Hebb, Donald Olding
HEBB, DONALD OLDING
psychology, neuropsychology, cognitive psychology, cognitive neuroscience.
Hebb was one of the preeminent neuropsychologists of the twentieth century. When Hebb arrived on the psychological scene in the 1930s, behavioristic formulations, which typically evaded questions of mind and reference to the nervous system, dominated North American academic psychology. In his major theoretical work, The Organization of Behavior (1949), Hebb presented a comprehensive neuropsychological account of behavior, grappling with essential mental events, while also confronting the learning theories of the behaviorists and the perceptual phenomena described by the Gestalt psychologists. By virtue of the ideas presented in The Organization of Behavior, the publication of Hebb’s unique Textbook of Psychology(1958), and the research emerging from McGill University laboratories in the 1950s and early 1960s, Hebb played a major role in sparking the cognitive revolution in psychology and, particularly, the development of cognitive neuroscience.
Early Life, Marriages, and Education . Both of Donald Hebb’s parents, Arthur Morrison Hebb and Mary Clara Olding, were physicians. He was the oldest child in the family. One younger brother, Andrew, was trained as a lawyer but subsequently became a businessman. A second brother, Peter, became a physician. Donald Hebb’s youngest sibling, Catherine, received her PhD in physiology from McGill University and later achieved international recognition for her work on acetylcholine. As for Hebb, until the age of eight he was educated at home by his mother. At school in Chester, Donald advanced rapidly until the eleventh grade, which he failed. He later stated that “things came too easily, I had never learned to work, I was bored by school from the day I entered to the day I left” (Hebb 1980, p. 277).
After repeating grade 11 in Chester and taking grade 12 at the Halifax Academy in Halifax, Nova Scotia, Hebb entered Dalhousie University, also in Halifax, Nova Scotia, in 1921 and graduated with a BA in English and philosophy in 1925. He intended to become a writer but obtained a teaching certificate from the Nova Scotia Teachers College in Truro, Nova Scotia, and worked for some years as an elementary school teacher and principal in Nova Scotia and Montreal, Quebec. During his recuperation from tuberculosis of the hip in 1931, Hebb married Marion Clark, but after only eighteen months of marriage, his wife died in an automobile accident. Hebb married Elizabeth Donovan in 1937, a union that produced two daughters, Jane and Mary Ellen. Elizabeth died in 1962; Hebb married Margaret Wright in 1966.
Discovering Psychology and Graduate Education . Hebb studied psychology in two philosophy courses at Dalhousie and was introduced to the ideas of Sigmund Freud, which he found interesting but insufficiently rigorous. While he was teaching in Montreal in 1929, Professors Clarke and Chester Kellogg from McGill University conducted IQ tests on his students, and Hebb discovered that children of all abilities were not performing as well as anticipated. To encourage students to study more, Hebb changed the classroom rules, making schoolwork a pleasure rather than a punishment. This educational experiment resulted in Hebb’s first published paper (in Teacher’s Magazine in 1930), demonstrated his unconventional turn of mind, and resulted in Hebb coming a part-time graduate student at McGill, completing his MA thesis under the supervision of Kellogg.
While recuperating from his tubercular hip in 1930–1931, Hebb read works by Charles S. Sherrington and Ivan Pavlov and completed a theoretical MA thesis that considered the possibility that spinal reflexes were influenced by neural activity in utero. A version of what was to become known as the “Hebb synapse” was presented for the first time in this thesis (described in Brown & Milner, 2003). Subsequently, Hebb did hands-on studies of Pavlovian conditioning of the salivary response in dogs with two of Pavlov’s students who were on the McGill faculty, Boris Babkin and Leonid Andreyev, but Hebb found fault with Pavlovian methodology.
