False Belief and Number: A Difficult Case for Concept Combination in Preschool Age and Middle Childhood

Very few if any studies address concept combination from a developmental perspective. Here we report a study of how concepts of integer number combine with those of mindreading. We used tasks that require explicit thought and verbal responses, and examined children between 6-10 years of age. We designed four experiments to look at the intersection of quantification and mindreading in development using two combination tasks: (i) visual perspective taking and number; (ii) false belief and number. In both, children needed to coordinate between simple mathematical operations (counting and addition), and reconstructing an agent's visual or mental perspective. Although all senior kindergarteners were proficient in counting, and the majority of them passed the false-belief task, the false belief and number task has proven surprisingly difficult, and was not mastered before age 8. We offer a performance-based explanation of this difficulty.