The single-format assumption in arithmetic fact retrieval

Current models of mental arithmetic disagree on whether the same mental representation is activated by numbers in different forms (single-format assumption). Two experiments examined if the response times in arithmetic fact retrieval from arabic digits, number words, or dice are independent of the graphical representation of the numbers. S. Sternberg's (1969) additive factors method was used to analyze which response time interactions are compatible with the single-format assumption. In accord with the assumption, additive effects of form and operation were found in Experiment 1. In contrast, Experiment 2 showed additive effects only when an operand was held in memory, but a strong Form x Operation interaction otherwise. The authors discuss how phonological interference and form-specific retrieval could produce these interactions and how the single-format assumption can be extended to handle the findings.