a contrast sensitivityfunction for
the humanvisual system, which takes the same inputsfrom the world to produce
a visual output (see Figure 2). The formal system that perceptualpsychologists
working within this paradigm study is not instantiated in any individual: it
includes but is not restrictedto the intrinsicpropertiesof an individual.This is
reflected in the actual methodology employed by such psychologists, which
involves the extensive and complex mathematicalanalysis of naturalscenes into
theircomputationalprimitives.Such analysis appearsto be an intrinsicpartof the
multiple spatial channels paradigm,not simply something preliminaryto real
perceptualpsychology.
Image contrast
as percentage
of targetcontrast
Clean
\
Buttered\
lens
~~~lens
\
\
\
Spatialfrequency(cycles/mm)
Figure 1 Two transferfunctionsfor a lens. The curves specify how contrastin the
image formed by the lens is relatedto contrastin the object.
(Both figuresreproducedfrom Sekuler,R. and Blake, R. 1990: Perception,with
permissionof McGrawHill.)
WideComputationalism 365
0.1
0.001
Spatialfrequency
(cycles/degree)
1
10
II
I
100
1,000
I
Invisible
-100
0.01
Sensitivity
(1/thresholdcontrast)
Threshold
contrast
Visible
0.1
1.0
10
1
l
0.1
I1
-I100
~10~~~~~~~~I
Spatialfrequency
(cycles/mm on retina)
Figure2 A contrastsensitivityfunctionfor an adulthuman.The upperhorizontal
axis is scaled in units specifying the numberof parisof light and darkbarsof the
gratingfalling within one degree of visual angles on the retina.
Gallistel (1989a) reportsresearchon the conceptions of space, time and number
that a variety of animals have, including bees, rats, and ants. One of Gallistel's
primaryconclusions is that purely sensory-based models of a range of animal
behaviour are inadequate.Rather,the evidence overwhelmingly suggests that
these animalsconstructquite complex representationsof theirenvironmentsand
use these to guide their behaviour.Gallistel arguesthat such representationsare
computational,that there is strong evidence that these animals instantiatemodules which are sensitive to the formal (e.g., the geometric)structureof theirenvironments,andthatthis sensitivityis responsiblefor theirnavigationthroughtheir
physical environments.For example, in ants and bees the computationalprocess
of dead reckoning (which integratesvelocity with respectto time) takes as inputs
the animal's solar heading,forwardspeed, and a representationof the solar azi
366 RobertA. Wilson
muth, producingas output a representationof the creature'sposition relative to
some landmark,such as a nest. The ephemerisfunction, which producesthe third
of these inputs,takes as its inputsa sighting of the sun and time on some endogenous clock (see Gallistel 1989b, pp. 70-76). In both of these cases, the computationalprocess extends beyond the boundaryof the individual.
Gallistel calls his view a computationalrepresentationalperspective on animal cognition. Of animal navigation,Gallistel says:
routine animal movements are governed by a navigational process
closely analogousto everydaymarinepractice.This practicerests on an
extensive isomorphismbetween the geometry of motion and position
and the computationalprocesses that underlienavigation.At the neurophysiological level of analysis, the hypothesis implies that the mathematical description of the processes in the animal brain that function
during animal navigationparallelsthe mathematicaldescriptionof the
computations a human or computerized navigation system makes.
(1989a, pp. 176-177)
This quotationsuggests that Gallistel, like those working in the multi-channels
paradigmin form perception, does not see anything mysterious in positing an
extensive isomorphismbetween the formally describedpropertiesof an environment and those of mentalprocesses.'4
Two centralpostulatesof these otherwisediverse researchprogrammesis that
the environmentof the organismhas a certainformal structureto it, and that the
organism's sensitivity to this structureexplains core parts of its cognitive performance.Characterizingthe specific natureof the environmentin computational
termsappearsto be a centralpartof the implicitconceptionof cognitive psychology in these researchprogrammes.Despite some of Gallistel's own claims about
the view he advocates(see below), I see no way in which this is merelyadditional
or peripheralto these researchprogrammes,and in the remainderof this section
I shall defend the view that both researchprogrammessupportthe view that we
and our biological kin are partsof wide computationalsystems.
