Kagan has shown that an infant's "temperament" is quite stable over time, in that certain behaviors in infancy are predictive of certain other behavior patterns in adolescence.[4] He did extensive work on temperament and gave insight on emotion.
In 2001, he was listed in the Review of General Psychology among the one hundred most eminent psychologists of the twentieth century. After being evaluated quantitatively and qualitatively, Kagan was twenty-second on the list, just above Carl Jung.[5]
^Kagan, J. (2004). The Long Shadow of Temperament. United States of America: President and Fellows of Harvard College.
^Haggbloom, S. J.; et al. (2002). "The 100 Most Eminent Psychologists of the 20th Century"(PDF). Review of General Psychology. 6 (2): 139–152. doi:10.1037/1089-2680.6.2.139. S2CID145668721. Archived from the original(PDF) on 2012-12-24. Haggbloom et al. combined three quantitative variables: citations in professional journals, citations in textbooks, and nominations in a survey given to members of the Association for Psychological Science, with three qualitative variables (converted to quantitative scores): National Academy of Sciences (NAS) membership, American Psychological Association (APA) President and/or recipient of the APA Distinguished Scientific Contributions Award, and surname used as an eponym. Then the list was rank ordered.