Differentiation-Dedifferentiation as a Guiding Principle for the Analysis of Lifespan Development

Abstract

Differentiation-dedifferentiation as a theoretical construct in lifespan developmental research has most often been used to describe increasingly similar versus dissimilar between-person differences in the changes of multiple intellectual abilities. Based on data from the Interdis- ciplinary Longitudinal Study of Adult Development (ILSE) we argue that differentiation- dedifferentiation may be used as a general guiding principle in developmental research. We demonstrate how the principle can be extended towards generally describing multiple traits between persons that include intellectual abilities and personality, towards describing within- person longitudinal development, and towards describing micro- and macrodevelopmental changes within- and between-persons aligning goal-related activities in a way that supports leading individually meaningful lifes.