When does cognitive functioning peak? The asynchronous rise and fall of different cognitive abilities across the life span

Abstract

Understanding how and when cognitive change occurs over the life span is a prerequisite for understanding normal and abnormal development and aging. Most studies of cognitive change are constrained, however, in their ability to detect subtle, but theoretically informative life-span changes, as they rely on either comparing broad age groups or sparse sampling across the age range. Here, we present convergent evidence from 48,537 online participants and a comprehensive analysis of normative data from standardized IQ and memory tests. Our results reveal considerable heterogeneity in when cognitive abilities peak: Some abilities peak and begin to decline around high school graduation; some abilities plateau in early adulthood, beginning to decline in subjects' 30s; and still others do not peak until subjects reach their 40s or later. These findings motivate a nuanced theory of maturation and age-related decline, in which multiple, dissociable factors differentially affect different domains of cognition.

Keywords: cognitive ability; cognitive development; individual differences; intelligence; language development.

Figure 1. Bootstrapped age of peak performance for WAIS-III and WMS-III tasks (Exp. 1)

Represented are the medians (central line), inter-quartile ranges (boxes) and 95% confidence intervals (whiskers). WM = Working Memory (immediate test after each trial); STM = Short-Term Memory (test soon after stimulus presentation); LTM = Long-Term Memory (test 20–30 min. after stimulus presentation).

Figure 2

Lifespan curves for representative early- and late-peaking WAIS-III and WMS-III tasks (Exp. 1). Shaded areas represent standard errors.

Figure 3. Results of Exps. 2 & 3

Panel A: Mean z-scored performance for each task in Exp. 2. Shaded regions represent SEs. Panel B: Mean z-scored performance in Exp. 3. Panel C: Bootstrapped age of peak performance for Exps. 1–2, plus replications.

Figure 4

Lifespan curves for vocabulary for participants tested in 1974–1987 (Panel A), 1988–1997 (Panel B), and 1998–2012 (Panel C). Estimated age-of-peak-performance is shown in Panel D, and mean score for each cohort is shown in Panel E.