Abstract
This thesis examines the emergence and use of short-term memory (STM) strategies in children, with respect to the working memory model (Baddeley & Hitch, 1974). Of interest are the developmental shifts observed in the use of coding and rehearsal strategies. The questions addressed refer to the extent to which STM development is affected by contextual factors, namely language characteristics or limitations in processing speed; how these factors affect the use of strategies; and how fixed, time- related factors (e.g. articulation rate, item length) interact with the maturation of strategies to determine STM capacity. It is suggested that children are able to use, or learn to use, STM strategies flexibly to adapt to such contextual factors. This affects the patterns of STM performance observed at different ages. To explore this suggestion, a cross-linguistic study was conducted. Greek and English children were compared, as Greek words are on average longer than English words. The question addressed was whether this difference would be reflected in the patterns of STM performance of the two language groups. A study on STM in children with Down syndrome was also conducted, to explore how limitations in verbal abilities affect STM and strategy use. Greek and English children aged 4 to 10 years were compared on a number of STM tasks. Dissociations between visuo-spatial and verbal tasks and effects of phonological similarity, visual similarity, and word length on recall of spoken words and pictures were examined. The developmental patterns of STM performance in the two language groups differed in the chronology of their emergence. Greek children relied on visual coding for longer than English children, who showed a shift towards a preference for verbal coding at an earlier age than Greek children. Children in both language groups seemed able to use strategies flexibly according to the length of the items to be remembered. Native language and differences in literacy acquisition were considered as possible causal factors for these differences. The study of STM development in children with Down syndrome suggested a preference for visual coding in STM tasks. Children with Down syndrome may rely more on visual strategies, but they should be taught how to benefit from them in STM tasks.