Utterance-Initial Prosodic Differences Between Statements and Questions in Infant-Directed Speech.

Cross-linguistically, statements and questions broadly differ in syntactic organization. To learn the syntactic properties of each sentence type, learners might first rely on non-syntactic information. This paper analyzed prosodic differences between infant-directed wh-questions and statements to determine what kinds of cues might be available. We predicted there would be a significant difference depending on the first words that appear in wh-questions (e.g., two closed-class words; meaning words from a category that rarely changes) compared to the variety of first words found in statements. We measured F0, duration, and intensity of the first two words in statements and wh-questions in naturalistic speech from 13 mother-child dyads in the Brent corpus of the CHILDES database. Results found larger differences between sentence-types when the second word was an open-class not a closed-class word, suggesting a relationship between prosodic and syntactic information in an utterance-initial position that infants may use to make sentence-type distinctions.

Boosting the input: 9-month-olds' sensitivity to low-frequency phonotactic patterns in novel wordforms.

To learn their first words, infants must attend to a variety of cues that signal word boundaries. One such cue infants might use is the language-specific phonotactics to track legal combinations and positions of segments within a word. Studies have demonstrated that, when tested across statistically high and low phonotactics, infants repeatedly reject the low-frequency wordforms. We explore whether the capacity to access low-frequency phonotactic combinations is available at 9 months when pre-exposed to wordforms containing statistically low combinations of segments. Using a modified head-turn procedure, one group of infants was presented with nonwords with low-frequency complex onsets (dr-), and another group was presented with zero-frequency onset nonwords (dl-). Following pre-exposure and familiarization, infants were then tested on their ability to segment nonwords that contained either the low- or the zero-frequency onsets. Only infants in the low-frequency condition were successful at the task, suggesting some experience with these onsets supports segmentation.

Preference for speech in infancy differentially predicts language skills and autism-like behaviors.

Early emerging biases for conspecific vocalizations are a hallmark of early development. Typically developing neonates listen to speech more than many other sounds, including non-biological non-speech sounds, but listen equally to speech and monkey calls. By 3 months of age, however, infants prefer speech over both non-biological non-speech sounds and monkey calls. We examined whether different listening preferences continue to develop along different developmental trajectories and whether listening preferences are related to developmental outcomes. Given the static preference for speech over non-biological non-speech sounds and the dynamic preference for speech over monkey calls between birth and 3 months, we examined whether 9-month-olds prefer speech over non-biological non-speech sounds (Experiment 1) and prefer speech over monkey calls (Experiment 2). We compared preferences for sounds in infants at low risk (SIBS-TD) and infants at high risk (SIBS-A) of autism spectrum disorder (ASD), a heterogeneous population who differ from typically developing infants in their preferences for speech, and examined whether listening preferences predict vocabulary and autism-like behaviors at 12 months for both groups. At 9 months, SIBS-TD listened longer to speech than to non-speech sounds and listened longer to monkey calls than to speech, whereas SIBS-A listened longer to speech than to non-speech sounds but listened equally to speech and monkey calls. SIBS-TD's preferences did not predict immediate developmental outcomes. In contrast, SIBS-A who preferred speech over non-speech or monkey calls had larger vocabularies and fewer markers of autism-like behaviors at 12 months, which could have positive developmental implications.

Word Level Stress and Lexical Processing in 17-Month-Old Infants.

Detailed representations enable infants to distinguish words from one another and more easily recognize new words. We examined whether 17-month-old infants encode word stress in their familiar word representations. In Experiment 1, infants were presented with pairs of familiar objects while hearing a target label either properly pronounced with the correct stress (e.g., baby /'beɪbi/) or mis-pronounced with the incorrect stress pattern (e.g., baby /beɪ'bi/). Infants mapped both the correctly stressed and mis-stressed labels to the target objects; however, they were slower to fixate the target when hearing the mis-stressed label. In Experiment 2, we examined whether infants appreciate that stress has a nonproductive role in English (i.e., altering the stress of a word does not typically signal a change in word meaning) by presenting infants with a familiar object paired with a novel object while hearing either correctly stressed or mis-stressed familiar words (Experiment 2). Here, infants mapped the correctly stressed label to the familiar object but did not map the mis-stressed label reliably to either the target or distractor objects. These findings suggest that word stress impacts the processing of familiar words, and infants have burgeoning knowledge that altering the stress pattern of a familiar word does not reliably signal a new referent.

