Speech rate and the development of short-term memory span

Two experiments are reported which examine the effects of word duration on memory span in subjects of different ages. The same linear function relating recall to speech rate (assessed by the speed of repeating words) fits the results of subjects ranging in age from 4 years old to adulthood. It is concluded that developmental increases in short-term memory span can be explained in terms of increases in speech rate and that there is no evidence for an increase in short-term memory capacity. Analyses of the children's speech suggests that increases in speech rate with age reflect increases in the speed of articulation of individual words, rather than any change in the duration of pauses between successive words or changes in coarticulation between words.