Abstract
Specific Language Impairment (SLI) is an established term for a widely researched spectrum of difficulties specific/exclusive to language. Research into SLI has, over time, expanded from focusing on the language to understanding sub-serving cognitive capacities, and processes and to the underlying biology.
Specific language impairment: Current trends in research effectively provides the reader with a comprehensive overview of this contemporary cross-disciplinary field. The main questions can be largely summed up as addressing the linguistic nature of SLI in various languages and its non-linguistic dimension in relation to other disorders, in particular ADHD and dyslexia. To address these questions, the book contains a wide variety of works from connectionist or genetic modelling to experimental studies and literature reviews.
Nudel et al. provide a review of genetic research into SLI. This chapter reviews a line of research largely novel to SLI researchers relying on genetics and statistical probability. As such the basic experimental paradigms (i.e. linkage and association studies) are outlined. Several large-scale studies are reviewed concluding that SLI is related to a multitude of chromosomes which have also been implicated in other neurodevelopmental disorders such as autism and ADHD.
The overlap between SLI and dyslexia is assessed in the next chapters. Guasti et al. examine language in dyslexic children using an elicited production task. Their findings show lower accuracy of dyslexic children and a higher rate of relative clause omission. Half the children scored similarly to children with SLI: 1.5 standard deviations below the average of age-matched controls. Talli et al. address the issue using measures of language comprehension, reading and phonological awareness. Group comparisons and likelihood ratios suggest partial but not causal overlap between the two disorders. Reading impairments were predominantly related to children with dyslexia while listening comprehension and phonological short-term memory impairments were more evident in children with SLI. Wijnen et al. also assess the potential overlap with a longitudinal design and argue for a dissociation of the disorders. Children with a familial risk of dyslexia perform worse than controls but still outperform children with SLI on a number of language-related tasks. Language and literacy measures also correlated differently for the two atypical groups.
Novogrodsky discusses the large heterogeneity in the profile of SLI and the resulting subtypes of the disorder. A multitude of clinical markers of SLI and how localised weaknesses are dissociable are reviewed. Novogrodsky ultimately proposes that emphasis needs to shift from identifying markers of SLI for an entire population to markers for individual children. Consequently, tests accessing multiple areas of language and deficit-driven intervention are called for.
Bavin’s chapter reviews research into children with SLI and memory limitations with a particular emphasis on working memory (WM). The chapter covers seminal models of WM and significant relevant studies suggesting an overall weakness in memory in SLI. Two studies addressing memory in comorbid SLI and ADHD or resolved late talkers are subsequently discussed. The latter do not indicate an additive effect from the comorbid disorder.
Karaminis and Thomas present results from an attempt to simulate language impairment using biology-driven artificial learning systems, each reflecting different domains in language: inflectional morphology, syntactic comprehension and syntactic production. The models involve fewer hidden layers and less salient phonological representation for impaired children. The successful results of the models are hence interpreted as evidence for a combination of general processing and perceptual deficits for the population in question. Processing cue weaknesses are assumed to be universal but result in different errors across languages as language-specific properties may alter the significance of each cue type.
Costa and Pratas’s study addressed SLI in relation to bilingualism using an elicited production task examining null/overt subject use in L1 and L2 typically developing and SLI Cape Verdean Portuguese. Bilinguals from both groups performed similarly and produced a high number of null subjects in stark contrast to the monolinguals.
Gavarró and Lite investigate quantification in Catalan SLI. Two truth value judgement tasks, one for the Catalan equivalent for the English ‘all’ and one for ‘each’ were used. Performance was found to improve with age and not be significantly different for children with SLI in relation to the age-matched controls on both tasks.
Hamann provides an extensive overview of the research into German L1 SLI. German morphosyntax, its acquisition and impairment in SLI are reviewed and related to other cross-linguistic findings. Hamann discusses linguistic accounts of SLI such as agreement deficit and the Extended Optional Infinitive Account (Clahsen, 1989; Rice, Noll, & Grimm, 1997 respectively). The weakness is argued not to lie in agreement but in a more general difficulty with complexity. The latter is then extended to a number of areas such as V2, wh-questions and subordinate clauses but also semantic weaknesses in children with SLI.
Varlokosta and Nerantzini examine past tense production in Greek, an area which has shown conflicting results in naturalistic data. Based on an elicited production task, they establish past tense formation as an area of weakness in Greek with no advantage of phonological saliency. Accuracy scores were lower for perfective forms and less frequent verbs. They hence claim that these findings are inconsistent with both the Surface Hypothesis and Extended Optional Infinitive Account.
Archibald reviews a series of theoretical accounts of SLI and discusses how these will impact decisions made by clinicians in treating the disorder. Archibald argues that interventions targeting deficits in working memory, procedural memory, statistical learning and executive functioning appear to have some effect but the effects may be differentiated depending on the domain addressed (e.g. verbal vs visual-spatial). Archibald advocates facilitating learning through enhancing quantity of input and quality of engagement therewith as well as basing teaching on the individual’s strengths.
There is no dearth of research into SLI. The term has been cited nearly 20,000 times the last 15 years (Bishop, 2014) and around 2000 times in the first 10 months of 2015 (Google search). Research on SLI has not only been ample but also multi-disciplinary; a Scopus search will reveal hundreds of papers in fields such as medicine, social sciences, health professionals, neuroscience, genetics, psychology and the arts and humanities.
It is this wealth of research that Specific language impairment: Current trends in research edited by Stavroula Stavrakaki selectively, coherently and successfully attempts to encompass. The book tackles the most central contemporary issues relevant to SLI with good quality and interesting works that are representative of the broader field. The inclusion of more work on bilingualism and/or executive functioning would be an asset to any future state-of-the-art review of SLI. Despite the wide range of issues covered, this book should be accessible to both experienced researchers in linguistics, psychology or speech and language therapy and postgraduate students, to whom it may be most valuable. The latter may use it as an initial stepping stone and inspiration into a broad area of interrelated research and therein lies the book’s greatest contribution.