Not speaking the same language: 17-month-olds shift their perception of novel labels following brief exposure to non-native language.

We examined if and when English-learning 17-month-olds would accommodate Japanese forms as labels for novel objects. In Experiment 1, infants (n = 22) who were habituated to Japanese word-object pairs looked longer at switched test pairs than familiar test pairs, suggesting that they had mapped Japanese word forms to objects. In Experiments 2 (n = 44) and 3 (n = 22), infants were presented with a spoken passage prior to habituation to assess whether experience with a different language would shift their perception of Japanese word forms. Here, infants did not demonstrate learning of Japanese word-object pairs. These findings offer insight into the flexibility of the developing perceptual system. That is, when there is no evidence to the contrary, 17-month-olds will accommodate forms that vary from their typical input but will efficiently constrain their perception when cued to the fact that they are not listening to their native language.

Fourteen-month-olds' sensitivity to acoustic salience in minimal pair word learning.

During the first two years of life, infants concurrently refine native-language speech categories and word learning skills. However, in the Switch Task, 14-month-olds do not detect minimal contrasts in a novel object-word pairing (Stager & Werker, 1997). We investigate whether presenting infants with acoustically salient contrasts (liquids) facilitates success in the Switch Task. The first two experiments demonstrate that acoustic differences boost infants' detection of contrasts. However, infants cannot detect the contrast when the segments are digitally shortened. Thus, not all minimal contrasts are equally difficult, and the acoustic properties of a contrast matter in word learning.

Nine-month-olds use frequency of onset clusters to segment novel words.

Before their first birthday, infants have started to identify and use information about their native language, such as frequent words, transitional probabilities, and co-occurrence of segments (phonotactics), to identify viable word boundaries. These cues can then be used to segment new words from running speech. We explored whether infants are capable of detecting a novel word form using the frequency of occurrence of the onset alone to further characterize the role of phonotactics in speech segmentation. Experiment 1 shows that English-learning 9-month-olds can successfully segment a word from natural speech if the onset is legal in English (i.e., pleet) but not if the onset is illegal (i.e., tleet). Experiment 2 shows that English-learning 9-month-olds are successful at word segmentation when presented with two onset clusters that vary in statistical frequency. Infants familiarized to a high-frequency onset (i.e., trom) were successful at segmenting the target word embedded in speech, but those familiarized to the low-frequency onset (i.e., drom) were unsuccessful. Together, these results show that infants use statistical information from the speech input and that low levels of exposure to onset phonotactics alone might not be sufficient in identifying word boundaries.

Infants' acceptance of phonotactically illegal word forms as object labels.

We investigated 16- and 20-month-olds' flexibility in mapping phonotactically illegal words to objects. Using an associative word-learning task, infants were presented with a training phase that either highlighted or did not highlight the referential status of a novel label. Infants were then habituated to two novel objects, each paired with a phonotactically illegal Czech word. When referential cues were provided, 16-, but not 20-month-olds, formed word-object mappings. In the absence of referential cues, infants of both ages failed to map the novel words. These findings illustrate the complex interplay between infants' developing sound system and their word learning abilities.

Attention to lexical stress and early vocabulary growth in 5-month-olds at risk for autism spectrum disorder.

