Cognitive influences on cross-language speech perception in infancy

The developmental pattern of native and non-native speech perception during the 1st year of life in Japanese infants

Language development during the 1st year of life is characterized by perceptual attunement: following language-general perception, a decline in the perception of non-native phonemes and a parallel increase in or maintenance of the perception of native phonemes. While this general pattern is well established, there are still many gaps in the literature. First, most evidence documenting these patterns comes from "Minority world countries" with only a limited number of studies from "Majority world countries", limiting the range of languages and contrasts assessed. Second, few studies test both the developmental patterns of native and non-native speech perception in the same group of infants, making it hard to draw conclusions on simultaneous decline in non-native and increase in native speech perception. Such limitations are in part due to the effort that goes into testing developing speech sound perception, where usually only discrimination of one contrast per infant can be tested at a time. The present study thus set out to assess the feasibility of assessing a given infant on their discrimination of two speech sound contrasts during the same lab visit. It leveraged the presence of documented patterns of the improvement of native and the decline of non-native phoneme discrimination abilities in Japanese, therefore assessing native and non-native speech perception in Japanese infants from 6 to 12 months of age. Results demonstrated that 76 % of infants contributed discrimination data for both contrasts. We found a decline in non-native speech perception evident in discrimination of the non-native /ɹ/-/l/ consonant contrast at 9-11, but not at 11-13 months of age. Additionally, a parallel increase in native speech perception was demonstrated evident in an absence of native phonemic vowel length discrimination at 6-7 and 9-11 months and a discrimination of this contrast at 11-13 months of age. These results, based on a simultaneous assessment of native and non-native speech perception in Japanese-learning infants, demonstrate the feasibility of assessing the discrimination of two contrasts in one testing session and corroborate theoretical proposals on two hallmarks of perceptual attunement: a decrease in non-native and a facilitation in native speech perception during the first year of life.

The maturational gradient of infant vocalizations: Developmental stages and functional modules

Stage models have been influential in characterizing infant vocalizations in the first year of life. These models are basically descriptive and do not explain why certain types of vocal behaviors occur within a particular stage or why successive patterns of vocalization occur. This review paper summarizes and elaborates a theory of Developmental Functional Modules (DFMs) and discusses how maturational gradients in the DFMs explain age typical vocalizations as well as the transitions between successive stages or other static forms. Maturational gradients are based on biological processes that effect the reconfiguration and remodeling of the respiratory, laryngeal, and craniofacial systems during infancy. From a dynamic systems perspective, DFMs are part of a complex system with multiple degrees of freedom that can achieve stable performance with relatively few control variables by relying on principles such as synergies, self-organization, nonlinear performance, and movement variability.

Toward a new model for speech perception: the Universal Perceptual Model (UPM) of second language

Several speech models have been formed in the past aiming to predict the abilities of nonnative listeners or learners in perceiving and producing speech sounds. The present paper proposes a new model for speech perception, the Universal Perceptual Model of Second Language (henceforth, UPM). UPM assumes that second language phone acquisition is strongly affected by the speakers' native language but still the window of phone learning is open due to the universality of speech sounds. Also, it supports that second language phones are initially activated as disoriented phonetic units. In this paper, we provide some initial insights into the predictability of the model. UPM uses degrees of overlap and chance criteria to form its predictions. We recruited Cypriot Greek novice learners of Italian who participated in two psychoacoustic tasks in which they classified and discriminated Italian vowels, respectively. The findings demonstrated that the degree of overlap between two nonnative phones may be a good predictor of the speakers' discrimination accuracy over these phones. UPM might be a useful model which aims to better explain speech perception mechanisms and patterns of speech acquisition.

Infant speech perception and cognitive skills as predictors of later vocabulary

Research has identified bivariate correlations between speech perception and cognitive measures gathered during infancy as well as correlations between these individual measures and later language outcomes. However, these correlations have not all been explored together in prospective longitudinal studies. The goal of the current research was to compare how early speech perception and cognitive skills predict later language outcomes using a within-participant design. To achieve this goal, we tested 97 5- to 7-month-olds on two speech perception tasks (stress pattern preference, native vowel discrimination) and two cognitive tasks (visual recognition memory, A-not-B) and later assessed their vocabulary outcomes at 18 and 24 months. Frequentist statistical analyses showed that only native vowel discrimination significantly predicted vocabulary. However, Bayesian analyses suggested that evidence was ambiguous between null and alternative hypotheses for all infant predictors. These results highlight the importance of recognizing and addressing challenges related to infant data collection, interpretation, and replication in the developmental field, a roadblock in our route to understanding the contribution of domain-specific and domain-general skills for language acquisition. Future methodological development and research along similar lines is encouraged to assess individual differences in infant speech perception and cognitive skills and their predictability for language development.

