Donald Olding Hebb, psychologist (b at Chester, NS 22 July 1904; d at Halifax, 20 Aug 1985). He was a brilliant pupil who completed grades 1 to 4 in one year and 5 to 6 the next. But school proved too easy, and when he graduated from Dalhousie, his record was undistinguished. A book by Freud stimulated him to go back to university and he earned an MA in psychology from McGill (1932) and a PhD from Harvard (1936). At that time, the brain was regarded as a relay station to process incoming and outgoing impulses; behaviour was just stimulus and response. Hebb believed more went on in the brain. He worked with Wilder Penfield 1937-39 and noted that loss of large parts of the brain did not necessarily diminish intelligence. He studied the development of behaviour in rats, primates and infants. He was convinced that neural circuits linking incoming and outgoing neurons were the loci for thought and emotions. In 1949 he published The Organization of Behaviour, which revolutionized psychology by putting "mind" back into the brain. His studies of development showed the importance of environmental stimulation in early childhood and led to the US adoption of Operation Headstart, a program to help children in disadvantaged families. He showed the requirement of constant input for normal brain activity by the abnormal response of subjects to sensory deprivation.