Abstract
Attention deficit hyperactivity disorder (ADHD) is commonly associated with deficits in executive functions executive functions (EF), but children with this disorder frequently demonstrate co-occurring morphosyntactic impairment when assessed using standardized tests. On the other hand, children with developmental language disorder (DLD), a population defined by impaired linguistic functioning, are often diagnosed with comorbid EF deficits. We investigated EF and morphosyntax in 60 French-speaking children aged six to 12: 20 with typical development (TD), 20 with ADHD, and 20 with DLD. To obtain an EF profile for the different cognitive groups, we used standardized tests to assess lower-order EF skills, (i) selective attention and (ii) short-term memory capacity, and higher-order EF skills, (i) working memory capacity and (ii) attention shifting. To test morphosyntax, we used (i) a standardized omnibus test that elicited a variety of complex structures and (ii) a more fine-grained probe test that assessed the production of third person object clitic pronouns, a clinical marker of DLD in French. Children with ADHD and DLD were associated with different EF and morphosyntactic profiles: children in the ADHD group demonstrated higher-order EF weakness and difficulty on the omnibus morphosyntax task, whereas children with DLD showed both lower- and higher-order limitations and struggled with both morphosyntax tasks. Our findings indicate that deficits in morphosyntax are not characteristic of ADHD but that the performance of children with ADHD can mimic morphosyntactic impairment when all-encompassing omnibus tests evaluating various and unpredictable structures are used. If morphosyntax is tested using reliable markers of atypical language development and external cognitive-load factors are optimally reduced, there are significant discrepancies in the observed ADHD-DLD outcomes. Clinical implications that include perspectives for the differential diagnosis of ADHD and DLD are discussed.
Highlights
Attention deficit hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder that affects roughly 5–7% of the population
Children with ADHD and developmental language disorder (DLD) have both been associated with executive functions (EF) and morphosyntactic weakness and differentiating the two populations is sometimes a challenge for practitioners involved in their evaluation (Redmond, 2005, 2016; Redmond et al, 2011)
The two aims of this study were (i) to compare the performance of typical development (TD) children, children with ADHD and children with DLD on various EF and morphosyntax tasks to see if similar profiles emerge in the clinical groups, and (ii) to investigate how children with ADHD perform on two different types of morphosyntactic measures, an omnibus test that assessed the production of a variety of unpredictable morphosyntactic structures and a more fine-grained probe test that assessed the production of structures containing a 3p object clitic pronoun
Summary
Attention deficit hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder that affects roughly 5–7% of the population. In what concerns EF abilities in children with ADHD and DLD, there is some evidence that both groups have difficulty executing tasks that require basic attentional processes, such as detecting and selectively attending to relevant stimuli. Richards et al (1990) found that the presence of ADHD in fourth-, fifth-, and sixth-grade students with learning difficulties led to an increase in the number of errors children made on a visual selective attention task in which they were asked to respond to a central stimulus that is flanked by distracting non-target stimuli. Similar results were reported by Shalev and Tsal (2003), who used a flanker task to show that younger children with ADHD (N = 5, M = 6;5) demonstrate impaired ability to selectively process relevant information by limiting visual attention to a restricted spatial area.
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