Code-switching in parents' everyday speech to bilingual infants.

Code-switching is a common phenomenon in bilingual communities, but little is known about bilingual parents' code-switching when speaking to their infants. In a pre-registered study, we identified instances of code-switching in day-long at-home audio recordings of 21 French-English bilingual families in Montreal, Canada, who provided recordings when their infant was 10 and 18 months old. Overall, rates of infant-directed code-switching were low, averaging 7 times per hour (6 times per 1,000 words) at 10 months and increasing to 28 times per hour (18 times per 1,000 words) at 18 months. Parents code-switched more between sentences than within a sentence; this pattern was even more pronounced when infants were 18 months than when they were 10 months. The most common apparent reasons for code-switching were to bolster their infant's understanding and to teach vocabulary words. Combined, these results suggest that bilingual parents code-switch in ways that support successful bilingual language acquisition.

Quebec-based Parents' Attitudes Towards Childhood Multilingualism: Evaluative Dimensions and Potential Predictors.

This is the first large-scale, quantitative study of the evaluative dimensions and potential predictors of Quebec-based parents' attitudes towards childhood multilingualism. Such attitudes are assumed to constitute a determinant of parental language choices, and thereby influence children's multilingual development. The newly-developed Attitudes towards Childhood Multilingualism Questionnaire was used to gather data from 825 participants raising an infant/toddler aged 0-4 years with multiple languages in the home. The results revealed three separate dimensions: status and solidarity (the same dimensions found in attitudes towards individual languages) as well as cognitive development (not previously attested as a separate dimension). Participants' approach to promoting multilingualism (specifically, whether they used the one-person-one-language-approach) and the combination of languages transmitted (specifically, whether this included a heritage language) correlated significantly with parental attitudes towards childhood multilingualism. Parents' linguistic background and location within Quebec were not significant predictors of attitudes. The paper discusses implications and directions for further research.

What do bilingual infants actually hear? Evaluating measures of language input to bilingual-learning 10-month-olds.

Examining how bilingual infants experience their dual language input is important for understanding bilingual language acquisition. To assess these language experiences, researchers typically conduct language interviews with caregivers. However, little is known about the reliability of these parent reports in describing how bilingual children actually experience dual language input. Here, we explored the quantitative nature of dual language input to bilingual infants. Furthermore, we described some of the heterogeneity of bilingual exposure in a sample of French-English bilingual families. Participants were 21 families with a 10-month-old infant residing in Montréal, Canada. First, we conducted language interviews with the caregivers. Then, each family completed three full-day recordings at home using the Language Environment Analysis recording system. Results showed that children's proportion exposure to each language was consistent across the two measurement approaches, indicating that parent reports are reliable for assessing a bilingual child's language experiences. Further exploratory analyses revealed three unique findings: (a) there can be considerable variability in the absolute amount of input among infants hearing the same proportion of input, (b) infants can hear different proportions of language input when considering infant-directed versus overheard speech, (c) proportion of language input can vary by day, depending on who is caring for the infant. We conclude that collecting naturalistic recordings is complementary to parent-report measures for assessing infant's language experiences and for establishing bilingual profiles.

Physiological measures of mother-infant interactional synchrony.

Mother-infant interactional synchrony has been hypothesized to be crucial for the development of many key neurodevelopmental behaviors in infants, including speech and language. Assessing synchrony is challenging because many interactive behaviors may be subtlety, if at all, observable in overt behaviors. Physiological measures, therefore, may provide valuable physiological/biological markers of mother-infant synchrony. We have developed a multilevel measurement platform to assess physiological synchrony, attention, and vocal congruency during dynamic face-to-face mother-infant interactions. The present investigation was designed to provide preliminary data on its application in a group of 10 mother-infant dyads (20 subjects) ranging in age from 7 to 8.5 months at the time of the experimentation. Respiratory kinematics, heart rate, and vocalization were recorded simultaneously from mothers and infants during nonstructured, face-to-face interactions. Novel statistical methods were used to identify reliable moments of synchrony from cross-correlated, mother-infant respiration and to tag infant attention from heart rate deceleration. Results revealed that attention, vocal contingency, and respiratory synchrony are temporally clustered within the dyad interaction. This temporal alignment is consistent with the notion that biological synchrony provides a supportive platform for infant attention and mother-infant contingent vocalization.

