Bilingualism goes to school: The interplay of (extra)linguistic factors in successful bilingual development

Migration is making Europe increasingly multilingual, and the United Kingdom is committed to
promoting this linguistic diversity for reasons of cultural identity, social integration and cohesion
(Social Mobility Commission, 2022). Heritage languages are the minority languages spoken at
home in situations where these family languages are not a dominant language of the larger
society. For example, Polish, Punjabi, and Portuguese are widely spoken heritage languages in the
United Kingdom. In 2021/2022, close to 20% of school pupils (1.6M pupils) spoke a language
different than English at home (Department for Education, 2022). Speaking these languages at
home permit migrant children to maintain ties to their parents' country of origin and to their cultural heritage. At the same time, it is clear that successful integration also requires a high level
of proficiency in the majority language of society (English) (Hutchinson, 2018).
The key question, and one to be addressed in this PhD project, is how to promote the
development of both languages so that these multilingual citizens can make use of the
educational and professional opportunities resulting from an increasingly integrated Europe. In
addressing this question, we will work in close collaboration with a major non-academic
stakeholder, Portugal's Camões Institute, which, as one of Europe's leading institutions promoting
bilingual education, has a significant interest in understanding the factors that facilitate bilingual
development.
Several factors have been identified for successful bilingual development. These include
the age of acquisition, the amount of contact with the heritage language through different family
constellations, socioeconomic status, formal schooling, and explicit grammar instruction in the
heritage language (e.g., Bayram et al., 2021; Torregrossa et al., 2022). However, most studies
consider variables in isolation, which means that the interplay of critical factors and their impact
on bilingual language development are not fully understood. In addition, most studies observe the
effects of these factors on the acquisition of very specific aspects of the heritage language rather
than a broader range of language properties. Finally, most studies consider the heritage language
independent of the majority language. This is problematic as we need to study the conditions that
enable children to develop their two native languages, and this requires testing their competence
in both. The objective of the proposed PhD project is to significantly advance our understanding of
the factors that determine successful bilingual development by directly addressing these
shortcomings. First, rather than considering variables in isolation, we will examine the interplay of
the critical factors above in bilingual development. Second, rather than focusing on just one
domain of language, we will observe the development of three linguistic domains (lexicon,
morphology, syntax). And third, rather than observing the effect of these factors on just one
language, we will investigate their effect on both the heritage and the majority language. We will
focus on English-Portuguese bilingual development as a test case, but the insights from this PhD
project will apply to other language constellations.