A multi-metric analysis of 50,000 linguistic profiles provides sparse evidence that language distance modulates bilingual cognition

Bilingualism can be thought of as an intensive mental gym for language control. However, the moderators that underlie bilingual adaptations are a matter of ongoing investigation. Degree of similarity in mental, linguistic representations between the languages of a bilingual has been argued to differentially condition recruitment of control mechanisms and, as such, would embody a contributing factor to relevant neurocognitive adaptations. While ample evidence exists for this claim, its empirical coverage is limited because testing in cognitive science disproportionally represents communities that speak big, Indo-European languages, thus potentially providing a biased view of bilingual cognition. In this work, we assess the role of language distance as a key moderator of bilingual adaptations through a large-scale aggregation analysis of 510 experiments. To measure distance, we develop a multi-metric approach, using state-of-the-art databases, such as Grambank, and tapping into different levels of linguistic granularity. Aggregating data from 56,173 participants who speak 79 different languages, spanning 11 language families and a language isolate, we find sparse evidence for a distance effect at the population level. Certain language pairs stand out as promising hosts for bilingual adaptations, but their representation in the sample is not robust enough to enable strong conclusions, attesting to the need to employ more representative samples. Our results suggest that language distance is a complex variable that has the potential to address the perennial question of what makes bilinguals distinct.