Julien Mayor

• Visser, Ingmar; Geambasu, Andreea; Kachergis, George; Oliveira, Cátia M.; Rocha‐Hidalgo, Joscelin & Zettersten, Martin [Show all 84 contributors for this article] (2026). ManyBabies 3: A Multi‐Lab Study of Infant Algebraic Rule Learning. Developmental Science. ISSN 1363-755X. 29(6). doi: 10.1111/desc.70259. Full text in Research Archive Show summary

  ABSTRACT 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.

• Bochynska, Agata; Kalandadze, Tamara; Korbmacher, Max; Mayiwar, Lewend; Mayor, Julien & Quintana, Daniel (2025). Grassroots networks can help implement and harmonize open research efforts. Nordic Perspectives on Open Science. ISSN 2464-1839. 10. doi: 10.7557/11.8343. Full text in Research Archive Show summary

  Grassroots networks are peer-led, bottom-up initiatives that can drive meaningful change in research reform. Norwegian Reproducibility Network (NORRN), a nation-wide initiative after the model from similar networks around the world, is an example of a grassroots network where a community of researchers works together towards more transparent, rigorous and robust research. By connecting with other researchers, librarians and research support staff across Norwegian universities and colleges as well as various stakeholders, including higher-education institutions and research funders, NORRN aims to help implement and harmonize open and reproducible research efforts across the country. In this paper, we describe the origins, mission, and structure of NORRN and similar networks, as well as successes, challenges and future directions of NORRN’s efforts that show a critical role of grassroots initiatives in supporting research improvement.

• Rosslund, Audun; Mayor, Julien & Kartushina, Natalia (2025). Norwegian parents do not modulate infant-directed speech based on their infants’ attributed word knowledge. Developmental Psychology. ISSN 0012-1649. doi: 10.1037/dev0002077. Full text in Research Archive Show summary

  Infant-directed speech (IDS), the register caregivers often use when interacting with infants, has been suggested to facilitate language learning. To assess its didactic role, we examined the acoustic modifications parents make in IDS for words they attribute to their infant as unknown, versus known, by analyzing data from three studies of Norwegian IDS with 8- to 18-month-old infants (N = 132 infants, N = 182 parents). Parents’ speech was recorded during a shared-reading interaction with their infant and with an experimenter (as a control register), ensuring that speech content was matched across participants and registers. Contrary to our hypotheses, we found no evidence that parents emphasized IDS for words attributed as unknown. Furthermore, Bayesian analyses suggested that Norwegian parents do not modulate IDS based on infants’ attributed word knowledge. Thus, our findings do not support the notion that parents use IDS as a didactic strategy to teach individual words, underscoring alternative motivations for engaging in such speech.

• Roettger, Timo; Askelund, Jo Adrian Dahl; Birkenæs, Viktoria; Bjørndal, Ludvig Daae; Bochynska, Agata & Glaser, Bernt Damian [Show all 13 contributors for this article] (2025). Transparency in epidemiological analyses of cohort data a case study of the Norwegian mother, father, and child cohort study (MoBa). BMC Medical Research Methodology. 25, p. 1–11. doi: 10.1186/s12874-025-02601-6. Full text in Research Archive Show summary

  Background Epidemiological research is central to our understanding of health and disease. Secondary analysis of cohort data is an important tool in epidemiological research but is vulnerable to practices that can reduce the validity and robustness of results. As such, adopting measures to increase the transparency and reproducibility of secondary data analysis is paramount to ensuring the robustness and usefulness of findings. The uptake of such practices has not yet been systematically assessed. Methods Using the Norwegian Mother, Father, and Child Cohort study (MoBa; [23, 24]) as a case study, we assessed the prevalence of the following reproducible practices in publications between 2007–2023: preregistering secondary analyses, sharing of synthetic data, additional materials, and analysis scripts, conducting robustness checks, directly replicating previously published studies, declaring conflicts of interest and publishing publicly available versions of the paper. Results Preregistering secondary data analysis was only found in 0.4% of articles. No articles used synthetic data sets. Sharing practices of additional data (2.3%), additional materials (3.4%) and analysis scripts (4.2%) were rare. Several practices, including data and analysis sharing, preregistration and robustness checks became more frequent over time. Based on these assessments, we present a practical example for how researchers might improve transparency and reproducibility of their research. Conclusions The present assessment demonstrates that some reproducible practices are more common than others, with some practices being virtually absent. In line with a broader shift towards open science, we observed an increasing use of reproducible research practices in recent years. Nonetheless, the large amount of analytical flexibility offered by cohorts such as MoBa places additional responsibility on researchers to adopt such practices with urgency, to both ensure the robustness of their findings and earn the confidence of those using them. A particular focus in future efforts should be put on practices that help mitigating bias due to researcher degrees of freedom – namely, preregistration, transparent sharing of analysis scripts, and robustness checks. We demonstrate by example that challenges in implementing reproducible research practices in analysis of secondary cohort data—even including those associated with data sharing—can be meaningfully overcome.

• Rosslund, Audun; Kartushina, Natalia; Serres, Nora Rose & Mayor, Julien (2025). Early Vocabulary Acquisition: From Birth Order Effect to Child-to-Caregiver Ratio. Child Development. ISSN 0009-3920. 96(4), p. 1343–1353. doi: 10.1111/cdev.14251. Full text in Research Archive Show summary

  Growing up with multiple siblings might negatively affect language development. This study examined the associations between birth order, sibling characteristics and parent-reported vocabulary size in 6163 Norwegian 8- to 36-month-old children (51.4% female). Results confirmed that birth order was negatively associated with vocabulary, yet exhibited a U-shaped pattern. A data-driven measure of “child-to-caregiver ratio” in the household was developed, in which old-enough siblings—females 1–3 years earlier than males—were considered caregivers for their younger siblings. This measure explained variance in vocabulary better than birth order, and indicates sex-differences in the age at which older siblings contribute to, rather than deplete, available resources. A child-to-caregiver ratio might better capture the interplay between language-learning resources and demands within households.

• Allegretta, Silvia; Gavrilova, Margarita; Kartushina, Natalia; Mayor, Julien; Roch, Maja & Kunst, Jonas R. (2025). Parental Attitudes and Children’s Language Development: A Cross-Cultural Evaluation of the Early Parenting Attitudes Questionnaire. Collabra: Psychology. ISSN 2474-7394. 11(1). doi: 10.1525/collabra.130882. Full text in Research Archive Show summary

  The Early Parenting Attitudes Questionnaire (EPAQ; Hembacher & Frank, 2020) was developed in the U.S. to assess parents’ beliefs, knowledge, ideas, and attitudes about parenting. Given the diversity of parenting practices among cultures, it is essential to establish the cross-cultural validity of the instruments used to measure them. For this reason, this study aims at (1) assessing the psychometric properties of the EPAQ in Norway, Russia, and the U.K. and (2) investigating whether the underlying structure aligns with the original one observed in the U.S. Moreover, we aimed at (3) exploring the potential relationship between parental attitudes and children’s language development using MacArthur-Bates Communicative Development Inventories (CDI; Fenson et al. 2007). Our sample consisted of 3333 parents of children between 0 and 156 months from Norway (n = 1060), the U.K. (n = 656) , and Russia (n = 1617). Analyses revealed a different factor solution in the countries of our sample, as compared to the original three-factor solution found in the original American sample. Especially in Russia, the structure of parental attitudes as measured by the EPAQ differs both from the original factor solution and from the factor solution identified in Norway and the U.K. Therefore, at least in the Russian context, different culture-sensitive scales need to be developed and, generally, new items for the EPAQ should be developed for further refinement. Moreover, our analyses highlighted a significant negative association between the factor Communicative and Emotional Detachment and vocabulary scores as a function of the child’s age in Russia.

