Limited evidence of test-retest reliability in infant-directed speech preference in a large preregistered infant experiment.

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. RESEARCH HIGHLIGHTS: We assessed test-retest reliability of infants' preference for infant-directed over adult-directed speech in a large pre-registered sample (N = 158). There was no consistent evidence of test-retest reliability in measures of infants' speech preference. Applying stricter criteria for the inclusion of participants may lead to higher test-retest reliability, but at the cost of substantial decreases in sample size. Developmental research relying on stable individual differences should consider the underlying reliability of its measures.

Becoming word meaning experts: Infants' processing of familiar words in the context of typical and atypical exemplars.

How do infants become word meaning experts? This registered report investigated the structure of infants' early lexical representations by manipulating the typicality of exemplars from familiar animal categories. 14- to 18-month-old infants (N = 84; 51 female; M = 15.7 months; race/ethnicity: 64% White, 8% Asian, 2% Hispanic, 1% Black, and 23% multiple categories; participating 2022-2023) were tested on their ability to recognize typical and atypical category exemplars after hearing familiar basic-level category labels. Infants robustly recognized both typical (d = 0.79, 95% CI [0.54, 1.03]) and atypical (d = 0.70, 95% CI [0.46, 0.94]) exemplars, with no significant difference between typicality conditions (d = 0.14, 95% CI [-0.08, 0.35]). These results support a broad-to-narrow account of infants' early word meanings. Implications for the role of experience in the development of lexical knowledge are discussed.

Nameability supports rule-based category learning in children and adults.

The present study tested the hypothesis that verbal labels support category induction by providing compact hypotheses. Ninety-seven 4- to 6-year-old children (M = 63.2 months; 46 female, 51 male; 77% White, 8% more than one race, 4% Asian, and 3% Black; tested 2018) and 90 adults (M = 20.1 years; 70 female, 20 male) in the Midwestern United States learned novel categories with features that were easy (e.g., "red") or difficult (e.g., "mauve") to name. Adults (d = 1.06) and-to a lesser extent-children (d = 0.57; final training block) learned categories composed of more nameable features better. Children's knowledge of difficult-to-name color words predicted their learning for categories with difficult-to-name features. Rule-based category learning may be supported by the emerging ability to form verbal hypotheses.

Peekbank: An open, large-scale repository for developmental eye-tracking data of children's word recognition.

The ability to rapidly recognize words and link them to referents is central to children's early language development. This ability, often called word recognition in the developmental literature, is typically studied in the looking-while-listening paradigm, which measures infants' fixation on a target object (vs. a distractor) after hearing a target label. We present a large-scale, open database of infant and toddler eye-tracking data from looking-while-listening tasks. The goal of this effort is to address theoretical and methodological challenges in measuring vocabulary development. We first present how we created the database, its features and structure, and associated tools for processing and accessing infant eye-tracking datasets. Using these tools, we then work through two illustrative examples to show how researchers can use Peekbank to interrogate theoretical and methodological questions about children's developing word recognition ability.

Good-Enough Production: Selecting Easier Words Instead of More Accurate Ones.

Dominant theories of language production suggest that word choice-lexical selection-is driven by alignment with the intended message: To talk about a young feline, we choose the most aligned word, kitten. Another factor that could shape lexical selection is word accessibility, or how easy it is to produce a given word (e.g., cat is more accessible than kitten). To test whether producers are also influenced by word accessibility, we designed an artificial lexicon containing high- and low-frequency words whose meanings correspond to compass directions. Participants in a communication game (total N = 181 adults) earned points by producing compass directions, which often required an implicit decision between a high- and low-frequency word. A trade-off was observed across four experiments; specifically, high-frequency words were produced even when less aligned with messages. These results suggest that implicit decisions between words are impacted by accessibility. Of all the times that people have produced cat, sometimes they likely meant kitten.

The representation of emotion knowledge across development.

