This is a competitive renewal for R01 AG 029672, which applied modern psychometric methods to neuropsychological data collected by the Alzheimer's Disease Neuroimaging Initiative (ADNI). This competitive renewal proposes to analyze data from ADNI and from the Australian Imaging, Biomarkers, and Lifestyles of Ageing (AIBL) study using state-of-the-art psychometric approaches to address substantively important questions in Alzheimer's disease (AD) research. This project in many ways serves as a bridge between fields that do not often talk with each other: modern psychometrics and cognitive neuroscience applied to neurodegenerative conditions. The investigators propose to tackle two important problems in AD research: improving the ability to detect preclinical disease at the earliest stages (Aim 1) and understanding the clinical relevance of heterogeneity in the presentation of AD (Aim 2). Advances in modern psychometrics have the potential to optimize understanding of these critical questions by translating clinical insights into quantitative analytic approaches. The investigators have a tradition of disseminating their tools to the broader research community and propose to continue this tradition with a dissemination aim (Aim 3). Support for the next cycle of funding for this project will ensure continued scientific leadership bridging modern psychometrics and cognitive neuroscience.