• Rosslund, Audun; Varjola, Nina; Mayor, Julien & Kartushina, Natalia (2025). Longitudinal changes in consonant production in infant-directed speech and infants’ early speech production from 6 to 12 months. Infant Behavior and Development. ISSN 0163-6383. 78. doi: 10.1016/j.infbeh.2024.102018. Full text in Research Archive Show summary

  Previous research suggests that acoustic features of infant-directed speech (IDS) might be beneficial for infants’ language development. However, consonants have gained less attention than vowels and prosody. In the current study, we examined voice onset time (VOT) – a distinguishing cue for stop consonant contrasts – in IDS and adult-directed speech (ADS), and its relation to infants’ speech production. We used a longitudinal sample of 48 Norwegian parent-infant dyads. Parents’ IDS and ADS were recorded in-lab at three timepoints (infants’ age: 6, 9, 12 months), and the VOTs of the stop consonants /b-p/, /d-t/, and /g-k/ were measured. In addition, at each timepoint, parents reported their infants’ production of the same consonants, as well as their babbling. Hypotheses were preregistered, and we used full-null model comparisons to minimise type I-errors in the analyses. Our results demonstrate that, while controlling for speaking rate, in IDS, parents’ VOTs were longer in voiceless stops, but shorter in voiced stops, resulting in overall less distinct consonant contrasts compared to ADS. Further, VOTs in IDS approached ADS values with infants’ age. However, we found no relationship between parents’ VOTs and infants’ consonant production or babbling. Consonants, like vowels, appear to be less distinct in IDS than ADS, thus reinforcing the interpretation that IDS may serve an attentional and/or affective aim, rather than a didactic purpose.

• Lucca, Kelsey; Yuen, Francis; Wang, Yiyi; Alessandroni, Nicolás; Allison, Olivia & Alvarez, Mario [Show all 94 contributors for this article] (2025). Infants’ Social Evaluation of Helpers and Hinderers: A Large-Scale, Multi-Lab, Coordinated Replication Study. Developmental Science. ISSN 1363-755X. 28(1). doi: 10.1111/desc.13581. Full text in Research Archive
• Muñoz, Luis Eduardo; Kartushina, Natalia & Mayor, Julien (2024). Sustained pacifier use is associated with smaller vocabulary sizes at 1 and 2 years of age: A cross-sectional study. Developmental Science. ISSN 1363-755X. doi: 10.1111/desc.13477. Full text in Research Archive Show summary

  Pacifier use during childhood has been hypothesized to interfere with language processing, but, to date, there is limited evidence revealing detrimental effects of prolonged pacifier use on infant vocabulary learning. In the present study, parents of 12- and 24-month-old infants were recruited in Oslo (Norway). The sample included 1187 monolingual full-term born (without visual, auditory, or cognitive impairments) infants: 452 (230 girls; 222 boys) 12-month-olds and 735 (345 girls; 390 boys) 24-month-olds. Parents filled out an online Norwegian Communicative Development Inventory (CDI), which assesses the vocabulary in comprehension and production for 12-month-old infants and in production only for 24-month-old infants. CDI scores were transformed into age- and sex-adjusted percentiles using Norwegian norms. Additionally, parents retrospectively reported their child's daytime pacifier use, in hours, at 2-month intervals, from birth to the assessment date. Maternal education was used to control, in the analyses, for the socio-economic status. We found that greater pacifier use in an infant's lifespan was associated with lower vocabulary size. Pacifier use later in life was more negatively associated with vocabulary size than precocious use, and increased the odds of being a low language scorer. In sum, our study moves beyond the findings of momentary effects of experimentally induced “impairment” in articulators’ movement on speech perception and suggests that, from 12 months of age, constraints on the infant's speech articulators (pacifier use) may be negatively associated with word comprehension and production.

• Sinkeviciute, Akvile; Mayor, Julien; Vulchanova, Mila Dimitrova & Kartushina, Natalia (2024). Active Language Modulates Color Perception in Bilinguals. Language Learning. ISSN 0023-8333. 74(1), p. 40–71. doi: 10.1111/lang.12645. Full text in Research Archive Show summary

  Color terms divide the color spectrum differently across languages. Previous studies have reported that speakers of languages that have different words for light and dark blue (e.g., Russian siniy and goluboy) discriminate color chips sampled from these two linguistic categories faster than speakers of languages that use one basic color term for blue (e.g., English blue). This effect has been reported to be disrupted when participants engaged in a verbal interference task, suggesting that active language use can modulate the linguistic category effect. The current study provided a stringent test of this hypothesis by examining color discrimination under verbal interference in bilinguals speaking Lithuanian (two blue categories) and Norwegian (one blue category). The results revealed that the language activated during verbal interference had a significant impact on bilinguals’ color discrimination. Specifically, Lithuanian–Norwegian bilinguals exhibited a color category effect only when performing the task under verbal interference in Lithuanian but not in Norwegian. This demonstrated, within the same individuals, the momentary effect of active language processing on color perception.

• Rosslund, Audun; Mayor, Julien; Cristia, Alejandrina & Kartushina, Natalia (2024). Native and non-native vowel discrimination in 6-month-old Norwegian infants. Infant Behavior and Development. ISSN 0163-6383. 77. doi: 10.1016/j.infbeh.2024.101992. Full text in Research Archive Show summary

  In the current preregistered study, we tested n = 67 6-month-old Norwegian infants’ discrimination of a native vowel contrast /y-i/ and a non-native (British) vowel contrast /ʌ-æ/ in an eye-tracking habituation paradigm. Our results showed that, on a group level, infants did not discriminate either contrast. Yet, exploratory analyses revealed a negative association between infants’ performance in each experiment, that is, better discrimination of the native contrast was associated with worse discrimination of the non-native contrast. Potentially, infants in this study might have been on the cusp of perceptual reorganisation towards their native language.

• Rosslund, Audun; Kartushina, Natalia & Mayor, Julien (2024). Associations between shared book reading, daily screen time and infants' vocabulary size. Journal of Child Language. ISSN 0305-0009. p. 1–13. doi: 10.1017/S0305000924000291. Full text in Research Archive Show summary

  In the current pre-registered study, we examined the associations between shared book reading, daily screen time, and vocabulary size in 1,442 12- and 24-month-old Norwegian infants. Our results demonstrate a positive association between shared reading and vocabulary in both age groups, and a negative association between screen time and vocabulary in 24-month-olds. Exploratory analyses revealed that the positive relationship between shared reading and expressive vocabulary in 12-month-olds was stronger in lower SES groups, suggesting that shared reading may act as a compensatory mechanism attenuating potentially impoverished learning environment and parent-infant interactions in low-SES families.

