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The Connectionist Mind:
A Study of Hayekian Psychology(1)
Barry Smith
Department of Philosophy
and Center for Cognitive Science, University at Buffalo
From S. F. Frowen (ed.), Hayek: Economist and Social Philosopher: A Critical
Retrospect, London: Macmillan, 1997, 9-29. French translation forthcoming in
Intellectica.
The archive of a HAYEK-L seminar on this paper is available for downloading at:
http://maelstrom.stjohns.edu/archives/hayek-l.html
Introduction
I shall begin my remarks with some discussion of recent work in cognitive
science, and the participants in this meeting might find it useful to note that
I might equally well have chosen as title of my paper something like
'Artificial Intelligence and the Free Market Order'. They might care to note
also that I am, as far as the achievements and goals of research in artificial
intelligence are concerned, something of a sceptic. My appeal to cognitive
science in what follows is designed to serve clarificatory ends, and to raise
new questions, of a sort which will become clear as the paper progresses.
Artificial intelligence research has two goals: that of simulating human
intelligence via the construction of machines whose operations will be in
crucial respects analogous to intelligent human performances;(2) but also that
of contributing thereby to our theoretical understanding of what human
intelligence is. For the practitioners of A. I. the human mind is itself some
sort of computer, and the structures and functions characteristic of mind are
in consequence seen as being capable of being realised in a range of different
sorts of material, both organic and inorganic.
A. I. research has for some time been dominated by two competing methodologies,
resting on two distinct paradigms as to what intelligence might be and what
sort of computer might best be employed to simulate or re-instantiate it. On
the one hand is the older and more orthodox 'symbolic' or 'symbol-processing'
paradigm, which sees intelligence as a matter of the sequential manipulation of
meaningful units (terms, concepts, ideas) of roughly the sort with which we are
familiar in reasoned introspection. The upholders of this paradigm seek to
construct artificially intelligent systems out of entities that are symbols
(have both semantic and syntactic properties), operated upon in ways which
model the rational processes studied by logic. On the other hand is the more
modern, and in some respects more challenging, 'connectionist' or
'sub-symbolic' paradigm. This sees intelligence as a matter of the processing
of units much more finely grained in character than those with which we
normally suppose ourselves to be familiar in conscious experience. Such
processing is to be conceived by analogy not with processes of reasoning as
standardly understood, but with the massively parallel processing of electrical
impulses by the billions of nerves distributed through the human brain, nerves
bound together in networks of a sort which are subject to a constant and subtle
forming and re-forming of connections. In the corresponding simulations,
sub-symbolic entities participate in numerical - not symbolic - computation,
and inter-nerve connections are modelled by applying variable weightings to the
numerical values (for example signal intensities) which pass through the system
from node to node. The models here are derived from neuroscience, but also from
statistical thermodynamics and from other disciplines dealing with processes of
a holistic sort.
Propositional vs. Non-Propositional Knowledge
For the defenders of the symbolic paradigm it is language, built up out of
discrete and repeatable units, which provides the dominant theoretical model of
cognition, and in his essay 'On the Proper Treatment of Connectionism' of 1987,
still the definitive formulation of the connectionist paradigm, Paul Smolensky
admits that the linguistic formalisation of knowledge brings with it important
advantages. It makes the knowledge in question accessible to different people
at different times and places, and it makes it possible for us reliably to
check whether conclusions have been validly reached. It helps also to guarantee
learnability: the beginner learns by following simple context-free rules which
can be understood with little or no experience of the relevant domain. Science,
accordingly, seeks in every case the sort of systematic clarity which
linguistic formulation provides.
Connectionists, however, are interested neither in the rule-bound, deliberative
efforts of the novice, nor in the sort of static knowledge that comes packaged
in the form of scientific theories. Rather, they are interested in the
spontaneous, intuitive, tacit, dynamic, practical knowledge of the expert, and
they would insist thereby that there are some spheres in which we might all of
us claim to possess huge amounts of knowledge of this sort. Thus we are all
experts, for example, in regard to the business of everyday motion and
perception, and this is true also in regard to common sense and to our native
language.
Certainly the defenders of the symbolic paradigm can develop views of their own
as concerns such intuitive knowledge. Thus for example they can embrace what we
might call the Helmholtz hypothesis to the effect that the intuitive processing
of the expert is merely a case of fast and unconscious processing of the
linguistically formalisable sort. Native speakers are seen from this
perspective as unconsciously interpreting linguistic rules which could in
principle be given explicit formulation in grammatical theories. Systems
constructed on the basis of the Helmholtz hypothesis have however proved too
brittle and too inflexible to model human expertise, and it has turned out that
the task of establishing the needed articulations of expert knowledge in terms
of context-free rules (e.g. for the domain of common sense) faces intractable
difficulties of a hitherto unforeseen sort. As Smolensky would have it, the
Helmholtz hypothesis 'has contributed essentially no insight into how knowledge
is represented in the brain.' (p. 7) Here, therefore, we shall concentrate our
attentions primarily on the work of the connectionists.
A Connectionist Machine
It will be useful to describe very briefly what a simple connectionist machine,
a classificatory engine, might look like. We are to imagine a series of
distinct numerical inputs (signals), derived, for example, from a battery of
photosensitive devices trained in succession upon objects which it is the
machine's job to recognise (classify). These signals, with given initial signal
strengths, become transformed in their passage through the system according to
the 'weights' of the links between successive nodes, weights which may be
either positive or negative. The values passing through the machine are finally
integrated together into a single output which is then associated with some
value from a pre-determined range of classificatory concepts (say: cat, rabbit,
elephant, etc.).
