ABSTRACT
This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book focuses on methodological, statistical, and modeling aspects of multivariate change, as well as applications of longitudinal models to the study of psychological processes. It discusses the implementation of Latent Change Score (LCS) models using a nonlinear mixed-effect modeling framework, where participants can be measured at unique points in time. The book presents an extension of LCS models based on additive curvilinear effects. It addresses issues related to measurement and testing in longitudinal models. The book investigates the effects of over-simplifying random components on the estimation of fixed effects in linear growth curves. It also focuses on measurement in developmental longitudinal modeling. The book demonstrates how longitudinal studies are sensitive to violations of interval level measurement, and argues that such violations have important implications regarding validity. It outlines important developments in the genetic studies of growth and development.
