Donald Olding Hebb Research Paper

1. Education And Early Life

Hebb was born, the eldest of four siblings, on July 22, 1904 in Chester, Nova Scotia. Both his parents were physicians. He was educated at home until the age of eight by his mother, using Montessori methods. He then attended the local school, which he hated.

Hebb’s ambition as a young man was to become a novelist. He graduated from Dalhousie University (Halifax, Nova Scotia) in 1925 with a BA in English and philosophy. While awaiting inspiration for the ‘Great Canadian Novel’ he returned to his village school as a teacher. In search of experience he spent the next summer as an itinerant farm worker in western Canada and tried, unsuccessfully, to get a job as a deckhand in Vancouver.

In 1927 Hebb was back East, teaching at a Montreal high-school. Becoming interested in Sigmund Freud’s ideas, he applied to McGill University to study psychology part time. The next year he was appointed principal of an elementary school and enthusiastically set about instituting and testing new teaching methods. In 1930 he was bedridden for a year with a tubercular hip, during which time he conceived a theory of how spinal reflexes might be learned in utero. This formed the basis of an MA thesis, now lost. Hebb (1980) later described it as nonsense.

In 1932 Hebb began doctoral research, still part-time, at McGill. The experiments, which involved conditioning dogs, were supervised by Leonid Andreyev, a former student of Pavlov, but Hebb soon became disillusioned with the technique and when his first wife was killed in a motor accident he abandoned the research.

Hebb enjoyed teaching and administration and was tempted to make a career of being a headmaster. He finally chose to continue his studies, however, and in 1934 he was accepted as a student at the University of Chicago by Karl Lashley, whose book, published a few years earlier (Lashley 1929), had established him as the pre-eminent physiological psychologist of the period.

Hebb spent a year in Chicago where, in addition to his close association with Lashley, he attended lectures by Wolfgang Kohler, Paul Weiss, C. J. Herrick, and the statistician L. L. Thurstone. Then Lashley accepted the offer of a professorship at Harvard and Hebb accompanied him. He was granted a Harvard PhD in 1936 for research on the effects of early experience on vision in the rat.

2. Montreal Neurological Institute

After a post-doctoral year of research with Lashley, Hebb was awarded a two year Fellowship to study mental changes resulting from brain operations at the newly established Montreal Neurological Institute (MNI). The operations were mostly frontal and temporal lobectomies performed by Wilder Penfield to combat epileptic seizures. Hebb made what is probably the first observation of a visual deficit after human right-temporal lobe removal. To his surprise he found no measurable effect of frontal lobectomy on standard measures of intelligence (Hebb and Penfield 1940). Attempts to understand this result lay at the foundation of much of Hebb’s later work.

3. Primate Research With Lashley

After his MNI Fellowship, Hebb obtained a post as Lecturer at Queen’s University (Kingston, Ontario). There he devised a variable rat-maze so that he could continue his brain lesion research using rats. In 1942 Lashley offered him a five year Fellowship to study effects of brain lesions in chimpanzees at the Yerkes Laboratories of Primate Biology, Florida. Partly because of his heavy teaching load at Queens, he accepted it.

The project was to study the effects of brain lesions on intelligence and emotion in chimpanzees. Lashley was to work on intelligence tests, Hebb on tests of emotion, but no lesions were made before 1947 when Hebb’s Fellowship ended. Hebb did, however, assemble a good stock of chimpanzee stories that contributed to the great popularity of his subsequent lectures, and in the intellectually stimulating surroundings he wrote his most influential work, The Organization of Behavior, which was published in 1949.

4. McGill Once More

After World War II, the McGill psychology department had dwindled to one part-time child psychologist, so in 1947 Hebb was one of four psychologists who were recruited to rebuild the department. The next year he was appointed chairman.

Having made a highly successful foray into the world of science, Hebb returned to teaching and administration with enthusiastic vigor. He taught the introductory course to overflow classes for the next 25 years, and wrote three editions of a highly respected textbook. He also conducted a seminar for all incoming graduate students, which gave him the opportunity to coach them in the presentation of succinct and closely timed talks, as well as to instill a thorough understanding of a range of theoretical issues. To test some predictions of his theory, he supervised research on early learning in rats and dogs, and effects of sensory deprivation on human thought processes.

