Jack Orbach (2000) Hebb's Theory and Lashley's Analogy. Psycoloquy: 11(119) Lashley Hebb (19)

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PSYCOLOQUY (ISSN 1055-0143) is sponsored by the American Psychological Association (APA).
Psycoloquy 11(119): Hebb's Theory and Lashley's Analogy

Reply to Palm on Orbach on Lashley-Hebb

Jack Orbach
Department of Psychology
Queens College
Flushing, NY 11367



Lashley saw himself as offering no more than analogies, not theories, in his quest for the neural mechanism of the reduplicated engram in the cerebral cortex.


cell assembly, central autonomous process, engram, equipotentiality, Hebb, Hebbian learning, Lashley, localization, memory trace, nativism, reverberatory circuit, Vanuxem Lectures
1. In the second paragraph of his review of "The Neuropsychological Theories of Lashley and Hebb" (Orbach 1998, 1999) Palm (2000) wrote, "The title of this book is misleading... It does not really explain the theories of Lashley and Hebb. To put it bluntly, this is because Lashley had no theory and the author did not understand Hebb's." Palm's first charge, that Lashley had no theory, can be challenged, but I believe that Lashley himself would not challenge it. At the end of his last public lecture, delivered at the University of Rochester in 1957 less than a year before he died, Lashley referred to his views as analogies, not as theories. "I have used the analogy of interacting waves on the surface of a lake... The analogy is farfetched, but I believe it is a closer representation of the events in the nervous system than is the classical notion of stable reflex paths." I quoted this passage unabbreviated on p.xi of the Prologue of my book.

2. My opinion is that Lashley offered important conceptions beyond the well known equipotentiality and mass action that were propaedeutic to the development of neuropsychological theory. Here are some examples:

    (i) Pattern of neural activity is more important than locus of the
    activity in the brain in understanding higher mental functions like
    memory. I believe that Lashley would still insist that locating the
    activity in, say, the left third frontal convolution of the left
    cerebral hemisphere does not reveal how the nervous system works,
    although the location of activity may prove to be important in the
    clinic. (see Lashley, 1929).

    (ii) The memory trace can be laid down and reduplicated in the
    brain in one trial. The improvement in memory with practice does
    not necessarily mean that resistance at the synapse is repeatedly
    reduced (see Lashley, 1924).

    (iii) The reverberatory circuit of Lorente de N can provide a
    mechanism for sustained activity in the brain after the stimulus
    has terminated (see Lashley, 1938).

    (iv) Non-continuity in discrimination learning is the rule in
    mammalian species (see Lashley, 1942a).

    (v) Sensory and motor equivalence are matters that deserve to be
    considered from a neural point of view. Lashley took up these
    matters in some detail in his 1942b paper reprinted in my book.

    (vi) "Lashley's lesson," that neurons unexcited during learning may
    still show the effects of learning. A more complete litany of
    Lashley's conceptual contributions may be found in my earlier book
    on Lashley (Orbach, 1982, pp. 2-14) and in the book under review
    (chapter 8).

3. Now, how can I reply to Palm's charge that I do not understand Hebb's theory, lacking any bill of particulars? Palm writes that he read mostly between the lines. Does his opinion rest on my treatment of Hebb's views of attention and stimulus generalisation? (chapter 7); or what is referred to today as the Hebb synapse? (chapter 2); or Hebb's experientially assembled neural lattice? (chapter 5). Or am I guilty of an error of omission? I wish I could respond with good humour, but without a more specific enumeration of my alleged failures to comprehend, I have no way of knowing what Palm is talking about.

4. In paragraph 4 of his review, Palm wrote that Lashley's experiments "finally convinced him that the memory trace could not be localized in a particular connection between two neurons in a particular place." I believe that this is a caricature of Lashley's view. I am not aware that any respected neuropsychological theorist in Lashley's day would have entertained such a possibility in any mammalian species -- certainly not Hebb.

5. Palm's characterisation of experimentalists deserves a comment. He sees Lashley as an experimentalist who "never fully committed himself to a theory because he knows that it is all too easy to falsify it experimentally" (paragraph 3). On this matter, Palm is probably right. I suggested as much in my book on p. 56, when I wrote "Throughout his professional career, Lashley seemed to have had a horror of being proved wrong. Hence his cautious writing."

6. In contrast, Palm writes, "The real strength and courage of Hebb was not just to formulate his theory of cell assemblies, but to rest all of his psychology on the hypothesis that this is it, and nothing else is needed. This strong commitment to a theoretical hypothesis is the real reason theoreticians insist on naming Hebb synapses after him." (paragraph 5). This is an interesting suggestion. Hebb himself demanded specificity in his theory so that it could be falsified. And, with good humour, he suggested that it would eventually be found false; it is just a matter of time! Keep in mind what has happened to Watson's strongly committed view that behaviour theory requires but two terms, stimuli and responses, and to Hull's stimulus-response-reinforcement theory, to which he too was strongly committed.


Hebb, D. O. (1949) The Organization of Behavior. NY: Wiley.

Lashley, K.S. (1924) Studies of cerebral function in learning. VI. The theory that synaptic resistance is reduced by the passage of the nerve impulse. Psychol. Rev. 31, 369-375. In Orbach, Jack (1998) The Neuropsychological Theories of Lashley and Hebb. MD: University Press of America.

Lashley, K. S. (1929) Brain Mechanisms and Intelligence. Chicago: University of Chicago Press. Reprinted in Dover Ed. 1963, with Introduction by D. O. Hebb.

Lashley, K. S. (1938) Experimental analysis of instinctive behavior. Psychol. Rev. 45, 445-471.

Lashley, K. S. (1942a) An examination of the "continuity theory" as applied to discriminative learning. J. Gen. Psychol. 26, 241-265

Lashley, K. S. (1942b) The problem of cerebral organization in vision. Biol. Symp. 7, 301-322. In Orbach, Jack (1998) The Neuropsychological Theories of Lashley and Hebb. MD: University Press of America.

Orbach, Jack (1982) Neuropsychology After Lashley. NJ: Erlbaum.

Orbach, Jack (1998) The Neuropsychological Theories of Lashley and Hebb. MD: University Press of America.

Orbach, J. (1999) Precis of: The Neuropsychological Theories of Lashley and Hebb. PSYCOLOQUY 10(029) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1999.volume.10/ psyc.99.10.029.lashley-hebb.1.orbach http://www.cogsci.soton.ac.uk/psyc-bin/newpsy?10.029

Palm, G. (2000) From Lashley to Hebb: the development of a biophysical theory of learning. PSYCOLOQUY (11)047 ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/2000.volume.11/ psyc.00.11.047.lashley-hebb.15.palm http://www.cogsci.soton.ac.uk/psyc-bin/newspy?11.047

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