Fine-tuning language discrimination: Bilingual and monolingual infants' detection of language switching.

The ability to differentiate between two languages sets the stage for bilingual learning. Infants can discriminate languages when hearing long passages, but language switches often occur on short time scales with few cues to language identity. As bilingual infants begin learning sequences of sounds and words, how do they detect the dynamics of two languages? In two studies using the head-turn preference procedure, we investigated whether infants (n = 44) can discriminate languages at the level of individual words. In Study 1, bilingual and monolingual 8- to 12-month-olds were tested on their detection of single-word language switching in lists of words (e.g., "dog… lait [fr. milk]"). In Study 2, they were tested on language switching within sentences (e.g., "Do you like the lait?"). We found that infants were unable to detect language switching in lists of words, but the results were inconclusive about infants' ability to detect language switching within sentences. No differences were observed between bilinguals and monolinguals. Given that bilingual proficiency eventually requires detection of sound sequences across two languages, more research will be needed to conclusively understand when and how this skill emerges. Materials, data, and analysis scripts are available at https://osf.io/9dtwn/.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech.

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

Building a collaborative Psychological Science: Lessons learned from ManyBabies 1.

The field of infancy research faces a difficult challenge: some questions require samples that are simply too large for any one lab to recruit and test. ManyBabies aims to address this problem by forming large-scale collaborations on key theoretical questions in developmental science, while promoting the uptake of Open Science practices. Here, we look back on the first project completed under the ManyBabies umbrella - ManyBabies 1 - which tested the development of infant-directed speech preference. Our goal is to share the lessons learned over the course of the project and to articulate our vision for the role of large-scale collaborations in the field. First, we consider the decisions made in scaling up experimental research for a collaboration involving 100+ researchers and 70+ labs. Next, we discuss successes and challenges over the course of the project, including: protocol design and implementation, data analysis, organizational structures and collaborative workflows, securing funding, and encouraging broad participation in the project. Finally, we discuss the benefits we see both in ongoing ManyBabies projects and in future large-scale collaborations in general, with a particular eye towards developing best practices and increasing growth and diversity in infancy research and psychological science in general. Throughout the paper, we include first-hand narrative experiences, in order to illustrate the perspectives of researchers playing different roles within the project. While this project focused on the unique challenges of infant research, many of the insights we gained can be applied to large-scale collaborations across the broader field of psychology.