Recall Segal's view of the relationshipbetweencomputationalismand individualism, discussed in ?2: that,as it turnsout, ourcognitive systems are narrow,not
wide, computationalsystems. Thus, wide computationalismshould be rejected
because although it is a coherent view there is no research which, in Segal's
words, treats "whole subjects plus embedding environments" as "integrated,
14 Cf. Gallistel's claim that the isomorphismbetween computationalprocesses instantiated in the head and certain"formalproperties"in the environmentis responsiblefor the
successful navigationbehaviourthat many animals exhibit: "thereis a rich formal correspondence between processes and relations in the environment and the operations the
brainperforms.Brain processes and relationsrecapitulateworld processes and relations.
The recapitulationis not fortuitous.To fit behaviourto the environment,the braincreates
models of the behaviour-relevantaspects of the environment.the formal propertiesof the
processes that realize these models reflect the formal propertiesof the correspondingexternalrealitybecause these processes have been subjectto evolution by naturalselection.
Selection has been based on the fidelityof these processesto the externalreality.Evolution
by naturalselection creates rich functioningisomorphismsbetween brain processes and
the environment,and learningis to be understoodin termsof these isomorphisms(1989b,
p. 27)."
WideComputationalism 367
computationalsystems". This is a strong empirical claim, one to which in this
section I have providedtwo primafacie counter-examples.The individualistwho
wishes to defend Segal's claim needs to explain away the appearances.Once the
coherence of wide computationalismis conceded-its mere possibility-there
are likely to be many such appearancesto explain away, and so such an individualist faces a primafacie difficulttask.
I think that the most promising way to defend the computationalargument
from the line of objection I have developed is to concede that even if one can
view the individualas embeddedwithin a wide computationalsystem, thereis no
explanatorymotivationfor doing so. For we can also view the individualitself
(or, more accurately,a part of that individual)as a computationalsystem, a narrow computationalsystem, and doing so is always adequatefor computational,
psychological explanation.Considerthe two examples that I have given of purportedlywide computationalresearch.Even if the multi-channelsparadigmdoes
seem to posit a formal structureto the environment,it could also be viewed as
claiming thatthe retinalimage has such a structure.If this view of the paradigm
is correct, then while one could view the paradigm as being computationally
wide, thereis no need to adoptthis view of it. Likewise, while the computational
representationalview that Gallistel defends might seem to view an individualas
part of a wide computationalsystem, a system which includes features of that
individual'senvironment,one could also see his view as positing an interesting
isomorphismbetween two formal systems, one of which is fully instantiatedin
the individual.Crucially,cognitive psychology is the study of this narrowcomputationalsystem. Since the form of this defence of the computationalargument
is the same in each of these two cases, I shall develop it andrespondto it by focusing only on Gallistel's view.
A generalfeatureof Gallistel's view of animalcognition thatmight be thought
difficultto reconcile with my interpretationof it is thatmuch animalbehaviouris
governedby internalmaps and mathematicalrepresentationsof the environment
ratherthandirect sensory input.This view ascribesto an animala high degree of
autonomyfrom its environment,andthis aspectto Gallistel's view at least sounds
individualistic:animals navigate,for example, by internalmaps, not by sensory
tracing,homing, or otherenvironmentallyinteractivemethods.In characterizing
how an animalnavigates,we abstractaway from its actualenvironmentand concentrateon the intrinsicfeaturesof its map or model of that environment.
Several of Gallistel's comments about his own project offer supportfor this
type of individualisticinterpretation.Gallistel says that his "agendais a reductionist one: to understandlearning as a neuronalphenomenon"(1989b, p. 24),
going on to say that studyingthe total [wide] computationalsystem is simply a
"necessaryprelude to understandingwhat the system does in terms of what its
elements do" (1989b, p. 24). Figuring out the computational structureto an
organism's environment,while methodologically necessary, is peripheralto an
understandingof the natureof learningitself, and suggests that there is no deep
sense in which Gallistel advocates a view of learning as a wide computational
368 RobertA. Wilson
process. In addition,in the conclusion to his book Gallistel says that"[t]hestructure of the computationalmechanismsis dictatedby the formal structureof the
representationsto be computedandby the sensoryor mnemonicdatafrom which
they are computed"(1989b, p. 581), suggesting that he sees the computational
system of interestto the psychologist as fully instantiatedin the individualorganism.
