It is generally presumed that as fluid cognitive abilities decline, crystallized abilities—those fixed in memory—become stronger. However, a study recently published in Scientific Advances shows the opposite: as fluid abilities decline, crystallized abilities also decline, though at a lower rate.
The researchers used data from 2 longitudinal studies on cognitive aging: the Virginia Cognitive Aging Project (VCAP) and the Betula Project (BETULA), each of which measures crystallized ability and multiple fluid abilities across time. Both studies measure episodic memory, perceptual speed, visuospatial reasoning, and crystallized ability. Age at baseline ranged from 18 to 99 years for the VCAP study and 25 to 86 years for the BETULA study.
The researchers conducted multivariate growth curve modeling, which showed a “strong dependency” between changes in fluid and crystallized ability. Individuals who showed the most dramatic decline in fluid ability over time exhibit very little gain, and in some cases, a decline, in crystallized ability. The researchers hypothesize vascular dysregulation and cortical atrophy partly attribute to their findings.
The researchers argue that it may be more difficult than previously thought to tailor interventions around cognitive decline because “individuals who experience particularly precipitous rates of fluid decline are likely to be those who exhibit the shallowest rate of gain, and perhaps even decline, in crystallized abilities,” they state.
“Directing attention toward identifying the domain-general mechanisms of adult cognitive decline and maintenance might help to reveal promising targets for individualized interventions.”
Tucker-Drob EM, de la Fuente J, Köhncke Y, Brandmaier AM, Nyberg L, Lindenberger U. A strong dependency between changes in fluid and crystallized abilities in human cognitive aging. Sci Adv. 2022;8(5):eabj2422. doi:10.1126/sciadv.abj2422