Searching for a graduate program where he could proceed with the study of neuropsychology, Hebb was offered admission at Yale University by Robert Yerkes, but Babkin persuaded him to go to the University of Chicago to study with Karl Lashley. More than any other single choice, the decision to work with Lashley was to shape the questions that Hebb addressed many years later in The Organization of Behavior. In the years preceding Hebb’s arrival in Chicago, Lashley had pioneered the experimental study of the brain and behavior, focusing on neocortical localization of visual discrimination and intellectual function in the laboratory rat. Lashley also had worked on Gestalt-like field interpretations of responses to visual stimuli and of the effects of deprivation of early visual experience on discrimination of distance. At Chicago, Hebb took classes from some of the most distinguished professors of the day, including L. L. Thurstone, Harvey A. Carr, Wolfgang Kohler, C. Judson Herrick, and Nathanial Kleitman. When Lashley moved to Harvard University in 1934, Hebb followed and completed his PhD thesis there in 1936. Hebb’s dissertation concerned the effects of deprivation of early visual experience on brightness and size discrimination learning. The dissertation was published in three articles, as “The Innate Organization of Visual Activity” in 1937 and 1938 (in the Journal of Genetic Psychology and the Journal of Comparative Psychology).
However, Hebb’s preferred topic involved spatial learning. In an ingenious series of experiments, Hebb demonstrated that rats relied on distal visual cues, rather than intramaze cues, in learning the optimal path from start to goal, and that lesions of the neocortex resulted in a switch from reliance on distal to proximal cues. The results of those experiments were published in the Journal of Comparative Psychology in 1938.
Human Neuropsychology . After completing his work at Harvard, Hebb was in an uncomfortable position, job hunting during the Great Depression of the 1930s. However, his sister Catherine, who was just completing her PhD at McGill, wrote with news of a position at the Montreal Neurological Institute (MNI) to study the effects of surgical intervention by Dr. Wilder Penfield on the intellectual capacity of human patients. Hebb was awarded this position and, in the course of studying Penfield’s patients, he discovered that removal of a large portion of one frontal lobe sometimes resulted in improved performance on standardized IQ tests. He subsequently postulated that general patterns of response, learned early in life, are dependent on frontal lobe activity, but that once acquired, the information can be processed in other brain areas. Hence, the effects of early brain injury could be more severe than later injury to the same tissue. Finally, Hebb recognized that there was more to cognitive function than IQ, suggesting the possible involvement of the right temporal lobe in human visual perception and developing novel tests of cognitive function.
In 1939 Hebb accepted a position as a lecturer at Queens University in Kingston, Ontario, followed by promotion to assistant professor of psychology for the 1941–1942 academic year. He was to remain at Queens until 1942, publishing papers based on his work at the MNI and pursing the development of a novel test of intellectual function in the rat. The Hebb-Williams maze required that the rat maintain visual orientation in order to choose an optimal route to the goal box when faced with shifting barriers between the start box and a goal box containing food. It was to be used in a variety of innovative studies by Hebb and his graduate students concerned with the effects of early experience and cortical lesions on adult learning.
The Yerkes Years . In 1942 Lashley was appointed director of the Yerkes Laboratories of Primate Biology in Orange Park, Florida, where a large colony of captive chimpanzees was available for study. Lashley proposed that Hebb join him in Florida to study the intellectual and emotional sequelae of brain lesions in chimpanzees. Although Hebb was to work at the Yerkes Labs from 1942 to 1947, the brain lesion research program was never pursued. But Hebb did describe the emotional behavior of chimpanzees, relying on the intuitive recognition of emotional states in the chimpanzee by human observers. In addition, Hebb published a set of innovative papers on the development of fear, the occurrence of spontaneous neuroses, and the assessment of individual differences in temperament. Observing complexity and planning in chimpanzee behavior also encouraged Hebb’s conviction that autonomous central processes (i.e., thought) had to be considered in the construction of psychological theories. Later, he would describe the years spent watching chimpanzees at Yerkes as teaching him more about human behavior than any other years—with the exception of the first. And, in the paper on “On the Nature of Fear” (1946), Hebb first used a hypothetical neural construct, the phase sequence, to account for behavior.
Hebb was engaged in much more than animal watching during the Yerkes years. In 1944 he began writing the manuscript that would become The Organization of Behavior. His goal, as stated in the preface, was “to bring together a number of different lines of research, in a general theory of behavior that attempts to bridge the gap between neurophysiology and psychology, as well as that between laboratory psychology and the problems of the clinic” (1949, p. vii). In addition to overcoming the theoretical aversion to physiologizing that characterized the psychological theories of the 1930s and 1940s, Hebb also focused on the phenomena of an active mind, not on a stimulus-response automaton. Early in the book, we find Hebb grappling with questions of set, attention, and the interaction between sensory input and an active brain.
