The role of working memory in the carry operation of mental arithmetic: number and value of the carry.

Two experiments were conducted to investigate the role of phonological and executive working-memory components in the carry operation in mental arithmetic. We manipulated the number of carry operations, as previous research had done, but also the value that had to be carried. Results of these experiments show that in addition to the number of carry operations, the value of the carry is also an important variable determining the difficulty of arithmetical sums.

The odd-even effect in addition: an analysis per problem type.

The odd-even effect is a well documented finding in the literature on mental arithmetic, at least for multiplication. It implies that false answers with the same parity as the correct answer are rejected more slowly than false answers with a different parity. For addition, this effect is not so well documented.