Multiple routes for reading words, why not numbers? evidence from a case of arabic numeral dyslexia

Abstract

This paper describes a patient (SF), suffering from a probable dementia of Alzheimer's type, with a severe difficulty in reading aloud arabic numerals and a spared ability to read aloud alphabetical material. This pattern of impairment completed a double dissociation with the “number sparing effect” observed in some alexic patients (e.g. Déjerine, 1892; Anderson, Damasio,&Damasio, 1990). Through a systematic investigation of the patient's performance on various tasks it was established that he could recognise and understand arabic numerals and produce verbal numerals as responses to number fact or “what comes next?” questions. This study allowed the conclusion that arabic numerals and alphabetically written stimuli are read by two processes which are at least partly dissociable. The patient's performance was interpreted as a consequence of damage to a postulated asemantic route for arabic numeral reading.