Typically developing infants differentiate strong-weak (trochaic) and weak-strong (iambic) stress patterns by 2months of age. The ability to discriminate rhythmical patterns, such as lexical stress, has been argued to facilitate language development, suggesting that a difficulty in discriminating stress might affect early word learning as reflected in vocabulary size. Children with autism spectrum disorder (ASD) often have difficulty in correctly producing lexical stress, yet little is known about how they perceive it. The current study tested 5-month-old infants with typically developing older siblings (SIBS-TD) and infants with an older sibling diagnosed with ASD (SIBS-A) on their ability to differentiate the trochaic and iambic stress patterns of the word form gaba. SIBS-TD infants showed an increased interest in attention to the trochaic stress pattern, which was also positively correlated with vocabulary comprehension at 12months of age. In contrast, SIBS-A infants attended equally to these stress patterns, although this was unrelated to later vocabulary size.

Trajectories of Vocabulary Development in Children with Autism Spectrum Disorder Across Multiple Measures.

This longitudinal study examined how receptive and expressive vocabulary assessments capture vocabulary development in children with Autism Spectrum Disorder (ASD) and typically developing (TD) children. Using mixed regression modelling, we explored when children with ASD significantly different from TD children. We also examined the variability of individual trajectories of vocabulary development in children with ASD. Children with ASD showed slowed trajectories and significantly differed from TD children by 24 months on all assessments except for picture-based assessments. Children with ASD also showed high heterogeneity in trajectories, with some showing inconsistent patterns of growth, stagnation, and regression across assessments. This suggests that conclusions based on individual assessments of vocabulary can vary and assessment characteristics must be considered when monitoring vocabulary development.

The maluma/takete effect is late: No longitudinal evidence for shape sound symbolism in the first year.

The maluma/takete effect refers to an association between certain language sounds (e.g., /m/ and /o/) and round shapes, and other language sounds (e.g., /t/ and /i/) and spiky shapes. This is an example of sound symbolism and stands in opposition to arbitrariness of language. It is still unknown when sensitivity to sound symbolism emerges. In the present series of studies, we first confirmed that the classic maluma/takete effect would be observed in adults using our novel 3-D object stimuli (Experiments 1a and 1b). We then conducted the first longitudinal test of the maluma/takete effect, testing infants at 4-, 8- and 12-months of age (Experiment 2). Sensitivity to sound symbolism was measured with a looking time preference task, in which infants were shown images of a round and a spiky 3-D object while hearing either a round- or spiky-sounding nonword. We did not detect a significant difference in looking time based on nonword type. We also collected a series of individual difference measures including measures of vocabulary, movement ability and babbling. Analyses of these measures revealed that 12-month olds who babbled more showed a greater sensitivity to sound symbolism. Finally, in Experiment 3, we had parents take home round or spiky 3-D printed objects, to present to 7- to 8-month-old infants paired with either congruent or incongruent nonwords. This language experience had no effect on subsequent measures of sound symbolism sensitivity. Taken together these studies demonstrate that sound symbolism is elusive in the first year, and shed light on the mechanisms that may contribute to its eventual emergence.

Class matters: 12-month-olds' word-object associations privilege content over function words.

A fundamental step in learning words is the development of an association between a sound pattern and an element in the environment. Here we explore the nature of this associative ability in 12-month-olds, examining whether it is constrained to privilege particular word forms over others. Forty-eight infants were presented with sets of novel English content-like word-object pairings (e.g. fep) or novel English function-like word-object (e.g. iv) pairings until they habituated. Results indicated that infants associated novel content-like words, but not the novel function-like words, with novel objects. These results demonstrate that the mechanism with which basic word-object associations are formed is remarkably sophisticated by the onset of productive language. That is, mere associative pairings are not sufficient to form mappings. Rather the system requires well-formed noun-like words to co-occur with objects in order for the linkages to arise.

12-month-olds' phonotactic knowledge guides their word-object mappings.

