Klinefelter syndrome (KS) is a sex chromosome abnormality associated with male infertility and mild cognitive deficits. Individuals with KS have been reported to have impaired verbal ability, as well as deficits in executive function. To further understand the nature of their deficits, we assessed specific elements of frontal lobe function such as working memory and relational reasoning. Men with KS exhibited a deficit in a transitive inference task in which participants ordered a set of names based on a list of propositions about the relative heights of the people named. This deficit was present even for items in which the propositions were given in order, so a chaining strategy could be used. Men with KS are also impaired on the n-back task, which uses letters as stimuli. In contrast, these men performed as well as controls in nonverbal reasoning (Raven's Progressive Matrices). These results suggest that men with KS have intact nonverbal reasoning abilities, but that a difficulty in encoding verbal information into working memory may underlie their executive and linguistic impairments. (JINS, 2003, 9, 839–846.)
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