Lost for words: investigating specific language impairments

Centred around her lifelong interest in language development, Professor Mabel Rice, of the University of Kansas, studies children who struggle to learn and develop their native language. Her investigations into the genetic and neurological elements of language acquisition have important implications for speech and language intervention methods and, ultimately, the quality of life of those for whom language is an everyday challenge.

Learning your native tongue is a skill that many develop without really thinking about it. But, for those with a Specific Language Impairment, learning this skill can take a lot longer. Luckily, Professor Mabel Rice’s research is currently shedding light on this area of research, and her lifelong fascination with language acquisition has seen her dedicate her career to understanding how children learn and develop language.

© Steve Puppe

In her early work, Professor Rice encountered children who struggled with simple tasks such as describing the colour or size of objects. It was these encounters that motivated Professor Rice to carry out further research into delayed language development. Ultimately, her research aims to broaden our understanding of why some children struggle to learn their native language, while for most children, the world over, this learning process happens automatically.

The art of communication
Children who are late to acquire language without an obvious reason for the delay, such as hearing loss or other developmental delays, are said to have Specific Language Impairment (SLI). Children with SLI have difficulties picking up, processing and interpreting language, and their overall language level (i.e., vocabulary size and ability to generate complete sentences) remains below the expected level throughout adolescence and adulthood. Subsequently, those with SLI often experience further complications, such as reading impairment, as well as significant challenges in their social, academic, personal and professional lives. Evidence suggests that SLI is heritable, and Professor Rice studies the genetics and neural pathways of children with SLI and their families, in twins as well as single-born children.

Professor Rice’s research aims to broaden understanding of why some children struggle to learn their native language, whilst for most children, the world over, this learning process happens automatically

Early identification of SLI
Professor Rice’s lab at the University of Kansas takes a comprehensive and unique approach to their research, with an emphasis on the identification of a grammar marker, indicating the presence of SLI in preschool children. One important finding from her research has been that children with SLI particularly struggle within the domain of tense and agreement marking. This discovery led Professor Rice and her team to develop the Test of Early Grammatical Impairment (TEGI) and other experimental grammatical judgement tasks that can be used to identify young people with a history of SLI. In addition, the lab was also the first to discover that vocabulary deficits are more likely to persist later into adolescence in girls than boys. This finding has strong implications for how adolescent girls with SLI can be identified and supported.

Unique longitudinal data
Professor Rice is currently involved in a long-term collaborative project that studies the genetics and epigenetics (traits that are inherited, but not through DNA) of SLI. Four previous funding rounds have created a unique ongoing empirical archive of data comprised of 5000 children and their families. When these children reach adulthood, Professor Rice studies their children, providing a unique, multi-generational perspective on SLI. Using this data, the study has three principal aims: firstly, to document how language, speech and reading abilities develop over time for children with SLI in comparison to their unaffected peers; secondly, to conduct family-based candidate gene investigations to identify the gene networks involved in language impairment; and, lastly, to carry out brain imaging studies to understand the neuroanatomy of language processing in children with and without SLI.

For children with SLI, findings from this ongoing study show a consistent pattern of a delayed onset of language and language development on a parallel growth trajectory, but at lower performance levels to those without SLI. These lower levels persist through adolescence and are often accompanied by reading impairments. Family-wide investigations have found elevated rates of affectedness in family members. Related genetic studies suggest that it is a set of genes known to influence the development of the central nervous system that is responsible for language, speech and reading impairments. The continuation of this study will allow Professor Rice and her collaborators to expand on these findings, with the hope of ultimately identifying the components of the brain that can provide the missing link between DNA and the characteristics of how an individual learns and develops language.

Children with Specific Language Impairment have difficulties picking up, processing and interpreting language, and their overall language level remains below the expected level throughout adolescence and adulthood

Strong partnerships
Professor Rice also directs a study of twins, in collaboration with colleagues in Perth, Western Australia, that investigates how SLI manifests in twins. These two parallel longitudinal studies allow for a unique opportunity to investigate the extent to which SLI can be attributed to genetic variation, known as heritability. With data from 2,000 twin children, the study has provided the first robust empirical evidence that demonstrates delayed language acquisition in twins, in comparison to singleton children. Twins have comparatively delayed language skills at 24 months, with the gap reducing at four and six years, suggesting that twins are able to catch up from an initially delayed start. Furthermore, the study found SLI to have relatively high heritability in twins and, as found in previous studies, this heritability increases with age. This finding essentially suggests that, for SLI, an individual’s underlying genetic makeup exerts increasingly more influence than the environment, as age increases.

It’s all in the detail
To investigate in more detail the influence of genetics on SLI, Professor Rice is currently collaborating with geneticists from multiple universities worldwide. These collaborations are exploring the genetics behind high-level cognitive abilities such as language and how delayed language development is transmitted genetically through families. Genetic studies in Professor Rice’s lab have documented growth curves for children with and without SLI. The similarities and differences between these curves have led to the hypothesis that malfunctioning inherited cell-level timing mechanisms could be responsible for how SLI develops and manifests throughout childhood, adolescence and into adulthood.

Communication is key
One of the overriding objectives that persists throughout all of Professor Rice’s research is the dissemination of research findings to those working practically with SLI children. Providing accessible information on SLI will help teachers and medical practitioners to appreciate which children are different, allowing them to better plan for their specific needs. The research outcomes will also aid clinical intervention methods not only in language-related impairments but also associated disabilities, such as autism and intellectual impairments. The ongoing work of Professor Rice and her team will make a great difference to children with language impairments whose differences are often misunderstood and under-provided for. Although Professor Rice and her team have already made great progress in this field, there is still some way to go before SLI can be fully understood. However, the future looks promising and, in the words of Professor Rice herself: “We’re dedicated to doing it.”