The existence of spontaneous activity in the central nervous system was a direct inference from Hans Berger’s 1929 account of the electroencephalogram (as summarized in Jasper, 1937), while R. Lorente do No’s description of reverberatory circuits in 1938 provided a potential mechanism for temporary storage of information.
At the heart of Hebb’s system lie two neurophysiological constructs, that is, inferences from behavior that are introduced to account for images and thought: “Any frequently repeated, particular stimulation will lead to the slow development of a ‘cell assembly,’ a diffuse structure comprising cells in the cortex and diencephalon … capable of acting briefly as a closed system, delivering facilitation to other such systems.… A series of such events constitutes a ‘phase sequence’—the thought process” (Organization of Behavior, 1949, p. xix). But the development of the cell assembly, and presumably the linkage of assemblies in a phase sequence, required a permanent, experience-dependent, change in the activity of the nervous system. This was accounted for by introducing what is known in contemporary neuroscience as the Hebb synapse: “When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B is increased” (Organization of Behavior, 1949, p. 62).
With this hypothetical machinery in place, Hebb developed a single theory to account for learning and memory as studied by the behaviorists as well as the perceptual phenomena emphasized by the Gestalt psychologists. For example, he had to account for the fact that form recognition is a stable, reliable process in an adult mammal, despite widely divergent patterns of stimulation on the retina, as an object is viewed from different perspectives. The Gestalt psychologists had presented this kind of result as posing an impossible obstacle for a connectionist theory of neurological function and proposed that there was an innate isomorphic organization of electrical fields in the brain, where relationships among stimuli were maintained.
Hebb was determined to account for the Gestalt phenomena of perception within the framework of a connectionist nervous system. His solution involved a crucial role for early visual experience, in which the immediate visual “constancies” experienced by an adult mammal were “assembled” during early life through successive fixations on objects from different perspectives. He drew heavily on data collected by Marius von Senden involving accounts of initial perception by congenital cataract patients whose vision had been restored by surgical intervention. In general, these patients had color vision and primitive figure-ground perception immediately following surgery but experienced an initial difficulty with perception of entire forms, often piecing together a percept from successive examinations of edges. In addition, Austin Riesen’s description of visual deficits in chimpanzees deprived of visual experience during infancy supported the possibility that the seemingly innate, instantaneous perceptions of the adult were actually dependent on early experience. These results forced Hebb to reexamine his own dissertation data and, for the first time, he noted that, although the discriminative capacities of dark-reared rats were ultimately the same as their normal counterparts, initial learning required many more trials.
The original drafts of The Organization of Behavior were critical of behavioristic and Gestalt interpretations of psychological phenomena, and Hebb began to reevaluate the previous work of Kohler, Lashley, and even himself in light of his new ideas. Hebb gave Lashley an early draft for comments and offered him coauthorship, but Lashley declined. Lashley’s comments on the manuscript strike the contemporary reader as focused on minor technical issues, never coming to grips with the central themes of the book. Although complimentary to Hebb in a personal letter, Lashley subsequently complained to a group of scientists at a dinner party, claiming that Hebb’s book presented a garbled version of ideas that he (Lashley) had developed over the years.
It seems more likely that Hebb, while grappling with the same questions as those raised by Lashley, had reached very different conclusions. For example, where Lashley had minimized the role of early experience in visually guided behavior, Hebb focused on early experience as an essential component in the development of adult visual perception. Another example of divergent conclusions concerned the synapse. In his celebrated address to the Ninth International Congress of Psychology in 1929, Lashley said: “There is no direct evidence for any function of the anatomical synapse; there is no evidence that synapses vary in resistance, or that, if they do, the resistance is altered by passage of the nerve impulse” (Lashley, 1930, p. 1). The synapse had still not been visualized when Hebb wrote The Organization of Behavior. But his speculative description of the “Hebb synapse” and its properties, was to prove an enormously generative answer to Lashley’s critique.
While in Florida, Hebb reared a group of rats at home and demonstrated that these rats were superior to laboratory-reared rats in learning the Hebb-Williams maze. Subsequent work by Hebb’s students at McGill established that early environmental enrichment enhanced later cognitive functioning, and this work was instrumental in the development of animal studies on environmental enrichment and brain function and on programs such as Head Start, which provided impoverished children with early environmental enrichment.
