Acoustic and phonological processes in Williams Syndrome: A systematic review and meta-analysis

This meta-analysis focuses on acoustic, phonetic and phonological aspects of language processing in Williams syndrome (WS), a rare neurodevelopmental genetic disorder. Based on N = 51 papers, we aimed at identifying the status of these languages processes in WS relative to different types of control groups and we examined possible sources of variability of results through moderator analyses. At the acoustic level, evidence for hearing loss and impaired acoustic discrimination was observed. At the phonetic and sublexical phonological level, results were inconclusive due to limited literature. At the metaphonological level, WS individuals demonstrated better phonological awareness than nonverbal age-matched peers but performed below typically developing (TD) peers matched for verbal mental age. For phonological working memory WS performed worse than mental age matched TD peers but outperformed participants with other disabilities. At the lexical phonological level, WS demonstrated better phonological fluency skills than younger mental age matched peers. A wide range of heterogeneity was observed (I²=0-92.26 %). In some cases, the heterogeneity was partly explained by differences in control groups, but the largest part of heterogeneity could not be accounted for by the moderator variables included in the analysis. Future research needs to address sublexical phonological levels, to consider developmental trajectories and WS group variability, and to examine how impaired acoustic processes impact linguistic processes.