The behaviour of the classical ('symbolic') machine is fixed in advance by its
program, so that the reaction of the machine to all admissible inputs is
predictable from the start. The idea behind the connectionist machine, in
contrast, is that it needs to be 'trained up' by means of a large numbers of
initial trials, the results of which are controlled (in the simplest case) by a
human operator who adjusts the relevant weightings by hand - and to some degree
at random - in order to bring about improvements in the classificatory success
that is achieved at each successive stage. If, on the basis of a given
distribution of weights, the classificatory output is incorrect, algorithms can
be used to adjust the weights of node-linkages in such a way that the machine
achieves a greater success-rate in future trails. It is possible to prove that
such adjustment will eventually, under certain reasonable sorts of initial
conditions, reach one of a perhaps infinite range of stable states and that the
machine in question will thereafter be able correctly to classify new objects
from the given set without the need for further human intervention.
The idea of linguistic or propositional knowledge (of knowing that), which
defenders of the symbolic paradigm take as their starting point, goes hand in
hand with the idea of knowledge as a memory store with which is associated a
set of fixed, explicit rules for cognitive processing. The designers of
connectionist systems, in contrast, set out to model the fact that knowing how
is an evolving capacity of the knowing subject and is such that the content of
knowledge and the process of gaining knowledge are not clearly separable from
each other. There is no storehouse of memories from the connectionist point of
view; rather, the connectionist system 'remembers' only in the sense that its
processing patterns are subject to change, being constantly and cumulatively
affected by what has been experienced in the way of processing in the past. The
'knowledge' in such a system is to a much greater degree than under the
symbolic paradigm itself such as to influence the course of processing. Hence
also from the connectionist perspective it is necessary to reject the
opposition between competence as a matter of knowing explicit rules and
performance as a matter of the application of such rules.
In the world of standard symbolic A. I. (as here somewhat simplistically
conceived), there is an initial plan (the program) controlling all the
successive stages of processing in ways worked out in advance. Each of these
successive stages is then intelligible on the symbolic level in virtue of the
fact that each unit (say 'cat' or 'horse') can be seen as enjoying an
intelligible meaning of its own which remains fixed through time. In the parallel
world of the connectionist machine, in contrast, knowledge and meaning come to
be distributed among the nodes of the machine, so that, as Smolensky points
out, what correspond to the concepts of which we are conscious are here
'complex patterns of activity distributed over many units. Each unit
participates in many such patterns.' (p. 8) The interactions between units are,
it is true, entirely simple in nature: they are essentially a matter of
numerical values being passed through the system and subjected to simple
numerical adjustments at successive stages. It is our knowledge of certain
numerical properties of these interactions which allows us, by adjusting
weights in succession, stumblingly to bring the system to one or other stable
state. But there is no way in which we can derive laws or principles which
would make these processes intelligible at the level of concepts and
meanings.(3)
Considered from this perspective the individual nodes of the machine have no
absolute values at all; their values are entirely a function of their position
in the system of relations determined across the whole network.
Work in symbolic A. I. (again from our somewhat simplified perspective) has
been marked by a tendency to produce simulations of intelligence which would
apply only to rigidly well-organised worlds with a relatively small number of
independent and well-behaved dimensions of variation. Such simulations have in
addition proved 'fragile' in the sense that they have revealed themselves to be
subject to almost instantaneous breakdown when the attempt is made to extend
them to new and more complicated sorts of cases. Connectionist machines, in
contrast, have been constructed which show a certain degree of elasticity.
This, however, as we have seen, is at the price of intelligibility: the
behaviour of the machine, while well understood mathematically, becomes from
the point of view of our conceptual understanding a black box. From this,
however, it follows too that the elasticity of even connectionist systems must
be of a very limited sort. For if we do not understand, conceptually, what is
going on inside the machine, then we have no means of re-configuring it in
systematic ways to take account of new circumstances or new sorts of problems.
Suppose, for example, that we have a system which we have taught to translate
spoken into written English, a machine which we have trained up in terms of
standard English pronunciation. If, now, we want our machine to transcribe,
say, English pronounced with a Welsh accent, then we have no way in which we
can adjust systematically what has been learned so far in order to take account
of this new problem, and we have to retrain the machine from scratch.(4)
Connectionism is in the eyes of some a radical position precisely because it is
held to embody a view according to which intelligent, cognitive processes are
themselves non-intelligible, i.e. are such as to resist our attempts at
theoretical understanding. This view has been most clearly expressed by Dreyfus
and Dreyfus, two long-standing critics of symbolic artificial intelligence
research, who affirm that the approach of classical A. I. 'seems to be failing
because it is simply false to assume that there must be a theory of every
domain. Neural network modelling, however, is not committed to this or any
other philosophical assumption.' (1988, p. 37) They conclude from this that any
success of the connectionist approach will imply that one of the two primary
goals of artificial intelligence research - namely that of contributing in
positive ways to a theoretical understanding of intelligence as such - will
have to be abandoned. We shall return in the sequel to this issue, of the sort
of knowledge we can have of mind and other 'complex phenomena'.
