Miller began his career when the reigning theory in psychology was behaviorism, which eschewed the study of mental processes and focused on observable behavior. Rejecting this approach, Miller devised experimental techniques and mathematical methods to analyze mental processes, focusing particularly on speech and language. Working mostly at Harvard University, MIT and Princeton University, he went on to become one of the founders of psycholinguistics and was one of the key figures in founding the broader new field of cognitive science, circa 1978. He collaborated and co-authored work with other figures in cognitive science and psycholinguistics, such as Noam Chomsky. For moving psychology into the realm of mental processes and for aligning that move with information theory, computation theory, and linguistics, Miller is considered one of the great twentieth-century psychologists. A "Review of General Psychology" survey, published in 2002, ranked Miller as the 20th most cited psychologist of that era.