Characteristics of dyslexia in a Dutch family.

This study investigates the characteristics of 19 members of a Dutch family. Nine of them, recognized as dyslexic in their early years, are compared with six non-dyslexic members, whereas four form a non-classified category. From their personal histories, it is clear that the dyslexics had a long and troublesome educational career, while the non-dyslexics did not. However, probably because the dyslexic members had considerable intellectual resources and talents in mathematics and technical skills, most succeeded in getting degrees of a reasonably high standard and jobs that more or less matched their talents. In cognitive terms, differences in non-word processing, independent of response mode (reading, spelling, oral repetition), and in speeded word reading suggest stable deficits in phonological processing and in task-specific automatization. The spelling of words was fairly accurate, possibly because compensatory strategies were used, also indicated by remarks of the dyslexic members. Outside the reading and spelling area, only small and non-significant differences appeared in tasks tapping verbal short-term memory, rapid naming and working memory. However, the predicted discrepancy between the conceptual and the sequential factor of the Wechsler intelligence test was shown by most dyslexics. Two of the four non-classified members of the family, who could not be classified as dyslexic because no early diagnosis was made, but had experienced learning problems at school, showed more or less the same characteristics, but were less successful at school and in society. In the discussion, the use of a family control group in studies with a large age range is recommended.