Hayekian Psychology
The significance of the opposition between symbolic and connectionist
approaches is not restricted to the field of artificial intelligence. It is
employed by Dreyfus and Dreyfus also as the basis for a new sort of history of
philosophy. According to the Dreyfusian scheme, philosophers are to be divided
into two groups: precursors of symbolic A. I. on the one hand - above all:
Plato, Descartes, Brentano, Husserl, the early Wittgenstein - and precursors of
connectionism on the other, among whom are to be included not least Heidegger,
Merleau-Ponty, Michael Polanyi, and the later Wittgenstein. From the point of
view of philosophers in the first group (according to the Dreyfus account),
human reasoning is a linear, propositional matter; it is constrained by context-free
rules and built up out of sensory and conceptual 'elements' which are in the
business of mirroring or picturing corresponding (pre-determined) elements of
external reality. From the point of view of the latter, in contrast, human
reason is an intuitive, creative, contextual, holistic affair - a matter,
again, of knowing how rather than of knowing that.
The philosophical story is of course a mite more complicated than Dreyfus would
have us believe. Consider the philosopher-scientist Mach, a thinker who
straddles the boundary between elementarism and holism in ways not readily
allowed for in the Dreyfusian historiography. Mach's philosophy is centred
around the idea that the world is built up out of 'elements' subjected to
constantly changing patterns of combination. The most important examples of
such elements are the 'sensations' of standard empiricist philosophies. For
Mach, however, sensations are classified differently from elements of other
sorts, not because of what they are intrinsically, but entirely in reflection
of their relations to other elements. For Mach, 'the elements of all complexes
prove on closer inspection to be homogeneous' (1959, p. 14). 'The antithesis
between ego and world, between sensation (appearance) and thing, … vanishes, and
we have simply to deal with the connexion of the elements …, of which this
antithesis was only a partially appropriate and imperfect expression.' (loc.
cit.)
Mach's ideas will prove of interest in what follows also because he embraces a
doctrine of what he calls the 'economy of thought': we are to understand the
constantly shifting world of elements-in-connection as subject through and
through to the law of least action; the world is a dynamic system within which
elements, in forming connections, seek always the path of least resistance in
such a way as to establish stable minima; and the behaviour of elements,
including psychological elements, is for Mach to be understood entirely from
this perspective (which Mach derives from evolutionary biology).
One thinker influenced tremendously by Mach, now, is Hayek, and the doctrines
at the heart of Hayek's psychology are in fact taken over directly from the
older thinker. Hayek tells us that the problem of The Sensory Order is that of
establishing the relation between the 'two orders' of the subjective, sensory,
perceptual, phenomenal, on the one hand, and of the objective, scientific,
physical on the other. (110.)(5) The main thesis of the work is indeed an
ambitious extrapolation of Mach's own thesis concerning the nature and status
of sensations. Hayek wants to show that all attributes of mental experience can
be explained by the place in a system of connections of corresponding groups or
patterns of nerve-excitations. He wants to show, in other words, that those
mental properties with which we suppose ourselves to be acquainted through
introspection, through the observation of other people's behaviour, through
history, poetry, etc., are - lock, stock and barrel - a matter of certain
structural or relational properties of the nervous system. Where Mach,
therefore, remains only on the threshold of connectionism in holding on to a
view of mind as an order of sensations (and thus of properly 'mental' entities
on the 'symbolic' level, to use Smolensky's terms), Hayek crosses this
threshold by embracing a conception of mental properties as relational features
of events occurring in the properly sub-symbolic domain of nerve-excitations.
On the other hand, however, Hayek is less radical than Mach. For where Hayek places
his faith in physics, and in the physicist's understanding of the nervous
system, Mach sees the physical order and the associated notions of space, time
and causality as themselves merely the spurious products of the 'economy of
thought'.(6)
To see how Hayek's conception works, we must note first of all that while the
external stimuli which cause processes in our nerve fibres can be classified in
physical terms, stimuli which are physically the same will in many cases not
appear to us as the same from the qualitative point of view. This is so, Hayek
holds, because it is not what is transmitted along a nerve fibre that is
responsible for its characteristic effects, but that the fibre is excited at
all. (127., 131., 142.) More precisely, Hayek rejects views, such as those
defended by Johannes Müller and Ewald Hering, according to which it must be
some property of the individual impulses proceeding in the different fibres
which in some sense 'corresponds' to the differences of the sensory qualities.
Hayek maintains, rather, that the specific character of the effect of a
particular impulse is due 'neither to the attributes of the stimulus which
caused it, nor to the attributes of the impulse, but may be determined by the
position in the structure of the nervous system of the fibre which carries the
impulse.' (135.)
What we call 'mind' is for Hayek nothing else than 'a particular order of a set
of events taking place in some organism and in some manner related to, but not
identical with, the physical order of events in the environment.' (149.) But
how, then, can certain relations between non-mental events turn them into
mental events? This question can be approached first of all from an adaptive
point of view: how is it possible that in a certain part of the physical order
(namely in the organism) there comes to be formed a sub-system which has the
property of intentionality in the sense that it can be said to reflect some
features of the physical order as a whole, in ways which have adaptive
significance? How does such reflection enable the organism to behave more
appropriately in relation to its surroundings?
Hayek is, in contrast to his predecessor, not concerned with questions of
'atomism' or 'elementarism'. Like Mach, however, he is a structuralist both
with respect to sensory qualities and with respect to the world as a whole.
Thus for example he affirms that 'the whole order of sensory qualities can be
exhaustively described in terms of (or "consists of nothing but") all
relationships existing between them.' (155.) Or again: 'the order of sensory
qualities no less than the order of physical events is a relational order -
even though to us, whose mind is the totality of the relations constituting
that order, it may not appear as such.' (156.)(7)
There are no absolute qualities of sensations from Hayek's point of view.