• Zettersen, Martin; Cox, Christopher J.; Bergmann, Christina; Tsui, Angeline Sin Mei; Soderstrom, Melanie & Mayor, Julien [Show all 15 contributors for this article] (2024). Evidence for Infant-directed Speech Preference Is Consistent Across Large-scale, Multi-site Replication and Meta-analysis. Open Mind. 8, p. 439–461. doi: 10.1162/opmi_a_00134. Full text in Research Archive Show summary

  There is substantial evidence that infants prefer infant-directed speech (IDS) to adult-directed speech (ADS). The strongest evidence for this claim has come from two large-scale investigations: i) a community-augmented meta-analysis of published behavioral studies and ii) a large-scale multi-lab replication study. In this paper, we aim to improve our understanding of the IDS preference and its boundary conditions by combining and comparing these two data sources across key population and design characteristics of the underlying studies. Our analyses reveal that both the meta-analysis and multi-lab replication show moderate effect sizes (d ≈ 0.35 for each estimate) and that both of these effects persist when relevant study-level moderators are added to the models (i.e., experimental methods, infant ages, and native languages). However, while the overall effect size estimates were similar, the two sources diverged in the effects of key moderators: both infant age and experimental method predicted IDS preference in the multi-lab replication study, but showed no effect in the meta-analysis. These results demonstrate that the IDS preference generalizes across a variety of experimental conditions and sampling characteristics, while simultaneously identifying key differences in the empirical picture offered by each source individually and pinpointing areas where substantial uncertainty remains about the influence of theoretically central moderators on IDS preference. Overall, our results show how meta-analyses and multi-lab replications can be used in tandem to understand the robustness and generalizability of developmental phenomena.

• Schreiner, Melanie S.; Zettersten, Martin; Bergmann, Christina; Frank, Michael C.; Fritzsche, Tom & Gonzalez-Gomez, Nayeli [Show all 16 contributors for this article] (2024). Limited evidence of test-retest reliability in infant-directed speech preference in a large preregistered infant experiment. Developmental Science. ISSN 1363-755X. doi: 10.1111/desc.13551. Full text in Research Archive Show summary

  Test-retest reliability—establishing that measurements remain consistent across multiple testing sessions—is critical to measuring, understanding, and predicting individual differences in infant language development. However, previous attempts to establish measurement reliability in infant speech perception tasks are limited, and reliability of frequently used infant measures is largely unknown. The current study investigated the test-retest reliability of infants’ preference for infant-directed speech over adult-directed speech in a large sample (N = 158) in the context of the ManyBabies1 collaborative research project. Labs were asked to bring in participating infants for a second appointment retesting infants on their preference for infant-directed speech. This approach allowed us to estimate test-retest reliability across three different methods used to investigate preferential listening in infancy: the head-turn preference procedure, central fixation, and eye-tracking. Overall, we found no consistent evidence of test-retest reliability in measures of infants’ speech preference (overall r = 0.09, 95% CI [−0.06,0.25]). While increasing the number of trials that infants needed to contribute for inclusion in the analysis revealed a numeric growth in test-retest reliability, it also considerably reduced the study's effective sample size. Therefore, future research on infant development should take into account that not all experimental measures may be appropriate for assessing individual differences between infants.

• Soderstrom, Melanie; Rocha-Hidalgo, Joscelin; Munoz, Luis Eduardo; Bochynska, Agata; Werker, Janet F. & Skarabela, Barbora [Show all 42 contributors for this article] (2024). Testing the relationship between preferences for infant-directed speech and vocabulary development: A multi-lab study. Journal of Child Language. ISSN 0305-0009. doi: 10.1017/S0305000924000254. Full text in Research Archive Show summary

  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.

• Rosslund, Audun; Mayor, Julien; Mundry, Roger; Singh, Arun Prakash; Cristia, Alejandrina & Kartushina, Natalia (2024). A longitudinal investigation of the acoustic properties of infant-directed speech from 6 to 18 months. Royal Society Open Science. 11(11), p. 1–33. doi: 10.1098/rsos.240572. Full text in Research Archive Show summary

  Caregivers often modulate their speech when interacting with infants, adapting a register that has been suggested to have attentional, affective and didactic purposes. The present preregistered study examined the longitudinal trajectories of a diverse range of acoustic features of infant-directed speech (IDS) and compared these with adult-directed speech (ADS), in Norwegian parents of 6- to 18-month-old infants. Sixty-nine families participated. Throughout five laboratory visits across one year, parents were recorded reading a picture-book to their infant (IDS) and an experimenter (ADS). The book was designed to tightly control for the linguistic content and context of speech between participants, timepoints and registers. Analyses of a total of 54 594 vowels and 22 958 phrases revealed, first, an overall effect of register: parents used higher pitch, wider pitch range, slower articulation rate, longer vowel duration and more variable and less distinct vowels in IDS than in ADS. Second, significant register-by-age interactions indicated that parents’ IDS, compared with their ADS, featured wider pitch range, larger vowel space and shorter vowel duration in older as compared with younger infants, while pitch, articulation rate and vowel variability and distinctiveness remained relatively stable with age. Results are discussed in the context of the proposed functions of IDS.

• Roepstorff, Ida Torp; Mayor, Julien; Havighurst, Sophie Seychelle & Kartushina, Natalia (2024). Same name, different representational levels? Misalignment of indirect parent-reported and direct alternative forced choice measures of emotion word comprehension in preschool children. Journal of Child Language. ISSN 0305-0009. p. 1–16. doi: 10.1017/S0305000923000727. Full text in Research Archive Show summary

  This study assessed the relationship between preschoolers’ directly and indirectly assessed emotion word comprehension. Forty-nine two-to-five-year-old Norwegian children were assessed in a tablet-based 4-alternative forced choice (AFC) task on their comprehension of six basic and six complex emotions using facial expression photographs. Parents reported emotion word comprehension and production of the same words. Parent-reported emotion word production interacted with age to predict preschoolers’ performance, with a parent-child alignment only observed for older children. Parent-reported word comprehension did not significantly predict accuracy. The results suggest that, in preschoolers, direct and indirect assessments might address distinct representational levels of emotion word comprehension.

• Rosslund, Audun; Hagelund, Silje; Mayor, Julien & Kartushina, Natalia (2023). Mothers' and fathers' infant-directed speech have similar acoustic properties, but these are not associated with direct or indirect measures of word comprehension in 8-month-old infants. Journal of Child Language. ISSN 0305-0009. doi: 10.1017/S0305000923000557. Full text in Research Archive Show summary

  Previous research on infant-directed speech (IDS) and its role in infants’ language development has largely focused on mothers, with fathers being investigated scarcely. Here we examine the acoustics of IDS as compared to adult-directed speech (ADS) in Norwegian mothers and fathers to 8-month-old infants, and whether these relate to direct (eye-tracking) and indirect (parental report) measures of infants’ word comprehension. Forty-five parent-infant dyads participated in the study. Parents (24 mothers, 21 fathers) were recorded reading a picture book to their infant (IDS), and to an experimenter (ADS), ensuring identical linguistic context across speakers and registers. Results showed that both mothers’ and fathers’ IDS had exaggerated prosody, expanded vowel spaces, as well as more variable and less distinct vowels. We found no evidence that acoustic features of parents’ speech were associated with infants’ word comprehension. Potential reasons for the lack of such a relationship are discussed.

