Normative reference values for executive function through the Early Years Toolbox (EYT) in preschoolers

The Early Years Toolbox (EYT) is a validated instrument for assessing early language, executive functioning (EF), self-regulation, and social development. However, normative data specific to Spanish-speaking preschoolers in Spain are lacking. This study aimed to develop age- and sex-specific normative reference values for EF in Spanish children aged 3-6 years, using the EYT battery. In this cross-sectional study, 567 Spanish preschoolers (49.2% female) were evaluated using four EYT tasks: Mr Ant (visual-spatial working memory), Not This (phonological working memory), Go/No-Go (inhibitory control), and Card Sorting (cognitive flexibility). Scores were organized by age group, and smoothed percentile curves were created using the LMS method, incorporating the L (λ), M (μ), and S (σ) parameters. Performance on all EF tasks increased with age, reflecting developmental differences throughout the preschool years. Girls outperformed boys in the Go/No-Go, Not This, and Card Sorting tasks. Percentile distributions indicated these age-related differences across EF domains, with the most noticeable changes seen in working memory and cognitive flexibility. Inhibitory control followed a more gradual pattern. Variability between individuals decreases with age, suggesting increased cognitive stability in older preschoolers. This study provides preliminary normative data illustrating the developmental trajectory of executive functioning in Spanish preschool-aged children. These benchmarks offer a culturally relevant reference for school-based EF assessments and enable meaningful cross-national comparisons.