The present study examined how children spontaneously represent facial cues associated with emotion. 106 three- to six-year-old children (48 male, 58 female; 9.4% Asian, 84.0% White, 6.6% more than one race) and 40 adults (10 male, 30 female; 10% Hispanic, 30% Asian, 2.5% Black, 57.5% White) were recruited from a Midwestern city (2019-2020), and sorted emotion cues in a spatial arrangement method that assesses emotion knowledge without reliance on emotion vocabulary. Using supervised and unsupervised analyses, the study found evidence for continuities and gradual changes in children's emotion knowledge compared to adults. Emotion knowledge develops through an incremental learning process in which children change their representations using combinations of factors-particularly valence-that are weighted differently across development.

Improving the generalizability of infant psychological research: The ManyBabies model.

Yarkoni's analysis clearly articulates a number of concerns limiting the generalizability and explanatory power of psychological findings, many of which are compounded in infancy research. ManyBabies addresses these concerns via a radically collaborative, large-scale and open approach to research that is grounded in theory-building, committed to diversification, and focused on understanding sources of variation.

Sampling to learn words: Adults and children sample words that reduce referential ambiguity.

How do learners gather new information during word learning? One possibility is that learners selectively sample items that help them reduce uncertainty about new word meanings. In a series of cross-situational word learning tasks with adults and children, we manipulated the referential ambiguity of label-object pairs experienced during training and subsequently investigated which words participants chose to sample additional information about. In the first experiment, adult learners chose to receive additional training on object-label associations that reduce referential ambiguity during cross-situational word learning. This ambiguity-reduction strategy was related to improved test performance. In two subsequent experiments, we found that, at least in some contexts, children (3-8 years of age) show a similar preference to seek information about words experienced in ambiguous word learning situations. In Experiment 2, children did not preferentially select object-label associations that remained ambiguous during cross-situational word learning. However, in a third experiment that increased the relative ambiguity of two sets of novel object-label associations, we found evidence that children preferentially make selections that reduce ambiguity about novel word meanings. These results carry implications for understanding how children actively contribute to their own language development by seeking information that supports learning.

Experience with research paradigms relates to infants' direction of preference.

Interpreting and predicting direction of preference in infant research has been a thorny issue for decades. Several factors have been proposed to account for familiarity versus novelty preferences, including age, length of exposure, and task complexity. The current study explores an additional dimension: experience with the experimental paradigm. We reanalyzed the data from 4 experiments on artificial grammar learning in 12-month-old infants run using the head-turn preference procedure (HPP). Participants in these studies varied substantially in their number of laboratory visits. Results show that the number of HPP studies is related to direction of preference: Infants with limited experience with the HPP setting were more likely to show familiarity preferences than infants who had amassed more experience with this paradigm. This evidence has important implications for the interpretation of experimental results: Experience with a given method or, more broadly, with the laboratory environment may affect infants' patterns of preferences.

The temporal structure of naming events differentially affects children's and adults' cross-situational word learning.

To acquire novel words, learners often need to integrate information about word meanings across ambiguous learning events distributed in time. How does the temporal structure of those word learning events affect what learners encode? How do the effects of temporal structure differ in children and adults? In the current experiments, we asked how 4- to 7-year-old children's (N = 110) and adults' (N = 90) performance on a cross-situational word learning task is influenced by the temporal distribution of learning events. We tested participants in three training conditions, manipulating the number of trials that separated naming events for specific objects. In the Unstructured condition, the temporal distribution was varied; in the Massed condition, naming events occurred with few interleaved trials; and in the Interleaved condition, naming events occurred with many interleaved trials. Adults showed substantially larger benefits from the Massed condition than children, whereas children were equally successful at learning in the Massed and Interleaved conditions. These results provide evidence that adults differ from children in how they exploit temporal structure during cross-situational word learning.

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.

The role of social interaction and pedagogical cues for eliciting and reducing overimitation in preschoolers.

The tendency to imitate causally irrelevant actions is termed overimitation. Here we investigated (a) whether communication of a model performing irrelevant actions is necessary to elicit overimitation in preschoolers and (b) whether communication of another model performing an efficient action modulates the subsequent reduction of overimitation. In the study, 5-year-olds imitated irrelevant actions both when they were modeled by a communicative and pedagogical experimenter and when they were modeled by a non-communicative and non-pedagogical experimenter. However, children stopped using the previously learned irrelevant actions only when they were subsequently shown the more efficient way to achieve the goal by a pedagogical experimenter. Thus, communication leads preschoolers to adapt their imitative behavior but does not seem to affect overimitation in the first place. Results are discussed with regard to the importance of communication for the transmission of cultural knowledge during development.

