Executive functions and theory of mind development in preschoolers: Insights from NIRS data

Numerous studies have highlighted the importance of executive functions (EFs) in the development of Theory of Mind (ToM) in preschoolers. However, research focusing on young children at the neural level has been limited. This study examined the relationship between EFs and ToM in twenty-nine healthy Japanese preschoolers aged 5–7 years, focusing on neural responses during EF and ToM tasks using near-infrared spectroscopy (NIRS) to monitor prefrontal cortex (PFC) activity. The study utilized EF tasks and the Sally-Anne scenario to assess false- and true-belief understanding, aiming to provide a comprehensive analysis of ToM capabilities. Results indicated that despite advanced EF capabilities and a ceiling effect across all EF tasks, there were no significant correlations between EF performance or verbal ability and ToM task performance. NIRS data revealed no PFC activation during the Stroop task. However, activation was observed in the left and right lateral PFC in the control false belief condition, the left lateral PFC in the false belief condition, and across all PFC regions in the true belief condition during ToM tasks. Significant relationships were found between behavioral performance in ToM tasks and neural activity in key brain regions. The study also identified a complex relationship between false and true belief reasoning, suggesting a nuanced developmental trajectory for ToM. These findings underscore the crucial role of early childhood in the development of ToM and the complex interplay between cognitive functions and neural efficiency in understanding others' mental states.