image17731James S. Roberts, Ph.D.

Associate Professor of Psychology


Phone: 404-894-6069


Research Interests

My research interests are in the development and application of item response theory (IRT) models to measure psychological constructs. Over the past decade, I have developed a family of polytomous IRT models to unfold responses to test or questionnaire items. These unfolding models imply higher item scores to the extent that an individual is located close to an item on a unidimensional latent continuum. Unfolding item response models can be used to measure attitudes using responses from traditional Likert or Thurstone scales. They can also be used to assess satisfaction, preference, and individual differences in certain developmental processes that occur in distinct stages. My research and development efforts with unfolding IRT models have been recognized by the National Science Foundation via its Faculty Early Career Development (CAREER) Award.

I have recently developed some mixed unfolding IRT models to identify random responders and ill-fitting respondents, and I continue to explore the capabilities and characteristics of these models. Additionally, I have developed some new polytomous IRT models to measure change across repeated measurements of the same respondents. These repeated measures models are generalizations of traditional cumulative IRT models and will enable measurement practitioners to assess changes in student proficiency over time. Multivariate extensions of these longitudinal models are under development too.

Educational Background

Ph.D. (1995)  Experimental Psychology РQuantitative
University of South Carolina

Selected Publications
  • Roberts, J.S. (2008). Modified likelihood-based item fit statistics for the generalized graded unfolding model. Applied Psychological Measurement, 32, 407-423.
  • Koenig, J.A., & Roberts. J.S. (2007). Linking parameters estimated with the Generalized Graded Unfolding Model: A comparison of the accuracy of the characteristic curve method. Applied Psychological Measurement, 31, 504-524.
  • Roberts, J.S., & Ma, Q. (2006). IRT Models for the Assessment of Change Across Repeated Measurements.¬† In R. Lissitz (Ed.), Longitudinal and Value Added Modeling of Student Performance.¬† Maple Grove, MN: JAM Press.
  • Roberts, J. S., Fang, H., Cui, W. And Wang, Y. (2006). GGUM2004: A Windows-based Program to Estimate Parameters in the Generalized Graded Unfolding Model. Applied Psychological Measurement, 30, 64-65.
  • Habing, B., Finch, H., Roberts, J. S. (2005). A Q3 statistic for unfolding item response theory models. Applied Psychological Measurement, 29, 457-471.
  • Deas, D., Roberts, J. S., Grindlinger, G. (2005). The utility of DSM IV criteria in diagnosing substance abuse/dependence in adolescents. Journal of Substance Abuse, 10, 10-21.
  • Roberts, J. S., Huang, C. (2003). GGUMLINK: A computer program to link parameter estimates of the generalized graded unfolding model from item response theory. Behavior Research Methods, Instrumentation and Computers, 35, 525 549.
  • Roberts, J. S., Donoghue, J. R., & Laughlin, J. E. (2002). Characteristics of MML/EAP parameter estimates in the generalized graded unfolding model. Applied Psychological Measurement, 26, 192-207.
  • Roberts, J. S. (2001). GGUM2000: Estimation of parameters in the generalized graded unfolding model. Applied Psychological Measurement, 25, 38.
  • Roberts, J. S., Lin, Y., & Laughlin, J. E. (2001). Computerized adaptive testing with the generalized graded unfolding model. Applied Psychological Measurement, 25, 177-196.
  • Roberts, J. S., Donoghue, J. R., & Laughlin, J. E. (2000). A general item response theory model for unfolding unidimensional polytomous responses. Applied Psychological Measurement, 24, 3-32.
  • Roberts, J. S., Anton, R. F., Latham, P. K., & Moak, D. H. (1999). Factor structure and predictive validity of the obsessive compulsive drinking scale. Alcoholism: Clinical and Experimental Research, 23, 1484-1491.
  • Roberts, J. S., Laughlin, J. E., & Wedell, D. H. (1999). Validity issues in the Likert and Thurstone approaches to attitude measurement. Educational and Psychological Measurement, 59, 211-233.
  • Roberts, J. S. (1998). GUMJML: A program to estimate parameters in the graded unfolding model using a joint maximum likelihood technique. Applied Psychological Measurement, 22, 70.
  • Roberts, J. S., & Laughlin, J. E. (1996). A unidimensional item response model for unfolding responses from a graded disagree-agree response scale. Applied Psychological Measurement, 20, 231-255.
  • Jannarone, R. J. & Roberts, J. S. (1984). Reflecting interactions among personality items: Meehl’s paradox revisited. Journal of Personality and Social Psychology, 47, 621 628.