The Sensitivity of Children with SLI to Phonotactic Probabilities During Lexical Access

The procedural deficit hypothesis (Ullman & Pierpont, 2005) has been proposed to account for the combination of linguistic and nonlinguistic deficits observed in specific language impairment (SLI). According to this proposal, SLI results from a deficit in procedural memory that prevents children from developing sensitivity to probabilistic sequences. We tested the ability of children with SLI to rely on a specific type of probabilities characterizing sequences that occur in a given language: phonotactic probabilities. Twenty French-speaking children with SLI (M = 10;1), 20 typically developing children matched for chronological age (M = 10;0) and 20 typically developing children matched for receptive vocabulary (M = 7;4) performed an auditory lexical decision task. Pseudoword stimuli were built with combinations of either frequently associated phonemes (high phonotactic probability) or infrequently associated phonemes (low phonotactic probability). Phonotactic probabilities had a significant impact on the accuracy and speed of pseudoword rejection in children with SLI, but not in the two control groups. SLI children's greater reliance on phonotactic probabilities relative to typically developing children appears to contradict the PD hypothesis. Phonotactic probabilities may help them to partially overcome their difficulties in accessing the phonological lexicon during spoken word recognition.