In later years Hebb received many honors; he was President of both the Canadian (1952) and the American (1960) Psychological Associations. He was elected a Fellow of the Royal Society of London (1966), a Foreign Associate of the National Academy of Sciences (USA), and an Honorary Member of the American Academy of Arts and Sciences. In 1970 he was appointed Chancellor of McGill University. In 1974 Hebb retired to his family home in Chester Basin and became active in the psychology department at Dalhousie University, where he was appointed Honorary Professor. He published his last monograph, Essay on Mind in 1980 and died in Halifax on the 20th of August, 1985 of heart failure during hip replacement surgery.

5. Hebb’s Contributions To Neuroscience

During his years as a graduate student Hebb learned the hard way what was wrong with contemporary psychology. At McGill, as is evident from the topic of his Masters thesis, he flirted with the extreme empiricism then rampant in North America. Influenced by Boris Babkin and Leonid Andreyev, students of Pavlov, he passed through a Pavlovian phase. When he moved to Chicago he entered the Gestalt enclave of Wolfgang Kohler and Karl Lashley; and at Harvard he encountered the historian, Boring, who taught him what psychology had been like before the Behaviorists. Sooner or later, for reasons that are cogently presented in the first few chapters of The Organization of Behavior (Hebb 1949), he turned against all the established schools of psychology.

Because of his research on cortical lesions and his neural theories, Hebb is often labeled as a physiological psychologist, but his interests were really much broader. The Organization of Behavior was an important catalyst, aiding the revival of cognitive psychology, and although he was a zealous proponent of the idea that the brain is the organ of mind, Hebb’s interest in neurophysiology took second place to his interest in thinking and other aspects of behavior. In his hands neurologizing was a tool to restore respectability to the study of mental functioning in psychology.

As a psychologist, Hebb was frustrated by the behaviorists’ refusal to acknowledge such important processes as attention, expectancy, and thought, lest they should be accused of vitalism. Hence his eagerness to show that those mental processes could be performed by an entirely material brain. He based his neural model as far as possible on established physiological principles, but neuroscience was on the brink of a revolution and many of those principles were soon to be revised.

For example, Eccles, whose defense of the electrical theory of synaptic transmission Hebb had embraced, recanted and demonstrated excitatory and inhibitory chemical synapses. Furthermore, the behavioral importance of subcortical structures such as the reticular arousal system, the amygdala and the hippocampus became clearer, and improved staining techniques revealed a much more complex visual system than was known to Hebb. The fact that these revelations had almost no effect on the impact of Hebb’s book shows to what extent the psychological implications of his neurologizing outweighed the underlying physiology. By proposing a material basis for concepts, Hebb demolished barriers to the study of cognitive processes that the behaviorists had erected a generation earlier. In his Presidential address to the Experimental Psychology Division of the American Psychological Association in 1954, Hebb introduced the reticular activating system into his model to extend his explanation of emotion, but apart from that he did little to revise the theory in the light of new neuroscientific data.

His most famous contribution to neuroscience was not based on neurophysiological research, it was inferred from behavior. Most physiologists thought that learning synapses were strengthened by use, but Hebb along with other psychologists realized that association involved at least two activities. Thus he postulated that learning changes at synapses require simultaneous firing of both presynaptic and postsynaptic neurons. Synapses with properties similar to those postulated were subsequently identified experimentally and are now known as Hebb synapses.

Hebb held strong views about the ‘nature–nurture’ question. After his early gyrations he adopted the unassailable position that both inheritance and experience are totally necessary for intelligent behavior, using the analogy of area as the product of length and breadth. Of course, one may still be interested in whether an area is square, long and narrow, or short and fat. In spite of Hebb’s bipartisanship, his concept of the development of vision was long in the ‘nurture’ dimension. Hebb’s visual cortex bore a strong resemblance to Locke’s tabula rasa.

Thus, Hebb assumed that neurons are randomly connected in the newborn visual cortex. With experience, synapses are strengthened between neurons activated simultaneously by sensory input, producing groups of connected neurons (cell assemblies) that then represent the input. Hebb further postulated that a complex figure elicits a series of eye movements, thereby activating a succession of associated cell assemblies that Hebb called a phase sequence.

