Theoretical implications of the hyperlexia syndrome: two new Italian cases.

Two Italian girls (ages 12.5 and 18.6) are reported in whom excellent reading and writing skills have developed against a background of severe mental retardation. The cases have poor short-term memory, very low verbal and performance IQs, and fail many traditional Piagetian tasks at the operational stage. They similarly fail many "metalinguistic" tasks that have been regarded as prerequisites for the development of adequate reading and writing skills. Despite these failures, the girls can accurately read aloud words, non-words, sentences, and texts. However, their comprehension of such material was poor, and consistent with the overall low level of cognitive functioning. What the cases do show, very clearly, is that reading and writing qua visual-to-auditory and auditory-to-visual transcoding tasks can develop independently of many other basic cognitive systems.