Quantifying Sources of Variability in Infancy Research Using the Infant-Directed-Speech Preference

Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, 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 in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). 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 IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure

Observation of the Bc+ → J/ψπ+π0 decay

The first observation of the Bc+→J/ψπ+π0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the Bc+→J/ψπ+ channel is measured to beBBc+→J/ψπ+π0BBc+→J/ψπ+=2.80±0.15±0.11±0.16, where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and Bc+→J/ψπ+ decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation

Lexical-semantic priming effects during infancy.

When and how do infants develop a semantic system of words that are related to each other? We investigated word-word associations in early lexical development using an adaptation of the inter-modal preferential looking task where word pairs (as opposed to single target words) were used to direct infants' attention towards a target picture. Two words (prime and target) were presented in quick succession after which infants were presented with a picture pair (target and distracter). Prime-target word pairs were either semantically and associatively related or unrelated; the targets were either named or unnamed. Experiment 1 demonstrated a lexical-semantic priming effect for 21-month olds but not for 18-month olds: unrelated prime words interfered with linguistic target identification for 21-month olds. Follow-up experiments confirmed the interfering effects of unrelated prime words and identified the existence of repetition priming effects as young as 18 months of age. The results of these experiments indicate that infants have begun to develop semantic-associative links between lexical items as early as 21 months of age

What's in a link: associative and taxonomic priming effects in the infant lexicon.

Infants develop a lexical-semantic system of associatively and semantically related words by the end of the second year of life. However, the precise nature of the lexical relationships that underpin the structure-building process remains under-determined. We compare two types of lexical-semantic relationship, associative and taxonomic, using a lexical-priming adaption of the intermodal preferential looking task with 21- and 24-month-olds. Prime-target word pairs were either associatively or taxonomically related or unrelated. A further control condition evaluated the facility of a prime word, in the absence of a target word, to promote target preferences. Twenty-four-month-olds, but not 21-month-old infants, exhibited a priming effect in both associative and taxonomic conditions, pointing to the formation of a lexical-semantic network driven by both associative and taxonomic relatedness late in the second year. The pattern of priming in 24-month-olds indicates the operation of inhibitory processes: unrelated primes interfere with target recognition whereas related primes do not. We argue that taxonomic and associative relationships between words are integral to the emergence of a structured lexicon and discuss the importance of inhibitory mechanisms in shaping early lexical-semantic memory

The effects of perceptual similarity and category membership on early word-referent identification.

We investigated the impact of perceptual and categorical relatedness between a target and a distracter object on early referent identification in infants and adults. In an intermodal preferential looking (IPL) task, participants looked at a target object paired with a distracter object that could be perceptually similar or dissimilar and drawn from the same or different global category. The proportion of target looking measures revealed that infants and adults were sensitive to the interplay between category membership and perceptual similarity. Online latency measures demonstrated an advantage for perceptually dissimilar items regardless of their categorical status, indicating that different IPL measures index different processes during target identification. Results suggest that perceptual similarity and category membership of the objects lead to competition effects in word recognition and referent identification in both adults and infants and that lexical categorization and nonlinguistic categorization processes are closely related during infancy

Is Tuba Masculine or Feminine? The Timing of Grammatical Gender

We used computer mouse tracking to investigate gender ratings of musical instruments in monolingual Spanish and English speakers. Musical instruments are tied to conceptual representations of gender. Consistent with previous research, English speakers rated the instruments male and female following these relatively stable conceptual representations, while Spanish speakers used grammar—in addition to their conceptual representations of gender—to perform their ratings. Interestingly, the responses of the Spanish speakers were influenced first by the grammatical information and 60 ms later by the conceptual representations. Measuring how participants\u27 responses unfold over time provides novel information regarding the timing of grammatical gender