Michael Daller – University of Reading, Institute for English Language and Applied Linguistics

A major focus of research on bilinguals has been the question whether bilingualism leads to cognitive advantages or disadvantages. Earlier research identified disadvantages, whereas recent research finds enhanced executive control in bilinguals (Kroll and Bialystok, 2013). However, the findings are inconclusive overall (see Daller and Ongun, 2017). An influential theoretical framework in this context is the threshold hypothesis (Cummins 1976 et passim), which assumes that a certain level of proficiency in both languages has to be achieved to ensure cognitive advantages. Cummins also emphasizes the importance of support for the first language (L1) of bilingual children; in the recent discussion also known as the heritage language. However, this framework has not been fully operationalised and an important aspect of the bilingual experience has not been taken into account: the role of parental support for the first language. In the present paper I compare two studies in two different bilingual settings. The first study investigates vocabulary knowledge and non-verbal intelligence of sequential Turkish-English bilingual children (aged 7 -11) in the UK from parents with a high socio-economic status. For these children parental support for L1 leads to comparable vocabulary scores and even higher non-verbal IQ scores when compared with age matched monolingual peers. The second study investigates a similar age group of Turkish-German bilinguals from a lower socio-economic status in Germany with less parental support for the heritage language. This study identifies clear vocabulary gaps in both languages when compared with monolinguals from a similar socio-economic background. Overall, I come to the conclusion that there is no bilingual advantage or disadvantage per se, but that a more fine-grained picture can be drawn when parental support for L1 is taken into account. The findings of both study have significant political and educational implication for the support of the heritage language in bilingual children.


Cummins, J. (1976). The influence of bilingualism on cognitive growth: a synthesis of research findings and explanatory hypotheses. Working Papers on Bilingualism 9, 1 – 43.

Daller, M., & Ongun, Z. (2017/ first view). The Threshold Hypothesis revisited: Bilingual lexical knowledge and non-verbal IQ development. International Journal of Bilingualism,1367006917690835.

Kroll, J. F., & Bialystok, E. (2013). Understanding the consequences of bilingualism for language processing and cognition. Journal of Cognitive Psychology, 25(5), 497-514.