Using magnetoencephalography to examine word recognition, lateralization, and future language skills in 14-month-old infants

Word learning is a significant milestone in language acquisition. The second year of life marks a period of dramatic advances in infants' expressive and receptive word-processing abilities. Studies show that in adulthood, language processing is left-hemisphere dominant. However, adults learning a second language activate right-hemisphere brain functions. In infancy, acquisition of a first language involves recruitment of bilateral brain networks, and strong left-hemisphere dominance emerges by the third year. In the current study we focus on 14-month-old infants in the earliest stages of word learning using infant magnetoencephalography (MEG) brain imagining to characterize neural activity in response to familiar and unfamiliar words. Specifically, we examine the relationship between right-hemisphere brain responses and prospective measures of vocabulary growth. As expected, MEG source modeling revealed a broadly distributed network in frontal, temporal and parietal cortex that distinguished word classes between 150-900 ms after word onset. Importantly, brain activity in the right frontal cortex in response to familiar words was highly correlated with vocabulary growth at 18, 21, 24, and 27 months. Specifically, higher activation to familiar words in the 150-300 ms interval was associated with faster vocabulary growth, reflecting processing efficiency, whereas higher activation to familiar words in the 600-900 ms interval was associated with slower vocabulary growth, reflecting cognitive effort. These findings inform research and theory on the involvement of right frontal cortex in specific cognitive processes and individual differences related to attention that may play an important role in the development of left-lateralized word processing.

Symbolic flexibility during unsupervised word learning in children and adults

Considerable debate in language acquisition concerns whether word learning is driven by domain-general (symbolically flexible) or domain-specific learning mechanisms. Prior work has shown that very young children can map objects to either words or nonlinguistic sounds, but by 20 months of age this ability narrows to only words. This suggests that although symbolically flexible mechanisms are operative early, they become more specified over development. However, such research has been conducted only with young children in ostensive teaching contexts. Thus, we investigated symbolic flexibility at later ages in more referentially ambiguous learning situations. In Experiment 1, 47 6- to 8-year-olds acquired eight symbol-object mappings in a cross-situational word learning paradigm where multiple mappings are learned based only on co-occurrence. In the word condition participants learned with novel pseudowords, whereas in the sound condition participants learned with nonlinguistic sounds (e.g., beeps). Children acquired the mappings, but performance did not differ across conditions, suggesting broad symbolic flexibility. In Experiment 2, 41 adults learned 16 mappings in a comparable design. They learned with ease in both conditions but showed a significant advantage for words. Thus, symbolic flexibility decreases with age, potentially due to repeated experiences with linguistic materials. Moreover, trial-by-trial analyses of the microstructure of both children's and adults' performance did not reveal any substantial differences due to condition, consistent with the hypothesis that learning mechanisms are generally employed similarly with both words and nonlinguistic sounds.

Motherese, affect, and vocabulary development: dyadic communicative interactions in infants and toddlers

Responsive parental communication during an infant's first year has been positively associated with later language outcomes. This study explores responsivity in mother-infant communication by modeling how change in guiding language between 7 and 11 months influences toddler vocabulary development. In a group of 32 mother-child dyads, change in early maternal guiding language positively predicted child language outcomes measured at 18 and 24 months. In contrast, a number of other linguistic variables - including total utterances and non-guiding language - did not correlate with toddler vocabulary development, suggesting a critical role of responsive change in infant-directed communication. We further assessed whether maternal affect during early communication influenced toddler vocabulary outcomes, finding that dominant affect during early mother-infant communications correlated to lower child language outcomes. These findings provide evidence that responsive parenting should not only be assessed longitudinally, but unique contributions of language and affect should also be concurrently considered in future study.

