Modeling intraindividual change in nonlinear growth models with latent change scores

Three central goals of longitudinal research are the modeling of intraindividual change, the examination of interindividual differences in intraindividual change, and the evaluation of determinants of intraindividual change (<citationReference id="cr1-1" rid="c1">Baltes & Nesselroade, 1979</citationReference>). The latent growth model is a commonly fit statistical model to examine these goals. However, the latent growth model has difficulty in this examination when change trajectories are nonlinear with respect to time and multiple latent variables impact intraindividual change. We consider a latent growth modeling approach based upon latent change scores (<citationReference id="cr11-1" rid="c11">McArdle, 2001</citationReference>, <citationReference id="cr12-1" rid="c12">2009</ citationReference>), which yields information related to these goals of longitudinal research when change trajectories are nonlinear. We illustrate this approach with longitudinal data from the Berkeley Guidance Study regarding lifespan changes in verbal ability.