To add or to remove? The role of working memory updating in preschool children's non-symbolic arithmetic abilities between addition and subtraction.

Early computational capacity sets the foundation for mathematical learning. Preschool children have been shown to perform both non-symbolic addition and subtraction problems. However, it is still unknown how different operations affect the representational precision of the non-symbolic arithmetic solutions. The current study compared 83 4- and 5-year-olds' ability to solve non-symbolic addition and subtraction problems and examined the role of working memory underlying the two arithmetic processes. In the task, children were shown two sets of arrays that were sequentially occluded and were asked to either sum the arrays up (addition) or remove one array from the other (subtraction). The solution was then compared with a visible array. Children also completed two working memory tasks to measure their working memory storage and updating abilities. Results showed that children's representational precision in addition was higher than that in subtraction. Although children's performance in both arithmetic operations were associated with working memory updating, solving subtractive problems imposed additional cognitive resources in working memory updating. These findings reveal early developmental differences between addition and subtraction. Children's computational capacity in both addition and subtraction develops early in childhood, and the operation in subtraction demands more mental manipulation in working memory.