Anatomical diagrams of the cortex suggested to Hebb that cell assemblies consist of networks of closed loops. This led him to speculate that once a cell assembly is activated impulses continue to circulate around the loops for some time (reverberation), constituting a short-term memory. In this way Hebb explained the persistence of an idea or mental image in the absence of the corresponding object. Today, short-term memory may be explained more plausibly by persistent chemical traces, but Hebb never abandoned his reverberation theory, which still dominates the thinking of many neural model builders and neurophysiologists who study the visual system.

According to Hebb, the impulses reverberating around the cortical loops of an activated cell assembly produce synaptic changes that bind the neurons together more permanently. This explains long-term memory. Ideas arouse other ideas by association, thus cell assemblies must acquire associations with each other whenever they are active at about the same time. Hebb never satisfactorily explained how, after linking in this way, they avoid merging to become bigger cell assemblies.

The capacity to explain intention, attention and other mental processes was an important goal of Hebb’s theorizing but one that, in The Organization of Behavior, he was content to achieve in principle rather than by rigorous neural modeling. Short-term expectancy and attention were explained in terms of the phase sequence getting ahead of the sensory input. Thus a previously experienced sequence of stimuli sets up a central process that facilitates cell assemblies in advance of the sensory input they represent. Hebb postulated higher order central processes that facilitate more extended sequences. In much of his writing Hebb treats the cell assembly as equivalent to an idea; its neural basis is tailored to fit behavioral observation.

6. Summary

The Organization of Behavior is now a classic. Half a century after it was written it is still frequently cited. Many psychologists regard it as the herald of an era of cognitive research that blossomed in the 1950s. Hebb’s ideas about the representation of concepts and their associations with each other are the common currency of almost all present-day psychologists, even those who prefer to ignore the brain, but devotees of neural networks and neurophysiologists studying sensory systems are those who most often refer explicitly to his theory.

After Hebb left Lashley’s ‘think tank’ in Florida and took up his duties as chairman of the McGill psychology department, most of his energies turned to building and running a strong department there, including teaching. Although Hebb took every opportunity to promote neurologizing in psychology, he showed little further inclination to keep pace with the rapid advances in neuroscience or to make any major changes to his neural theory.

Apart from his own characteristically stylish and witty account (Hebb 1980a), there have been several more recent commentaries that complement this paper for those who wish to learn more about Hebb’s life and work. These include nine essays in his honor, written by former students and edited by Jusczyk and Klein (1980), and a delightful chapter by Stephen Glickman (1996) which accurately portrays the man and his achievements. Fentress (1999) and Klein (1999) edited a special issue of the Canadian Journal of Experimental Psychology that contains a further collection of papers on Hebb and on research inspired by his ideas. Orbach, a student of both Hebb and Lashley, published a book (1998) in which the contributions of his two mentors are discussed and compared.

Bibliography:

1. Fentress J C 1999 The organization of behavior revisited. Canadian Journal of Experimental Psychology 53: 8–20
2. Glickman S E 1996 Donald Olding Hebb: Returning the nervous system to psychology. In: Kimble G A, Boneau C, Wertheimer M (eds.) Portraits of Pioneers in Psychology. Erlbaum Press, Mahwah, NJ, Vol. 2, pp. 227–44
3. Hebb D O 1949 The Organization of Behavior: a Neuropsychological Theory. Wiley, New York, pp. 1–335
4. Hebb D O 1955 Drives and the C.N.S. (conceptual nervous system). Psychology Review 62: 243–54
5. Hebb D O 1980 Essay on Mind. Erlbaum Press, Hillsdale, NJ
6. Hebb D O 1980a D. O. Hebb. In: Lindzey G (ed.) A History of Psychology in Autobiography. Freeman, San Francisco, CA, Vol. 7, 273–303
7. Hebb D O, Penfield W 1940 Human behavior after extensive bilateral removal from the frontal lobes. Archives of Neurology and Psychiatry 44: 421–38
8. Jusczyk P W, Klein R M (eds.) 1980 The Nature of Thought. Essays in Honor of D. O. Hebb. Erlbaum Press, Hillsdale, NJ
9. Klein R M 1999 The Hebb legacy. Canadian Journal of Experimental Psychology 53: 1–7
10. Lashley K S 1929 Brain Mechanisms and Intelligence. University of Chicago Press, Chicago, pp. 1–186
11. Orbach J 1998 The Neuropsychological Theories of Lashley and Hebb. University Press of America, Lanham, MD