Indeed, belief in absolute qualities 'is probably one of the main roots of the
belief in a peculiar mental substance.' (191.) Another such root is the belief
in a storehouse of memories, which Hayek also rejects. Hayek anticipates also
the central thesis of A. I. research to the effect that mind (intelligence,
cognition) can in principle be realised in a wide range of different material
structures. As the very same pattern of movements can be instantiated in a
swarm of flies and in a flock of birds, so the very same abstract pattern can
be instantiated in a musical score and a gramophone record. And then, as Hayek
points out:
It is at least conceivable that the particular kind of order which we call mind
might be built up from any one of several kinds of different elements -
electrical, chemical or what not; all that is required is that by the simple
relationship of being able to invoke each other in a certain order they
correspond to the structure we call mind. (229.)
Mental Topology
We are to imagine the mind as a receptor organ subjected to a constant barrage
of physical stimuli. Some patterns of stimuli will tend to occur frequently
together. This, Hayek hypothesises, will tend in turn to bring about especially
close connections between the corresponding groups of fibres and it will tend
to lead also to the formation of especially dense connections to corresponding
central neurons. (Here Hayek defends a view very similar to that which was
formulated by Donald Hebb in 1949, a view which still today serves to define
one of the standard types of models used in connectionist research.(8)) It is
in this way that impulses occurring in different fibres may come to be
experienced as qualitatively equivalent. The nervous system thereby acquires a
new sort of topological structure: a distance-function comes to be defined upon
it, reflecting the degree to which different quality groups 'belong together'
as a result of bonds (or 'cell assemblies') between them.(9)
The 'position' of a neuron in the resultant system is then a matter of
connections, of the paths laid down to other neurons: 'groups of neurons may
have a larger or smaller part of their connexions in common. We can thus speak
of greater or smaller degrees of similarity of the position of the different
neurons in the whole system of such connexions.' (326.) And then: 'A very high
degree of similarity in the position of the different neurons in the system of
connexions is likely to exist wherever the neurons are served by receptors
sensitive to stimuli which always or almost always occur together.' (328.)
Further, because we can expect those receptors which are sensitive to the same
kind of physical stimuli to be frequently excited at the same time,(10) it will
follow that correspondingly dense networks of connexions will be established
also laterally between the corresponding central neurons.
In addition, the formation of cell-assemblies will be similarly affected by
changes in the inner states of the body (with the occurrence of feelings of
pain, hunger, etc.) as well as by corresponding actions. Thus we can take a
step towards explaining the adaptive properties of the 'mind' as a system of
relations:
in many instances it is likely that certain kinds of stimuli will usually act
together on the organism when the organism itself is in a particular state of
balance or of activity, either because the stimulus regularly occurs under
conditions producing that state, or because it occurs periodically so as to
coincide with some rhythm of the body. The impulses which register such
external stimuli will then become connected with impulses received from the
proprioceptors which register the different states of the organism itself.
(333.)
A system of connections hereby grows up in which is recorded the relative
frequency with which, in the history of the organism, the different groups of
internal and external stimuli have acted together.
The psychological classification of physical stimuli is then effected, in the
simplest case, as follows. Each separate primary impulse has, as a result of
these acquired connections, a certain following (a train or wake) of secondary
impulses (recall the passage of numerical values through the nodes of the connectionist
system). It is the total or partial identity of this following which makes
given primary impulses count as members of the same class. (334.)(11)
Note that the followings are a matter of purely physiological connections
between impulses - they are not a matter of associations between (meaningful)
mental events. Here again, therefore, Hayek is at one with the connectionist
tendency within contemporary cognitive science.
Multiple Classification
The classificatory system hereby constituted is of great sophistication. Each
impulse becomes a member, first of all, 'not merely of one class but of as many
distinct classes as will correspond, not only to the number of other impulses
which constitute its following, but in addition also to the number of possible
combinations (pairs, triples...) of such other impulses' (335.). This generates
a system of multiple classification of a sort in which classificatory
competence and classificatory performance are (as for the connectionists) one
and the same:
the classificatory responses are not different in kind from, but are events of
the same sort as, those which are the object of classification. In consequence
it is possible that one and the same event may appear both as an object of
classification and as an act of classification. (336.)
It is this internal nesting structure, Hayek holds, which explains how what is
after all a mere system of impulses 'can produce "models" of
extremely complex relationships between stimuli, and indeed can reproduce the
order of any conceivable structure.' (336.) This in turn would explain not
merely outer- and inner-directed intentionality (or in other words
consciousness of world and of self), but also the unlimited range of mental
comprehension (our capacity to direct ourselves intentionally to objects in all
conceivable categories).
The sophistication of the system is increased still further via the distinction
between effective and potential connections between neurons (two kinds of
following). Hayek recognises also - with his connectionist successors - that
there are influences transmitting inhibition (or in other words negative
weightings), the existence of which 'extends the range of possible differences
in the position which any one impulse may occupy in the whole system of
connexions' by introducing the possibility of impulses having effects which are
directly opposed to each other (346.). The whole resultant process is then not
so much a matter of 'classification' as of 'evaluation', since the processing
engine is capable of making distinctions of degree (both positive and negative)
as well as distinctions of kind. (357.)
