The influence of linguistic structure on memory span : repetition tasks as a measure of language ability

摘要

This thesis evaluated the extent to which long-term memory linguistic representations (syntactic, semantic, prosodic and lexical) affect immediate verbal repetition performance. The effects of these linguistic factors on short-term memory span were explored through an experiment with 140 English- and Czech-speaking participants. The experiment employed nine experimental conditions which varied the presence/well-formedness of linguistic information in four domains: the lexicon, morphosyntax, semantics, and suprasegmental phonology. This resulted in a spectrum of stimuli with semantically, syntactically and prosodically well-formed sentences with real lexical items at one end, through to a list of nonwords with lexical, semantic, prosodic and syntactic information removed. One hundred typically developing children (50 Czech- speaking; 50 English-speaking) aged 4-5 years and 40 adults (20 Czech-speaking; 20 English-speaking) participated in the study. In each condition, participants were asked to repeat blocks of successively longer stimuli to establish their maximum spans. The results were similar between age groups and across languages. Each linguistic factor had a significant effect on short-term memory span. The presence of nonwords and syntactic violations dramatically reduced memory span, while semantic implausibility and the removal of sentence prosody played a smaller yet significant role. Despite the typological differences between Czech and English, the same robust differences between conditions were found in both languages. The results provide further evidence that immediate verbal repetition is highly sensitive to the linguistic structures present in the stimuli. It is argued that theories which aim to account for data from immediate repetition should not be limited to lexical phonology but also need to address how syntactic, prosodic, semantic and lexical representations contribute to repetition performance. The findings of this thesis support the theoretical framework of verbal short-term memory emerging from a temporary activation of long-term memory representations and reinforce the view that language and memory are inextricable.