ABSTRACT
Growth is fundamental to understanding phenomena in all scientific disciplines. Fascination with explaining how things change over time has dominated scientific investigations for hundreds of years (McArdle & Nesselroade, 2003). Learning, memory, intelligence, development, personality, mood, and motivation are just a few of the topics that psychologists study that exhibit changes over time. Examining the dynamics of these processes can yield insights that are not apparent in static research. One such discovery is that, frequently, a great deal of heterogeneity exists in the growth process of individuals (Collins & Horn, 1991; Collins & Sayer, 2001). Interest in explaining these interindividual differences in intraindividual change has led to an increase in the number of longitudinal studies in recent years (Collins, 2006).
