As a way to organize most concepts of adult development we use the theory of "fluid and crystallized intelligence" (Gf/Gc). The original form of this theory considered only two broad factors, crystallized knowledge (Gc) and fluid reasoning (Gf), and made three key predictions about the complex nature of human intellectual abilities. When viewed in a broad perspective, the structural, kinematic and kinetic aspects of adult cognitive development have wide empirical support.
As a way to organize most of these concepts of adult development we use the theory of “fluid and crystallized intelligence” (Gf/Gc). The original form of this theory considered only two broad factors, crystallized knowledge (Gc) and fluid reasoning (Gf), and made three key predictions about the complex nature of human intellectual abilities. When viewed in a broad perspective, the structural, kinematic and kinetic aspects of adult cognitive development have wide empirical support.
The current form of Gf/Gc theory integrates results from studies of adult aging using experimental and differential paradigms, and includes 8 broad cognitive functions:
This form of Gf/Gc theory is useful as a set of guiding hypotheses and as a classification system for the collection of key cognitive abilities. Repeated examination using independent sets of data have led to broad support for Gf/Gc theory in both cross-sectional and longitudinal studies. The empirical synthesis of over 400 research studies showed a remarkable set of similarities among the theories used by most researchers in this area, to the degree there is evidence for a central G, it is most closely aligned with Gf. The current 8-factor model has been related to many widely-used test batteries, and used as the theoretical foundation of the popular Woodcock-Johnson tests (WJ-R, WJ III). These 8 factors are important in aging research because they are expected to change over age in different ways, and expected to have different relations to health, decision making, dementia, and other non-cognitive outcomes.
The evaluation and extrapolation of this 8-factor theory has been a focal activity of the PI’s program of research. The first of these five studies is based on our 30-year collation of longitudinal and family data on the WAIS – now termed CogWAIS. The second set is the CogNGCS data, and this has formed the basis of our prior published research suggesting that a single general factor (G) is not a useful dynamic concept for adult cognition, whereas the 8-factor structure is a useful starting point. The third data set is the CogUSA data where we have worked with the HRS to collect both in-person face-to-face measures as well as telephone measures of cognition. The fourth data set comes from the CogECON survey, which is a recent follow-up of he CogUSA participants using a new measure of financial literacy. The final study is the CogGENE project where we are currently following up on the highly informative Intergenerational Studies (IGS) data at Berkeley to collect saliva samples for DNA extraction and typing candidate genes for cognition and cognitive changes.