Inference deficits in women with Fragile X Syndrome: A problem in working memory.

Inferential processing and its component processes-working memory and set shifting-were examined in women with Fragile X Syndrome (FXS), in an attempt to understand the language phenotype of FXS and to better understand discourse processing by examining which components are affected by a biological breakdown. Participants read short passages and answered both factual and inference questions, and performance was correlated with neuropsychological measures of working memory and set-shifting. Three groups of nonretarded women were examined: (a) 12 women with FXS who carry the full mutation; (b) 22 women who carry the premutation; and (c) 16 women without the fragile X mutation. The results show that full mutation women do more poorly on both factual and inference questions. They do not appear to have a specific deficit in inferencing, however, because even though they do worse on inference questions than on factual questions, they do no worse, proportionately speaking, than the comparison groups. Analysis of the types of errors indicates that what underlies their poor performance on this discourse task is a specific deficit in working memory; the working memory deficit appears to be due specifically to FXS and not just to lower IQ. The deficits in discourse and working memory are also shown to relate to molecular measures of the syndrome.