Exposure to multiple accents supports infants' understanding of novel accents

Accented speech poses a challenge for listeners, particularly those with limited knowledge of their language. In a series of studies, we explored the possibility that experience with variability, specifically the variability provided by multiple accents, would facilitate infants' comprehension of speech produced with an unfamiliar accent. 15- and 18-month-old American-English learning infants were exposed to brief passages of multi-talker speech and subsequently tested on their ability to distinguish between real, familiar words and nonsense words, produced in either their native accent or an unfamiliar (British) accent. Exposure passages were produced in a familiar (American) accent, a single unfamiliar (British) accent or a variety of novel accents (Australian, Southern, Indian). While 15-month-olds successfully recognized real words spoken in a familiar accent, they never demonstrated comprehension of English words produced in the unfamiliar accent. 18-month-olds also failed to recognize English words spoken in the unfamiliar accent after exposure to the familiar or single unfamiliar accent. However, they succeeded after exposure to multiple unfamiliar accents, suggesting that as they get older, infants are better able to exploit the cues provided by variable speech. Increased variability across multiple dimensions can be advantageous for young listeners.

Foundational tuning: how infants' attention to speech predicts language development

Orienting biases for speech may provide a foundation for language development. Although human infants show a bias for listening to speech from birth, the relation of a speech bias to later language development has not been established. Here, we examine whether infants' attention to speech directly predicts expressive vocabulary. Infants listened to speech or non-speech in a preferential listening procedure. Results show that infants' attention to speech at 12 months significantly predicted expressive vocabulary at 18 months, while indices of general development did not. No predictive relationships were found for infants' attention to non-speech, or overall attention to sounds, suggesting that the relationship between speech and expressive vocabulary was not a function of infants' general attentiveness. Potentially ancient evolutionary perceptual capacities such as biases for conspecific vocalizations may provide a foundation for proficiency in formal systems such language, much like the approximate number sense may provide a foundation for formal mathematics.

Development of non-native vowel discrimination: Improvement without exposure

The present study tested Japanese 4.5- and 10-month old infants' ability to discriminate three German vowel pairs, none of which are contrastive in Japanese, using a visual habituation-dishabituation paradigm. Japanese adults' discrimination of the same pairs was also tested. The results revealed that Japanese 4.5-month old infants discriminated the German /bu:k/-/by:k/ contrast, but they showed no evidence of discriminating the /bi:k/-/be:k/ or /bu:k/-/bo:k/ contrasts. Japanese 10-month old infants, on the other hand, discriminated the German /bi:k/-/be:k/ contrast, while they showed no evidence of discriminating the /bu:k/-/by:k/ or /bu:k/-/bo:k/ contrasts. Japanese adults, in contrast, were highly accurate in their discrimination of all of the pairs. The results indicate that discrimination of non-native contrasts is not always easy even for young infants, and that their ability to discriminate non-native contrasts can improve with age even when they receive no exposure to a language in which the given contrast is phonemic.

Speech preference is associated with autistic-like behavior in 18-months-olds at risk for Autism Spectrum Disorder

We examined whether infants' preference for speech at 12 months is associated with autistic-like behaviors at 18 months in infants who are at increased risk for autism spectrum disorder (ASD) because they have an older sibling diagnosed with ASD and in low-risk infants. Only low-risk infants listened significantly longer to speech than to nonspeech at 12 months. In both groups, relative preference for speech correlated positively with general cognitive ability at 12 months. However, in high-risk infants only, preference for speech was associated with autistic-like behavior at 18 months, while in low-risk infants, preference for speech correlated with language abilities. This suggests that in children at risk for ASD an atypical species-specific bias for speech may underlie atypical social development.

The effects of bilingualism on toddlers' executive functioning

Bilingual children have been shown to outperform monolingual children on tasks measuring executive functioning skills. This advantage is usually attributed to bilinguals' extensive practice in exercising selective attention and cognitive flexibility during language use because both languages are active when one of them is being used. We examined whether this advantage is observed in 24-month-olds who have had much less experience in language production. A battery of executive functioning tasks and the cognitive scale of the Bayley test were administered to 63 monolingual and bilingual children. Native bilingual children performed significantly better than monolingual children on the Stroop task, with no difference between groups on the other tasks, confirming the specificity of bilingual effects to conflict tasks reported in older children. These results demonstrate that bilingual advantages in executive control emerge at an age not previously shown.

