Donald Olding Hebb (1904-1985) was a Canadian psychologist, often called the father of neuropsychology, who spent the central part of his career at McGill University. He returned to McGill as a professor of psychology in 1947 and served as department chairman, vice-dean for biological sciences, and finally chancellor of the university. His McGill biography calls him probably the most influential psychologist of the twentieth century, crediting him with persuading a generation of researchers that to understand behavior you must study the neural machinery responsible for it.
Hebb’s landmark contribution was his 1949 book “The Organization of Behavior,” in which he proposed that learning is grounded in physical changes between brain cells. His central idea, now called Hebbian learning, is usually summarized as “neurons that fire together, wire together”: when one neuron repeatedly helps to fire another, the connection between them strengthens. He framed this in terms of “cell assemblies,” groups of co-active neurons that he argued were the material basis of mental concepts.
For the library’s reader, Hebb supplies the missing half of the early neural-network story. The McCulloch-Pitts model of 1943 showed that networks of neurons could compute, but it had no way to learn. Hebb gave a concrete, biologically motivated rule for how a network could adapt and store information from experience. That rule directly influenced the first trainable artificial neural networks, and the principle remains central to both neuroscience and modern machine learning.