The representation of arithmetic facts in memory: results from retraining a brain-damaged patient.

This single case study was designed to gather evidence regarding whether the mental representations mediating multiplication fact retrieval make use of single or multiple codes. MC is a brain-damaged volunteer whose numerical processing impairments were limited to multiplication fact retrieval. He relearned three sets of multiplication facts. Each set was relearned in one of three input formats: Arabic, written verbal, or spoken verbal. Following training all facts were tested in all input formats. MC's posttraining performance was virtually error free and showed no effects of input format. However, reaction-time data showed fact retrieval was fastest when the training format matched the test format. Results are discussed in relation to single- and multiple-code models of multiplication fact retrieval.