The system of multiple classification can cope not only with isolated sensory
inputs but also with complex Gestalt structures (higher-order categorial formations)
of a range of different sorts:
The fact that chains of further processes ('associations') can be evoked not
only by the 'elementary' sensory qualities ... but also by certain 'abstract'
attributes of different groups of sensations (such as figures, tunes, rhythms,
or abstract concepts), has usually been regarded as an insurmountable obstacle
to any physiological explanation of mental processes.(12)
For the approach followed here no such difficulty arises: the problem of the
equivalence of 'similar' complexes of stimuli is not different in principle
from the problem why the same associations should become attached to different
impulses which correspond to the same 'elementary' qualities. (369.)(13)
This sensitivity to Gestalt structures in the environment is built up only
slowly, as the brain becomes tuned to those abstract patterns which are of
adaptive significance. There is formed thereby a 'map' reproducing relations
between classes of events in the environment in a process which is affected
both by the sector of the world where the individual lives and by the
individual's own body. This map (or 'mental model') is then of course not only
very imperfect but also subject to continuous although very gradual change.
(526.)
Its representations are structural (compare the imperfect and abstract way in
which cartographical maps represent), and they are a matter of accumulated
knowledge, so that the map represents only the kind of world which the organism
has experienced in the past. The map's job, from Hayek's perspective, is to
facilitate a certain sort of cognitive laziness (or what Mach called 'thought
economy'). It allows the organism to avoid the need to classify individual
events and combinations of events from scratch in each successive occasion of
confrontation. The map's structural character may help to explain also that
central feature of animal intelligence which is its plasticity: the capacity to
re-use rules learned in one context in other structurally similar but perhaps
otherwise quite alien contexts (a capacity which may be illustrated also, on
the level of high intellect, in the use of analogy in science.)
The map thus plays the role of memory in Hayek's theory - not however that of a
passive memory-storehouse, but of an active memory-competence. Moreover, this
active competence in a certain sense precedes our articulate mental experience.
For as Hayek points out,
we do not first have sensations which are then preserved by memory, but it is
as a result of physiological memory that the physiological impulses are
converted into sensations. The connexions between the physiological elements
are thus the primary phenomenon which creates the mental phenomena. (250.)
But now, because this memory-competence-cum-classificatory-order is subject to
constant evolution, it follows that so also is the sensory world in which we
live. The richness of this world, 'is not the starting point from which the
mind derives abstraction, but the product of a great range of abstractions
which the mind must possess in order to be capable of experiencing that
richness of the particular.' (Hayek 1978, pp. 43f.) It is as if we create the
world as we go along by imposing classificatory schemes upon that materia prima
which is the physical substrate. The particular qualities we attribute to an
object in our experience are in this sense 'not properties of that object at
all, but a set of relations by which our nervous system classifies them' (637.)
As was pointed out by John Gray (1986), there is a certain grain of Kantianism
here,(14) though it is questionable whether this Kantian element (and the
solipsism which threatens in its wake) can be seen as being extended through
the whole of Hayek's thinking if the latter is to retain any degree of
coherence. Note, too, that the thesis that we create the world as we go along
by imposing neurally determined classificatory demarcations upon physical
stimuli, while it may be capable of being defended in relation to the world of
sensory qualities, faces obvious difficulties when the attempt is made to
extend it to the 'objective' worlds of physics and neurology. There is
fortunately nothing in Hayek's work to suggest that these domains, too, might
be merely the reflections of evolved classificatory competences of physicists
and neurologists.
Hayek's contention is that human beings in the course of their development
build up a system of differentiations between stimuli in which each stimulus is
given a definite place in a slowly changing 'objective' order of increasing complexity
and sophistication. It is this place in the objective order which 'represents
the significance which the occurrence of that stimulus in different
combinations with other stimuli has for the organism.' (217.)
The central nervous system is an adaptive engine for the constant
reclassification on many levels (including conceptual and emotional levels) of
the legion of impulses proceeding in it at any moment. We create the world in
which we live in the sense that there are, on the side of nerve-excitations, no
fixed conceptual units able to mirror or picture corresponding (pre-determined)
elements of external reality in a one-to-one way. Only insofar as the nervous
system has learnt to treat a particular stimulus event as a member of a certain
class of events, can this event be perceived at all, for only thus can it
obtain a position in the system of sensory qualities.(15)
Arguments against Hayekian-Hebbian Connectionism
1. One important argument against a view of the sort outlined above is of a
type which has been marshalled against neurologically oriented work in
cognitive science quite generally and which relates to a characteristic misuse
of language which consists in imputing to parts of the human organism what can
properly - if words are to retain their standard meanings - be imputed only to
the whole. This occurs, for example, in phrases like 'the nervous system
perceives', 'the system of acquired connections remembers', 'the processing
engine learns', and so on. It seems not possible to specify the meanings of
terms such as 'perceives', 'remembers', 'learns' in these phrases in ways which
will be consistent with our normal use and understanding of these terms (so
that there is a sense in which we do not really know what these phrases mean).
2. Hayek's view, like that of Ryle in The Concept of Mind, has further no way
of dealing with deliberate, conscious thinking (with reasoning as a logical
process) - this, too, is a standard failing of connectionist approaches - and
its account of consciousness is correspondingly weak. Hayek himself treats
'conscious experience as merely a special instance of a more general
phenomenon', holding that the sphere of mental events, i.e. the sphere of
events which are ordered on principles analogous to those revealed in
introspection, 'evidently transcends the sphere of conscious events and there
is no justification for the attitude frequently met that either identifies the
two or even maintains that to speak of unconscious mental events is a
contradiction in terms.' (172f.) This implies, however, that Hayek has, like
Mach and his Gestaltist successors, no means of drawing a clear distinction
between intentionality as a matter of reflection (or 'isomorphism') and
intentionality as a matter of 'consciousness of' or 'aboutness' in the sense of
Brentano and his followers.
