Neuroscience Vol. 5, pp. 1389 to 1391 Pergamon Press Lid 1980. Printed in Great Britain © IBRO

0306..4522/80/0701 - 1389$02.00/0

LETTER TO THE EDITORS

T H E I N T E R D E P E N D E N C E O F M I N D A N D BRAIN

D. M. MACKAY Research Department of Communication and Neuroscience, University of Keele, Staffordshire ST5 5BG, U.K.

The commentary on 'Mind-Brain Interaction' by my good friend ROGER SPE~Y (1980a) prompts me to write a few lines to clarify the relationship between our respective pos- itions. May I say at the outset that his detailed analysis and critique of the options he rejects, including those he himself once favoured, should go far to stimulate clearer and more articulate thinking among neuroscientists on this thorny issue, whether or not they agree with him. If I focus here on a few points of difference, this is largely because our area of agreement will be obvious to those who have read our respective 'Commentaries'.

Let me begin with a brief note on chronology. Although SPERRY (1980a) describes me as having 'recently arrived at' the position I outlined (MACKAY, 1978) as an alternative to the interactionism of PoppeR & ECCL~ (1977), I have in fact been arguing each of its main points (though some- times in journals not readily accessible in the U.S.A.) since the early 50s. It was in 1951, at the end of a paper showing how naturally 'mindlike' behaviour could issue from the activity of a hierarchically organized information-flow sys- tem, that I first ventured to suggest an option of the kind that Sperry calls 'holistic', which could do justice to what mechanistic materialism and Cartesian interactionism were respectively trying to conserve, without their negative im- plications (MACKAY, 1951a). I proposed that we think of a conscious agent, at the information-engineering level, as a particular kind of information-flow system (characterized by circulation of information in a hierarchic organization capable of forming internal representations of its own ac- tivity), embodied in the physical structure of the brain in something of the sense in which a goal-directed pro- gramme is embodied in an automaton, or a triangle is embodied in a pattern of three dots (loc. cit., pp. 116-17). From this it would follow that what peculiarly identifies and characterizes conscious agency is its information-flow topology, rather than its physical structure. What makes us responsible for our actions, I suggested, is not that the physical works of our brains are pushed or pulled around by a non-physical 'mental force', but that (at the informa- tional level) the form of our cerebral workings is deter- mined by our conscious thinking, evaluating and deciding even while (at the physiological level) physical causality might reign undisturbed (MACKAY, 1951a; 1952; 1953a).

Unity of conscious experience

On this basis, the brain-correlate of the unity of the con- scious T would be sought at the informational level, in the topological unity of the internal organizing activity made possible by information-linkages between the participating brain-elements (MACKAY, 1951a, p. 119). The correlate of perception, as distinct from mere sensory stimulation, would be an internally generated matching response that set up a conditional state of readiness for action in the situation-as-perceived (MACKAY, 1951a,b; 1956). The con-

tinuity of our perceptual experience would thus correlate not necessarily with continuity of incoming sensory signals, but with 'the persistency of the (internal) command- pattern' evoked in matching response (MACKAY, 1951a, p. 119).

The 'seat of the mind'

The implications of this position, which (pace SPERRY, 1980a) is in essence the one I still hold (MAcKAy, 1980) took a lot of spelling out. (1) In the first place, it meant that although looking for 'the seat of the mind' was not mean- ingless, it was not something to be achieved by analysis of the brain into components and looking for 'action of the mind' on individual parts. Mental activity would be mean- ingfully locatable (in principle) in specific flow-structures of the information-diagram; but this meant that the relevant flow-lines would in general extend beyond the confines of any one component structure, and during conscious action might even run out-and-back through the environment. Mentality, as a system-property, could be rendered invi- sible or destroyed by attempts to localize its action to any subsystem of the total information-flow pattern in which it was currently embodied (MACKAY, 1951a, p. 118).