• Lo, Chang Huan; Hermes, Jonas; Kartushina, Natalia; Mayor, Julien & Mani, Nivedita (2023). e-Babylab: An open-source browser-based tool for unmoderated online developmental studies. Behavior Research Methods. ISSN 1554-351X. doi: 10.3758/s13428-023-02200-7. Full text in Research Archive
• Steffan, Adrian; Zimmer, Lucie; Arias-Trejo, Natalia; Bohn, Manuel; Ben, Rodrigo Dal & Flores-Coronado, Marco A. [Show all 33 contributors for this article] (2023). Validation of an open source, remote web-based eye-tracking method (WebGazer) for research in early childhood. Infancy. ISSN 1525-0008. doi: 10.1111/infa.12564. Full text in Research Archive
• Visser, Ingmar; Bergmann, Christina; Byers-Heinlein, Krista; Ben, Rodrigo Dal; Duch, Wlodzislaw & Forbes, Samuel [Show all 27 contributors for this article] (2022). Improving the generalizability of infant psychological research: The ManyBabies model. Behavioral and Brain Sciences. ISSN 0140-525X. 45(E35). doi: 10.1017/S0140525X21000455. Full text in Research Archive
• Kartushina, Natalia & Mayor, Julien (2022). Coping with dialects from birth: Role of variability on infants’ early language development. Insights from Norwegian dialects. Developmental Science. ISSN 1363-755X. 26(1), p. 1–19. doi: 10.1111/desc.13264. Full text in Research Archive Show summary

  Previous research suggests that exposure to accent variability can affect toddlers’ familiar word recognition and word comprehension. The current preregistered study addressed the gap in knowledge on early language development in infants exposed to two dialects from birth and assessed the role of dialect similarity in infants’ word recognition and comprehension. A 12-month-old Norwegian-learning infants, exposed to native Norwegian parents speaking the same or two Norwegian dialects, took part in two eye-tracking tasks, assessing familiar word form recognition and word comprehension. Their parents’ speech was assessed for similarity by native Norwegian speakers. First, in contrast to previous research, our results revealed no listening preference for words over nonwords in both monodialectal and bidialectal infants, suggesting potential language-specific differences in the onset of word recognition. Second, the results showed evidence for word comprehension in monodialectal infants, but not in bidialectal infants, suggesting that exposure to dialectal variability impacts early word acquisition. Third, perceptual similarity between parental dialects tendentially facilitated bidialectal infants’ word recognition and comprehension. Forth, the results revealed a strong correlation between the raters and parents’ assessment of similarity between dialects, indicating that parental estimations can be reliably used to assess infants’ speech variability at home. Finally, our results revealed a strong relationship between word recognition and comprehension in monodialectal infants and the absence of such a relationship in bidialectal infants, suggesting that either these two skills do not necessarily align in infants exposed to more variable input, or that the alignment might occur at a later stage.

• Bergmann, Christina; Dimitrova, Nevena; Alaslani, Khadeejah; Almohammadi, Alaa; Alroqi, Haifa & Aussems, Suzanne [Show all 19 contributors for this article] (2022). Young children’s screen time during the first COVID-19 lockdown in 12 countries. Scientific Reports. 12(2015). doi: 10.1038/s41598-022-05840-5. Full text in Research Archive Show summary

  Abstract Older children with online schooling requirements, unsurprisingly, were reported to have increased screen time during the first COVID-19 lockdown in many countries. Here, we ask whether younger children with no similar online schooling requirements also had increased screen time during lockdown. We examined children’s screen time during the first COVID-19 lockdown in a large cohort (n = 2209) of 8-to-36-month-olds sampled from 15 labs across 12 countries. Caregivers reported that toddlers with no online schooling requirements were exposed to more screen time during lockdown than before lockdown. While this was exacerbated for countries with longer lockdowns, there was no evidence that the increase in screen time during lockdown was associated with socio-demographic variables, such as child age and socio-economic status (SES). However, screen time during lockdown was negatively associated with SES and positively associated with child age, caregiver screen time, and attitudes towards children’s screen time. The results highlight the impact of the COVID-19 lockdown on young children’s screen time.

• Richie-Halford, A.; Cieslak, M.; Ai, L.; Cafarra, S.; Covitz, S. & Franco, A. R. [Show all 50 contributors for this article] (2022). An analysis ready and quality controlled resource for pediatric brain white-matter research. Scientific Data. 9. doi: 10.1038/s41597-022-01816-2. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2022). Parents’ hyper-pitch and low vowel category variability in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary. Language Development Research. 2(1), p. 223–267. doi: 10.34842/2022.0547. Full text in Research Archive Show summary

  The present study examines the acoustic properties of infant-directed speech (IDS) as compared to adult-directed speech (ADS) in Norwegian parents of 18-month-old toddlers, and whether these properties relate to toddlers’ expressive vocabulary size. Twenty-one parent-toddler dyads from Tromsø, Northern Norway participated in the study. Parents (16 mothers, 5 fathers), speaking a Northern Norwegian dialect, were recorded in the lab reading a storybook to their toddler (IDS register), and to an experimenter (ADS register). The storybook was designed for the purpose of the study, ensuring identical linguistic contexts across speakers and registers, and multiple representations of each of the nine Norwegian long vowels. We examined both traditionally reported measures of IDS: pitch, pitch range, vowel duration and vowel space expansion, but also novel measures: vowel category variability and vowel category distinctiveness. Our results showed that Norwegian IDS, as compared to ADS, had similar characteristics as in previously reported languages: higher pitch, wider pitch range, longer vowel duration, and expanded vowel space area; in addition, it had more variable vowel categories. Further, parents’ hyper-pitch, that is, the within-parent increase in pitch in IDS as compared to ADS, and lower vowel category variability in IDS itself, were related to toddlers' vocabulary. Our results point towards potentially facilitating roles of increase in parents’ pitch when talking to their toddlers and of consistency in vowel production in early word learning.

• Kartushina, Natalia; Mani, Nivedita; Aslı, Aktan-Erciyes; Alaslani, Khadeejah; Aldrich, Naomi J. & Almohammadi, Alaa [Show all 52 contributors for this article] (2022). COVID-19 first lockdown as a window into language acquisition: associations between caregiver-child activities and vocabulary gains. Language Development Research. 2, p. 1–36. doi: 10.34842/abym-xv34. Full text in Research Archive Show summary

  The COVID-19 pandemic, and the resulting closure of daycare centers worldwide, led to unprecedented changes in children’s learning environments. This period of increased time at home with caregivers, with limited access to external sources (e.g., daycares) provides a unique opportunity to examine the associations between the caregiver-child activities and children’s language development. The vocabularies of 1742 children aged8-36 months across 13 countries and 12 languages were evaluated at the beginning and end of the first lockdown period in their respective countries(from March to September 2020). Children who had less passive screen exposure and whose caregivers read more to them showed larger gains in vocabulary development during lockdown, after controlling for SES and other caregiver-child activities. Children also gained more words than expected (based on normative data) during lockdown; either caregivers were more aware of their child’s development or vocabulary development benefited from intense caregiver-child interaction during lockdown.

• Lo, Chang Huan; Rosslund, Audun; Chai, Jun Ho; Mayor, Julien & Kartushina, Natalia (2021). Tablet assessment of word comprehension reveals coarse word representations in 18–⁠20‐month‐old toddlers. Infancy. ISSN 1525-0008. 26(4), p. 596–616. doi: 10.1111/infa.12401. Full text in Research Archive Show summary

  The present study explores the viability of using tablets in assessing early word comprehension by means of a two‐alternative forced‐choice task. Forty‐nine 18–20‐month‐old Norwegian toddlers performed a touch‐based word recognition task, in which they were prompted to identify the labeled target out of two displayed items on a touchscreen tablet. In each trial, the distractor item was either semantically related (e.g., dog–cat) or unrelated (e.g., dog–airplane) to the target. Our results show that toddlers as young as 18 months can engage meaningfully with a tablet‐based assessment, with minimal verbal instruction and child–administrator interaction. Toddlers performed better in the semantically unrelated condition than in the related condition, suggesting that their word representations are still semantically coarse at this age. Furthermore, parental reports of comprehension, using the Norwegian version of the MacArthur–Bates Communicative Development Inventories, predicted toddlers’ performance, with parent–child agreement stronger in the semantically unrelated condition, indicating that parents declare a word to be known by their child if it is understood at a coarse representational level. This study provides among the earliest evidence that remote data collection in 18‐20 month‐old toddlers is viable, as comparable results were observed from both in‐laboratory and online administration of the touchscreen recognition task.

