A Study of Inhibition in Preschool Children at Risk of Developmental Language Disorder

Abstract

Background: For many years, research and practice have noted the impact of the heterogeneous nature of Developmental Language Disorder (DLD - also known as language impairment or specific language impairment) on diagnosis and assessment. Recent research suggests the disorder is not restricted to the language domain and against this background, the challenge for the practitioner is to provide accurate assessment and effective therapy. The speech and language therapist (SLT) aims to support the child and their carers to achieve the best outcomes. However, little is known about the experiences of the SLT in the assessment process, in contrast to other childhood disorders, yet their expertise is central in the assessment and diagnosis of children with language disorder. The overall aims of the research were; firstly, to understand the issues in the diagnosis and assessment of children with language impairment and to synthesize the knowledge of SLTs working directly with children in this field; secondly, to investigate whether executive function abilities (i.e. inhibition and prospective memory) may be impaired in children at risk of developing DLD in the preschool period and thirdly, to investigate whether executive function tests correlate with a test of nonword repetition suitable for use with bilingual children. Study 1 aimed to gain an in-depth understanding of the experiences of speech and language therapists involved in the assessment and diagnosis of children with DLD including the linguistic and nonlinguistic aspects of the disorder. Three focus groups were used to provide a credible and rich description of the experiences of SLTs involved in the assessment of DLD. The analysis of the data showed three main themes relating to the SLTs’ experience in assessment and diagnosis of DLD. These themes were the participants’ experiences of the barriers to early referral, factors in assessment and the concerns over continued future support. These findings informed the design of Study 2 which compared the inhibition abilities of typically developing preschool children, with monolingual preschool children and bilingual preschool children who had already been referred to specialist language units and were therefore classed as “at risk” of developing DLD. Three inhibition tasks were used (motor inhibition, verbal inhibition and self-control) along with a prospective memory task and a nonword repetition test. The results indicated that children deemed “at risk” of DLD performed significantly worse than typically developing children on all tasks. Correlational analysis revealed significant relationships between the nonword repetition test and inhibition in the typically developing group but different relationships were seen in the “at risk” groups. For the monolingual at risk group the association was with nonword repetition and verbal inhibition but in the bilingual group, nonword repetition was associated with nonverbal inhibition. These findings suggest that inhibition deficits can be observed in children who are “at risk” of DLD but the nature of the deficit may differ in monolingual children compared to bilingual children. The results are discussed in terms of theory and implications for therapeutic practice.