Neuropsychologists often assess cognitive function to distinguish normal aging from pathological conditions. For elders, interpretation hinges on accurate conceptualization of cognitive performances associated with normal neurological aging versus deficits indicative of central nervous system injury or illness, such as those found in neurodegenerative dementias. Early research indicated that aging in the absence of disease is not associated with standard focal deficits that are typical of an injured central nervous system [1, 2]. Rather, age-related declines were characterized as a more diffuse, gradual loss of efficiency and flexibility. Cross-sectional observations provided an important foundation for estimating abilities across various age groups, and these normative studies have traditionally informed models of normal aging.

More recently, neuropsychologists and neuroscientists have expanded our understanding of the longitudinal course of neurological function in older adults by including intraindividual observations of anatomical and functional changes over time. And yet, the relationship between aging and cognitive function is actually quite complex and difficult to characterize for several reasons. For instance, there are considerable methodological challenges to conducting well-controlled longitudinal studies that span beyond 5–7 years, such that aging models typically rely on relative snapshots of neurodevelopment when considered within the context of a 70–80-year lifespan. Also, influences on how humans age continue to evolve in a manner that probably parallels societal and technological progress. It appears that environmental, nutritional, and technological factors that can influence aging are changing with increasing speed.