With political scientist Charles Murray, he co-wrote The Bell Curve, a controversial 1994 book on human intelligence.

In 1955, Herrnstein obtained his Ph.D. at Harvard University, with a thesis titled Behavioral Consequences of the Removal of a Discriminative Stimulus Associated with Variable-Interval Reinforcement.

[2] His major research finding as an experimental psychologist is the matching law, the tendency of animals to allocate their choices in direct proportion to the rewards they provide.

To illustrate the phenomenon, if there are two sources of reward, one of which is twice as rich as the other, Herrnstein found that animals often chose at twice the frequency the alternative that was seemingly twice as valuable.

He also developed melioration theory with William Vaughan, Jr. Herrnstein was considered a "star pupil" of B. F. Skinner while working for his PhD at Harvard.

[5] Herrnstein's research focused first on natural concepts and human intelligence in the 1970s, and became prominent with the publication of his and Charles Murray's controversial book, The Bell Curve.