3. Hayek has no way of dealing with what we might call 'mental causality', or
in other words with the connection, so central to the work of Mises, between
reason, choice and action. The system of The Sensory Order leaves no apparent
room for planning, for self-control and for the deliberate self-shaping of the
conscious subject (no room, indeed, for any self or ego or for the unity of
consciousness(16)). A conclusion of this sort might well be acceptable to the
followers of Hume and Mach, for whom consciousness is in any case dispersed and
reactive.(17) But what, then, is to serve as basis for that methodological
individualism which so pervades Hayek's work in the social sciences?
4. Hayek's view has no way of explaining the relative stability over time of
our cognitive faculties and of our qualitative contents, and it has no way of
explaining the massive similarities in cognitive capacities as between one
individual and another. Klüver inadvertently reveals the weakness of Hayek's
position in this respect when, in his "Introduction" to The Sensory
Order, he praises Hayek's theory because it suggests certain definite lines of
experimentation. 'For instance, it should be possible not only to change sensory
qualities experimentally, but to create altogether new sensory qualities which
have never been experienced before.'(18)
The problem for Klüver and Hayek (as also for Hebb and his successors) is that
it seems not to be possible to change or invent sensory qualities in this way
at all: a certain fixity of species seems to pertain to the world of
qualitative experience. The hypothesis of cognitive universals has indeed found
empirical support across a wide range of sensory and intellectual phenomena in recent
years, and it seems that most linguists and anthropologists would nowadays
assume as a matter of course that the truth of this hypothesis is presupposed
not merely by the intertranslatability of all known languages but already by
the very fact of linguistic communication itself. Hayek's account of the
acquisition of perceptual and conceptual classification skills seems moreover
to amount in the end to a sort of tabula rasa view of these matters that seems
difficult to square with what is now known about the impressive mental
competences of new-born babies.
5. It is not clear how an approach along Hayekian-Hebbian lines can do justice
to the creative open-endedness that seems to be involved even in our day-to-day
activities of mental classification (a feature of our mental life which Hayek
is otherwise at pains to insist upon). For in the real world, as Wittgenstein,
among others, has emphasised, classification is often far from being a neat and
tidy affair, yet it is a limitation of standard connectionist systems that they
can be made to operate (the corresponding algorithms of back-propagation can be
applied) only if the relevant classificatory space is fixed in advance.(19)
The Theory of Complex Phenomena
What, then, can be learned in a positive sense from Hayek's work in psychology?
Hayek shows, most importantly, that the central idea behind the connectionist
paradigm is at home not only in psychology and neurology but also in the sphere
of economics. For the mind, from the perspective of The Sensory Order, turns
out to be a dynamic, relational affair that is in many respects analogous to a
market process. The mind is a 'continuous stream of impulses, the significance
of each and every contribution of which is determined by the place in the pattern
of channels through which they flow', in such a way that the flow of
representative" neural impulses can be compared 'to a stock of capital
being nourished by inputs and giving a continuous stream of outputs' (Hayek
1982, p. 291).(20)
In 'The Use of Knowledge in Society' (first published in 1945), Hayek describes
the price system as a mechanism for communicating information; and then, in the
mind, as also in the market system, it is remarkable how little explicit
(conscious) knowledge is required by the agent in order for him to be able to
react in appropriate ways to changes in his circumstances. In the mind as in
the market the most essential information is passed on in the form of
abbreviated 'signals' (as contextually situated nerve impulses or prices,
respectively). The price system is
a kind of machinery for registering change, or a system of telecommunications
which enables individual producers to watch merely the movement of a few
pointers, as an engineer might watch the hands of a few dials, in order to
adjust their activities to changes of which they may never know more than is
reflected in the price movement. … The marvel is that in a case like that of a
scarcity of one raw material, without an order being issued, without more than
perhaps a handful of people knowing the cause, tens of thousands of people
whose identity could not be ascertained by months of investigation, are made to
use the material or its products more sparingly; that is, they move in the
right direction. (Hayek 1949, p. 87)
Both the mind and the system of the market order are products of thousands of
years of evolution, and both evolved through a massive number of trials and
errors and through associated processes of 'training up', as each successive
generation of individuals learned, on the one hand to be conscious, and on the
other hand to play the role of market participant. On the other hand however
the analogy between mind and market breaks down at least in this respect: that
the former cannot on pain of contradiction be seen as having come into being ab
initio as the unintended consequence of intended actions.
The structural similarity between the psychological and the economic sphere is
understandable further in terms of the fact that both have the same dynamic
root, for economic change rests to no small part not on absolute values but on
our (always relative) valuations, and the latter are a psychological matter, a
matter of constantly shifting and changing networks of relations determined
through and through by context and perspective and by the 'economy of thought'.