• Kartushina, Natalia; Rosslund, Audun & Mayor, Julien (2021). Toddlers raised in multi-dialectal families learn words better in accented speech than those raised in monodialectal families. Journal of Child Language. ISSN 0305-0009. doi: 10.1017/S0305000921000520. Full text in Research Archive Show summary

  Abstract Multi-accent environments offer rich but inconsistent language input, as words are produced differently across accents. The current study examined, in two experiments, whether multi-accent variability affects infants’ ability to learn words and whether toddlers’ prior experience with accents modulates learning. In Experiment 1, two-and-a-half-year-old Norwegian toddlers were exposed, in their kindergarten, twice per day for one week, to a child-friendly audiovisual tablet-based e-book containing four novel pseudowords. Half of the toddlers heard the story in three Norwegian accents, whereas the other half heard it in one Norwegian accent. The results revealed no differences between conditions, suggesting that multi-accent variability did not hinder toddlers’ word learning. In experiment 2, two-and-a-half-year-old Norwegian toddlers were exposed, in their homes, for one week, to the e-book featuring three Norwegian accents. The results revealed overall better learning in toddlers raised in bi-dialectal households, as compared to mono-dialectal peers – suggesting that accent exposure benefits learning in multi-accent environments.

• Sia, Ming Yean & Mayor, Julien (2021). Improvements of Statistical Learning Skills Allow Older Children to Go Beyond Single-Hypothesis Testing When Learning Words. Journal of Child Language. ISSN 0305-0009. doi: 10.1017/S0305000921000532. Full text in Research Archive Show summary

  Abstract Children learn words in ambiguous situations, where multiple objects can potentially be referents for a new word. Yet, researchers debate whether children maintain a single word-object hypothesis – and revise it if falsified by later information – or whether children establish a network of word-object associations whose relative strengths are modulated with experience. To address this issue, we presented 4- to 12-year-old children with sets of mutual exclusivity (fast-mapping) trials: offering them with obvious initial hypotheses (that the novel object is the referent for the novel word). We observe that children aged six years and above, despite showing a novelty bias and retaining this novel word – novel object association, also formed an association between the novel word and the name-known object, thereby suggesting that older children attend to more than one word-object association, in a manner similar to associative learning. We discuss our findings in the context of competing theoretical accounts related to word learning.

• Chai, Jun Ho; Low, Hui Min; Wong, Tze Peng; Onnis, Luca & Mayor, Julien (2021). Extra-linguistic modulation of the English noun-bias: evidence from Malaysian bilingual infants and toddlers. Journal of Cultural Cognitive Science. ISSN 2520-100X. 5, p. 49–64. doi: 10.1007/s41809-021-00078-5. Full text in Research Archive Show summary

  Early vocabularies typically contain more nouns than verbs. Yet, the strength of this noun-bias varies across languages and cultures. Two main theories have aimed at explaining such variations; either that the relative importance of nouns vs. verbs is specific to the language itself, or that extra-linguistic factors shape early vocabulary structures. To address this debate, the present study compares the relative distribution of verbs and nouns within the same language—English—between Malay–English and Mandarin–English bilingual infants and toddlers. The English receptive lexicons of Mandarin–English bilingual children contained more verbs than those of Malay–English bilinguals, suggesting that the noun-bias is modulated by factors external to English. We discuss the potential role of socio-cultural differences on the composition of children early vocabularies.

• Sia, Ming Yean & Mayor, Julien (2020). Syntactic cues help disambiguate objects referred to with count nouns: Illustration with Malay children. Child Development. ISSN 0009-3920. 92(1), p. 101–114. doi: 10.1111/cdev.13401. Full text in Research Archive Show summary

  Children employ multiple cues to identify the referent of a novel word. Novel words are often embedded in sentences and children have been shown to use syntactic cues to differentiate between types of words (adjective vs. nouns) and between types of nouns (count vs. mass nouns). In this study, we show that children learning Malay (N = 67), a numeral classifier language, can use syntactic cues to perform even finer‐grained disambiguation–between count nouns. The manipulation of congruence between lexical and syntactic cues reveals a clear developmental trajectory: while 5‐year‐olds use predominantly lexical cues, older children increasingly rely on syntactic cues, such that by 7 years of age, they disambiguate between objects referred to with count nouns using syntactic rather than lexical cues.

• Althaus, Nadja; Gliozzi, Valentina; Mayor, Julien & Plunkett, Kim (2020). Infant categorization as a dynamic process linked to memory: Infant categorisation linked to memory. Royal Society Open Science. 7:200328(10), p. 1–18. doi: 10.1098/rsos.200328. Full text in Research Archive
• Althaus, Nadja; Gliozzi, Valentina; Mayor, Julien & Plunkett, Kim (2020). Infant categorization as a dynamic process linked to memory. Royal Society Open Science. 7(200328). doi: 10.1098/rsos.200328. Full text in Research Archive Show summary

  Recency effects are well documented in the adult and infant literature: recognition and recall memory are better for recently occurring events. We explore recency effects in infant categorization, which does not merely involve memory for individual items, but the formation of abstract category representations. We present a computational model of infant categorization that simulates category learning in 10-month-olds. The model predicts that recency effects outweigh previously reported order effects for the same stimuli. According to the model, infant behaviour at test should depend mainly on the identity of the most recent training item. We evaluate these predictions in a series of experiments with 10-month-old infants. Our results show that infant behaviour confirms the model’s prediction. In particular, at test infants exhibited a preference for a category outlier over the category average only if the final training item had been close to the average, rather than distant from it. Our results are consistent with a view of categorization as a highly dynamic process where the end result of category learning is not the overall average of all stimuli encountered, but rather a fluid representation that moves depending on moment-to-moment novelty. We argue that this is a desirable property of a flexible cognitive system that adapts rapidly to different contexts.

• Bobb, Susan; Holzen, Katie Von; Mayor, Julien; Mani, Nivedita & Carreiras, Manuel (2020). Co-activation of the L2 during L1 auditory processing: An ERP cross-modal priming study. Brain and Language. ISSN 0093-934X. 203, p. 104739–104739. doi: 10.1016/j.bandl.2019.104739. Full text in Research Archive Show summary

  Several studies have shown that unbalanced bilinguals activate both of their languages simultaneously during L2 processing; however, evidence for L2 activation while participants are tested exclusively in their L1 has been more tenuous. Here, we investigate whether bilingual participants implicitly activate the label for a picture in their two languages, and whether labels activated in L2 can prime activation of cross-linguistically related L1 lexical targets. We tested highly proficient early Spanish-Basque bilinguals on an ERP cross-modal priming task conducted only in their L1, Spanish. Participants activated prime picture labels in both Spanish and Basque. More importantly, participants activated Basque translations of Spanish auditory targets, even in a Spanish experimental environment with no reference to Basque. Results provide strong evidence for non-selective bilingual lexical access, showing co-activation extending to lexical levels beyond phonological overlap. Our results add to the growing body of evidence for the interconnective nature of bilingual language activation.

