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, pre-vious studies have suggested that children start their learning process in preschool. The current research aims to exa-mine 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.