Minds and markets are comparable also in respect of the fact that the
understanding we can have of each is of a quite different nature from that
which we can have of physical systems. This is indeed for our present purposes
the most important respect in which Hayek anticipates contemporary
connectionism. As Hayek points out, the operations of the mind are
non-perspicuous because we are not explicitly aware of the relations between
the different qualities which constitute the mental order: we merely manifest
these relations in the discriminations which we perform (a case of knowing how
rather than of knowing that). Furthermore, the number and complexity of these
relations is so great, and they are subject to such continual variation, that
we could in any case never reach the point where we could exhaustively describe
them.
On the other hand however the theory of connectionist devices - of Hebb Models
and Boltzmann Machines, of Hopfield Nets and Multilayer Perceptrons - is
mathematically well-developed, and the question thus arises whether this new
body of theory might not be used to throw new light on those 'complex
phenomena' which are at the centre of Hayek's interests not only in psychology
but also in economics and in the social sciences in general. Does connectionist
theory yield a new solution to the old problem at the heart of all economic
theorizing in the Austrian tradition, a problem (crudely put) which turns on
the fact that the phenomena with which the Austrians wish to deal in their
theory are seen by the Austrians themselves as being in a sense too 'complex'
to be theorised about? Hayek himself, familiarly, holds that in relation to the
complex phenomena of the social and psychological sciences we can have only
'qualitative' understanding, and not exact prediction. The complex phenomenon
that is the economic system can thus not be made rational or subject to
'control'.(21)
Indeed prediction and control are already impossible in biology (consider the
problem of predicting how a given species will evolve), and social,
psychological and biological phenomena are such that the notion of a law of
nature as a relationship obtaining between a few phenomena, linked together by
a simple relation such as cause and effect - a notion most at home in the field
of astronomy - cannot be applied. As Weimer puts it, 'the prejudice that in
order to be scientific one must produce laws may yet prove to be one of the
most harmful of methodological conceptions' (1982, p. 244). And as we are all
of us by now only too familiar, the prejudice that scientific knowledge in this
sense has already been attained in relation to the social world has proved
already to be one of the most harmful concepts in the sphere of political
economy.
References
Brentano, Franz 1973 Psychology from an Empirical Standpoint, trans. from 1st
German edition of 1874, London: Routledge and Kegan Paul.
Cowan, Jack D. and Sharp, David H. 1988 'Neural Nets and Artificial
Intelligence', Daedalus, vol. 117, number 1, 85-122.
Dreyfus, H. L. and Dreyfus, S. E. 1988 'Making a Mind versus Modeling the
Brain. Artificial Intelligence Back at a Branchpoint', Daedalus, vol. 117,
number 1, 15-43.
Gray, John 1986 Hayek on Liberty, Second Edition, Oxford: Blackwell.
Hayek, F. A. 1949 Individualism and Economic Order, London: Routledge and Kegan
Paul.
Hayek, F. A. 1952 The Sensory Order. An Inquiry into the Foundations of
Theoretical Psychology, London: Routledge and Kegan Paul.
Hayek, F. A. 1978 'The Primacy of the Abstract' in New Studies in Philosophy,
Politics, Economics and the History of Ideas, London and Henley: Routledge and
Kegan Paul, 35-49.
Hayek, F. A. 1982 'The Sensory Order After 25 Years', in Weimer and Palermo,
eds., 287-93.
Hebb, D. O. 1949 The Organization of Behavior. A Neuropsychological Theory, New
York and London: John Wiley.
Klüver, H. 1952 'Introduction' to Hayek 1952, xv-xxii.
Lavoie, D., Baetjer, H. and Tulloh, W. 1990 'High-Tech Hayekians: Some Possible
Research Topics in the Economics of Computation', Market Process, 8, 120-41.
Mach, Ernst 1917 Erkenntnis und Irrtum: Skizzen zur Psychologie der Forschung,
3rd ed., Leipzig: Barth.
Mach, Ernst 1959 The Analysis of Sensations, trans. from 1st German edition of
1886, New York: Dover.
Mulligan, Kevin and Smith, Barry 1988 ''Mach and Ehrenfels: The Foundations of
Gestalt Theory'' in B. Smith, ed., Foundations of Gestalt Theory, Munich and
Vienna: Philosophia, 124-57.
Partridge, D. 1990 'Connectionism is Better for Engineers than for Scientists',
in Tiles, et al. ed., 55-84.
Petitot, Jean and Smith, Barry (forthcoming) 'Physics and the Phenomenal World'
in R. Poli and P. M. Simons, eds., Formal Ontology, Dordrecht/Boston/Lancaster:
Kluwer.
Ryle, Gilbert 1949 The Concept of Mind, London: Hutchinson.
Schulzki, Ewald 1979 Der Mensch als Elementenkomplex und als
denkökonomische Einheit. Zur Anthropologie Ernst Machs, Dissertation,
University of Münster.
Shackle, G. L. S. 1972 Epistemics and Economics. A Critique of Economic
Doctrines, Cambridge: Cambridge University Press.
Smith, Barry 1990 'Aristotle, Menger, Mises: A Categorial Ontology for
Economics', History of Political Economy, Annual Supplement to vol. 22, 263-88.
Stout, G. F. 1915 Manual of Psychology, 3rd ed., London: University Tutorial
Press.
Smolensky, Paul 1987 'On the Proper Treatment of Connectionism', University of
Colorado at Boulder, Department of Computer Science, variously reprinted.
Tiles, J. E., McKee, G. T. and Dean, C. G., eds., Evolving Knowledge in Natural
Science and Artificial Intelligence, London: Pitman Publishing.
Weimer, Walter B. 1982 'Hayek's Approach to the Problems of Complex Phenomena:
An Introduction to the Theoretical Psychology of The Sensory Order', in Weimer
and Palermo, eds., 241-85.
