Why do children from age four fail true belief tasks? A decision experiment testing competence versus performance limitation accounts

The dataset comprises structured developmental behavioral data obtained from a decision-experiment study with 165 children aged 4 to 7 years examining performance on true belief (TB) and false belief (FB) theory-of-mind tasks. It includes trial-level choice and accuracy data for both TB and FB tasks under standard and pragmatically modified experimental conditions designed to isolate competence versus performance limitations. The dataset contains binary and categorical response outcomes for each trial, task condition labels indicating task version and modification type, age group identifiers, and participant identifiers enabling cross-sectional comparisons. Participant demographic information (age in months, gender), detailed task sequencing metadata, and complete metadata on experimental design, task materials, pragmatic modification procedures, and scoring criteria are provided. Data were collected under standardized developmental testing protocols and enable reproducible analyses of children’s theory-of-mind performance, the impact of pragmatic task factors, and age-related changes in mental state reasoning from early to middle childhood.