#6: He Expands His Theory of Universal Grammar at MIT in 1965
In 1965, while teaching at MIT, he published a major academic work that expanded his earlier ideas about how language works. He argued that all humans are born with a built-in system for understanding grammar, which he called “universal grammar.”

This theory suggested that children do not learn language only by copying adults. Instead, they are biologically prepared to recognize patterns and rules. The idea moved linguistics closer to psychology and brain science, and it helped establish him as a leading figure in the growing field of cognitive science.
