 He has a Ph.D. from Johns Hopkins University.He is also the editor-in-chief of the journal "Intelligence" since 2016.In 1994, he was one of 52 signatories on "Mainstream Science on Intelligence," an editorial written by the American psychologist Linda Gottfredson and published in the "Wall Street Journal", which summarized findings from intelligence research, especially as they related to issues raised in "The Bell Curve".