In 1928, he became a graduate student at
McGill University. But, at the same time, he was appointed headmaster of Verdun High School in the suburbs of
Montreal. He worked with two colleagues from the university, Kellogg and Clarke, to improve the situation. He took a more innovative approach to education—for example, assigning more interesting schoolwork and sending anyone misbehaving outside (making schoolwork a privilege). He completed his master's degree in psychology at
McGill in 1932 under the direction of the eminent psychologist
Boris Babkin. Hebb's master's thesis, entitled
Conditioned and Unconditioned Reflexes and Inhibition, tried to show that skeletal reflexes were due to cellular learning. By the beginning of 1934, Hebb's life was in a slump. His wife had died, following a car accident, on his twenty-ninth birthday (July 22, 1933). His work at the Montreal school was going badly. In his words, it was "defeated by the rigidity of the curriculum in Quebec's protestant schools." The focus of study at McGill was more in the direction of education and intelligence, and Hebb was now more interested in physiological psychology and was critical of the methodology of the experiments there. He decided to leave Montreal and wrote to
Robert Yerkes at Yale, where he was offered a position to study for a
PhD. Babkin, however, convinced Hebb to study instead with
Karl Lashley at the
University of Chicago. In July 1934, Hebb was accepted to study under Karl Lashley at the
University of Chicago. His thesis was titled "The problem of spatial orientation and place learning". Hebb, along with two other students, followed Lashley to
Harvard University in September 1935. Here, he had to change his thesis. At Harvard, he did his thesis research on the effects of early visual deprivation upon size and brightness perception in a rat. That is, he raised rats in the dark and some in the light and compared their brains. In 1936, he received his PhD from Harvard. The following year he worked as a research assistant to Lashley and as a teaching assistant in introductory psychology for
Edwin G. Boring at
Radcliffe College. His Harvard thesis was soon published, and he finished the thesis he started at University of Chicago. In 1937, Hebb married his second wife, Elizabeth Nichols Donovan. That same year, on a tip from his sister Catherine (herself a PhD student with Babkin at McGill University), he applied to work with
Wilder Penfield at the
Montreal Neurological Institute. Here he researched the effect of brain surgery and injury on human brain function. He saw that the brain of a child could regain partial or full function when a portion of it is removed but that similar damage in an adult could be far more damaging, even catastrophic. From this, he deduced the prominent role that external stimulation played in the thought processes of adults. In fact, the lack of this stimulation, he showed, caused diminished function and sometimes
hallucinations. He also became critical of the
Stanford-Binet and
Wechsler intelligence tests for use with brain surgery patients. These tests were designed to measure overall intelligence, whereas Hebb believed tests should be designed to measure more specific effects that surgery could have had on the patient. Together with N.W. Morton, he created the
Adult Comprehension Test and the
Picture Anomaly Test. Putting the Picture Anomaly Test to use, he provided the first indication that the right temporal lobe was involved in visual recognition. He also showed that removal of large parts of the frontal lobe had little effect on intelligence. In fact, in one adult patient, who had a large portion of his frontal lobes removed in order to treat his
epilepsy, he noted "a striking post-operative improvement in personality and intellectual capacity." From these sorts of results, he started to believe that the frontal lobes were instrumental in learning only early in life. In 1939, he was appointed to a teaching position at
Queen's University. In order to test his theory of the changing role of the frontal lobes with age, he designed a variable path maze for rats with Kenneth Williams called the
Hebb-Williams maze, a method for testing animal intelligence later used in countless studies. He used the maze to test the intelligence of rats blinded at different developmental stages, showing that "there is a lasting effect of infant experience on the problem-solving ability of the adult rat." This became one of the main principles of
developmental psychology, later helping those arguing the importance of the proposed
Head Start programs for preschool children in economically poor neighborhoods. In 1942, he moved to
Orange Park, Florida to once again work with Karl Lashley who had replaced Yerkes as the Director of the Yerkes Laboratories of Primate Biology at the
Yerkes National Primate Research Center. Here, studying primate behavior, Hebb developed emotional tests for
chimpanzees. The experiments were somewhat unsuccessful, however because chimpanzees turned out to be hard to teach. During the course of the work there, Hebb wrote
The Organization of Behavior: A Neuropsychological Theory, He was survived by two daughters (both by his second marriage), Mary Ellen Hebb and Jane Hebb Paul. ==Honors and awards==