Lloyd Humphreys

Who was Lloyd Humphreys?

Lloyd G. Humphreys was a differential psychologist and methodologist who focused on assessing individual differences in human behavior.

His work is among the most widely cited in intelligence research, and he received many prestigious awards in this field. Born in Lorane, Oregon, Humphreys earned his undergraduate degree at the University of Oregon in 1935, a master's from Indiana University in 1936, where he first learned about factor analysis, then received his doctorate at Stanford in 1938, studying under Ernest Hilgard. His dissertation on the partial reinforcement effect, is considered a classic in the field.

His first position was at Northwestern University. He was a Carnegie Fellow in Anthropology during that time, then taught at the University of Washington and Stanford. He then took a post as Research Director, Personnel Laboratory, for the United States Air Force. He then spent the remainder of his career at the University of Illinois at Urbana-Champaign.

Humphreys argued that much psychological research fails to replicate because of inadequate sample sizes, because correlations fluctuate when Ns are small. His own empirical research typically involved large-scale longitudinal studies such as Project Talent.