Weimer, W. B. and Palermo, D. S. eds. 1982 Cognition and the Symbolic
Processes, Hillsdale, NJ: Lawrence Erlbaum, vol. II.
Endnotes
1. Work on the present paper has been carried
out as part of the project "Formal-Ontological Foundations of Artificial
Intelligence Research", sponsored by the Swiss National Foundation. I am
grateful to Graham White, Wojciech Zelaniec, Gloria Zúñiga, as well
as to participants in the Hayek Memorial Symposium for helpful comments.
2. Current chess-playing computers are not the results of research in
artificial intelligence in this sense, since they operate on the basis of
exhaustive search strategies quite different from those employed by human
chess-players.
3. The sub-symbolic programs of connectionism
can, as is often pointed out, be translated in such a way that they can be
implemented also on classical (von Neumann) machines; but the translated
programs are then not the kind of 'symbolic' program that the Helmholtz
hypothesis requires.
4. Partridge 1990, p. 71.
5. References in this form are to the numbered sections in The Sensory Order
(Hayek 1952), with decimal point removed.
6. See Mulligan and Smith 1988, pp. 150f.
7. As Hayek notes, a structuralist approach of this sort does however very well
explain the existence of certain patterns of which we are aware. Thus for
example it can explain the existence of those 'intermodal' attributes which are
revealed in our pervasive use of adjectives such as strong, weak, mild, mellow,
tingling, sharp, thick, rough, bright, heavy, hot, gritty, coarse, hollow,
luscious, astringent, smooth, etc. in relation to sensory qualities of every
sort. (158.- 163.)
8. On the role of 'Hebb models' in the development of connectionism see Cowan
and Sharp (1988, pp. 88f). In a note to this paper it is suggested also that
there is a link between Hayek's work and the 'Boltzmann models' of more recent
connectionist research (op. cit., p. 119, n. 57). Hayek himself adverts to Hebb
at various points in The Sensory Order (see p. vii, and also 249., 315., 334.,
538.).
9. The idea of mental topology can be conceived
as a generalisation of the marginal approach adopted by Hayek and other members
of the Austrian school in economic theory.
10. As Hayek writes:
we shall expect fairly close connexions to be formed between the neurons served
by neighbouring receptors which are sensitive to stimuli which occur frequently
together because they emanate from the same physical objects, such as pressure
and temperature, certain chemical agents acting simultaneously on mouth and
nose, etc., etc. (331.)
11. In his 1982, Hayek draws attention to the dispositional connotations of
this terminology of followings, and also to the redundancy and randomness
involved in the workings of the neural classificatory system:
The 'followings' of all the impulses proceeding in the central nervous system
at any one time are thus assumed to determine the potential or readiness of the
system to do new things - internally or externally. Which of these potential
neural events (toward which the system is inclined at any particular moment)
eventuates would be decided by the partial overlapping of these followings
through which, by summation, the potential effects of those linkages would be made
actual. Only where a sufficient number of impulses converged on any one neuron
would it be made to 'fire' and to send out impulses to hundreds or thousands of
other neurons. (p. 290)
12. E.g. by Stout 1915.
13. Mach too allowed his sensory elements to picture certain qualities of
higher order. Cf. Schulzki 1979, pp. 158ff.
14. See also Petitot and Smith (forthcoming), but contrast my 1990, p. 265.
15. At one point Hayek goes so far as to assert that an event which sets up via
peripheral stimulation impulses in the brain of an entirely new kind 'could not
be perceived at all.' (636.)
16. As Brentano stresses (1973, Book II, Ch. IV), mere similarity and regular
association, however complex and many-levelled, do not as such add up to unity.
17. The self, for Mach, 'is not a monad isolated
from the world, but a part of the world and caught up in its flow … so that we
will no longer be tempted to see the world as some unknowable something. We are
then close enough to ourselves and sufficiently closely related to the other
parts of the world as to be able to hope for genuine knowledge.' (Mach 1917, p.
462)
18. Klüver 1952, pp. xxif.
19. Compare the remark of Dreyfus to the effect that:
All neural net modelers agree that for a net to be intelligent it must be able
to generalize; that is, given sufficient examples of inputs associated with one
particular output, it should associate further inputs of the same type with
that same output. The question arises, however: What counts as the same type?
(1988, pp. 38f)
The opposition at issue here is neatly captured in the following remark by
Shackle on what is, in effect, the classification problem faced each day in the
business world:
Kaleidic effects, typically the response of asset values to 'the news', the
abrupt and necessarily unforeseeable reaction of expectation-formers to
announcements which in their nature are unheralded and of a purport quite
unknown in advance, pose important problems of notation. The basic and
essential character of the kaleidic phenomenon renders inappropriate the
accepted methods of analysis of fully- known problems. It is the fact,
astonishing and yet natural, that in economics we habitually and, it seems,
unthinkingly assume that the problem facing an economic subject, in especial a
business man, is of the same kind as those set in examinations in mathematics,
where the candidate unhesitatingly (and justly) takes it for granted that he
has been given enough information to construe a satisfactory solution. Where, in
real life, are we justified in assuming that we possess 'enough' information?
(1972, p. 184)
20. Cf. also Lavoie, et al., 1990.
21. 'The rationality of complex systems is not
localizable in a single locus of control, and it is therefore never
"conscious"'. (Weimer 1982, p. 245)
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