Noncommutability of The N + 0 Arithmetical Rule: A Case Study of Dissociated Impairment

Abstract

It has been shown that some arithmetical problems are stored in the form of individual facts representations (e.g., 3 × 4 = 12) whereas others are solved by general stored rules (e.g., 0 × N = 0). We describe the performance of a brain-damaged subject who presented a mild impairment in arithmetical fact retrieval. Although her performance was almost perfect for rule-based problems in all arithmetical operations, she was severely impaired for 0 + n problems in contrast with her relatively good performance for the corresponding n + 0 problems. This dissociation extends to addition the noncommutability of arithmetical rules described in multiplication.