Evidence for Infant-directed Speech Preference Is Consistent Across Large-scale, Multi-site Replication and Meta-analysis.

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.

The map trap: Why and how word learning research should move beyond mapping.

A pervasive goal in the study of how children learn word meanings is to explain how young children solve the mapping problem. The mapping problem asks how language learners connect a label to its referent. Mapping is one part of word learning, however, it does not reflect other critical components of word meaning construction, such as the encoding of lexico-semantic relations and socio-pragmatic context. In this paper, we argue that word learning researchers' overemphasis of mapping has constrained our experimental paradigms and hypotheses, leading to misconceived theories and policy interventions. We first explain how the mapping focus limits our ability to study the richness and complexity of what infants and children learn about, and do with, word meanings. Then, we describe how our focus on mapping has constrained theory development. Specifically, we show how it has led to (a) the misguided emphasis on referent selection and ostensive labeling, and (b) the undervaluing of diverse pathways to word knowledge, both within and across cultures. We also review the consequences of the mapping focus outside of the lab, including myopic language learning interventions. Last, we outline an alternative, more inclusive approach to experimental study and theory construction in word learning research. This article is categorized under: Psychology > Language Psychology > Theory and Methods Psychology > Learning.

Finding categories through words: More nameable features improve category learning.

What are the cognitive consequences of having a name for something? Having a word for a feature makes it easier to communicate about a set of exemplars belonging to the same category (e.g., "the red things"). But might it also make it easier to learn the category itself? Here, we provide evidence that the ease of learning category distinctions based on simple visual features is predicted from the ease of naming those features. Across seven experiments, participants learned categories composed of colors or shapes that were either easy or more difficult to name in English. Holding the category structure constant, when the underlying features of the category were easy to name, participants were faster and more accurate in learning the novel category. These results suggest that compact verbal labels may facilitate hypothesis formation during learning: it is easier to pose the hypothesis "it is about redness" than "it is about that pinkish-purplish color". Our results have consequences for understanding how developmental and cross-linguistic differences in a language's vocabulary affect category learning and conceptual development.

Tuning in to non-adjacencies: Exposure to learnable patterns supports discovering otherwise difficult structures.

Non-adjacent dependencies are ubiquitous in language, but difficult to learn in artificial language experiments in the lab. Previous research suggests that non-adjacent dependencies are more learnable given structural support in the input - for instance, in the presence of high variability between dependent items. However, not all non-adjacent dependencies occur in supportive contexts. How are such regularities learned? One possibility is that learning one set of non-adjacent dependencies can highlight similar structures in subsequent input, facilitating the acquisition of new non-adjacent dependencies that are otherwise difficult to learn. In three experiments, we show that prior exposure to learnable non-adjacent dependencies - i.e., dependencies presented in a learning context that has been shown to facilitate discovery - improves learning of novel non-adjacent regularities that are typically not detected. These findings demonstrate how the discovery of complex linguistic structures can build on past learning in supportive contexts.

The company objects keep: Linking referents together during cross-situational word learning.

Learning the meanings of words involves not only linking individual words to referents but also building a network of connections among entities in the world, concepts, and words. Previous studies reveal that infants and adults track the statistical co-occurrence of labels and objects across multiple ambiguous training instances to learn words. However, it is less clear whether, given distributional or attentional cues, learners also encode associations amongst the novel objects. We investigated the consequences of two types of cues that highlighted object-object links in a cross-situational word learning task: distributional structure - how frequently the referents of novel words occurred together - and visual context - whether the referents were seen on matching backgrounds. Across three experiments, we found that in addition to learning novel words, adults formed connections between frequently co-occurring objects. These findings indicate that learners exploit statistical regularities to form multiple types of associations during word learning.