Cognitive dispersion in established adulthood: etiology and implications for cognitive aging

Area of Science:

• Behavioral neuroscience
• Cognitive psychology
• Psychometrics

Background:

• Cognitive dispersion (intraindividual variability across tasks) is a potential marker for dementia risk in older adults.
• Its origins and relevance before midlife remain unclear.
• This study investigates cognitive dispersion as a marker of cognitive reserve in established adulthood.

Purpose of the Study:

• To examine cognitive dispersion as a potential marker of cognitive reserve in established adulthood.
• To distinguish cognitive dispersion from general cognitive ability using heritability analyses.
• To explore the relationship between cognitive dispersion, cognitive ability, and developmental gains.

Main Methods:

• Assessed 1,245 twins and siblings around age 33 using two cognitive batteries.
• Employed Bayesian mixed-effects location scale models to estimate mean performance and dispersion.
• Standardized cognitive tasks against current (age 33) and adolescent (age 16) norms.

Main Results:

• Greater cognitive dispersion correlated with higher general ability (r=0.23-0.56) and developmental gains (r=0.62-0.93).
• Verbal tasks exhibited lower dispersion than performance tasks.
• Cognitive dispersion was strongly heritable (43%-84%) and moderately heritable independent of general ability (36%-37%) and growth (2%-16%).

Conclusions:

• Before midlife, cognitive dispersion is distinct from general ability and moderately heritable.
• Dispersion is associated with higher cognitive ability and growth but not directly with educational or occupational attainment.
• Cognitive dispersion may relate to cognitive reserve through pathways distinct from direct achievement.