Testing two different models of verb-marking error in children with Developmental Language Disorder and language-matched controls. (1)
List, C., Ambridge, B., Lieven, E. & Pine, J.M., (2017). Testing two different models of verb-marking error in children with Developmental Language Disorder and language-matched controls. Paper presented at the 3rd annual LuCiD conference, Lancaster, UK.
The aim of this study was to test two different models of the pattern of verb-marking error in German-speaking children with Developmental Language Disorder (DLD) and languagematched controls. According to the (Extended) Optional Infinitive ((E)OI) Hypothesis (Wexler, 1994; Rice et al., 1995), children’s verb-marking errors reflect a stage in which their grammars allow non-finite forms (e.g. ‘build’) in contexts in which finite forms (e.g. ‘builds’) are required — a stage which extends higher up the MLU range in children with DLD. According to the Dual-Factor Model (Freudenthal, et al., 2007, 2015), children’s verb-marking errors reflect the learning of non-finite forms from compound-finite constructions (which, in German, take the form ‘He can a house build-INF’), and to default to high-frequency nonfinite forms in simple-finite contexts — with children with DLD being more likely to default than typically developing children. In order to test these models, a verb-elicitation experiment was designed and conducted with a group of 50 German-speaking children with DLD and a group of 50 language-matched controls. This study involved eliciting a range of verbs that differ in the relative frequency with which they occur in finite and non-finite form in two conditions: a simple-finite condition (e.g. ‘Lisa builds a tower. Peter …’) and a compound-finite condition (e.g. ‘Peter can a house build-INF. Lisa …’). An example context from the elicitation task is given in Figure 1. The participants also completed a battery of linguistic and non-verbal IQ tests to establish that they met the criteria for inclusion in the study. The critical predictions of the study were that a) children with DLD would make more OI errors than language-matched controls, particularly in simple-finite contexts (EOI Hypothesis) and b) both groups would make more OI errors in compound-finite than in simple-finite contexts (Dual-Factor Model). In order to test these predictions the rates at which the children produced correct responses (as opposed to OI errors) were entered into a 2x2 Mixed ANOVA, where the between-groups factor was Group (DLD, TD) and the within-groups factor was Condition 25/05/2017 (Simple-Finite, Compound-Finite). The results, which are plotted in Figure 2, show a significant main effect of condition, with higher rates of correct responses in simple-finite contexts and no significant main effect of group. However, there was a marginally significant Condition x Group interaction, which reflected the fact that the DLD group performed better than the TD group in the compound-finite condition. These results count against the EOI Hypothesis, since they fail to show higher rates of OI errors in DLD children than in language-matched controls. On the other hand, they are broadly consistent with the Dual-Factor Model, since they show higher rates of OIs in the compound-finite than the simple-finite Condition. A stronger test of the Dual-Factor Model would be to investigate whether it is possible to predict children’s tendency to produce OI errors on a verb-by-verb basis in terms of the relative frequency with which verbs occur in infinitive and finite form in German child-directed speech. Further analysis (using mixed effect models) will address this question.