Normal age-associated memory decline is not
uniform. Older adults evidence worse performance
on long-term memory tasks compared to younger
adults, but these differences are relatively greatest
on tasks of declarative episodic memory. Semantic
memory, on the other hand, remains relatively stable
across the adult life span or may even increase as
more semantic knowledge is accumulated with age.
Similarly, working memory, or the manipulation of
information that is held in conscious awareness,
shows marked decline in with normal aging, and
some theorists propose that working memory deficits
mediate age-associated decline in other cognitive
domains.
In terms of the course of memory changes across
the adult life span, results from cross-sectional and
longitudinal studies suggest that subtle memory
changes can begin as early as the early or middle
twenties and continue to decline linearly with age.
Some authors distinguish between ‘lifelong decline’
and ‘late-life decline.’ Performance on tasks of episodic
and working memory seems to begin to decline in the
twenties and continues to decline linearly across
the life span, which is supported by cross-sectional
aging and cognition studies. Some longitudinal studies,
however, suggest a curvilinear course of memory
decline, with a more precipitous decline after about
age 60 years, preceded by relatively little decline with
age. Short-term memory store appears to remain relatively
stable until about age 70, at which point it begins
to drop, and, as noted, semantic abilities appear to
remain relatively stable, at least until late life.