One response to this interpretationcorrespondsto and reinforcesthe weak or
negative claim thatI made in ?2. Even if one can see Gallistel's view as a narrow
computationalapproach,the fact that it also can be given a wide computational
interpretationshows that computationalismitself does not entail individualism:
computationalsystems need not be individualistic. Yet this response does not
addressthe issue of which of these interpretationsof Gallistel's view has greater
explanatoryadequacy.A second response, correspondingto one of the stronger
claims made in ?2-about the plausibilityor even necessity of wide computationalism in psychology-addresses this issue.
Thereare two aspects to this second response,one elaboratingon the concepts
of explanationand explanatoryadequacy,the otherconcentratingon the application of these concepts so understood to particularexamples within computational, cognitive psychology. Let me say somethingbrief about the first of these
aspects. Were the individualistto claim, in effect, that there is no explanatory
need to posit wide computationalsystems because wheneverwe can do so we can
also identify a corresponding,narrowcomputationalsystem,15she would be presupposing some conception of explanatory adequacy, although one yet to be
explicitly articulated.Elsewhere (Wilson 1994) I have developed a concept of
explanatory adequacy in terms of the notions of causal depth and theoretical
appropriatenessand arguedthat wide psychological explanationsare sometimes
causally deeper and more theoreticallyappropriatethan individualisticpsychological explanations.I think that this argumentcan be adaptedto apply specifically to show that wide computational explanations are sometimes more
explanatorilyadequatethan narrowcomputationalexplanationsin psychology,
thoughI shall not arguethis point here.WhatI wantto do insteadis make several
points pertinentto the second aspect of the issue of explanatoryadequacy,points
aboutthe researchreportedby Gallistel discussed above.
The sortsof behaviourthatGallistel is tryingto explain involve a flow of information from the environmentto the organism.One of Gallistel's main points is
that this is not a constant flow of information,as suggested by simple sensory
15 This claim is very similar to one that proponentsof the narrowcontent programin
psychology have sometimes made: that whateverexplanatorywork a wide taxonomy of
psychological states (e.g., thatof folk psychology) does can also be done by a corresponding narrowtaxonomyof those states.This claim has sometimesbeen expressedas the view
that wide taxonomies, insofaras they are explanatory,can be factoredinto narrowtaxonomies, plus some externalremainder,in much the way that the concept of weight can be
factoredinto the concept of mass, plus that of gravitationalforce (see Field 1981; Fodor
1987, Ch. 2). I have arguedagainst such views (1992, 1993, in press, forthcoming).
WideComputationalism 369
accounts.Yet it would be a mistaketo think of his view as denying that (formal)
propertiesof the environmentplay any significantrole in a complete, cognitive
explanationof animalnavigation.
First, even if an animal's behaviour in navigation is primarilygoverned by
internalmaps,these mapsareupdatedby periodicallyacquiredinformationabout
the organism'smovementand the relativeposition of objects in the environment.
An accountof these updates("fix-taking",in Gallistel's terms)is a necessarypart
of a complete psychological explanationof the behaviour.If one takes the computationalrepresentationalview to provide a comprehensive paradigmfor the
investigationof animal learning and cognition, then fix-taking must be accommodated within that paradigm.The narrow computationalistview allows that
relations between psychological states themselves can be computational.The
wide computationalistproposes a naturalextension of this view to allow organism-environmentinteractions,such as fix-taking,to be subject to a (wide) computationalapproach.The individualistmust explain processes such as fix-taking
in some otherway, since her claim is thatcomputationalsystems are fully instantiatedin individuals.The wide computationalistis able to offer a view of fix-taking that has greaterexplanatoryunity than that availableto the individualist.