Identifying bilingual talkers after a language switch: Language experience matters.

The current study investigates the role of language experience in generalizing indexical information across languages within bilingual speech. Participants (n = 48) learned to identify bilingual talkers speaking in one of their languages and were then tested on their ability to identify the same talker when speaking the same language and when speaking their other language. Both monolingual and bilingual participants showed above chance performance in identifying the talkers in both language contexts. However, bilingual participants outperformed monolinguals in generalizing knowledge about the speaker's voice across their two familiar languages, which may be driven by their experience with language mixing.

Monolingual and bilingual infants' word segmentation abilities in an inter-mixed dual-language task.

Previous studies show that young monolingual infants use language-specific cues to segment words in their native language. Here, we asked whether 8 and 10-month-old infants (N = 84) have the capacity to segment words in an inter-mixed bilingual context. Infants heard an English-French mixed passage that contained one target word in each language, and were then tested on their recognition of the two target words. The English-monolingual and French-monolingual infants showed evidence of segmentation in their native language, but not in the other unfamiliar language. As a group, the English-French bilingual infants segmented in both of their native languages. However, exploratory analyses suggest that exposure to language mixing may play a role in bilingual infants' segmentation skills. Taken together, these results indicate a close relation between language experience and word segmentation skills.

The consonant bias in word learning is not determined by position within the word: Evidence from vowel-initial words.

The current study used an object manipulation task to explore whether infants rely more on consonant information than on vowel information when learning new words even when the words start with a vowel. Canadian French-learning 20-month-olds, who were taught pairs of new vowel-initial words contrasted either on their initial vowel (opsi/eupsi) or following consonant (oupsa/outsa), were found to have learned the words only in the consonant condition and performed significantly better in the consonant condition than in the vowel condition. These results extend to Canadian French-learning infants the consonant bias in word learning previously found in French-learning infants from France and, crucially, shows that vocalic information has less weight than consonant information in new word learning even when it is the initial sound of the target words, confirming the consonant bias at the lexical level postulated by Nespor et al. (2003). The current findings also suggest that French-learning infants are able to segment vowel-initial words as early as 20 months of age.

Segmenting words from fluent speech during infancy - challenges and opportunities in a bilingual context.

Previous research shows that word segmentation is a language-specific skill. Here, we tested segmentation of bi-syllabic words in two languages (French; English) within the same infants in a single test session. In Experiment 1, monolingual 8-month-olds (French; English) segmented bi-syllabic words in their native language, but not in an unfamiliar and rhythmically different language. In Experiment 2, bilingual infants acquiring French and English demonstrated successful segmentation for French when it was tested first, but not for English and not for either language when tested second. There were no effects of language exposure on this pattern of findings. In Experiment 3, bilingual infants segmented the same English materials used in Experiment 2 when they were tested using the standard segmentation procedure, which provided more exposure to the test stimuli. These findings show that segmenting words in both their native languages in the dual-language task poses a distinct challenge for bilingual 8-month-olds acquiring French and English. Further research exploring early word segmentation will advance our understanding of bilingual acquisition and expand our fundamental knowledge of language and cognitive development.

Directional asymmetries reveal a universal bias in adult vowel perception.

Research on cross-language vowel perception in both infants and adults has shown that for many vowel contrasts, discrimination is easier when the same pair of vowels is presented in one direction compared to the reverse direction. According to one account, these directional asymmetries reflect a universal bias favoring "focal" vowels (i.e., vowels whose adjacent formants are close in frequency, which concentrates acoustic energy into a narrower spectral region). An alternative, but not mutually exclusive, account is that such effects reflect an experience-dependent bias favoring prototypical instances of native-language vowel categories. To disentangle the effects of focalization and prototypicality, the authors first identified a certain location in phonetic space where vowels were consistently categorized as /u/ by both Canadian-English and Canadian-French listeners, but that nevertheless varied in their stimulus goodness (i.e., the best Canadian-French /u/ exemplars were more focal compared to the best Canadian-English /u/ exemplars). In subsequent AX discrimination tests, both Canadian-English and Canadian-French listeners performed better at discriminating changes from less to more focal /u/'s compared to the reverse, regardless of variation in prototypicality. These findings demonstrate a universal bias favoring vowels with greater formant convergence that operates independently of biases related to language-specific prototype categorization.

