The results from the experiments reported in Chapters 4 and 5 seem to be well explained in terms of the concept of an articulatory loop (Baddeley & Hitch, 1974). Normal children show increases in memory span with age that are closely related to corresponding developmental increases in speech rate. Speech rate is seen as an index of the speed with which information can be rehearsed within the articulatory loop. In normal children of different ages there is a close quantitative relationship between how quickly words can be spoken and how well they are recalled. This relationship is particularly important because it offers an explanation for differences between both materials and subjects of different ages. Indeed, even within an age group, differences in speech rate correlate quite well with individual differences in memory span (e.g. Baddeley et al., 1975; Standing et al., 1980).