"Causal efficacy'

(2) By the same token, this approach offered hardnosed reasons for rejecting the 'nothing-buttery' of epiphenomen- alism, and insisting that mental activity was a vital factor in determining behaviour (MACKAY, 1951, p. 118; 1952, pp. 83-84; 1953a, pp. 17, 18, 25). In that general sense, in com- mon with writers as diverse as FEIGL (1958) and POPPER & ECCLES (1977) as well as SPERRY (1965; 1980a), I have always insisted on what they call the 'causal efficacy' of mental activity. The information-engineering analogy, however, led me to urge that in order to avoid confusion we needed different terms from 'causality' and 'interaction' to denote the interdependence of 'mind' and 'matter' (MACKAY 1953a). To reduce the risk of misunderstanding. I proposed that we reserve 'interaction' and 'causality' for the links between events or entities at the same categorical level, whether mental or physical (MACKAY 1953a, p. 24), and perhaps speak of 'necessity' for the inter-level relation- ship (MACKAY, 1955, p. 25). The two-way link between mental activity and the physical activity in which it is im- mediately embodied is (I suggested) 'a relationship more intimate than that of cause-and-effect' (MACKAY, 1960). Admittedly, in terms of Aristotle's fourfold classification of 'causes', it might be fair enough to describe mental activity as the ~formaF cause of the immediately correlated brain activity; but I felt that if we must use 'causality' in this context it would be less confusing to the restive physiolo- gist to insert at least some distinguishing adjective (MACKAY, 1953a, p. 24).

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Complementarity

(3) Although I found it appropriate (and still do) to speak of mental and physical categories as logically 'com- plementary', I had to point out that, unlike the comple- mentary 'wave' and 'particle' aspects of light, the two were not symmetrically related (MACKAY, 1951a, p. l l8), but belonged to different conceptual levels which were not intertranslatable (MACKAY, 1957; 1958; 1962). Nor did the term imply, as with some 'double-aspect' identity-theorists, that mental activity was merely an inside aspect of brain activity, as if the physical had some ontological priority (MACKAY 1957), still less that mind-talk was an 'optional extra' (MACKAY, 1962). I argued rather that the mental is one of a hierarchy of complementary determinative aspects of the mysterious unity we know as human agency, of which the physical (brain activity) is a lower aspect and the spiri- tual (I suggested) a still higher one (MACKAY, 1951a, p. 118; 1953a, p. 25; 1960).

As I put it in the paper I wrote in 1964 for the Rome Symposium (MACKAY, 1966). "Mind has 'working contact' with matter, more intimate than that of one form of energy upon another . . . It is not that control by Mind or cons- ciousness is an exclusive alternative to control by a physi- cal system--something which 'takes over' where physical control leaves off. It is rather . . , that a particular kind of complexity of control mechanism in an organism is . . . the expression or embodiment of the personal agency of con- sciousness and Mind."

Physical indeterminacy

(4) From the outset I favoured (on scientific grounds) a stochastic model of cerebral information processing (MACKAY, 1951a,b; 1956); but I pointed out (MACKAY, 1953b) that any physical indeterminacy in the brain would be likely to affect the 'freedom' of spontaneity and caprice rather than that of responsible choice; and I have argued since 1954 that to deny physical determinism in order to maintain the responsibility of a human agent for his deci- sions is both unnecessary and misguided (MACKAY, 1954; 1957; 1958b; 1980).

Relation to Sperry's position

It will be obvious that when SPERRY (1964; 1965) came to his own anti-materialist position, we had much ground in common. Where I preferred to speak of conscious agency as 'embodied in' physiological processes, he spoke of it as 'emergent from' them; but comparison of our argu- ments and illustrations shows that we were advocating rather similar concepts of the mind-body relationship. I welcomed his robust support in contending against the idea that consciousness is merely 'an epiphenomenon' or 'just an inner aspect of the one material brain process', and in fighting what he called 'the pervasive influence of creep- ing materialism' (SPERRY, 1965, pp. 74 and 76).

We had, however, two main points of amicable disagree- ment. First, SPERRY (1965, p. 76) at that time talked consis- tently in terms of 'an interjection into (the brain's) causal machinery of mental or conscious forces'. 'Mind and con- sciousness', he claimed, ' . . , push and haul around the physi- ology and the physical and chemical processes' (ibid., p. 78). Despite his insistence that 'all physiological forces... continue to operate' (SPERRY, 1965, p. 82) he felt that he had to oppose the notion that in the brain 'no physical action waits on anything but another physical action' (MACKAY, 1966). Furthermore, as stated in SPERRY, 1980a,

he saw his argument as "refuting' the 'classical physicalist assumption of a purely physical determinancy of the CNS', speaking of 'the simpler electric, atomic, molecular and cellular forces and laws, though still present and operative ~ as 'superseded by the configurational forces of higher-level mechanisms' (SPERRY, 1964). He has recently (SPERRY, 1980b) repeated the claim that 'the physical brain pro- cess.., is not...causally complete without including the subjective mental properties... Mind does actually move matter within the brain' (all italics mine).

