Early bilingual experience is associated with change detection ability in adults

www.nature.com/scientificreports OPEN Early bilingual experience is associated with change detection ability in adults Dean D’Souza1*, Daniel Brady2, Jennifer X. Haensel3,4 & Hana D’Souza5 To adapt to their more varied and unpredictable (language) environments, infants from bilingual homes may gather more information (sample more of their environment) by shifting their visual attention more frequently. However, it is not known whether this early adaptation is age-specific or lasts into adulthood. If the latter, we would expect to observe it in adults who acquired their second language early, not late, in life. Here we show that early bilingual adults are faster at disengaging attention to shift attention, and at noticing changes between visual stimuli, than late bilingual adults. In one experiment, participants were presented with the same two visual stimuli; one changed (almost imperceptibly), the other remained the same. Initially, participants looked at both stimuli equally; eventually, they fixated more on the changing stimulus. This shift in looking occurred in the early but not late bilinguals. It suggests that cognitive processes adapt to early bilingual experiences. Experiences such as musical instrument and video game training are known to modify cognitive control processes1,2. So, claims that practising more than one language increases cognitive demands, and thus cognitive control, come as no surprise3. Because words in both lexicons are activated during language use4–6, it is possible that bilinguals rely on domain-general cognitive control processes to monitor and inhibit the activation of words in the non-target language when speaking7. This ‘bilingual advantage’ in cognitive control has even been reported in children as young as 7 months8. In Kovács and Mehler’s pioneering s tudy8, infants raised in bilingual homes inhibited a learned response, but infants raised in monolingual homes did not. However, 7-month-old infants do not produce words, so they do not need to inhibit words in one language in order to produce words in the other9. Moreover, when we tried to replicate Kovács and Mehler’s study but with a larger sample, we could not10. In our preregistered s tudy10, infants from bilingual homes did indeed inhibit the learned response—but so too did infants from monolingual homes. Furthermore, recent meta-analyses and reviews of the adult literature call into question the strength—or veracity—of the bilingual advantage. They suggest that the bilingual advantage is rare (found in only 14.7% of all comparisons), barely discernible (g < 0.12), and may altogether disappear when publication bias is taken into account11–14. Given these controversial findings, many researchers (e.g. Ref.14) argue that adaptations to language are specific to language rather than to cognition more generally. Does this mean that, unlike musicians versus non-musicians, we should not expect to find any (non-language) differences in the cognitive domain between bilinguals and monolinguals? We have argued that exposure to more varied, less predictable environments drive infants to minimise uncertainty by sampling more of their environment for supplementary visual i nformation9. Because the bilingual environment may be more varied and less predictable than the monolingual environment (see Ref.15 for discussion), we hypothesised that infants from bilingual homes would switch attention between visual stimuli more frequently, and more rapidly disengage attention from one stimulus in order to shift it to another, than infants from monolingual homes. Our data provided evidence in favour of both these h ypotheses10. But rather than label it as a ‘bilingual advantage’ as convention dictates, we suggested it was an adaptation to a particular set of constraints—i.e. to a more varied and unpredictable environment. It is not necessarily a lasting ‘advantage’, because constraints change over time. For example, an infant may rely on visual information (such as facial expressions, hand gestures, or lip movements) to disambiguate speech sounds, but an older child or adult could simply use sentential context or ask speakers for clarification. 1 Faculty of Science and Engineering, Anglia Ruskin University, Cambridge, UK. 2School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK. 3Department of Ophthalmology, Stanford University School of Medicine, Palo Alto, CA, USA. 4Centre for Brain and Cognitive Development, Birkbeck, University of London, London, UK. 5Department of Psychology & Newnham College, University of Cambridge, Cambridge, UK. *email: Scientific Reports | (2021) 11:2068 | https://doi.org/10.1038/s41598-021-81545-5 1 Vol.:(0123456789) www.nature.com/scientificreports/ If we should be looking for adaptations to particular sets of constraints, rather than searching for bilingual ‘advantages’ per se, it raises the question of whether the adaptations we found in early development (rapid attentional disengagement and more frequent attention-switching) are age-specific or persist through to adulthood. This is the focus of the current paper. We would like to know whether the early adaptations we found in infants can be found in adults. To this end, we administered the same tasks but to a different population: bilingual and monolingual adults. Our preliminary aim was to find out whether it is possible to detect a bilingual adaptation in adults: do bilingual adults, like bilingual infants, disengage attention faster and switch attention more frequently than their monolingual peers? But because we are particularly interested in whether the early adaptation persists through to adulthood (rather than reflecting a difference between bilingual and monolingual groups more generally), our primary aim was to investigate the effects of bilingual experience on attention. Specifically, we wanted to compare bilingual adults who (like the infants i n10) had been exposed to two or more languages from an early age with bilingual adults who had learned their second language much later in life. Methods We followed the same protocol as the one in the registered report10, but this time we compared bilingual and monolingual adults, and investigated the role of bilingual experience. Participants. Data were collected from 127 adults, of whom 92 were bilingual (mean age = 24.82 years, SD = 6.18, 69.6% women) and 35 were monolingual (mean age = 24.20 years, SD = 5.97, 69.7% women). The bilingual and monolingual groups did not significantly differ on either age (t(125) = 0.51, p = 0.614, d = 0.10) or gender (x2(1) < 0.01, p = 0.989). We also obtained from each participant a socioeconomic status (SES) score. The SES score was a composite score based on self-report measures of education and household income. The education score ranged from 1 (no formal education) to 7 (doctorate or equivalent). The household income score ranged from 1 (less than £14,000 per year) to 11 (over £120,00 (...truncated)