Abstract of the day #3: Is the visual analyzer orthographic-specific? Reading words and numbers in letter position dyslexia

May 15th, 2013

Friedmann et al. (2010).Is the visual analyzer orthographic-specific? Reading words and numbers in letter position dyslexia

Cortex. 2010 Sep;46(8):982-1004.

Letter position dyslexia is a deficit in the encoding of letter position within words. It is characterized by errors of letter migration within words, such as reading trail as trial and form as from. In order to examine whether Letter position dyslexia is domain-specific, and to assess the domain specificity of the visual analysis system, this study explored whether Letter position dyslexia extends to number reading, by testing whether individuals who have letter migrations in word reading also show migrations while reading numbers. The reading of words and numbers of 12 Hebrews-peaking individuals with developmental Letter position dyslexia was assessed. Experiment 1 tested reading aloud of words and numbers, and Experiment 2 tested same-different decisions in words and numbers. The findings indicated that whereas the participants with developmental Letter position dyslexia showed a large number of migration errors in reading words, 10 of them read numbers well, without migration errors, and not differently from the control participants. A closer inspection of the pattern of errors in words and numbers of two individuals who had migrations in both numbers and words showed qualitative differences in the characteristics of migration errors in the two types of stimuli. In word reading, migration errors appeared predominantly in middle letters, whereas the errors in numbers occurred mainly in final (rightmost) digits. Migrations in numbers occurred almost exclusively in adjacent digits, but in words migrations occurred both in adjacent and in nonadjacent letters. The results thus indicate that words can be selectively impaired, without a parallel impairment in numbers, and that even when numbers are also impaired they show different error pattern. Thus, the visual analyzer is actually an orthographic-visual analyzer, a module that is domain-specific for the analysis of words.


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