Cognitive effects of developmental dyslexia in bilingual children in Scotland: an experimental approach to inform inclusive evidence-based assessment

Despite national statistics reporting over forty-thousand bilingual children in Scottish schools (National Statistics, 2018), bilingual experiences of DD are not represented in current education and public health assessment procedures, leading to mis- or under-diagnoses. For instance, if bilingual children show learning difficulties that fail to be appropriately assessed, these may be attributed to bilingualism, reinforcing the myth that bilingualism impairs children's language development (Barac and Bialystok, 2011; European Commission, 2018).
The majority of research on dyslexia was conducted by testing monolingual speakers and does not account for potentially differing factors for bilinguals. Studies show that bilingual children are likely to be good phoneme-grapheme decoders due to their experience of two different phonological systems resulting in enhanced phonological awareness (Bialystok, 1988; Gregory, 1996). This may mean that while phoneme-grapheme conversion deficits are predominantly seen in monolingual children with dyslexia (Snowling, 1980), DD in bilingual children may instead manifest in relation to different cognitive processes.
Executive control (EC) is a cognitive process that regulates a variety of activities, as it manages "the selection, initiation, execution, and termination" of multiple-task performances (Rubinstein et al, 2001:763). Executive functions are involved in the development of reading and comprehension skills, as they supervise reading speed, gaze duration and prioritisation of word identification over lexical access (Britton and Glynn, 2013). However, EC has remained largely unexplored in relation to dyslexia, and the few studies that investigated this correlation only did so in a monolingual context.
Research Questions
Given the role of EC in monolingual and bilingual processes, including literacy and comprehension skills, this research will implement EC tasks to explore and compare the performances of the participants. These results will be compared to decoding and speech production performances which are the predominant focus in current assessment paradigms. The research aims to answer the following questions:
1. Do the EC performances of bilingual children with DD differ from the performances of monolingual children with DD and of bilingual children with no learning difficulties?
2. Do the decoding performances of bilingual children with DD differ from the performances of the other groups?
3. Does an EC-based assessment for bilingual children identify deficits which go unnoticed in a decoding-based one?
4. Do bilingual children with DD outperform monolingual children with DD?
Methodology
Participants
The participants for this study will be children attending Primary 1-2 (aged 5-7). Within this age range, the children will be divided into three groups, namely (i) Italian/English bilingual children suspected of being affected by DD, (ii) monolingual children with assessed DD, and (iii) Italian/English bilingual children with no literacy or comprehension difficulties. In regard to bilingual proficiency, the study will consider children who were brought up speaking Italian and English from birth, to prevent largely unbalanced proficiency from skewing the results.
Experiments
The current study employs a series of EC experiments to probe for signs of DD and compare these results with those obtained from decoding-based tasks.
The groups' EC will be tested through quick naming-tasks (Meuter and Allport, 1999; Everatt et al, 2000), and task-switching tests (Rubinstein et al, 2001; Calabria et al, 2012).
To test decoding skills, the speech production of the groups will be analysed in reading and speaking tasks, such as reading and repeating real words and invented words of different syllable length to investigate phonemic deficits (Snowling, 1980; Snowling, 1981).