Good division, but bad addition, subtraction and multiplication. A “leftmost-first” bug?

• Published in: Cortex Vol. 47; no. 2; pp. 250 - 258
• Main Authors: Chiarelli, Valentina, Menichelli, Alina, Zadini, Antonietta, Semenza, Carlo
• Format: Journal Article
• Language: English
• Published: Italy Elsevier Srl 01-02-2011
• Subjects: Acalculia following right hemisphere lesions; Aged; Arithmetic procedural error; Brain Ischemia - complications; Brain Ischemia - psychology; Functional Laterality - physiology; Humans; Magnetic Resonance Imaging; Male; Math-language relation; Mathematics; Mental Disorders - psychology; Mental Processes - physiology; Neuropsychological Tests; Problem Solving; Psychomotor Performance - physiology; Spared division procedure; Stroke - etiology; Stroke - psychology; Written multi-digit calculation; Arithmetic procedural error; Spared division procedure; Acalculia following right hemisphere lesions; Math-language relation; Written multi-digit calculation
• ISSN: 0010-9452; 1973-8102
• DOI: 10.1016/j.cortex.2010.08.004

The present investigation reports the case of patient AS, ambidextrous, who showed a selective problem with arithmetical procedures in addition, subtraction and multiplication, contrasting with complete sparing of division. AS displayed a specific and never described “bug” error, involving the selection of digits that have to be added, subtracted or multiplied. This bug consisted in inverting the order of the numbers that have to be selected to correctly solve the operation. In particular, AS selected the numbers beginning from the leftmost position. This bug spared division, since it is the only operation that requires starting from the leftmost digit(s). The present case would suggest that some aspects of arithmetical procedures are operation independent. Moreover, an account of the nature of the syntactic rule getting lost in AS’s performance has been proposed.