Lexical learning by children with specific language impairment: effects of linguistic input presented at varying speaking rates.

The purpose of this study was to investigate the impact of speaking rate variations in the linguistic input provided to children during a novel word learning task. Thirty-two school-age children participated in this investigation, including 16 children with specific language impairment (SLI) and 16 normal language (NL) controls matched on mental age (MA). The younger half of the NL group also served as a vocabulary level comparison for the older half of the children with SLI. No significant rate effects were found for comprehension of novel words, with all children performing at relatively high levels of accuracy. The group with SLI demonstrated the same recognition accuracy pattern as MA matched controls for target labels versus phonetically similar/dissimilar foils only for words trained at slow rate. Rate effects were most pronounced for items with the highest difficulty level, namely production of novel words. Children with SLI produced significantly fewer words that had been presented at fast rate during training than NL children matched on mental age or vocabulary level. Individual differences and production error patterns on fast rate items were examined. The finding that variations in speaking rate had a disproportionate impact upon word learning for children with SLI was interpreted within a framework of limited processing capacity.