Karl John Holzinger (August 9, 1892 – January 15, 1954)[1] was an American educational psychologist known for his work in psychometrics.
He subsequently studied at University College London with both Karl Pearson and Charles Spearman.
[3][4] Holzinger spent almost his entire academic career at the University of Chicago, teaching in the Department of Education there for thirty-two years.
[7] He conducted much of his research as a member of the Unitary Traits Committee, which he and Edward Thorndike had established in 1931.
[8][9] He also collaborated with Horatio Newman and Frank N. Freeman on an early, large-scale twin study that began in 1927.