This study examined whether 12-month-olds will accept words that differ phonologically and phonetically from their native language as object labels in an associative learning task. Sixty infants were presented with sets of English word-object (N = 30), Japanese word-object (N = 15), or Czech word-object (N = 15) pairings until they habituated. Infants associated CVCV English, CCVC English, and CVCV Japanese words, but not CCVC Czech words, with novel objects. These results demonstrate that by 12 months of age, infants are beginning to apply their language-specific knowledge to their acceptance of word forms. That is, they will not map words that violate the phonotactics of their native language to objects.

Mapping novel labels to actions: how the rhythm of words guides infants' learning.

We investigated the effect of lexical stress on 16-month-olds' ability to form associations between labels and paths of motion. Disyllabic English nouns tend to have a strong-weak (trochaic) stress pattern, and verbs tend to have a weak-strong (iambic) pattern. We explored whether infants would use word stress information to guide word-action associations during learning. Infants heard two novel words with either verb-like iambic stress or noun-like trochaic stress. Each word was paired with a single novel object performing one of two path actions and was tested using path-switch trials. Only infants in the iambic stress condition learned the association between the novel words and the path actions. To further investigate infants' difficulty in mapping the trochaic labels to the actions, we conducted an additional study in which infants were given an object switch task using the trochaic labels. In this case, infants were able to associate the trochaic labels with the objects, providing further support that infants use lexical stress to guide label-referent associations. This study demonstrates that by 16months, English-learning infants have developed a bias to expect disyllabic action labels to have iambic stress patterns, consistent with native language stress patterns.

Twelve-month-olds privilege words over other linguistic sounds in an associative learning task.

We examined whether 12-month-old infants privilege words over other linguistic stimuli in an associative learning task. Sixty-four infants were presented with sets of either word­object, communicative sound­object, or consonantal sound­object pairings until they habituated. They were then tested on a 'switch' in the sound to determine whether they were able to associate the word and/or sound with the novel objects. Infants associated words, but not communicative sounds or consonantal sounds, with novel objects. The results demonstrate that infants exhibit a preference for words over other linguistic stimuli in an associative word learning task. This suggests that by 12 months of age, infants have developed knowledge about the nature of an appropriate sound form for an object label and will privilege this form as an object label.

Do newly formed word representations encode non-criterial information?

Lexical stress is useful for a number of language learning tasks. In particular, it helps infants segment the speech stream and identify phonetic contrasts. Recent work has demonstrated that infants aged 1;0 can learn two novel words differing only in their stress pattern. In the current study, we ask whether infants aged 1;0 store stress information in their representations of words even when it not required for the task. To this end, we taught infants novel, three-syllable word-object pairings. At test, we manipulated the word by presenting infants with forms that shared the stress pattern of the familiar words but differed in the segments, and forms that shared the segments of the familiar word but differed in the stress pattern. Our findings reveal that infants' representations of new words include word-level stress information and do not simply contain the information critical for distinguishing between different forms.

Young infants encode lexical stress in newly encountered words.

In this study, we examined the nature of infants' representations of newly encountered word forms. Using a word-object association task, we taught 14-month-olds novel three-syllable words differing in segments and stress patterns. At test, we manipulated the stress pattern of the word or the position of the stressed syllable in the word. Our findings reveal that young infants store the stress information about the word, including the position in which the stressed syllable occurs, suggesting that infants form prosodically rich lexical representations of newly encountered words.

Does an Early Speech Preference Predict Linguistic and Social-Pragmatic Attention in Infants Displaying and Not Displaying Later ASD Symptoms?

Human infants show a robust preference for speech over many other sounds, helping them learn language and interact with others. Lacking a preference for speech may underlie some language and social-pragmatic difficulties in children with ASD. But, it's unclear how an early speech preference supports later language and social-pragmatic abilities. We show that across infants displaying and not displaying later ASD symptoms, a greater speech preference at 9 months is related to increased attention to a person when they speak at 12 months, and better expressive language at 24 months, but is not related to later social-pragmatic attention or outcomes. Understanding how an early speech preference supports language outcomes could inform targeted and individualized interventions for children with ASD.