'Physical determinacy' in the CNS?

I fear I am no more happy now with this way of express- ing the mutual interdependence of brain activity and men- tal activity than I was in 1964 or indeed in 1953. In the case of a computer, I ask myself, would it be accurate to speak of the mathematical determinants as 'pushing and hauling around' the transistors, or 'superseding and out- classing' the physical factors that operate at the level of energetics? Could we, on the grounds that its behaviour is determined by the equation it is solving, persuade the com- puter engineer that this 'refutes the assumption of purely physical determinacy' in his machine, or that his physical explanation of what the transistors are doing is "not cau- sally complete without including the equation being solved'? What we want to say, surely, is that even though in the computer the chain-mesh of physical factors is cau- sally complete, so that indeed 'no physical action waits on anything but another physical action', nevertheless the whole point of the thing has been missed, and no under- standing of what it is doing has been given, unless our explanation includes the equation that determines its be- haviour. As I argued in my commentary (MACKAY, 1978), claims to determination at different levels are not necess- arily exclusive rivals. 'Purely physical determinacy of the CNS' (whether we believe in it or not) is thus fully com- patible with the determination of the informational func- tion of the CNS by the mental activity it embodies, and has no need to be 'refuted' in order to make room for the causal efficacy of human thinking and deciding. The trouble with physical analysis (as with the electronic analy- sis of a computer) is simply that it misses the point made by the higher-level explanation. Physics is unable to answer certain questions about behaviour under mental control (e.g. 'Why did he get up and go out?') because it has no categories in terms of which to express the point made by saying (e.g.) 'Because he felt he ought not to be a party to what was going on.'

In short, despite the substantial similarities between the thesis of SPERRY (1965) and.mine of the 1950s, I fear that in his use of interactionist language he overstates his case. This does indeed, as he points out, make him sound at times rather like Eccles and Popper (or vice versa): but I would think that their dualism (which I do not accept) offers a more rational basis for such interactionist talk than Sperry's monism. As SPERRY (1980a) himself recognizes they do sometimes use the term 'interaction' in the specific sense (which he rejects) of 'an actual disturbance of physio- logical events' (though he chides me for having 'misinter- preted their meaning' when I criticized this usage!).

Conscious after-life?

Finally, and briefly, I must mention one further point of disagreement. SPERRY (1980a) seems to suggest that his monistic model would 'say "no" to' the possibility of 'a conscious after-life'. This would I think be a mistaken

Letter to the Editors 1391

inference. If (as I gather he would agree) our conscious agency is embodied in the activity of our CNS, in some- thing of the sense in which the solving of an equation is embodied in the activity of a computer, then I think he and I would agree that what identifies us specifically (as John or Mary or whoever) is to be found in the total information-flow system thus embodied, rather than at the level of specific brain molecules or cells. If so, then what- ever our attitude to the theology that speaks of it, the notion of the Creator's re-embodying us as conscious agents after death would seem no more to be logically excluded than the notion of a mathematician's setting up

the very same equation in some new embodiment. Such a holistic view of the mind-body relationship is, no doubt, inimical to some specific theories of human nature advanced in the name of religion; but with the biblical concept of man, as I have argued elsewhere (MACKAY, 1953a; 1960: 1980) it appears to have no incompatibility whatsoever.

Acknowledgements--I am grateful to ROGER SPERRY for the opportunity to discuss these matters, and for access to pre- prints of his recent writings, during an enjoyable stay in his laboratory as a Sherman Fairchild Scholar in 1980.

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SPERRY R. W. (1964) Problems Outstanding in the Evolution of Brain Function. James Arthur Lecture. New York: American Museum of Natural History.

SPERRY R. W. (1965) Mind, brain and humanist values. In New Views of the Nature of Man (ed. PLATT J. R.), pp. 71-92. Univ. of Chicago Press, Chicago.

SPERRY R. W. (1980a) Mind-brain interaction: mentalism, yes; dualism, no. Neuroscience 5, 195-206. SPERRY R. W. (1980b) Consciousness, personal identity and the divided brain. In The Human Mind. The 1977-1978 Frank

K. lq~elson Doubleday Lectures.

(Accepted 17March 1980)