Verbal short-term memory span in speech-disordered children: implications for articulatory coding in short-term memory.

One influential explanation of the development of verbal short-term memory in children argues that short-term memory capacity is a direct function of speech rate. This theory predicts that children with pathologically slow speech will show reduced verbal short-term memory capacity and will show less evidence of speech-base coding on verbal memory tasks. To test this prediction, verbal short-term memory span was assessed using a task that did not require a verbal response in 37 speech-disordered children and 37 age- and sex-matched controls (age range 4-15 years). The speech-disordered group had a significantly lower short-term memory capacity, a smaller word length effect, and reduced speech-motor activity during rehearsal periods. Covariance analyses revealed that these differences were not a function of general intellectual or motor speed differences between the groups, and that speech rate as a covariate abolished group differences in short-term memory. These results suggest that speech rate may be a causal determinant of verbal short-term memory capacity.