Examining relations between performance on non-verbal executive function and verbal self-regulation tasks in demographically-diverse populations.

Self-regulation is a widely studied construct, generally assumed to be cognitively supported by executive functions (EFs). There is a lack of clarity and consensus over the roles of specific components of EFs in self-regulation. The current study examines the relations between performance on (a) a self-regulation task (Heads, Toes, Knees Shoulders Task) and (b) two EF tasks (Knox Cube and Beads Tasks) that measure different components of updating: working memory and short-term memory, respectively. We compared 107 8- to 13-year-old children (64 females) across demographically-diverse populations in four low and middle-income countries, including: Tanna, Vanuatu; Keningau, Malaysia; Saltpond, Ghana; and Natal, Brazil. The communities we studied vary in market integration/urbanicity as well as level of access, structure, and quality of schooling. We found that performance on the visuospatial working memory task (Knox Cube) and the visuospatial short-term memory task (Beads) are each independently associated with performance on the self-regulation task, even when controlling for schooling and location effects. These effects were robust across demographically-diverse populations of children in low-and middle-income countries. We conclude that this study found evidence supporting visuospatial working memory and visuospatial short-term memory as distinct cognitive processes which each support the development of self-regulation.

Life in the slow lane revisited: ontogenetic separation between chimpanzees and humans.

This study investigates the evolution of human growth by analyzing differences in body mass growth trajectories among three populations: the Ache of eastern Paraguay, the US (NHANES, 1999-2000), and captive chimpanzees. The relative growth statistic "A" from the mammalian growth law is allowed to vary with age and proves useful for comparing growth across different ages, populations, and species. We demonstrate ontogenetic separation between chimpanzees and humans, and show that interspecific differences are robust to variable environmental conditions. The human pattern of slow growth during the lengthened period from weaning to the beginning of the adolescent growth spurt is found among the Ache (low energy availability and high disease load) and also in the US (high energy availability and low disease load). The human growth pattern contrasts with that of the chimpanzee, where absolute growth rates and relative "A" values are faster and less prolonged. We suggest that selection has acted to decrease human growth rates to allow more time for increased cognitive development with lower body-maintenance costs.