Supplementary materials [Research Data]. The related article is Karlsson, A. M. C., Skagerlund, K., Skagenholt, M., Träff, U. (2026). Exploring cognitive predictors: Examining varied impact on early number skills in a longitudinal study. Journal of Numerical Cognition, 2026, Vol. 12, Article e15049, https://doi.org/10.5964/jnc.15049

The Supplementary Materials consist of the research data and codebook: Dataset (CSV): Full longitudinal dataset including demographics (age, gender, handedness),domain-specific numerical skills (Counting Skills, Digit Magnitude Comparison, Number Line Estimation), and domain-general cognitive abilities (Phonological Awareness, Phonological Verbal Fluency, RAN, General Processing Speed, Nonverbal Logical Reasoning, Verbal Working Memory) measured at three time points (Kindergarten, 1st Grade, 2nd Grade); Codebook (PDF): Variable definitions, coding schemes, labels, measurement-year mapping, and notes on transformations (e.g., inverted timing/efficiency, NLE = 100 – PAE).