Short-term memory, articulation rate and subvocal rehearsal in Down's syndrome

Gathercole (1994) show that in normal young children there is no significant link between articulation rate and immediate memory span, but that these variables are closely related in adults. These results are in contradiction with the short-term memory development hypotheses stated by the working memory model. According to these hypotheses, children are sensitive to word-length effect providing that stimuli are presented auditorily. We also know that word-length effect is strongly related to articulation rate and to subvocal rehearsal. This conception of mnemonic development has been recently challenged. Some authors show that, in adults, word-length effect can be a consequence of the delay at recall. According to Gathercole, the same conclusion can be applied to results obtained with children : word-length effect can be due to delay at recall of long words rather than to the utilization of subvocal rehearsal. Previous studies seem to confirm this hypothesis by showing that children are not affected by articulatory suppression. These results have clear implications for the short-term memory development hypothesis. It seems that in spite an strong word-length effect, children do not rehearse during auditory memory span tasks. The following experiments are based: (1) on the assumption that mental retarded individuals do not rehearse and (2) on the highly significant word-length effect in our Down's syndrome subjects. Our hypothesis, as Gathercole's one, is that if subjects really rehearse, then memory span and articulation rate will be highly correlated.