The stability of cognitive abilities: A meta-analytic review of longitudinal studies.

Abstract

Cognitive abilities, including general intelligence and domain-specific abilities such as fluid reasoning, comprehension knowledge, working memory capacity, and processing speed, are regarded as some of the most stable psychological traits, yet there exist no large-scale systematic efforts to document the specific patterns by which their rank-order stability changes over age and time interval, or how their stability differs across abilities, tests, and populations. Determining the conditions under which cognitive abilities exhibit high or low degrees of stability is critical not just to theory development but to applied contexts in which cognitive assessments guide decisions regarding treatment and intervention decisions with lasting consequences for individuals. In order to supplement this important area of research, we present a metaanalysis of longitudinal studies investigating the stability of cognitive abilities. The meta-analysis relied on data from 205 longitudinal studies that involved a total of 87,408 participants, resulting in 1,288 testretest correlation coefficients among manifest variables. For an age of 20 years and a test-retest interval of 5 years, we found a mean rank-order stability of ρ = .76. The effect of mean sample age on stability was best described by a negative exponential function, with low stability in preschool children, rapid increases in stability in childhood, and consistently high stability from late adolescence to late adulthood. This same functional form continued to best describe age trends in stability after adjusting for test reliability. Stability declined with increasing test-retest interval. This decrease flattened out from an interval of approximately 5 years onward. According to the age and interval moderation models, minimum stability sufficient for individual-level diagnostic decisions (r tt = .80) can only be expected over the age of 7 and for short time intervals in children. In adults, stability levels meeting this criterion are obtained for over 5 years. Public Significance StatementThis meta-analytic review finds that cognitive abilities are highly stable from adolescence to late adulthood, but only moderately stable in young children. Stability decreases with increasing time intervals and varies across different cognitive abilities. General intelligence was found to be the most stable cognitive ability, but many specific cognitive abilities are similarly stable. These results provide important standards with respect to the "shelf-life" of cognitive test scores across development and time.