Developmental Language Disorder—a Language Specific Disorder or a Domain General Disorder?
By Annika Andersson, Hanna Lindfors & Kristina Hansson
Annika Andersson, Linnaeus University, Department of Swedish, Växjö, Sweden, Linnaeus University Language Processing Lab, LiLa-lab
Hanna Lindfors, Linnaeus University, Department of Swedish, Växjö, Sweden
Kristina Hansson, Lund University, Department of Clinical Sciences, Lund, Logopedics, Phoniatrics and Audiology, Sweden
Developmental language disorder (DLD; prior called specific language impairment, (Bishop et al., 2017) is one of the most frequent childhood disorders. Efficient intervention requires that we understand the underlying nature of the disorder. In this paper we will present our ongoing study of children with DLD that has been made possible by the Marcus and Amalia Wallenberg Foundation. Our hypothesis is that the underlying deficit in DLD is not domain specific, (i.e., affects language only) but rather domain general and as such relates to general cognitive mechanisms. If results from our study confirms our hypotheses this could affect how interventions for children with DLD should be developed and designed.
The prevalence of DLD is 3-9% depending on age and criteria (Norbury et al., 2016). Children are diagnosed with DLD when they do not develop language as expected, compared to their peers, in spite of normal hearing and typical development in other respects (Bishop, et al., 2016; Bishop et al., 2017; Leonard, 2014). Their language difficulties are persistent and can limit their participation in both social relations and education (Bishop et al., 2017). Different theories have been put forth to explain the underlying deficit. It is not until we understand the reasons for DLD that we can successfully help these children to develop their language proficiencies, so that they can reach optimal success in education, and attain a rich and broad social life.
While some researchers have proposed difficulties with grammatical operations such as required to formulate relative clauses (van der Lely, 1998), finite forms of verbs (Rice, Wexler, & Cleave, 1995), or agreement between different words (Clahsen, 1989) others have proposed that the deficit is due to domain general cognitive mechanisms, such as reduced speed of processing or memory capacity limitations (Bishop, 1994; Gathercole & Baddeley, 1990; Kail & Salthouse, 1994; Leonard, McGregor, & Allen, 1992; Montgomery, 2002). Our study aims to explore this further and may even give us an answer to the question of domain specificity or domain generality of the disorder.
The research team consists of a PhD student with a degree in speech and language pathology and close to 10 years of experience working with children with DLD, one associate professor and specialist in DLD, and the principal investigator with a degree in psychology (cognitive neuroscience) and who is a specialist in language acquisition, along with national and international collaborators in the US and the Netherlands. With our collected broad knowledge of the disorder, of language acquisition, and language processing as recorded with electroencephalogram (EEG) in the form of event-related potentials (ERP) we will pursue this aim.
With ERPs we can record how the brain processes language millisecond by millisecond by putting a cap with electrodes on the participants head while s/he is listening to sentences or looking at pictures or movies. Thus, we can listen in what is happening in the brain just as a stethoscope listens to the beats of the heart. Besides being online and a temporally sensitive measure it does not require active responses. In prior studies comparing adults’ and children’s processing of rhyme with ERPs and their timed judgment of rhyming it was found that adults were better at judging word pairs as rhyming or nonrhyming and they did so faster than 6-8-year old children (Coch, Grossi, Coffey-Corina, Holcomb, & Neville, 2002). However, when the ERP effects were compared there were no differences between the adults and children. It is likely that adults are more familiar with the concept of rhyming and have faster reaction times than children although there is no difference in how their brains process words that rhyme or do not rhyme. This study speaks to the advantage of using ERP measurements when comparing groups that typically differ in how well they can perform on tasks, such as e.g., language proficiency tests.
From previous studies comparing children with DLD and children with typical language development (TLD) we know that children with DLD rely on other neural generators to process spoken language than do children with TLD (e.g., Neville, Coffey, Holcomb, & Tallal, 1993). What we want to know now is if there are differences also in how these groups process visual narratives. The narratives will be presented as images from a comic strip (Peanuts). Numerous studies by our colleague Neil Cohn at Tilburg University show how this “visual language” (comic strips with no text) is processed similarly to spoken or written language by adults (e.g., Cohn, Jackendoff, Holcomb, & Kuperberg, 2014; Cohn & Kutas, 2015, 2017; Cohn, Paczynski, Jackendoff, Holcomb, & Kuperberg, 2012). Results from our pilot study (Andersson, Cohn, Blomberg, & Hansson, 2019; Hansson, Blomberg, Cohn, & Andersson, 2019) suggest children with TLD, as do adults, process visual language similarly to a spoken language. But how do children with DLD process this visual language?
Our working hypotheses is that children with DLD have a domain general disorder that will affect how their brains’ process not only spoken language but also visual language or visual narratives if you like. If we are correct, then the results from our study where we present spoken language will 1) replicate findings of differences in processing of spoken language for children with DLD compared to children with TLD, and crucially 2) will find similar group differences in processing of visual language. This would indicate that DLD is indeed a domain general disorder and should be treated as such, which would affect how future interventions are developed and designed. We hypothesize that the disorder becomes more apparent in language, which we use frequently and cannot avoid using, while it is not as noticeable in other domains where difficulties may be circumvented more easily.
If you recognize the need for this research and would like to be part of this study, help us recruit participants (10-12-year olds with TLD or DLD), or if you have questions regarding the study please contact us.
Annika Andersson, Linnaeus University, Trummenvägen, SE-351 95 Växjö, Sweden, Ph.: +46 470 767434. Email: firstname.lastname@example.org
If you interested in our research of developmental language disorder (DLD) as a domain specific or domain general disorder, if you would like to be part of our study, or help us recruit participants (10-12-year olds with typical language development or with DLD), or if you just have questions regarding the study please contact us by email (email@example.com).
Andersson, A., Cohn, N., Blomberg, F., & Hansson, K. (2019). The first step to study neurophysiological processing of visual and verbal language in children with developmental language disorder. Paper presented at the the 40th annual Symposium on Research in Child Language Disorders, Madison, Wisconsin.
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