Investigating mechanisms of suppression in preschool children with specific language impairment

PURPOSE

This study investigated 2 suppression mechanisms--(a) resistance to distracter interference and (b) inhibition of a prepotent response--in preschool children with specific language impairment (SLI) and their typically developing peers.

METHOD

Twenty-two preschool children with SLI and 22 typically developing controls participated in this study. The resistance to distracter interference task involved suppressing distracters (nonverbal auditory, linguistic, and visual) that were external and irrelevant to the task goal. Inhibition was assessed using a stop-signal paradigm to evaluate the ability to suppress a prepotent, conflicting response.

RESULTS

The children with SLI exhibited decreased resistance to distracter interference regardless of distracter modality and poor inhibitory control relative to their typically developing peers.

CONCLUSION

These results identify suppression weaknesses in preschool-age children with SLI. Specifically, children with this disorder exhibited difficulty suppressing both irrelevant and contradictory information.

Developmental shift in the discrimination of vowel contrasts in bilingual infants: is the distributional account all there is to it?

A shift from language-general to language-specific sound discrimination abilities has been largely attested in different populations of infants during the second half of the first year of life; however, data are still scarce regarding bilingual populations. Previous research with 4-, 8- and 12-month-old Catalan-Spanish bilingual infants had offered evidence of a U-shaped pattern in their ability to discriminate a language-specific vowel contrast. This research explores monolingual and bilingual 4- and 8-month-olds' capacities to discriminate two common vowel contrasts: /o-u/ and /e-u/. All groups succeeded except 8-month-old bilinguals tested on the phonetically close /o-u/ contrast. Discrimination was not facilitated when talker and token variability were reduced. A U-shaped pattern was again found when data from an additional group of 12-month-olds were included. These results confirm bilinguals' specific developmental pattern of perceptual reorganization for acoustically close vowels and challenge an interpretation merely based on a distributional account.

Phonetic learning as a pathway to language: new data and native language magnet theory expanded (NLM-e)

Infants' speech perception skills show a dual change towards the end of the first year of life. Not only does non-native speech perception decline, as often shown, but native language speech perception skills show improvement, reflecting a facilitative effect of experience with native language. The mechanism underlying change at this point in development, and the relationship between the change in native and non-native speech perception, is of theoretical interest. As shown in new data presented here, at the cusp of this developmental change, infants' native and non-native phonetic perception skills predict later language ability, but in opposite directions. Better native language skill at 7.5 months of age predicts faster language advancement, whereas better non-native language skill predicts slower advancement. We suggest that native language phonetic performance is indicative of neural commitment to the native language, while non-native phonetic performance reveals uncommitted neural circuitry. This paper has three goals: (i) to review existing models of phonetic perception development, (ii) to present new event-related potential data showing that native and non-native phonetic perception at 7.5 months of age predicts language growth over the next 2 years, and (iii) to describe a revised version of our previous model, the native language magnet model, expanded (NLM-e). NLM-e incorporates five new principles. Specific testable predictions for future research programmes are described.

Infants show a facilitation effect for native language phonetic perception between 6 and 12 months

Patterns of developmental change in phonetic perception are critical to theory development. Many previous studies document a decline in nonnative phonetic perception between 6 and 12 months of age. However, much less experimental attention has been paid to developmental change in native-language phonetic perception over the same time period. We hypothesized that language experience in the first year facilitates native-language phonetic performance between 6 and 12 months of age. We tested 6-8- and 10-12-month-old infants in the United States and Japan to examine native and nonnative patterns of developmental change using the American English /r-l/ contrast. The goals of the experiment were to: (a) determine whether facilitation characterizes native-language phonetic change between 6 and 12 months of age, (b) examine the decline previously observed for nonnative contrasts and (c) test directional asymmetries for consonants. The results show a significant increase in performance for the native-language contrast in the first year, a decline in nonnative perception over the same time period, and indicate directional asymmetries that are constant across age and culture. We argue that neural commitment to native-language phonetic properties explains the pattern of developmental change in the first year.

