This study examines convergence between parental reports and behavioral measures in assessing early word knowledge of twenty-eight 14-month-old Korean infants. We compared infants' word recognition patterns with parental reports using full and shorter versions of the Korean MacArthur-Bates Communicative Development Inventories (MCDI-K). Our analyses revealed three key patterns. First, while parents showed consistent judgment between the full CDI and the target-word checklist, the checklist demonstrated better convergence with eye-tracking measures, which accounted for baseline looking biases. Second, parents' reporting accuracy varied systematically with item difficulty: for early-acquired words, parents showed higher agreement with eye-tracking than for later-acquired words. Third, exploratory analyses suggested a possible asymmetry in word category recognition, with infants showing stronger recognition of nouns than verbs in the eye-tracking task, contrasting with more balanced verb-noun knowledge in parental reports. These findings show that assessment methods capture different aspects of early word knowledge.

This study investigates how corpus-level properties in Korean child- and adult-directed speech shape word segmentation across four algorithms: Transitional Probability, Diphone-Based Segmentation, PUDDLE, and Adaptor Grammar. Utterance length consistently impacts segmentation, with shorter utterances improving performance, particularly for PUDDLE, DiBS, and AG. Word length affects transitional probability algorithms, while hapax legomena introduce challenges for forward TP and AG. Interjections negatively influence AG, but not the others, and larger corpus size benefits PUDDLE. Register effects are limited, with forward TP and PUDDLE performing better on child-directed speech. These patterns highlight algorithm-specific sensitivities, with utterance length emerging as the most consistent factor. Our findings underscore the importance of considering both input properties and algorithm design when studying word segmentation in Korean. Future work should explore cross-linguistic comparisons, larger balanced corpora, and the role of multimodal cues in segmentation.

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.