Donald O. Hebb was a Canadian psychologist, best known for his work in neuropsychology and learning theory. He introduced the concept of Hebbian learning, which suggests that the connections between neurons strengthen when they are activated together. This idea has had a significant impact on our understanding of how the brain processes information and forms memories. Hebb's influential book, The Organization of Behavior, published in 1949, laid the groundwork for modern neuroscience and cognitive psychology. His theories emphasized the importance of experience in shaping the brain's structure and function, influencing later research in areas such as cognitive development and artificial intelligence.