This review summarizes empirical findings and theoretical concepts in cognitive aging and
late-life dementia research, with emphases on (a) person-to-person heterogeneity in
trajectories of cognitive change over time,(b) how trajectories of child cognitive development
determine peak levels of adult cognitive function from which aging-related cognitive declines
occur, and (c) how lifelong trajectories of cognitive function relate to the timing of severe
cognitive impairments characteristic of dementia. I consider conceptual issues surrounding …