The McGill Years . In 1947 Hebb returned to McGill as professor of psychology, and in 1948 he became chair of the Psychology Department. He was instrumental in creating a graduate program that minimized formal course-work and emphasized the generation of independent research programs by individual graduate students (Glickman, 1996). Hebb’s graduate seminar and a statistics course were the only required coursework. The system worked exceptionally well. In “A Neuropsychological Theory” (1959), Hebb described an impressive array of experiments conducted by graduate students and postdoctoral fellows, as the result of his unusual approach to graduate (and postdoctoral) training. In particular, Hebb identified the examination of the effects of enriched infant experience on maze learning in rats, and of early reading experience in humans on adult perceptual tendencies, as significant research that was initiated in response to the theory; on the other hand, he described studies of sensory deprivation on perception and thought, habituation of the arousal reaction, and the discovery of self-stimulation (“pleasure”) systems in the brain as filling in gaps in his theorizing. Hebb had created an atmosphere in which attention was directed to problems that would endure, whether or not specific details of his theory proved to be true.
In the studies of sensory deprivation mentioned above, McGill undergraduates were paid to lie in cubicles without patterned visual, auditory, or somesthetic stimulation (for a maximum of one week), which were instigated with support from the Defence Research Board of Canada. There were two goals: to understand the importance of the normal human sensory environment for maintenance of functional thought and perception, and to understand why prisoners of war had “confessed” to things they had not done (during the Korean War) when sensory isolation, but not “conventional” torture, had been the only identifiable tool of the captors. Deprivation-induced disturbances of perception and thought were identified in these students and, in response to listening to self-requested positive lectures on ghosts, student attitudes toward that phenomenon shifted in the direction of increased belief. Although “classified” by the Defence Research Board of Canada for some years, the essential results were published in an article by Hebb’s former student, Woodburn Heron (1961), with an introduction by Hebb.
Hebb’s A Textbook of Psychology was published in 1958. It contains his construction of the essential components of the field. In “Donald Olding Hebb (1904– 1985)” (Beach, 1987), an obituary, the distinguished comparative psychologist Frank Beach placed this book alongside The Organization of Behavior as one of Hebb’s two most significant publications. In the preface, Hebb presented his goal as “to clarify and codify the ideas which make up the main structure of psychological theory” (1958, p. vii). He added that “in doing so I have omitted (or treated very succinctly) matters that have traditionally made up a good proportion of the introductory course; and have included others that are, as far as I know, here stated formally for the first time” (1958, p. vii). He proceeded to state that psychology is fundamentally a biological science and that “the student’s approach to either social or applied psychology … is through … theories of learning, perception, emotion … which are biological because they have always been profoundly influenced by neurophysiology, neuroanatomy, and evolutionary and genetic theory” (1958, p. vii). Where Hebb’s mentor Lashley once accused his fellow psychologists of including an obligatory chapter on the nervous system in their textbooks “in order to provide an excuse for pictures to an otherwise dry and monotonous text,” Hebb used the structure of the nervous system to explain the difference between sense-dominated behavior and behavior involving mediating processes—the latter constituting the phenomena of greatest interest to psychologists—and stated that incorporating relevant neural substrates is essential for understanding these phenomena, not simply added on and, afterwards, dismissed (Lashley, 1930, p. 1).
Following his retirement as professor of psychology in 1970, Hebb was appointed chancellor of McGill University. In 1975 he retired from McGill and returned to his boyhood surroundings in Nova Scotia. Dalhousie University provided an appointment as a professor emeritus and office space, and Hebb continued to attend seminars at the university until his death in 1985.
Awards and Honors . Hebb received many honors in his lifetime, including membership in the Royal Society of Canada and the Royal Society of London, along with election to the presidencies of the Canadian Psychological Association and the American Psychological Associations, and an honorary presidency of the Royal Society of Canada. He was also awarded honorary degrees by fifteen universities. Hebb was nominated for, but did not receive, the Nobel Prize in 1965. The nominators had several problems. First, his primary contribution involved theoretical writing, whereas Nobel Prizes are traditionally awarded for “discoveries.” Then, Hebb’s name was not on the masthead of the research papers published by his students on enriched environments or sensory deprivation, and these were the highlighted research accomplishments that formed the basis for the Nobel Prize nomination. In contrast to the dominant traditions of contemporary science, Hebb refused to have his name on work done by students, even when the work was clearly inspired by his theorizing and supported by his grants.
