Melanie Soderstrom

The ability to learn and apply rules lies at the heart of cognition. In a seminal study, Marcus et al. (1999) reported that 7‐month‐old infants learned abstract rules over syllable sequences and were able to generalize those rules to novel syllable sequences. Dozens of studies have since replicated that finding and extended it using different rules, modalities, stimuli, participants (human adults and non‐human animals) and experimental procedures. Yet questions remain about the generalizability of the core findings in Marcus et al., and sources of variation across these findings. In the current study, we address this issue by testing 839 infants (650 after exclusions) of a wide age range (5;0–12;0 months) in a multi‐laboratory (30 laboratories, [31 samples]) conceptual replication of the Marcus et al. study. This study and the analysis plan were submitted as a registered report. A mixed‐model analysis of the looking times at consistent versus inconsistent test trials indicated no significant effect. The current study therefore finds no evidence for rule‐learning; to the contrary, a Bayesian analysis of the data indicated strong evidence for a null effect. This was similarly the case for the moderating factors that were part of the design: mono‐ versus multilingualism, age, and experimental paradigm; none of these factors showed significant effects. Robustness analyses indicated that the results were not different in the case of different choices in the (pre‐)processing of the data. A follow‐up analysis for single labs indicated that there was no evidence of rule‐learning in 30 of the 31 contributed samples. The current finding raises fundamental issues about rule‐learning that are presented in the Discussion section.

This study examines variation sets (VS) – structured repetitions of words in different morphosyntactic contexts – in child-directed speech (CDS) compared to adult-directed speech (ADS) across two communities (Argentinian Spanish and North American English) and socioeconomic groups. Drawing on naturalistic recordings from 101 families, results show that VS are more frequent in CDS than in ADS. In Argentinian Spanish, they are more prevalent in middle socioeconomic status (SES) households, whereas no SES-related differences emerged in the North American sample. Across languages, they were often anchored in verbs. However, SES-related differences in lexical anchoring varied by community: in Argentinian middle-SES households, CDS includes more VS anchored in adjectives, whereas in middle-SES North American English households, noun-based VS were less frequent relative to verb-based VS. Findings indicate that linguistic typology – particularly the pro-drop versus non-pro-drop distinction – and socioeconomic context are associated with the lexical distribution and organization of repetition with variation in children’s everyday linguistic environments.

The ability to learn and apply rules lies at the heart of cognition. In a seminal study, Marcus et al.(1999) reported that 7-month-old infants learned abstract rules over syllable sequences and wereable to generalize those rules to novel syllable sequences. Dozens of studies have since replicatedthat finding and extended it using different rules, modalities, stimuli, participants (human adultsand non-human animals) and experimental procedures. Yet questions remain about thegeneralizability of Marcus et al.’s (1999) core findings, and sources of variation across thesefindings. In the current study, we address this issue by testing 839 infants of a wide age range(5;0-12;0 months) in a multi-laboratory (30 laboratories, [31 samples]) conceptual replication ofthe Marcus et al. (1999) study. This study and the analyses were submitted as a registered report.A mixed-model analysis of the looking times at consistent vs. inconsistent test trials indicated nosignificant effect. The current study therefore finds no evidence for rule-learning; to the contrary, aBayesian analysis of the data indicated strong evidence for a null effect. This was similarly thecase for the moderating factors that were part of the design: mono- vs. multilingualism, age, andexperimental paradigm; none of these factors showed significant effects. Robustness analysesindicated that the results were not different in the case of different choices in the (pre-)processingof the data. A follow-up analysis for single labs indicated that there was no evidence ofrule-learning in 30 of the 31 contributed samples. The current finding raises fundamental issuesabout rule-learning that are presented in Discussion.

A decade of ManyBabies research, testing thousands of babies across hundreds of labs, has shown that some, but not all findings in infant research replicate well. Collectively, these projects have shown us that our methods carry limitations that larger samples alone cannot resolve. Here we present three lessons that point toward a more reliable, inclusive developmental science.

A decade of ManyBabies research, testing thousands of babies across hundreds of labs, has shown that some, but not all findings in infant research replicate well. Collectively, these projects have shown us that our methods carry limitations that larger samples alone cannot resolve. Here we present three lessons that point toward a more reliable, inclusive developmental science. A decade of ManyBabies research, testing thousands of babies across hundreds of labs, has shown that some, but not all findings in infant research replicate well. Collectively, these projects have shown that current methods carry limitations that larger samples alone cannot resolve. Here three lessons that point toward a more reliable, inclusive developmental science are presented.

