The articulation of lifespan developmental theory has made great strides in the past
decade. In recent years there has also been considerable growth in analytical design and
modeling procedures. However, these theoretical and methodological advancements have
not yet been fully integrated within the study of behavioral change over the lifespan. We
present two “alternative” methods that may allow for more precise articulation and
testing of hypotheses regarding how developmental processes that are universal are
expressed in idiosyncratic ways and how individual structures re-organize across the
lifespan. Using simulations and empirical data, we demonstrate the potential utility of
these methods for examining increases in intellectual ability thought to occur in
adulthood (e.g., gains in domain-specific knowledge and expertise) and differences (and
changes) in emotional complexity over the lifespan (e.g., differentiationdedifferentiation).
More generally, we illustrate how questioning “traditional” notions of
factorial invariance and how “combining” idiographic and nomothetic approaches may
allow us to link our theoretical predictions and our data more closely.