Executive function skills, including cognitive flexibility, inhibitory control, and working memory, are foundational for children’s learning, self-regulation, and engagement in complex tasks. Understanding how these capacities relate to broader cognitive development can shed light on the mechanisms that support school readiness. Also, there is a lack of recent research focusing on differences in young children's executive function and cognitive development by sex. This study examined the relationships between young children’s sex, cognitive development, and executive function.

We analyzed data from 136 children aged 3–6 years who participated in two experimental studies conducted as part of a broader research program. Cognitive development was assessed using the Wechsler Preschool and Primary Scale of Intelligence—Fourth Edition (Canadian), capturing verbal reasoning, visual–spatial problem-solving, fluid reasoning, working memory, processing speed, and overall cognitive functioning. Executive function was measured with the Head–Toes–Knees–Shoulders Task (HTKS), which requires children to inhibit automatic responses and apply rule-based behaviour, thereby assessing cognitive flexibility, working memory, and inhibitory control. Parents provided demographic information and details about the home learning environment.

Spearman correlations indicated that HTKS performance was strongly associated with most Wechsler subcomponents, including verbal (ρ = .33, p < .001), visual–spatial (ρ = .45, p < .001), fluid reasoning (ρ = .41, p < .001), and processing speed (ρ = .38, p < .001), but showed a weaker association with working memory (ρ = .29, p < .001). Gender differences were minimal, with only processing speed showing a modest effect (ρ = –.22, p = .025), favouring girls slightly. Overall cognitive functioning was strongly linked to all composite scores, particularly visual–spatial reasoning (ρ = .60, p < .001) and HTKS performance (ρ = .56, p < .001). These findings suggest that (1) executive function relates broadly to cognitive development but not strongly to working memory specifically, (2) visual–spatial abilities contribute substantially to general cognitive performance, and (3) sex differences in cognitive development are minimal. Thus, standardized measures of cognitive development and HTKS may capture distinct yet complementary aspects of cognitive processes.