• Chai, Jun Ho; Lo, Chang Huan & Mayor, Julien (2020). A Bayesian-Inspired Item Response Theory–Based Framework to Produce Very Short Versions of MacArthur–Bates Communicative Development Inventories. Journal of Speech, Language and Hearing Research. ISSN 1092-4388. doi: 10.1044/2020_JSLHR-20-00361. Full text in Research Archive Show summary

  Purpose This study introduces a framework to produce very short versions of the MacArthur–Bates Communicative Development Inventories (CDIs) by combining the Bayesian-inspired approach introduced by Mayor and Mani (2019) with an item response theory–based computerized adaptive testing that adapts to the ability of each child, in line with Makransky et al. (2016). Method We evaluated the performance of our approach—dynamically selecting maximally informative words from the CDI and combining parental response with prior vocabulary data—by conducting real-data simulations using four CDI versions having varying sample sizes on Wordbank—the online repository of digitalized CDIs: American English (a very large data set), Danish (a large data set), Beijing Mandarin (a medium-sized data set), and Italian (a small data set). Results Real-data simulations revealed that correlations exceeding .95 with full CDI administrations were reached with as few as 15 test items, with high levels of reliability, even when languages (e.g., Italian) possessed few digitalized administrations on Wordbank. Conclusions The current approach establishes a generic framework that produces very short (less than 20 items) adaptive early vocabulary assessments—hence considerably reducing their administration time. This approach appears to be robust even when CDIs have smaller samples in online repositories, for example, with around 50 samples per month-age.

• Frank, Michael; Alcock, Katherine; Arias-Trejo, Natalia; Ascherslegen, Gisa; Baldwin, Dare & Barbu, Stephanie [Show all 56 contributors for this article] (2020). Quantifying sources of variability in infancy research using the infant-directed speech preference. Advances in Methods and Practices in Psychological Science (AMPPS). ISSN 2515-2459. 3(1), p. 24–52. doi: 10.1177/2515245919900809. Full text in Research Archive Show summary

  The field of psychology has become increasingly concerned with issues related to methodology and replicability. Infancy researchers face specific challenges related to replicability: high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations, amongst other factors. Addressing these concerns, we report on a large-scale, multi-site study aimed at 1) assessing the overall replicability of a single theoretically-important phenomenon and 2) examining methodological, situational, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult were created using semi-naturalistic laboratory-based audio recordings in North American English. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, and Asia using the three commonly-used infant discrimination methods (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35 [0.29 - 0.42], which was reliably above zero but smaller than that found in a previous meta-analysis (0.72). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together these findings replicate the infant-directed speech preference but suggest that its magnitude is modulated by development, native language experience, and testing procedure.

• Ackermann, Lena; Lo, Chang Huan; Mani, Nivedita & Mayor, Julien (2020). Word learning from a tablet app: Toddlers perform better in a passive context. PLOS ONE. doi: 10.1371/journal.pone.0240519. Full text in Research Archive Show summary

  In recent years, the popularity of tablets has skyrocketed and there has been an explosive growth in apps designed for children. Howhever, many of these apps are released without tests for their effectiveness. This is worrying given that the factors influencing children’s learning from touchscreen devices need to be examined in detail. In particular, it has been suggested that children learn less from passive video viewing relative to equivalent live interaction, which would have implications for learning from such digital tools. However, this so-called video deficit may be reduced by allowing children greater influence over their learning environment. Across two touchscreen-based experiments, we examined whether 2- to 4-year-olds benefit from actively choosing what to learn more about in a digital word learning task. We designed a tablet study in which “active” participants were allowed to choose which objects they were taught the label of, while yoked “passive” participants were presented with the objects chosen by their active peers. We then examined recognition of the learned associations across different tasks. In Experiment 1, children in the passive condition outperformed those in the active condition (n = 130). While Experiment 2 replicated these findings in a new group of Malay-speaking children (n = 32), there were no differences in children’s learning or recognition of the novel word-object associations using a more implicit looking time measure. These results suggest that there may be performance costs associated with active tasks designed as in the current study, and at the very least, there may not always be systematic benefits associated with active learning in touchscreen-based word learning tasks. The current studies add to the evidence that educational apps need to be evaluated before release: While children might benefit from interactive apps under certain conditions, task design and requirements need to consider factors that may detract from successful performance.

• Kartushina, Natalia & Mayor, Julien (2019). Word knowledge in six- to nine-month-old Norwegian infants? Not without additional frequency cues. Royal Society Open Science. 6(9). doi: 10.1098/rsos.180711. Full text in Research Archive Show summary

  The past 5 years have witnessed claims that infants as young as six months of age understand the meaning of several words. To reach this conclusion, researchers presented infants with pairs of pictures from distinct semantic domains and observed longer looks at an object upon hearing its name as compared with the name of the other object. However, these gaze patterns might indicate infants' sensibility to the word frequency and/or its contextual relatedness to the object regardless of a firm semantic understanding of this word. The current study attempted, first, to replicate, in Norwegian language, the results of recent studies showing that six- to nine-month-old English-learning infants understand the meaning of many common words. Second, it assessed the robustness of a ‘comprehension’ interpretation by dissociating semantic knowledge from confounded extra-linguistic cues via the manipulation of the contingency between words and objects. Our planned analyses revealed that Norwegian six- to nine-month-old infants did not understand the meaning of the words used in the study. Our exploratory analyses showed evidence of word comprehension at eight to nine months of age—rather than from six to seven months of age for English-learning infants—suggesting that there are cross-linguistic differences in the onset of word comprehension. In addition, our study revealed that eight- to nine-month-old infants cannot rely exclusively on single extra-linguistic cues to disambiguate between two items, thus suggesting the existence of early word-object mappings. However, these mappings are weak, as infants need additional cues (such as an imbalance in frequency of word use) to reveal word recognition. Our results suggest that the very onset of word comprehension is not based on the infants' knowledge of words per se. Rather, infants use a converging set of cues to identify referents, among which frequency is a robust (pre-semantic) cue that infants exploit to guide object disambiguation and, in turn, learn new words.

• Mayor, Julien; Arias-Trejo, Natalia & Alva, Elda (2018). The Impact of Household Size on Lexical Typicality: An Early Link Between Language and Social Cognition? Frontiers in Psychology. 9, p. 1445–1445. doi: 10.3389/fpsyg.2018.01445. Full text in Research Archive Show summary

  To communicate successfully, speakers need to use words that are understood by their listeners; they thus need to understand that others have vocabularies different than their own. A key question is whether this social cognition skill is already present in infancy, and whether it can have an impact on early language production. Analysis of the vocabularies of 550 Mexican children revealed that, at 24 months of age, but not at 18 nor at 30 months of age, those who were raised in households with larger numbers of children had more stereotypical vocabularies than those with fewer children. This finding is discussed in light of the hypothesis that communicative pressure may shape early word production; it suggests that bidirectional effects between social cognition and language acquisition are present at two years of age.