When infants talk, infants listen: pre-babbling infants prefer listening to speech with infant vocal properties.

To learn to produce speech, infants must effectively monitor and assess their own speech output. Yet very little is known about how infants perceive speech produced by an infant, which has higher voice pitch and formant frequencies compared to adult or child speech. Here, we tested whether pre-babbling infants (at 4-6 months) prefer listening to vowel sounds with infant vocal properties over vowel sounds with adult vocal properties. A listening preference favoring infant vowels may derive from their higher voice pitch, which has been shown to attract infant attention in infant-directed speech (IDS). In addition, infants' nascent articulatory abilities may induce a bias favoring infant speech given that 4- to 6-month-olds are beginning to produce vowel sounds. We created infant and adult /i/ ('ee') vowels using a production-based synthesizer that simulates the act of speaking in talkers at different ages and then tested infants across four experiments using a sequential preferential listening task. The findings provide the first evidence that infants preferentially attend to vowel sounds with infant voice pitch and/or formants over vowel sounds with no infant-like vocal properties, supporting the view that infants' production abilities influence how they process infant speech. The findings with respect to voice pitch also reveal parallels between IDS and infant speech, raising new questions about the role of this speech register in infant development. Research exploring the underpinnings and impact of this perceptual bias can expand our understanding of infant language development.

Reading ability influences native and non-native voice recognition, even for unimpaired readers.

Research suggests that phonological ability exerts a gradient influence on talker identification, including evidence that adults and children with reading disability show impaired talker recognition for native and non-native languages. The present study examined whether this relationship is also observed among unimpaired readers. Learning rate and generalization of learning in a talker identification task were examined in average and advanced readers who were tested in both native and non-native language conditions. The results indicate that even among unimpaired readers, phonological competence as captured by reading ability exerts a gradient influence on perceptual learning for talkers' voices.

Who's talking now? Infants' perception of vowels with infant vocal properties.

Little is known about infants' abilities to perceive and categorize their own speech sounds or vocalizations produced by other infants. In the present study, prebabbling infants were habituated to /i/ ("ee") or /a/ ("ah") vowels synthesized to simulate men, women, and children, and then were presented with new instances of the habituation vowel and a contrasting vowel on different trials, with all vowels simulating infant talkers. Infants showed greater recovery of interest to the contrasting vowel than to the habituation vowel, which demonstrates recognition of the habituation-vowel category when it was produced by an infant. A second experiment showed that encoding the vowel category and detecting the novel vowel required additional processing when infant vowels were included in the habituation set. Despite these added cognitive demands, infants demonstrated the ability to track vowel categories in a multitalker array that included infant talkers. These findings raise the possibility that young infants can categorize their own vocalizations, which has important implications for early vocal learning.

Early word segmentation in infants acquiring Parisian French: task-dependent and dialect-specific aspects.

Six experiments explored Parisian French-learning infants' ability to segment bisyllabic words from fluent speech. The first goal was to assess whether bisyllabic word segmentation emerges later in infants acquiring European French compared to other languages. The second goal was to determine whether infants learning different dialects of the same language have partly different segmentation abilities, and whether segmenting a non-native dialect has a cost. Infants were tested on standard European or Canadian French stimuli, in the word-passage or passage-word order. Our study first establishes an early onset of segmentation abilities: Parisian infants segment bisyllabic words at age 0;8 in the passage-word order only (revealing a robust order of presentation effect). Second, it shows that there are differences in segmentation abilities across Parisian and Canadian French infants, and that there is a cost for cross-dialect segmentation for Parisian infants. We discuss the implications of these findings for understanding word segmentation processes.

