Shared versus separate processes for letter and digit identification

Michael McCloskey, Teresa Schubert

Research output: Contribution to journalArticle


Letters and digits, although similar in many respects, also differ in potentially significant ways. Most importantly, letters are elements of an alphabetic writing system, whereas digits are logographs. In this article, we explore whether letters and digits are identified by a single character identification process that makes no fundamental distinction between the two types of characters, or whether instead letter and digit identification processes diverge at least in some respects. We present evidence from an acquired dyslexic patient, L.H.D., who is impaired in both letter and digit identification. Working within a theoretical framework specifying the levels of representation implicated in letter identification, we systematically compare L.H.D.'s letter and digit processing. The results provide evidence that letter and digit identification implicate the same levels of representation, and further that L.H.D.'s identification errors for both letters and digits arise at the same point in processing. On the basis of these results, we argue for a shared process that mediates identification of both letters and digits. Finally, we discuss relevant previous results in light of this conclusion.

Original languageEnglish (US)
Pages (from-to)437-460
Number of pages24
JournalCognitive neuropsychology
Issue number5-6
StatePublished - Aug 2014



  • Acquired dyslexia
  • Digits
  • Letters
  • Numerical
  • Pure alexia
  • Reading

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Experimental and Cognitive Psychology
  • Developmental and Educational Psychology
  • Arts and Humanities (miscellaneous)
  • Cognitive Neuroscience

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