Involvement of short-term memory in complex mental calculation

The aim of this study was to examine the involvement of the short-term memo ry system in complex mental addition by manipulating the phonological and v isual similarity of two numbers to be added. The phonological similarity of the problems appeared to have a major effect on both speed and accuracy. H owever, the manipulation of visual similarity failed to have any measurable impact. This suggests that the phonological loop, rather than the visual-s patial sketch pad, would be used preferably for temporary storage of addend s. An interpretation of these results in terms of the nature of the interna l code underlying this task is discussed.