Quebec-based parents' concerns regarding their children's multilingual development.

Many parents express concerns for their children's multilingual development, yet little is known about the nature and strength of these concerns - especially among parents in multilingual societies. This pre-registered, questionnaire-based study addresses this gap by examining the concerns of 821 Quebec-based parents raising infants and toddlers aged 0-4 years with multiple languages in the home. Factor analysis of parents' Likert-scale responses revealed that parents had (1) concerns regarding the effect of children's multilingualism on their cognition, and (2) concerns regarding children's exposure to and attainment of fluency in their languages. Concern strength was moderate to weak, and cognition concerns were weaker than exposure-fluency concerns. Transmission of a heritage language, transmission of three or more languages, presence of developmental issues, and less positive parental attitudes towards childhood multilingualism were associated with stronger concerns. These findings have both theoretical and practical implications: they advance our understanding of parental concerns and facilitate the development of support for multilingual families.

Comparing Different Measures of Bilingual Input Derived From Naturalistic Daylong Recordings.

PURPOSE: Measuring language input, especially for infants growing up in bilingual environments, is challenging. Although the ways to measure input have expanded rapidly in recent years, there are many unresolved issues. In this study, we compared different measurement units and sampling methods used to estimate bilingual input in naturalistic daylong recordings. METHOD: We used the Language Environment Analysis system to obtain and process naturalistic daylong recordings from 21 French-English bilingual families with an infant at 10 and 18 months of age. We examined global and context-specific input estimates and their relation with infant vocal activeness (i.e., volubility) when input was indexed by different units (adult word counts, speech duration, 30-s segment counts) and using different sampling methods (every-other-segment, top-segment). RESULTS: Input measures indexed by different units were strongly and positively correlated with each other and yielded similar results regarding their relation with infant volubility. As for sampling methods, sampling every other 30-s segment was representative of the entire corpus. However, sampling the top segments with the densest input was less representative and yielded different results regarding their relation with infant volubility. CONCLUSIONS: How well the input that a child receives throughout a day is portrayed by a selected sample and correlates with the child's vocal activeness depends on the choice of input units and sampling methods. Different input units appear to generate consistent results, while caution should be taken when choosing sampling methods. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22335688.

Mixed-Language Input and Infant Volubility: Friend or Foe?

Language mixing is a common feature of many bilingually-raised children's input. Yet how it is related to their language development remains an open question. The current study investigated mixed-language input indexed by observed (30-second segment) counts and proportions in day-long recordings as well as parent-reported scores, in relation to infant vocal activeness (i.e., volubility) when infants were 10 and 18 months old. Results suggested infants who received a higher score or proportion of mixed input in one-on-one social contexts were less voluble. However, within contexts involving language mixing, infants who heard more words were also the ones who produced more vocalizations. These divergent associations between mixed input and infant vocal development point for a need to better understand the causal factors that drive these associations.

Word Segmentation in Monolingual Infants Acquiring Canadian English and Canadian French: Native Language, Cross-Dialect, and Cross-Language Comparisons.

In five experiments, we tested segmentation of word forms from natural speech materials by 8-month-old monolingual infants who are acquiring Canadian French or Canadian English. These two languages belong to different rhythm classes; Canadian French is syllable-timed and Canada English is stress-timed. Findings of Experiments 1, 2, and 3 show that 8-month-olds acquiring either Canadian French or Canadian English can segment bi-syllable words in their native language. Thus, word segmentation is not inherently more difficult in a syllable-timed compared to a stress-timed language. Experiment 4 shows that Canadian French-learning infants can segment words in European French. Experiment 5 shows that neither Canadian French- nor Canadian English-learning infants can segment two syllable words in the other language. Thus, segmentation abilities of 8-month-olds acquiring either a stress-timed or syllable-timed language are language specific.

Setting the Stage for Speech Production: Infants Prefer Listening to Speech Sounds With Infant Vocal Resonances.

PURPOSE: Current models of speech development argue for an early link between speech production and perception in infants. Recent data show that young infants (at 4-6 months) preferentially attend to speech sounds (vowels) with infant vocal properties compared to those with adult vocal properties, suggesting the presence of special "memory banks" for one's own nascent speech-like productions. This study investigated whether the vocal resonances (formants) of the infant vocal tract are sufficient to elicit this preference and whether this perceptual bias changes with age and emerging vocal production skills. METHOD: We selectively manipulated the fundamental frequency (f0 ) of vowels synthesized with formants specifying either an infant or adult vocal tract, and then tested the effects of those manipulations on the listening preferences of infants who were slightly older than those previously tested (at 6-8 months). RESULTS: Unlike findings with younger infants (at 4-6 months), slightly older infants in Experiment 1 displayed a robust preference for vowels with infant formants over adult formants when f0 was matched. The strength of this preference was also positively correlated with age among infants between 4 and 8 months. In Experiment 2, this preference favoring infant over adult formants was maintained when f0 values were modulated. CONCLUSIONS: Infants between 6 and 8 months of age displayed a robust and distinct preference for speech with resonances specifying a vocal tract that is similar in size and length to their own. This finding, together with data indicating that this preference is not present in younger infants and appears to increase with age, suggests that nascent knowledge of the motor schema of the vocal tract may play a role in shaping this perceptual bias, lending support to current models of speech development. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.17131805.

Disentangling the roles of formant proximity and stimulus prototypicality in adult vowel perception.

The present investigation examined the extent to which asymmetries in vowel perception derive from a sensitivity to focalization (formant proximity), stimulus prototypicality, or both. English-speaking adults identified, rated, and discriminated a vowel series that spanned a less-focal/prototypic English /u/ and a more-focal/prototypic French /u/ exemplar. Discrimination pairs included one-step, two-step, and three-step intervals along the series. Asymmetries predicted by both focalization and prototype effects emerged when discrimination step-size was varied. The findings indicate that both generic/universal and language-specific biases shape vowel perception in adults; the latter are challenging to isolate without well-controlled stimuli and appropriately scaled discrimination tasks.

Neurophysiological Correlates of Asymmetries in Vowel Perception: An English-French Cross-Linguistic Event-Related Potential Study.

Behavioral studies examining vowel perception in infancy indicate that, for many vowel contrasts, the ease of discrimination changes depending on the order of stimulus presentation, regardless of the language from which the contrast is drawn and the ambient language that infants have experienced. By adulthood, linguistic experience has altered vowel perception; analogous asymmetries are observed for non-native contrasts but are mitigated for native contrasts. Although these directional effects are well documented behaviorally, the brain mechanisms underlying them are poorly understood. In the present study we begin to address this gap. We first review recent behavioral work which shows that vowel perception asymmetries derive from phonetic encoding strategies, rather than general auditory processes. Two existing theoretical models-the Natural Referent Vowel framework and the Native Language Magnet model-are invoked as a means of interpreting these findings. Then we present the results of a neurophysiological study which builds on this prior work. Using event-related brain potentials, we first measured and assessed the mismatch negativity response (MMN, a passive neurophysiological index of auditory change detection) in English and French native-speaking adults to synthetic vowels that either spanned two different phonetic categories (/y/vs./u/) or fell within the same category (/u/). Stimulus presentation was organized such that each vowel was presented as standard and as deviant in different blocks. The vowels were presented with a long (1,600-ms) inter-stimulus interval to restrict access to short-term memory traces and tap into a "phonetic mode" of processing. MMN analyses revealed weak asymmetry effects regardless of the (i) vowel contrast, (ii) language group, and (iii) MMN time window. Then, we conducted time-frequency analyses of the standard epochs for each vowel. In contrast to the MMN analysis, time-frequency analysis revealed significant differences in brain oscillations in the theta band (4-8 Hz), which have been linked to attention and processing efficiency. Collectively, these findings suggest that early-latency (pre-attentive) mismatch responses may not be a strong neurophysiological correlate of asymmetric behavioral vowel discrimination. Rather, asymmetries may reflect differences in neural processing efficiency for vowels with certain inherent acoustic-phonetic properties, as revealed by theta oscillatory activity.