The Science of Each and Every Person: The Enduring Problem of Intraindividual Variance and Structure in Personality Psychology Ian J. Davidson, MA PhD Candidate Psychology Department - History & Theory York University email: ianjd777@yorku.ca twitter: @iamjdavidson

Science of the Individual? Nomothetic (Universal) Individual Differences (Interindividual) Idiographic (Individual)

The Perfect Cockpit Psychologist Ted Rose reminds us of this event. 1940s US Air Force Research. Physical measurements of 4,063 pilots. The perfect cockpit for the average pilot— but the average pilot was no pilot in particular.

The Lamiell Critique We are studying “persons-as-groups,” not “persons-as-persons.” Only gaining knowledge about the spaces between persons. Knowledge gained at interindividual level is erroneously extended to individual and universal levels.

The Science of the Intraindividual Borsboom and colleagues revisited problem of Disjuncture between inter- and intra-individual levels. Trait structure approach influenced by R.B. Cattell’s methodological writings. Is the FFM: Locally Homogeneous? Locally Heterogeneous? Locally Irrelevant? (Cattell, 1952)

Historical and Public Connectionss The variety of new approaches to the intraindividual mirror the disciplinary splintering of personality theory. The intraindividual shares Lamiell’s vision in spirit, but shirks epistemological transgression. How do psychologists reconcile these innovations with their field’s effects on the public?

Selected References Allik, J., Realo, A., Mottus, R., Borkenau, P., Kuppens, P., & Hrebickova, M. (2012). Person-Fit to the Five Factor Model of Personality. Swiss Journal of Psychology, 71(1), 35–45. https://doi.org/10.1024/1421-0185/a000066 Allport, G. W. (1937). Personality: A psychological interpretation. H. Holt and Company. Borkenau, P., & Ostendorf, F. (1998). The Big Five as States: How Useful Is the Five-Factor Model to Describe Intraindividual Variations over Time? Journal of Research in Personality, 32(2), 202–221. https://doi.org/10.1006/jrpe.1997.2206 Borsboom, D., Mellenbergh, G. J., & van Heerden, J. (2003). The theoretical status of latent variables. Psychological Review, 110(2), 203–219. https://doi.org/10.1037/0033- 295X.110.2.203 Cervone, D. (2005). Personality Architecture: Within-Person Structures and Processes. Annual Review of Psychology, 56(1), 423–452. https://doi.org/10.1146/annurev.psych.56.091103.070133 Daniels, G. S. (1952). DTIC AD0010203: THE “AVERAGE MAN” ? Defense Technical Information Center. Retrieved from http://archive.org/details/DTIC_AD0010203 Eysenck, H. J. (1954). The science of personality: Nomothetic. Psychological Review, 61(5), 339– 342. https://doi.org/10.1037/h0058333 Lamiell, J. T. (1987). The psychology of personality: An epistemological inquiry. New York, NY, US: Columbia University Press.

Selected References Lamiell, J. T. (1997). Individuals and the differences between them. In R. Hogan, J. A. Johnson, & S. R. Briggs (Eds.), Handbook of personality psychology (pp. 117–141). San Diego, CA, US: Academic Press. Lerner, R. M., & Murray, E. D. (2016). Finally! A Developmental Science that Privileges Development. Human Development, 59(6), 377–385. https://doi.org/10.1159/000455030 McAdams, D. P. (2015). The Art and Science of Personality Development. New York: The Guilford Press. Molenaar, P. C. M., & Campbell, C. G. (2009). The New Person-Specific Paradigm in Psychology. Current Directions in Psychological Science, 18(2), 112–117. https://doi.org/10.1111/j.1467-8721.2009.01619.x Molenaar, P. C. M., Sinclair, K. O., Rovine, M. J., Ram, N., & Corneal, S. E. (2009). Analyzing developmental processes on an individual level using nonstationary time series modeling. Developmental Psychology, 45(1), 260–271. https://doi.org/10.1037/a0014170 Pervin, L. A. (1989). Persons, situations, interactions: The history of a controversy and a discussion of theoretical models. Academy of Management Review, 14(3), 350–360. https://doi.org/10.5465/AMR.1989.4279066 Rose, T. (2016). The End of average: How we succeed in a world that values sameness. New York: HarperOne.

Thank you! email: ianjd777@yorku.ca twitter: @iamjdavidson