Donald Hebb was a Canadian psychologist best known for his work in neuropsychology and learning theory. He is most famous for the concept of "Hebbian learning," which suggests that the connections between neurons strengthen when they are activated together. This principle is often summarized by the phrase "cells that fire together, wire together," highlighting the relationship between neural activity and learning. Hebb's influential book, The Organization of Behavior, published in 1949, laid the groundwork for modern neuroscience and cognitive psychology. His ideas have significantly impacted various fields, including artificial intelligence and behavioral science, shaping our understanding of how experiences influence brain function and behavior.