Second, as shown by the above examples of environmentalinputs in Gallistel's account, characterizingcognitive, computationalstates as representations
sometimes requires non-individualisticdescriptions. If a representationalpsychology may violate individualismin the descriptionsit offers of psychological
states, then why must a computationalpsychology be individualistic?This question is not rhetorical,for (i) whetherrepresentationalpsychology violates individualism in particular cases is a substantial question, and (ii) the width of
representationalcontent might be thought compatible with the narrowness of
computationalpsychology because of the differentfunctionsthat intentionaland
computationalascriptionsserve. Egan (1992) has arguedthat the role of semantics in computationalpsychology is to provideexplanatorymodels, models which
may be either narrowor wide, for individualisticcomputations.If Egan is right
about the differentexplanatoryroles that content and computationalascriptions
play, then this provides a principledreasonfor distinguishingbetween computational and representationalaspects to psychology with respect to individualism.
To discuss this issue furtherone would need to re-examinethe often-invokedtrichotomy between the physical, the syntactic (formal, computational),and the
semantic (representational).My own view is that it is most plausible to see the
computationaland representationallevels of descriptionas playing very similar
explanatoryroles in psychology. Again, however, the issue here cannotbe suitably resolved without some discussion of the notion of explanatoryadequacyand
its applicationto computationalpsychology.
370 RobertA. Wilson
6. Conclusion
The computationalargumentfor individualism should be rejected because its
second premise,the assumptionthatcomputationalprocesses in generalare individualistic, is false in light of the possibility and plausibilityof wide computationalismin cognitive psychology. Much of my discussion of the second premise
of the computationalargumentaims to explain the coherence of wide computationalism,what I have been calling its mere possibility.I think,however,thatthe
most interestingissue concerns not the coherenceof wide computationalismbut
the extent to which a wide computational research strategy is and could be
employed within cognitive psychology. Given that, why have I concentratedon
the mere possibility of wide computationalism,ratherthanits plausibilityin cognitive psychology?
The centralidea behindwide computationalismis extremelysimple. However,
fleshing out the idea and being explicit aboutthe implicationsit has for issues in
philosophicalpsychology allow one to see the respects in which it representsa
radicaldeparturefrom the conception of the mind underlyingmuch contemporaryresearchin computationalpsychology, what I have called Cartesiancomputationalism. Precisely because Cartesian computationalism is typically
unidentifiedand unexamined,even the basic idea behindwide computationalism
is likely to produceknee-jerkpuzzlement.It is for this reasonthatI have spent so
much time in ??2-4 demystifying wide computationalismby articulatingwhat
the mere possibility of wide computationalismamountsto.
The more interestingissue of the plausibilityof wide computationalismas a
perspectiveon researchin cognitive psychology is one whose resolution,as we
have seen, turnspartiallyon furtherdiscussion of generalnotions, such as thatof
explanatoryadequacyand causal role, as well as an analysis of notions more specific to computationalpsychology, such as modularityand formality.Of particular importance is furtherdiscussion of the relationship between the notion of
formality and representationalism in psychology. Such discussion and analysis
ought to shed furtherlight on the purportedexamples of wide computational
researchthat I providedin ?5, though I am far from suggestingthat the illumination will be unidirectional.The examinationof actualresearchin computational
psychology on which the issue of the plausibility of wide computationalismin
psychology turnsshould also facilitatethe more conceptualwork thatremainsto
be done.
While I think that much contemporaryresearchin computationalpsychology
and (especially) artificialintelligence operateswithin a Cartesiancomputational
framework, I am not offering an external, a priori critique of such research.
Rather,accepting the assumptionthat psychological states are computational,I
am questioning anotherassumption-that computational,cognitive systems are
always completely instantiatedin individuals-that usually goes along with it. If
I am correctin thinkingboth that this assumptionis typically unquestionedand
that it is, in some cases, false, then wide computationalpsychology would seem
WideComputationalism371
worthfurtherinvestigation.If wide computationalismis not only coherentbut a
plausible view of at least some existing researchwithin the computationalparadigm, then the computationalargumentcan be turnedon its head: individualism
does not impose a constraint on the individuation of mental states precisely
because, in at least some cases, psychological states are considered as (wide)
computationalstates for the purposesof psychological explanation.16
ROBERTA. WILSON
Departmentof Philosophy
Queen's University
Kingston
Ontario
K7L3N6
Canada
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