Statistical word learning in Catalan-Spanish and English-speaking children with and without developmental language disorder.

BACKGROUND: A growing body of work shows that children with developmental language disorder (DLD) perform poorly on statistical word learning (SWL) tasks, consistent with the predictions of the Procedural Deficit Hypothesis that predicts that procedural memory is impaired in DLD. To date, however, SWL performance has not been compared across linguistically heterogeneous populations of children with DLD. AIMS: To compare SWL performance in a group of age, sex and non-verbal IQ-matched Catalan-Spanish and English-speaking children with and without DLD. METHODS & PROCEDURES: Two cohorts of children: (1) 35 Catalan-Spanish-speaking children with DLD (Mage = 8;7 years) and 35 age/sex-matched typical developing (TD) children (Mage = 8;9 years), and (2) 24 English-speaking children with DLD (Mage = 9;1 years) and 19 age/sex matched TD controls (Mage = 8;9 years) completed the tone version of a SWL task from Evans et al. (2009). Children listened to a tone language in which transitional probabilities within tone words were higher than those between words. OUTCOMES &
RESULTS: For both Catalan-Spanish and English cohorts, overall performance for the children with DLD was poorer than that of the TD controls regardless of the child's native language. Item analysis revealed that children with DLD had difficulty tracking statistical information and using transitional probability to discover tone word boundaries within the input. For both the Catalan-Spanish and English-speaking children, SWL accounted for a significant amount of unique variance in Receptive and Expressive vocabulary. Likelihood ratio analysis revealed that for both Catalan-Spanish and English cohorts, children having performance ≤ 45% on the SWL task had an extremely high degree of likelihood of having DLD. The analysis also revealed that for the Catalan-Spanish and English-speaking children, scores of ≥ 75% and ≥ 70%, respectively, were highly likelihood to be children with normal language abilities. CONCLUSIONS & IMPLICATIONS: The findings add to a pattern suggesting that SWL is a mechanism that children rely on to acquire vocabulary. The results also suggest that SWL deficits, in particular when combined with other measures, may be a reliable diagnostic indicator for children with DLD regardless of the child's native language, and whether or not the child is bilingual or monolingual. WHAT THIS PAPER ADDS: What is already known on the subject Although there is some disagreement, a small but growing body of work suggests that deficits in procedural memory, as measured either by motor sequencing (Serial Reaction Time-SRT) or SWL tasks, may be part of the deficit profile of children with DLD. To date, studies have not examined SWL across linguistically heterogeneous populations of children with DLD to determine if it is a unique clinical marker of the disorder. What this paper adds to existing knowledge The results show that children with DLD, regardless of their native language, or whether the child is bi- or monolingual, have difficulties on SWL tasks, and that these deficits are linked to severity of the language disorder. Taken together, these results indicate that procedural memory deficits may be a core feature of DLD. This suggests that statistical-learning tasks using tone stimuli can also advance our understanding of statistical-learning abilities in children with DLD more globally. What are the potential or actual clinical implications of this work? The current study shows that statistical-learning tasks using tone stimuli can be used in conjunction with standardized assessment measures to differentiate children with DLD from children with typical language ability.