Development of Additive Reasoning in Young Children: The Case of Partitioning and the Successor Function

Additive reasoning is a fundamental mathematical skill that children learn during elementary school. However, previous studies have suggested that children start their learning process in preschool. The current research aims to examine how two additive reasoning skills, successor function and partitioning, emerge in the preschool years. To this purpose, a group of 56 children of 4 and 5 years of age were tested on three additive tasks, a cardinality task, and a counting task. The results show a similar developmental trajectory for children’s performance on the successor function task and the partitioning tasks, with significantly better performance in 5-year-olds. The results also show that children’s cardinality knowledge and counting skills are good predictors in both additive reasoning tasks. These findings suggest that preschool is a critical period for learning the additive structure of the number system and that knowledge of verbal counting boosts this acquisition.