My primary focus in research is on the measurement of broad cognitive and personality changes associated with aging. My methodological work includes development of methods for analyzing longitudinal data, including factor analysis, growth curve analysis, and dynamic modeling, as well as methods to handle non-random attrition and incomplete data. I have also conducted work on new methods for item response analysis, including extension of the principles of adaptive testing. I am the director of the Unified Studies of Cognition(CogUSC) Laboratory, a collection of longitudinal studies of cognitive changes over the adult portion of the life span. I am a Co-PI on the Health and Retirement Study (HRS) and am the Principal Investigator for the “Assessing and Improving Cognitive Measures in the HRS” which is funded by an NIA MERIT award.