• Mayor, Julien & Mani, Nivedita (2018). A short version of the MacArthur–Bates Communicative Development Inventories with high validity. Behavior Research Methods. ISSN 1554-351X. 51, p. 1–2248. doi: 10.3758/s13428-018-1146-0. Full text in Research Archive Show summary

  The MacArthur–Bates Communicative Development Inventories (CDIs) are among the most widely used evaluation tools for early language development. CDIs are filled in by the parents or caregivers of young children by indicating which of a prespecified list of words and/or sentences their child understands and/or produces. Despite the success of these instruments, their administration is time-consuming and can be of limited use in clinical settings, multilingual environments, or when parents possess low literacy skills. We present a new method through which an estimation of the full-CDI score can be obtained, by combining parental responses on a limited set of words sampled randomly from the full CDI with vocabulary information extracted from the WordBank database, sampled from age-, gender-, and language-matched participants. Real-data simulations using versions of the CDI-WS for American English, German, and Norwegian as examples revealed the high validity and reliability of the instrument, even for tests having just 25 words, effectively cutting administration time to a couple of minutes. Empirical validations with new German-speaking participants confirmed the robustness of the test.

• Klinger, Joern; Mayor, Julien & Colin, Bannard (2016). Children’s faithfulness in imitating language use varies cross-culturally, contingent on prior experience. Child Development. ISSN 0009-3920. 87(3), p. 820–833. doi: 10.1111/cdev.12503. Full text in Research Archive
• Mayor, Julien & Plunkett, Kim (2014). Infant Word Recognition: Insights from TRACE Simulations. Journal of Memory and Language. ISSN 0749-596X. 71(1), p. 89–123. doi: 10.1016/j.jml.2013.09.009. Full text in Research Archive
• Mayor, Julien & Plunkett, Kim (2014). Shared Understanding and Idiosyncratic Expression in Early Vocabularies. Developmental Science. ISSN 1363-755X. 17(3), p. 412–423. doi: 10.1111/desc.12130. Full text in Research Archive
• Mayor, Julien & Plunkett, Kim (2011). A statistical estimate of infant and toddler vocabulary size from CDI analysis. Developmental Science. ISSN 1363-755X. 14(4), p. 769–785. doi: 10.1111/j.1467-7687.2010.01024.x. Full text in Research Archive
• Mayor, Julien (2010). Are Scientists Nearsighted Gamblers? The Misleading Nature of Impact Factors. Frontiers in Psychology. 1(215). Full text in Research Archive
• Mayor, Julien & Plunkett, Kim (2010). A neurocomputational account of taxonomic responding and fast mapping in early word learning. Psychological review. ISSN 0033-295X. 117(1), p. 1–1. Full text in Research Archive
• Gliozzi, Valentina; Mayor, Julien; Hu, Jon-Fan & Plunkett, Kim (2009). Labels as features (not names) for infant categorization: A neurocomputational approach. Cognitive Science. ISSN 0364-0213. 33(4), p. 709–738. Full text in Research Archive
• Mayor, Julien & Gerstner, Wulfram (2005). Signal buffering in random networks of spiking neurons: Microscopic versus macroscopic phenomena. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 72(5). Full text in Research Archive
• Mayor, Julien & Gerstner, Wulfram (2005). Noise-enhanced computation in a model of a cortical column. NeuroReport. ISSN 0959-4965. 16(11), p. 1237–1240. Full text in Research Archive
• Mayor, Julien & Gerstner, Wulfram (2004). Transient information flow in a network of excitatory and inhibitory model neurons: Role of noise and signal autocorrelation. Journal of Physiology - Paris. ISSN 0928-4257. 98(4-6), p. 417–428. Full text in Research Archive

View all works in NVA

• Boskovic, Ana; Rosslund, Audun Rørvik; Mayor, Julien & Kartushina, Natalia (2026). Statistical learning and word segmentation in Norwegian infants: No evidence across dialectal variability. Full text in Research Archive
• Kartushina, Natalia; Rosslund, Audun Rørvik; Vangsnes, Øystein Alexander & Mayor, Julien (2026). Dialect exposure in infancy: Hurdle or help? New insights into language processing. Full text in Research Archive
• Rosslund, Audun Rørvik; Serres, Nora Rose; Kartushina, Natalia & Mayor, Julien (2025). Early language acquisition: From birth order effect to child-to-caregiver ratio. Full text in Research Archive
• Otto, Sofie; Kartushina, Natalia; Rosslund, Audun Rørvik & Mayor, Julien (2025). Parents’ attitudes and early parent-child interactions: Insights from a language-generic intervention on multilingual families. Full text in Research Archive
• Boskovic, Ana; Kartushina, Natalia; Mayor, Julien & Rosslund, Audun Rørvik (2025). The impact of dialectal variability on word segmentation in infancy: Insights from Norway. Full text in Research Archive
• Serres, Nora Rose; Mayor, Julien; Kartushina, Natalia & Rosslund, Audun Rørvik (2025). Dialectal variability shapes early language development: Evidence from mispronunciation sensitivity in 13-month-old infants. Full text in Research Archive
• Rosslund, Audun Rørvik; Kartushina, Natalia; Serres, Nora Rose & Mayor, Julien (2025). Negative sibling effects revised: When a sibling becomes a caregiver. Full text in Research Archive
• Rosslund, Audun Rørvik; Mayor, Julien & Kartushina, Natalia (2025). No evidence that Norwegian parents tailor infant-directed speech based on attributed word knowledge. Full text in Research Archive
• Kartushina, Natalia; Mayor, Julien; White, Michelle Jennifer; Gundersen, Anni Sofie Myrtveit; Onnis, Luca & Hagelund, Silje [Show all 9 contributors for this article] (2025). Reliability of acoustic measures of infant-directed speech between lab and home environments and play and reading contexts. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Mundry, Roger; Singh, Arun Prakash; Cristia, Alejandrina & Kartushina, Natalia (2024). A longitudinal investigation of the acoustic properties of infant-directed speech from 6 to 18 months. Full text in Research Archive
• Munoz, Luis Eduardo; Rosslund, Audun; Kartushina, Natalia & Mayor, Julien (2024). Pacifier use is associated with reduced word comprehension in early childhood. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Mundry, Roger; Singh, Arun Prakash; Cristia, Alejandrina & Kartushina, Natalia (2024). A longitudinal investigation of the acoustic properties of infant-directed speech from 6 to 18 months. Full text in Research Archive
• Rosslund, Audun; Hatlevoll, Nina Emilie Varjola; Mayor, Julien & Kartushina, Natalia (2024). Longitudinal changes in consonant production in infant-directed speech and infants’ early speech production from 6 to 12 months. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Cristia, Alejandrina & Kartushina, Natalia (2024). Native and non-native vowel discrimination in 6-month-old Norwegian infants. Full text in Research Archive
• Munoz, Luis Eduardo; Rosslund, Audun; Kartushina, Natalia & Mayor, Julien (2024). No evidence of native sound discrimination in Norwegian 9-month-old infants using an eye-tracking habituation paradigm. Full text in Research Archive
• Hatlevoll, Nina Emilie Varjola; Rosslund, Audun; Mayor, Julien & Kartushina, Natalia (2023). Voice onset time in Norwegian infant directed speech: A longitudinal study on the relationship between consonant production in parents’ IDS and infants’ babbling. Full text in Research Archive
• Rosslund, Audun; Hagelund, Silje; Mayor, Julien & Kartushina, Natalia (2023). Mothers’ and fathers’ infant- directed speech have similar acoustic properties, but these are not associated with direct or indirect measures of word comprehension in 8-month-old infants. Full text in Research Archive
• Rosslund, Audun; Kartushina, Natalia & Mayor, Julien (2023). Associations between shared book reading and vocabulary size are stronger among lower-SES infants. Full text in Research Archive
• Munoz, Luis Eduardo; Rosslund, Audun; Mayor, Julien & Kartushina, Natalia (2023). No evidence of native sound discrimination in Norwegian 9-month-old infants using an eye-tracking habituation paradigm. Full text in Research Archive
• Richie-Halford, Adam; Cieslak, Matthew; Ai, Lei; Caffarra, Sendy; Covitz, Sydney & Franco, Alexandre R. [Show all 121 contributors for this article] (2023). Author Correction: An analysis-ready and quality controlled resource for pediatric brain white-matter research (Scientific Data, (2022), 9, 1, (616), 10.1038/s41597-022-01695-7). Scientific Data. 10(1). doi: 10.1038/s41597-023-02137-8. Full text in Research Archive
• Serres, Nora Rose; Mayor, Julien & Kartushina, Natalia (2023). The role of dialect variability on mispronunciation sensitivity: An insight to infants’ early language development from a Norwegian context. Full text in Research Archive
• Bochynska, Agata; Quintana, Daniel; Mayor, Julien; Leknes, Siri; Roettger, Timo & Mayiwar, Lewend [Show all 7 contributors for this article] (2022). Fram for troverdig forskning: Forskningen må være gjennomsiktig og etterprøvbar. 54(4), p. 38–39. Full text in Research Archive Show summary