Hebb’s influence, and the style employed in service of his goals, have been superbly summarized by Ernest Hilgard in his book Psychology in America: An Historical Survey (1987):
Theoretical interest in brain mechanisms lessened among psychologists following Lashley’s important work. Lashley … had argued against neurologizing by psychologists; Skinner … had warned against the unjustified fictions of the conceptual nervous system. This flagging interest was reversed by the appearance of a book by Donald O. Hebb.… The qualities of Hebb’s Organization of Behavior (1949) that appealed were a combination of great originality in both breadth and specificity, a willingness to examine arguments on their merits, and an ability to dispose of them with incisive criticisms that were without polemic. Hebb was considerate of those he was attacking, while always sticking to his guns. The capacity and style required to achieve his results are difficult to define, but they are unusual in revolutionary scientific writing, and Hebb represented them well. (pp. 435–436)
Hebb’s correspondence can be found in the archives of the McGill University library.
WORKS BY HEBB
“The Innate Organization of Visual Activity: I. Perception of Figures by Rats Reared in Total Darkness.” Journal of Genetic Psychology 51 (1937): 101–126.
“The Innate Organization of Visual Activity. II. Transfer of Response in the Discrimination of Brightness and Size by Rats Reared in Total Darkness.” Journal of Comparative Psychology 24 (1937): 277–299.
“The Innate Organization of Visual Activity. III. Discrimination of Brightness after Removal of the Striate Cortex in the Rat.” Journal of Comparative Psychology 25 (1938): 427–437.
“Studies of the Organization of Behavior. I. Behavior of the Rat in a Field Orientation.” Journal of Comparative Psychology 25 (1938): 333–353.
“Studies of the Organization of Behavior. II. Changes in the Field Orientation of the Rat after Cortical Destruction.” Journal of Comparative Psychology 26 (1938): 427–441.
“On the Nature of Fear.” Psychological Review 53 (1946): 259–276.
The Organization of Behavior: A Neuropsychological Theory. New York: Wiley, 1949.
A Textbook of Psychology. Philadelphia: Saunders, 1958.
“A Neuropsychological Theory.” In Psychology: A Study of a Science. Vol. 1. Edited by Sigmund Koch. New York: McGraw-Hill, 1959.
“D. O. Hebb.” In A History of Psychology in Autobiography. Vol. 7. Edited by Gardner Lindzey. San Francisco: W.H. Freeman, 1980.
Beach, Frank A. “Donald Olding Hebb (1904–1985).” American Psychologist 42 (1987): 186–187.
Brown, Richard E., and P. M. Milner. “The Legacy of Donald O. Hebb: More than the Hebb Synapse.” Nature Reviews Neuroscience 4 (2003): 1013–1019.
Glickman, Stephen E. “Donald Olding Hebb: Returning the Nervous System to Psychology.” In Portraits of Pioneers in Psychology. Vol. 2, edited by G. A. Kimble, C. A. Boneau, and Michael Wertheimer. Washington, DC: American Psychological Association, 1996.
Heron, Woodburn. “Cognitive and Physiological Effects of Perceptual Isolation.” In Sensory Deprivation, edited by P. Solomon, P. E. Kubzansky, P. H. Leiderman, et al. Cambridge, MA: Harvard University Press, 1961.
Hilgard, Ernest R. Psychology in America: An Historical Survey. New York: Harcourt Brace Jovanovich, 1987.
Jasper, H. H. “Electrical Signs of Cortical Activity.” Psychological Bulletin 34 (1937): 411–481.
Lashley, Karl. “Basic Neural Mechanisms in Behavior.” Psychological Review 37 (1930): 1–24. The first published version of Lashley’s address to the Ninth International Congress of Psychology in 1929.
Lorente de No, R. “Analysis of the Activity of the Chains of Internuncial Neurons.” Journal of Neurophysiology 1 (1938): 207–244.
Milner, Peter M. “The Mind and Donald O. Hebb.” Scientific American 268 (1993): 124–129.
Richard E. Brown