to explain the same variations in cognition. It is also important to examine a broad representative sample of the population, sometimes oversampling in subgroups whose health status or responses to life experiences are expected to illuminate important theoretical questions, and to encompass a wide age range. Moreover, by following individuals into very old age, promising new findings suggesting the existence of unexpected linkages between cognitive functioning and survival could be investigated. The requirements for long-term longitudinal studies are discussed in more detail in Chapter 5.
The conjunction of improved measurement, advances in modeling, and the comprehensive collection of longitudinal data on cognitive functioning and associated factors can have a synergistic effect in advancing knowledge. Longitudinal studies can make a quantum improvement by employing new fine-grained neural and behavioral measures; renewed attention to modeling can make better sense of the patterns that underlie associations between these neural and behavioral measures and that can be drawn from the longitudinal data.