He was a professor of psychology and gerontology at the University of Southern California (USC), where he was also director of the Unified Studies of Cognition (CogUSC) Lab.
He was known for his work on quantitative research methodology[1] and on the changes in cognitive function and personality that occur as individuals age.
He then began postdoctoral work at the University of Denver with John L. Horn.
In 1984, he joined the faculty of the University of Virginia to begin a quantitative methods program.
He is now a professor of psychology and gerontology at USC, the head of their Quantitative Methods training program, the director of their CogUSC lab, and a co-principal investigator of the Health and Retirement Study.