Developmental changes in electrophysiology and speech during problem-solving as predictors of inhibitory control in preschool

The current study examined developmental changes in electrophysiological indices of frontal cortical maturity across the toddler years and assessed how variation between children in the initial level and amount of change were associated with variation in their inhibitory control (IC) abilities in preschool. Additionally, to provide information about the role of language in the development of IC, the study also examined children’s speech during problem-solving at 3 years and assessed how variation between children in the overall amount and content of their private (i.e., self-directed) and social speech in this context were associated with variation in their IC. Finally, the current study assessed whether the amount of speech during problem-solving was a mediating mechanism through which the overall level of frontal cortical maturity across the toddler years was associated with children’s IC in preschool. One-hundred and eighty children (54% male) participated in the study. Frontal cortical maturity was assessed from resting-state electroencephalography (EEG) at 10, 24, and 36 months; spectral power (6-9 Hz) at frontal scalp sites was computed and averaged to yield composites. Children’s problem-solving speech was observed at 3 years from a challenging puzzle task; mothers were nearby but unavailable to help. Utterances were transcribed and coded based on orientation (social vs. private) and content. Children’s IC was assessed at 4 years from a battery of observational tasks and surveys completed by mothers and experimenters. Frontal EEG power composites were modeled in a growth curve using structural equation modeling; associations between individual variation around growth parameters (intercept, slope), speech variables, and IC were examined in Mplus. Results indicated that there was significant, positive linear change in children’s resting frontal EEG power values from 10 months to 3 years, suggesting this is a period of maturational growth in the frontal cortex. Although a significant amount of variance in the initial level (intercept) and amount of change (slope) were observed, it was not associated with variation in children’s IC at age 4 or in the amount of speech they produced during problem-solving at age 3. However, the amount of speech children produced during problem-solving was significantly negatively associated with their IC, suggesting that young children who are more vocally reactive to challenges (e.g., frustration) may have lower IC in the preschool period. Additionally, the proportion of children’s private speech that was ‘mature’ (i.e., semantically on-task, coordinated with task-relevant manual actions) was positively associated with their IC, which is consistent with theory and previous research. Finally, a significant positive association between the proportion of children’s social speech that was classified as ‘help-seeking’ and their IC was observed, suggesting that motivation to comply with adults’ requests is an important factor in this developmental process. Collectively, these findings suggest that characteristics of young children’s speech during problem-solving at 3 years help explain variance in their IC skills at age 4, but that additional research is needed to understand the underlying mechanisms and the role of children’s frontal cortical maturity