D.O. Hebb Father of Cognitive Psychobiology
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 D.O. Hebb
 Father of Cognitive Psychobiology
 1904-1985

 
    When one is not equipped to write an objective biographical tributeon the occasion of a great man's passing, all one can offer is one's ownpersonal recollection and appreciation.
When I enrolled inPsychology21atMcGill Universitytwenty-oneyears ago, it was with the usual undergraduate expectation that Freudianpsychology was psychology, and that it would help you understand your ownmind and everyone else's. The instructor for this enormous introductorycourse looked anything but Freudian. This gaunt maritimer called Hebb,with his stern spectacles and portentous limp, who pronounced "calm" "cam,"looked more qualified to teach us about practical seamanship than aboutthe mysteries of the psyche (although his tone was incongruously gentle,sometimes even dreamy). He warned us from the outset that he was goingto wean us of our preconceptions about psychology. And so he did. Not allat once, but gradually---with his emphasis on the role of our biologicalheritage (through those unforgettable anecdotes about "Booie" and the otherchimps Hebb had worked with atYerkes'primate center) as well as our early experience (and experience ingeneral) in shaping those thought processes that we had all been so readyto interpret symbolically in terms of old Greek myths recirculated in lateVictorian Vienna---he succeeded in distancing us at least from the inclinationto change courses in favor of something more like what we had been expecting.

For me, however, the transformation was unforgettable and very specific.I can remember that when I was a child and people spoke of the "brain,"I had always assumed that it was just a figure of speech. It seemed obviousthat my mind was not a material substance, so people couldn't really meanit when they said that we had a physical organ that was responsible forour minds in the same way that a heart was responsible for circulationand a stomach for digestion. When I had learned that there really was abrain, I just filed it away as a kind of oddity, never even tying it togetherwith my only other early contact withthemind/body problem(one solipsistic summer).

But then Hebb reminded us of the problem anew, first through suggestiveaccounts of his work withPenfieldon the localization of memories in the brain, and then from the viewpointof his own specific hypothesis that thoughts could actually be the activityof reverberating circuits of neurons called "cell-assemblies." I don'tthink his idea had its full impact on me at the moment he described it.Rather, it was after the lecture, as I thought about it, and thought thatmy thoughts may well consist of those physical things I was thinking about,that I realized what a radically different world view such a theory represented,and that it all had a ring of reality to it that made the Freudian notionsI had been flirting with sound like silly fairy tales. Here were the realunconscious processes underlying our thinking, instead of the anthropomorphicmachinations of some Freudian "unconscious mind," which now began to lookrather like a supernumerary and supererogatory alter homunculus:Onemind/body problem was enough!

Then, almost before the revelation his hypothesis represented had hada chance to take effect, Hebb took it back, informing us that his theorywas almost certainly wrong. What followed was his second revelation: Thata theory need not be right in order to be informative and to guide us inthe right direction. And the cell assembly theory (together with otherideas in Hebb's epochal 1949 monograph,The Organization of Behaviour)had indeed inspired an enormous wealth of research findings, from the effectsof sensory enrichment and deprivation to electrical and chemical pleasurecenters in the brain totheoreticalmodeling of neural networks,as we went on to learn panoramically fromthe rest of Psychology 21 (based, as it was, onHebb'sTextbookof Psychology, which was itself based largely on research inspiredand organized by his ideas).

Hebb himself was not only altogether unpretentious but also ever scepticalabout his ideas. He saw them as pointing the way toward answers, ratherthan representing the answers themselves. In this I believe he had hada veridical insight into the state of contemporary psychology: he did notsee much that was lapidary in it. A student of KarlLashley,whose own contribution had been mainly critical and heuristic, Hebb alwaysstated with complete conviction that he regardedB.F. Skinneras the greatest psychologist of the century. This, despitethe fact that (in my opinion) Hebb's own work and the research it provoked(rather thanChomsky'scelebrated review ofSkinner'sVerbalLearning) may well turn out to be seen historically as having providedthe real empirical alternative to behaviorism.

Contemporary cognitive science lays claim to a variety of roots (linguistic,philosophical, computational), but it also takes a lot for granted. Withoutany particular brief for symbolic representation, Hebb had been arguingfor four decades that thoughts are processes represented in the head, andthat behaviorism, in an over-reaction against introspectionism, was beggingthe important questions in psychology. For Hebb, the business of scientificpsychology was to make inferences about the unobservable physical substratesof behavior, thinking, personality and emotion. Such inferences were risky(unlike behaviorism's reinforcement schedules), in that they might be verywrong; but as long as they suggested testable predictions and successfullyguided research, they were leading toward the truth about the mind. Anothernegative lesson Hebb had learned from behaviorism was that it is unwisescientific practice to ignore anything, be it our brain, our biologicalheritage, our cognition or our conscious experience. There is the room---indeedthe need---in Hebb's cognitive psychobiology for studying all of these.And just as he avoided arbitrary dismissiveness and question-begging, Hebbresisted any sense of premature closure, of already having found the answers.(Contemporary cognitive science might do well to introspect somewhat asto whether, in its own animistic interpretations of symbolic processes,it has not inadvertently rejoinedthehermeneutic roadto Vienna.)

Hebb may well have been taking the proper measure of his subject whenhe declined the honor of having been its greatest contributor to date.In my view, his tribute to Skinner expressed his conviction that whereastheoretical ideas will come and go for some time to come in scientificpsychology, its methodological commitment to ultimate behavioral testability(which is to say,empiricaltestability) is here to stay.

I went on to do honors psychology at McGill, and to write my honorsthesis under Hebb (the last thesis he supervised, to my knowledge), andI continue to regard everything I do in psychology as Hebb-inspired. Manypeople feel this way about their own personal intellectual debt to Hebb(although "debt" is not really the right word---it's much more like "credit"),especially McGill people. There is also a related tendency on the partof the students of "D. O." (as Hebb was affectionately known locally) tosee all good things in psychology as having issued from him. Perhaps thisis a weakness of the students of all great teachers, and D. O. would certainlyhave been the first to pooh-pooh it. But before I set it down to mere discipialbias, I shall await the judgment of objective historians.

Historians have been relatively silent about D.O. so far, partly, nodoubt, out of deference for the fact that he was still alive. For his part,D.O. had, in his wisdom, been electing to keep his own counsel in his lastyears, declining the many invitations to pronounce on the past, presentand future of psychology that inevitably accrue to the grand old men ofa field. He abstained in part because he remained ever the shrewd and dispassionateobserver of life-cycle effects in his cognitive capacities (and those ofothers). And in part it was out of the perennial modesty and scepticismof this down-to-earth and very humane man.

But now that the old mariner's body has completed its last voyage, itis time we evaluated in earnest the treasures left us by his mind.

 Stevan Harnad,Princeton,1985

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