Evaluating whether someone's behavior is praiseworthy or blameworthy is a fundamental human trait. A seminal study by Hamlin and colleagues in 2007 suggested that the ability to form social evaluations based on third‐party interactions emerges within the first year of life: infants preferred a character who helped, over hindered, another who tried but failed to climb a hill. This sparked a new line of inquiry into the origins of social evaluations; however, replication attempts have yielded mixed results. We present a preregistered, multi‐laboratory, standardized study aimed at replicating infants’ preference for Helpers over Hinderers. We intended to (1) provide a precise estimate of the effect size of infants’ preference for Helpers over Hinderers, and (2) determine the degree to which preferences are based on social information. Using the ManyBabies framework for big team‐based science, we tested 1018 infants (567 included, 5.5–10.5 months) from 37 labs across five continents. Overall, 49.34% of infants preferred Helpers over Hinderers in the social condition, and 55.85% preferred characters who pushed up, versus down, an inanimate object in the nonsocial condition; neither proportion differed from chance or from each other. This study provides evidence against infants’ prosocial preferences in the hill paradigm, suggesting the effect size is weaker, absent, and/or develops later than previously estimated. As the first of its kind, this study serves as a proof‐of‐concept for using active behavioral measures (e.g., manual choice) in large‐scale, multi‐lab projects studying infants.

From early on, infants show a preference for infant-directed speech (IDS) over adult-directed speech (ADS), and exposure to IDS has been correlated with language outcome measures such as vocabulary. The present multi-laboratory study explores this issue by investigating whether there is a link between early preference for IDS and later vocabulary size. Infants’ preference for IDS was tested as part of the ManyBabies 1 project, and follow-up CDI data were collected from a subsample of this dataset at 18 and 24 months. A total of 341 (18 months) and 327 (24 months) infants were tested across 21 laboratories. In neither preregistered analyses with North American and UK English, nor exploratory analyses with a larger sample did we find evidence for a relation between IDS preference and later vocabulary. We discuss implications of this finding in light of recent work suggesting that IDS preference measured in the laboratory has low test-retest reliability.

We present an exploratory cross-linguistic analysis of the quantity of target-child-directed speech and adult-directed speech in North American English (US & Canadian), United Kingdom English, Argentinian Spanish, Tseltal (Tenejapa, Mayan), and Yélî Dnye (Rossel Island, Papuan), using annotations from 69 children aged 2–36 months. Using a novel methodological approach, our cross-linguistic and cross-cultural findings support prior work suggesting that target-child-directed speech quantities are stable across early development, while adult-directed speech decreases. A preponderance of speech from women was found to a similar degree across groups, with less target-child-directed speech from men and children in the North American samples than elsewhere. Consistently across groups, children also heard more adult-directed than target-child-directed speech. Finally, the numbers of talkers present in any given clip strongly impacted children’s moment-to-moment input quantities. These findings illustrate how the structure of home life impacts patterns of early language exposure across diverse developmental contexts.

Long-form audio recordings are increasingly used to study individual variation, group differences, and many other topics in theoretical and applied fields of developmental science, particularly for the description of children's language input (typically speech from adults) and children’s language output (ranging from babble to sentences). The proprietary LENA software has been available for over a decade, and with it, users have come to rely on derived metrics like adult word count (AWC) and child vocalization counts (CVC), which have also more recently been derived using an open-source alternative, the ACLEW pipeline. Yet, there is relatively little work assessing the reliability of long-form metrics in terms of the stability of individual differences across time. Filling this gap, we analyzed eight spoken-language datasets: four from North American English-learning infants, and one each from British English-, French-, American English-Spanish, and Quechua-Spanish-learning infants. The audio data were analyzed using two types of processing software: LENA and the ACLEW open-source pipeline. When all corpora were included, we found relatively low to moderate reliability (across multiple recordings, intraclass correlation coefficient attributed to the child identity (Child ICC), was <50% for most metrics). There were few differences between the two pipelines. Exploratory analyses suggested some differences as a function of child age and corpora. These findings suggest that, while reliability is likely sufficient for various group-level analyses, caution is needed when using either LENA or ACLEW tools to study individual variation. We also encourage improvement of extant tools, specifically targeting accurate measurement of individual variation.

In recent years, psychological researchers have been heavily criticized for generalizing broadly from narrow samples, a concern that intersects with questions about the validity, reproducibility, replicability, and generalizability of the psychological literature. One issue is the limited reporting of participants’ identities, backgrounds, and lived experiences. To address this issue, several journals have begun to require greater reporting of participants’ sociodemographic information. In this article, we address both challenges and considerations with respect to sociodemographic reporting for researchers, reviewers, and journal editors. We provide guidance for recording, evaluating, protecting, and interpreting sociodemographic data.