The longitudinal contributions of child language, negative emotionality, and maternal positive affect on toddler executive functioning development.

Executive functions (EF) develop rapidly across early childhood and play a prominent role in promoting adaptive outcomes later in development. Although the existing literature suggests that the development of early EF is sensitive to the influence of intrinsic and extrinsic factors, limited research has examined the joint contributions of multiple child and contextual factors in infancy/toddlerhood. The purpose of our longitudinal study was therefore to identify early environmental, behavioral, biologically-based factors that influence children's EF outcomes in late toddlerhood. Participants included 409 mother-child dyads (209 girls) and the data was collected across children's first three postnatal years. Parent-report measures were used to assess infant negative affectivity (5-months; IBQ-R) and toddler language (age 2; MCDI), and both maternal positive affect (5-months) and toddler frustration (age 2) were coded during mother-child interaction tasks. A battery of behavioral tasks was used to measure child EF in late toddlerhood (age 3). After controlling for maternal education (a proxy for children's socio-economic environment), path analysis indicated that both infant and maternal affect at 5-months directly predicted toddlers' language skills and frustration expression at age 2. Toddler language (but not frustration) also predicted child performance on multiple EF tasks at age 3. Finally, 5-month infant and maternal affect indirectly predicted age 3 EF via age 2 language. Our results identify language as a mechanism through which children's early caregiving environment influences their EF development. Taken together, these findings illustrate the importance of applying a biopsychosocial perspective to the examination of early childhood EF development.