Phonological and visuo-spatial working memory in individuals with intellectual disability.

Differences in the storage and rehearsal components of the phonological loop and visuo-spatial sketchpad were investigated in individuals with and without intellectual disability matched on memory span. The group with intellectual disability had specific difficulty in the rehearsal component of the phonological loop, as demonstrated by a weak word length effect compared to the group without intellectual disability. Groups did not differ in the storage component of the phonological loop as indexed by the phonological similarity effect. Also, groups did not differ in the storage or maintenance components of the visuo-spatial sketchpad, having comparable visual similarity and visual complexity effects. However, visual complexity task performance suggested that some aspects of visual processing surpass developmental level expectations for individuals with intellectual disability.