  Forskere ved Universitetet i Oslo, Handelshøyskolen BI og Høgskolen i Østfold har etablert det nasjonale nettverket Norwegian Reproducibility Network (NORRN). NORRN skal bidra til god forskningspraksis i Norge gjennom å fremme og legge til rette for åpenhet og etterprøvbarhet av forskningsresultater.

• Rosslund, Audun; Mayor, Julien & Kartushina, Natalia (2022). Barns ordforråd skjøt fart når barnehagene stengte ned under pandemien. Første steg. ISSN 1504-1891. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2022). Parents’ hyper pitch and vowel category compactness in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary. Full text in Research Archive
• Richie-Halford, Adam; Cieslak, Matthew; Ai, Lei; Caffarra, Sendy; Covitz, Sydney & Franco, Alexandre R. [Show all 139 contributors for this article] (2022). Publisher Correction: An analysis-ready and quality controlled resource for pediatric brain white-matter research (Scientific Data, (2022), 9, 1, (616), 10.1038/s41597-022-01695-7). Scientific Data. 9(1). doi: 10.1038/s41597-022-01770-z. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2022). Parents’ hyper pitch and vowel category compactness in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2022). Parents’ hyper pitch and vowel category compactness in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2022). Parents’ hyper pitch and vowel category compactness in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary. Full text in Research Archive
• Rosslund, Audun; Roepstorff, Ida; Lo, Chang Huan; Chai, Jun Ho; Mayor, Julien & Kartushina, Natalia (2022). Alignments between direct tablet-based assessment of word comprehension and parent reports depend on child’s age and word properties. Full text in Research Archive
• Muñoz, Luis Eduardo; Kartushina, Natalia & Mayor, Julien (2022). Sustained Pacifier Use is Associated with Smaller Vocabulary sizes at 1 and 2 Years of Age. Full text in Research Archive
• Munoz, Luis Eduardo; Kartushina, Natalia & Mayor, Julien (2022). Season-of-Birth Effects on Infant Vocabulary Size. Full text in Research Archive
• Munoz, Luis Eduardo; Kartushina, Natalia & Mayor, Julien (2022). Season-of-birth effects on infant vocabulary size. Full text in Research Archive
• Munoz, Luis Eduardo; Kartushina, Natalia & Mayor, Julien (2022). Sustained Pacifier Use is Associated with Smaller Vocabulary Sizes at 1 and 2 Years of Age. Full text in Research Archive
• Kartushina, Natalia; Robberstad, Silje & Mayor, Julien (2021). The Role of Parental Speech in Infant Language Development: Insights from 8-9-month-old Norwegian Infants . Full text in Research Archive
• Kartushina, Natalia; Robberstad, Silje; Munoz, Luis Eduardo & Mayor, Julien (2021). Acoustic properties of Norwegian infant-directed speech and their role in language development of 8-9-month-old infants. Full text in Research Archive
• Rosslund, Audun; Kartushina, Natalia; Mayor, Julien; Chai, Jun Ho & Lo, Chang Huan (2021). Tablet assessment of word comprehension reveals coarse word representations in 18-20-month-old toddlers. Full text in Research Archive
• Rosslund, Audun; Mayor, Julien; Óturai, Gabriella & Kartushina, Natalia (2021). Babytalk in Tromsø. Full text in Research Archive
• Rother, Nicolas; Burtscher, Michael Josef; Gobet, Fernand; Mantzouranis, Gregory; Mayor, Julien & Pirrone, Angelo [Show all 9 contributors for this article] (2021). The beginning of a new era. Swiss Psychology Open (SPO). 1(1), p. 1–1. doi: 10.5334/spo.27. Full text in Research Archive
• Kartushina, Natalia; Rosslund, Audun Rørvik & Mayor, Julien (2020). Toddlers raised in multi- dialectal families learn words better in accented speech than those raised in monodialectal families. Full text in Research Archive
• Kartushina, Natalia; Rosslund, Audun Rørvik & Mayor, Julien (2020). Toddlers raised in multi- dialectal families learn words better in accented speech than those raised in monodialectal families. Full text in Research Archive
• Kartushina, Natalia; Rosslund, Audun Rørvik & Mayor, Julien (2020). Toddlers raised in multi- dialectal families learn words better in accented speech than those raised in monodialectal families. Full text in Research Archive
• Mayor, Julien; Gomez, Pablo; Chang, Franklin & Lupyan, Gary (2014). Connectionism coming of age: legacy and future challenges. Frontiers in Psychology. 5(187). Full text in Research Archive
• Rosslund, Audun; Kartushina, Natalia & Mayor, Julien (2024). The acoustic properties and role of infant-directed speech in early language development – Longitudinal and cross-sectional studies. Universitetet i Oslo. Full text in Research Archive Show summary

  How do caregivers fine-tune their speech when interacting with infants? Do these potential modulations support infants’ language development? In this dissertation, Rosslund and colleagues tackle these questions and address gaps in the scientific literature on so-called infant-directed speech (IDS). Accumulated across four preregistered studies, the dissertation provides both longitudinal and cross-sectional evidence that Norwegian parents modulate the intonational, temporal, and segmental features of their speech to infants. However, some of these acoustic modulations challenge the notion that IDS is directly tailored to facilitate language learning. This is further supported by the lack of associations between properties of parents’ IDS and infants’ language outcomes from 6 to 12 months of age. Additionally, at 18 months, infants who receive speech input with more variable vowel categories have smaller vocabularies than their peers. Yet, at the same age, parents who adapt a more exaggerated pitch height in IDS have infants with larger vocabularies. Thus, IDS might only indirectly support language development by attracting infants’ attention to the parent and speech stream, in turn bootstrapping language processing mechanisms. This dissertation contributes to the empirical evidence and theoretical debate regarding IDS by presenting analyses of a comprehensive set of acoustic properties of speech and their relationship with infants’ language outcomes, thereby providing a more explicit test of its proposed role in language development. Notably, our studies are coupled with open materials and data, inviting continued exploration and promoting scientific progress.

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