Eleven-Month-Olds Link Sound Properties With Animal Categories.

We examined 11-month-olds' tendency to generalize properties to category members, an ability that may contribute to the inductive reasoning abilities observed in later developmental periods. Across three experiments, we tested 11-month-olds' (N = 113) generalization of properties within the cat and dog categories. In each experiment, infants were familiarized to animal-sound pairings (i.e., dog barking; cat meowing) and tested on this association and the generalization of the sound property to new members of the familiarized categories. After familiarization with a single exemplar, 11-month-olds generalized the sound to new category members that were both highly similar and less similar to the familiarized animal (Experiment 1). When familiarized with mismatched animal-sound pairings (Experiment 2; i.e., dog meowing; cat barking), 11-month-olds did not learn or generalize the sound properties, suggesting that infants have pre-existing expectations about the links between the characteristic sound properties and the animal categories. When familiarized with unfamiliar sound-animal pairings (Experiment 3; i.e., dog-unfamiliar sound), 11-month-olds linked the animals with the novel sounds but did not generalize to new category members. Taken together, these findings highlight the conditions under which young infants generalize properties from one exemplar to other category members.

Developmental Trajectories of Infants With Multiplex Family Risk for Autism: A Baby Siblings Research Consortium Study.

Importance: Autism spectrum disorder (ASD) is a neurodevelopmental disorder associated with different genetic etiologies. Prospective examination of familial-risk infants informs understanding of developmental trajectories preceding ASD diagnosis, potentially improving early detection. Objective: To compare outcomes and trajectories associated with varying familial risk for ASD across the first 3 years of life. Design, Setting, and Participants: This longitudinal, prospective cohort study used data from 11 sites in the Baby Siblings Research Consortium database. Data were collected between 2003 and 2015. Infants who were younger siblings of children with ASD were followed up for 3 years. Analyses were conducted in April 2018. Of the initial 1008 infants from the database, 573 were removed owing to missing necessary data, diagnostic discrepancies, or only having 1 older sibling. Exposures: Number of siblings with ASD. Main Outcomes and Measures: Outcomes included ASD symptoms, cognitive abilities, and adaptive skills. Diagnosis (ASD or no ASD) was given at 36-month outcome. The no-ASD group was classified as atypical (developmental delays and/or social-communication concerns) or typical for some analyses. Generalized linear mixed models examined developmental trajectories by ASD outcome and familial-risk group. Results: In the 435 analyzed participants (age range at outcome, 32-43 months; 246 male [57%]), 355 (82%) were from single-incidence families (1 sibling with ASD and ≥1 sibling without ASD) and 80 (18%) were from multiplex families (≥2 siblings with ASD). There were no significant group differences in major demographics. Children from multiplex families were more likely than those from single-incidence families to be classified as having ASD (29 of 80 [36%] vs 57 of 355 [16%]; 95% CI, 9%-31%; P < .001) and less likely as typical (26 of 80 [33%] vs 201 of 355 [57%]; 95% CI, -36% to -13%; P < .001), with similar rates of atypical classifications (25 of 80 [31%] vs 97 of 355 [27%]; 95% CI, -7% to 15%; P = .49). There were no differences in ASD symptoms between multiplex and single-incidence groups after controlling for ASD outcome (95% CI, -0.02 to 0.20; P = .18). During infancy, differences in cognitive and adaptive abilities were observed based on ASD outcome in the single-incidence group only. At 36 months, the multiplex/no-ASD group had lower cognitive abilities than the single-incidence/no-ASD group (95% CI, -11.89 to -2.20; P = .02), and the multiplex group had lower adaptive abilities than individuals in the single-incidence group after controlling for ASD outcome (95% CI, -9.01 to -1.48; P = .02). Conclusions and Relevance: Infants with a multiplex family history of ASD should be monitored early and often and referred for early intervention at the first sign of concern. Direct examination of genetic contributions to neurodevelopmental phenotypes in infants with familial risk for ASD is needed.