Abstract
The study of cognitive change across a life span, both in pathological and healthy samples, has been heavily influenced by developments in cognitive psychology as a theoretical paradigm, neuropsychology and other bio-medical fields; this alongside the increase in new longitudinal and cohort designs, complemented in the last decades by the evaluation of experimental interventions. Here, a review of aging databases was conducted, looking for the most relevant studies carried out on cognitive functioning in healthy older adults. The aim was to review not only longitudinal, cross-sectional or cohort studies, but also by intervention program evaluations. The most important studies, searching for long-term patterns of stability and change of cognitive measures across a life span and in old age, have shown a great range of inter-individual variability in cognitive functioning changes attributed to age. Furthermore, intellectual functioning in healthy individuals seems to decline rather late in life, if ever, as shown in longitudinal studies where age-related decline of cognitive functioning occurs later in life than indicated by cross-sectional studies. The longitudinal evidence and experimental trials have shown the benefits of aerobic physical exercise and an intellectually engaged lifestyle, suggesting that bio-psycho-socioenvironmental factors concurrently with age predict or determine both positive or negative change or stability in cognition in later life.
Highlights
Performance on tasks that involve working memory, processing speed and cognitive plasticity steadily declines after midlife, possibly due to an age-related loss of biological potential [45,46,47,48,49]
The results suggest the importance of the sensoriomotor functioning related to intellectual functioning, which accounted for 59% of the total variance in general intelligence [56], and “differences in intellectual functioning in old and very old age showed a greater degree of consistency across abilities and ability domains than differences in intellectual functioning during earlier periods of the adult life-span”: a substantial amount of inter-individual difference was related to perceptual speed (38% of the reliable variance), while only about a third was related to chronological age [55] (p. 339)
As addressed by the cross-sectional authors, older adults show a great range of inter-individual variability in cognitive functioning due to age but authors agree that this decline occurs in some abilities, while there is stability or even growth in others
Summary
When psychology was born as a science (see Figure 1) in the last third of the 19th century, life expectancy was less than 40 years. Developmental psychology initially referred only to children and adolescents, with most of the early work in the study of aging being done by scientists from several disciplines who were not psychologists. Authors agree that an early pioneer in the scientific study of aging in the 19th century was the Belgian statistician and astronomer Adolphe Quêtelet, who said: “man is born, grows up, and dies, according to certain laws which have never been properly investigated, either as a whole or in the mode of their mutual reactions”; some “proper investigations” about changes along aging will be described here [1] About nine thousand individuals (men and women from age 5 to 80)
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