Lexical stress constrains English-learning infants' segmentation in a non-native language.

Infants' ability to segment words in fluent speech is affected by their language experience. In this study we investigated the conditions under which infants can segment words in a non-native language. Using the Head-turn Preference Procedure, we found that monolingual English-learning 8-month-olds can segment bisyllabic words in Spanish (trochees and iambs) but not French (iambs). Our results are incompatible with accounts that rely on distributional learning, language rhythm similarity, or target word prosodic shape alone. Instead, we show that monolingual English-learning infants are able to segment words in a non-native language as long as words have stress, as is the case in English. More specifically, we show that even in a rhythmically different non-native language, English-learning infants can find words by detecting stressed syllables and treating them as word onsets or offsets

Short-term exposure alters adult listeners’ perception of segmental phonotactics

This study evaluates the malleability of adults' perception of probabilistic phonotactic (biphone) probabilities, building on a body of literature on statistical phonotactic learning. It was first replicated that listeners categorize phonetic continua as sounds that create higher-probability sequences in their native language. Listeners were also exposed to skewed distributions of biphone contexts, which resulted in the enhancement or reversal of these effects. Thus, listeners dynamically update biphone probabilities (BPs) and bring this to bear on perception of ambiguous acoustic information. These effects can override long-term BP effects rooted in native language experience

Perceptual Similarity Modulates Context Effects in Online Compensation for Phonological Variation

Using a cross-modal word identification task and an eye-tracking visual-world experiment, we investigated the importance of phonological context in the recovery of tap variants of /t/- and /d/-final words in American English. In Experiment 1, listeners were less accurate when they heard a tap variant of a /t/ word in a non-licensing environment (before a consonant) than when they heard it in a licensing environment (before an unstressed vowel). Contrastively, there was no difference in accuracy for tap variants of /d/ words across different contexts. Similarly, in Experiment 2, listeners looked less often at the target word when they heard tap variants of /t/ words in a mismatching context than a matching one. A mismatch context, however, did not result in fewer looks to the target with tap variants of /d/ words. Importantly, both accuracy and proportion of looks to the target word were higher in the mismatch phonological context than when presented with mispronounced forms. Our results contrast with previous findings on tap variants of /t/. These findings also suggest that contextual information is less important when a surface form is a closer perceptual match to the lexical representation (canonical stops and tap variants of /d/). Thus a model of word recognition must take into account both frequency of a variant in context and the perceptual distance between a variant and its lexical representation

The perception of boundary tones in infancy

We investigated English-learning 4-month-olds’ ability to discriminate a final rise versus fall in pitch that distinguishes questions from statements in Portuguese and English. Using visual habituation, we showed that English-learning 4-month-olds failed to categorize segmentally varied Portuguese statements vs. questions. They only succeeded when tested with restricted segmental variability in a more sensitive procedure. Finally, we showed that Basque-learning 4-month-olds have no difficulty categorizing Portuguese statements and questions. Thus, unlike their Portuguese-learning peers, English-learning 4-mo-olds are limited in their ability to distinguish Portuguese statements vs. questions. This is not simply because of the use of non-native speech stimuli, as demonstrated by the success of the Basque infants. This implies that infants’ perception of boundary tones is already language-specific at 5-months. Additionally, our results provide a way to reconcile previous puzzling findings about English-learning infants’ difficulty in categorizing English statements from questions

A multilab study of bilingual infants: Exploring the preference for infant-directed speech

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) compared with adult-directed speech (ADS). Yet IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multisite study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants’ IDS preference. As part of the multilab ManyBabies 1 project, we compared preference for North American English (NAE) IDS in lab-matched samples of 333 bilingual and 384 monolingual infants tested in 17 labs in seven countries. The tested infants were in two age groups: 6 to 9 months and 12 to 15 months. We found that bilingual and monolingual infants both preferred IDS to ADS, and the two groups did not differ in terms of the overall magnitude of this preference. However, among bilingual infants who were acquiring NAE as a native language, greater exposure to NAE was associated with a stronger IDS preference. These findings extend the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger IDS preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes similar contributions to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments