While consonant acquisition clearly requires mastery of different articulatory configurations (segments), sub-segmental features and suprasegmental contexts influence both order of acquisition and mismatch (error) patterns (Bérubé, Bernhardt, Stemberger & Ciocca, 2020). Constraints-based nonlinear phonology provides a comprehensive framework for investigating the impact of sub- and suprasegmental impacts on acquisition (Bernhardt & Stemberger, 1998). The current study adopted such a framework in order to investigate these questions for Granada Spanish. Single-word samples of monolingual preschoolers in Granada (29 typically developing; 30 with protracted phonological development) were transcribed by native Spanish speakers in consultation with an international team. Beta regression analyses showed significant effects of age, developmental group, and word structure variables (word length, stress, position of consonants and syllables within the word); salience, markedness and/or frequency across the phonological hierarchy accounted for many patterns. The study further demonstrates the impacts of sub- and suprasegmental constraints of the phonological system on consonant acquisition.

Much like early speech, early signing is characterised by modifications. Sign language phonology has been analysed on the feature level since the 1980s, yet acquisition studies predominately examine handshape, location, and movement. This study is the first to analyse the acquisition of phonology in the sign language of a Balinese village with a vibrant signing community and applies the same feature analysis to adult and child data. We analyse longitudinal data of four deaf children from the Kata Kolok Child Signing Corpus. The form comparison of child productions and adult targets yields three main findings: i) handshape modifications are most frequent, echoing cross-linguistic patterns; ii) modification rates of other features differ from previous studies, possibly due to differences in methodology or KK’s phonology; iii) co-occurrence of modifications within a sign suggest feature interdependencies. We argue that nuanced approaches to child signing are necessary to understand the complexity of early signing.

Index-finger pointing is foundational to language acquisition. Less is known about its emergence. In lab-based monthly longitudinal assessments from 8-13 months (N = 31) the study measured longitudinal predictors of index-finger pointing: parent pointing and infants’ earlier emerging showing, hand-pointing, and point-following. All behaviors increased significantly with age and showed inter-individual stability. At 11 months all behaviors except hand pointing were synchronously interrelated, with no evidence for an earlier synchronous interrelation between behaviors. Caregiver pointing and infants’ earlier behaviors longitudinally predicted the age of emergence of index-finger pointing. An additional cross-sectional comparison of parent pointing at 5 and 7 months (N = 44) showed that significantly fewer caregivers of 5- compared to 7-month-olds pointed for their infants. Findings suggest that pointing emerges as an outcome of social co-construction across the first year of life.

While socioeconomic disparities in the home language environment have been well established, the mechanisms explaining these disparities are poorly understood. One plausible mechanism is heightened stress. The current study investigated whether maternal perceived stress was 1) associated with measures of the home language environment, and 2) mediated the relation between socioeconomic disparities and the home language environment. Data from three independent studies were analyzed, which together comprised 322 mother-child dyads. Two studies included mothers and their six- to twelve-month-old infants (N = 227). The third included mothers and their five- to nine-year-old children (N = 95). Mothers reported their educational attainment, income, and stress. Language Environment Analysis (LENA) measured the home language environment. As has been previously reported, socioeconomic disparities were observed in adult words and conversational turns. Stress did not mediate these associations, nor was it associated with adult words or conversational turns. Alternate mechanisms for future exploration are discussed.

While adult studies show that consonants are more important than vowels in lexical processing tasks, the developmental trajectory of this consonant bias varies cross-linguistically. This study tested whether British English-learning 11-month-old infants’ recognition of familiar word forms is more reliant on consonants than vowels, as found by Poltrock and Nazzi (2015) in French. After establishing that infants prefer listening to a list of familiar words over pseudowords (Experiment 1), Experiment 2 examined preference for consonant versus vowel mispronunciations of these words. Infants listened to both alterations equally. In Experiment 3, using a simplified version of the task with one familiar word only (‘mummy’), infants’ preference for its correct pronunciation over a consonant or a vowel change confirmed an equal sensitivity to both alterations. British English-learning infants’ word form recognition appears to be equally impacted by consonant and vowel information, providing further evidence that initial lexical processes vary cross-linguistically.

Norwegian embedded clauses give children two options for subject placement: preceding or following negation (S-Neg/Neg-S). In the adult language, S-Neg is the ‘default’ and highly frequent option, and Neg-S is infrequent in children’s input. However, Neg-S may be argued to be the structurally less complex. We investigate whether children are aware of the existence of both subject positions, and if they prefer the more frequent or the less complex position. Through an elicited production task with monolingual Norwegian children (N=33, age 3;1-6;1) we find that children in general overuse the Neg-S option, and we suggest that children have an inherent preference for the less complex position, due to a principle of structural economy. We also find that a group of children display U-shaped development, first using only S-Neg, then only Neg-S and finally S-Neg again, and we relate this to structure building and economy of movement.

The English modal system is complex, exhibiting many-to-one, and one-to-many, form-function mappings. Usage-based approaches emphasise the role of the input in acquisition but rarely address the impact of form-function mappings on acquisition. To test whether consistent form-function mappings facilitate acquisition, we analysed two dense mother-child corpora at age 3 and 4. We examined the influence on acquisition of input features including form-function mapping frequency and the number of functions a modal signifies, using innovative methodological controls for other aspects of the input (e.g., form frequency) and child characteristics (e.g., age as a proxy for socio-cognitive development). The children were more likely to produce the frequent modals and form-function mappings of their input but modals with fewer functions in caregiver speech did not promote acquisition of these forms. Our findings support usage-based approaches to language acquisition and demonstrate the importance of applying appropriate controls when investigating relationships between input and development.

This study is a validation of the LENA system for the Italian language. In Study 1, to test LENA’s accuracy, seventy-two 10-minute samples extracted from daylong LENA recordings were manually transcribed for 12 children longitudinally observed at 1;0 and 2;0. We found strong correlations between LENA and human estimates in the number of Adult Word Count (AWC) and Child Vocalisations Count (CVC) and a weak correlation between LENA and human estimates in Conversational Turns Count (CTC). In Study 2, to test the concurrent validity, direct and indirect language measures were considered on a sample of 54 recordings (19 children). Correlational analyses showed that LENA’s CVC and CTC were significantly related to the children’s vocal production, a parent report measure of prelexical vocalizations and the vocal reactivity scores. These results confirm that the automatic analyses performed by the LENA device are reliable and powerful for studying language development in Italian-speaking infants.

Infant-directed speech (IDS) produced in laboratory settings contains acoustic cues, such as pauses, pitch changes, and vowel-lengthening that could facilitate breaking speech into smaller units, such as syntactically well-formed utterances, and the noun- and verb-phrases within them. It is unclear whether these cues are present in speech produced in more natural contexts outside the lab. We captured LENA recordings of caregiver speech to 12-month-old infants in daylong interactions (N = 49) to address this question. We found that the final positions of syntactically well-formed utterances contained greater vowel lengthening and pitch changes, and were followed by longer pauses, relative to non-final positions. However, we found no evidence that these cues were present at utterance-internal phrase boundaries. Results suggest that acoustic cues marking the boundaries of well-formed utterances are salient in everyday speech to infants and highlight the importance of characterizing IDS in a large sample of naturally-produced speech to infants.

Previous studies have shown that caregivers’ sensitive, responsive interactions with young children can boost language development. We explored the association between caregivers’ sensitivity and the vocabulary development of their 8-to-36-month-olds during COVID-19 when family routines were unexpectedly disrupted. Measuring caregivers’ sensitivity from home interaction videos at three timepoints, we found that children who experienced more-sensitive concurrent interactions had higher receptive and expressive vocabularies (N=100). Children whose caregivers showed more-sensitive interactions at the beginning of the pandemic showed greater expressive vocabulary growth six (but not 12) months later (n=58). Significant associations with receptive vocabulary growth were not observed. Our findings highlight the importance of sensitivity at a time when other positive influences on language development were compromised.

Infant-directed speech often has hyperarticulated features, such as point vowels whose formants are further apart than in adult-directed speech. This increased “vowel space” may reflect the caretaker’s effort to speak more clearly to infants, thus benefiting language processing. However, hyperarticulation may also result from more positive valence (e.g., speaking with positive vocal emotion) often found in mothers’ speech to infants. This study was designed to replicate others who have found hyperarticulation in maternal speech to their 6-month-olds, but also to examine their speech to a non-human infant (i.e., a puppy). We rated both kinds of maternal speech for their emotional valence and recorded mothers’ speech to a human adult. We found that mothers produced more positively valenced utterances and some hyperarticulation in both their infant- and puppy-directed speech, compared to their adult-directed speech. This finding promotes looking at maternal speech from a multi-faceted perspective that includes emotional state.