Speech Perception in Infancy Predicts Language Development in the Second Year of Life: A Longitudinal Study

Infants' early phonetic perception is hypothesized to play an important role in language development. Previous studies have not assessed this potential link in the first 2 years of life. In this study, speech discrimination was measured in 6-month-old infants using a conditioned head-turn task. At 13, 16, and 24 months of age, language development was assessed in these same children using the MacArthur Communicative Development Inventory. Results demonstrated significant correlations between speech perception at 6 months of age and later language (word understanding, word production, phrase understanding). The finding that speech perception performance at 6 months predicts language at 2 years supports the idea that phonetic perception may play an important role in language acquisition.

Infant perception of non-native consonant contrasts that adults assimilate in different ways

Numerous findings suggest that non-native speech perception undergoes dramatic changes before the infant's first birthday. Yet the nature and cause of these changes remain uncertain. We evaluated the predictions of several theoretical accounts of developmental change in infants' perception of non-native consonant contrasts. Experiment 1 assessed English-learning infants' discrimination of three isiZulu distinctions that American adults had categorized and discriminated quite differently, consistent with the Perceptual Assimilation Model (PAM: Best, 1995; Best et al., 1988). All involved a distinction employing a single articulatory organ, in this case the larynx. Consistent with all theoretical accounts, 6-8 month olds discriminated all contrasts. However, 10-12 month olds performed more poorly on each, consistent with the Articulatory-Organ-matching hypothesis (AO) derived from PAM and Articulatory Phonology (Studdert-Kennedy & Goldstein, 2003), specifically that older infants should show a decline for non-native distinctions involving a single articulatory organ. However, the results may also be open to other interpretations. The converse AO hypothesis, that non-native between-organ distinctions will remain highly discriminable to older infants, was tested in Experiment 2, using a non-native Tigrinya distinction involving lips versus tongue tip. Both ages discriminated this between-organ contrast well, further supporting the AO hypothesis. Implications for theoretical accounts of infant speech perception are discussed.

Simultaneous bilingualism and the perception of a language-specific vowel contrast in the first year of life

Behavioral studies have shown that while young infants can discriminate many different phonetic contrasts, a shift from a language-general to a language-specific pattern of discrimination is found during the second semester of life, beginning earlier for vowels than for consonants. This age-related decline in sensitivity to perceive non-native contrasts has been generally attested in monolinguals. In order to analyze the impact of bilingual exposure on the perception of native-sound contrasts and the early building of language-specific contrastive categories, four-month-old and eight-month-old infants from Spanish monolingual, Catalan monolingual and Spanish-Catalan bilingual environments have been tested with a familiarization-preference procedure on a vowel contrast present only in Catalan: /e/-/epsilon/. As expected, younger infants were all able to perceive this contrast, independently of the language of exposure. However, by eight months, only infants from Catalan monolingual environments succeeded. Although the decline in sensitivity with the monolingual Spanish group was expected, the results with the bilingual group challenge the view that mere exposure is enough to maintain the capacity to perceive a contrast. An additional experiment at 12 months of age indicated that bilinguals finally regained discrimination. Together these results suggest a specific developmental pattern of perceptual reorganization in bilingual exposure.

Speech perception and spoken word recognition: past and present

OBJECTIVE

The scientific study of the perception of spoken language has been an exciting, prolific, and productive area of research for more than 50 yr. We have learned much about infants' and adults' remarkable capacities for perceiving and understanding the sounds of their language, as evidenced by our increasingly sophisticated theories of acquisition, process, and representation. We present a selective, but we hope, representative review of the past half century of research on speech perception, paying particular attention to the historical and theoretical contexts within which this research was conducted. Our foci in this review fall on three principle topics: early work on the discrimination and categorization of speech sounds, more recent efforts to understand the processes and representations that subserve spoken word recognition, and research on how infants acquire the capacity to perceive their native language. Our intent is to provide the reader a sense of the progress our field has experienced over the last half century in understanding the human's extraordinary capacity for the perception of spoken language.

Infant sensitivity to distributional information can affect phonetic discrimination

For nearly two decades it has been known that infants' perception of speech sounds is affected by native language input during the first year of life. However, definitive evidence of a mechanism to explain these developmental changes in speech perception has remained elusive. The present study provides the first evidence for such a mechanism, showing that the statistical distribution of phonetic variation in the speech signal influences whether 6- and 8-month-old infants discriminate a pair of speech sounds. We familiarized infants with speech sounds from a phonetic continuum, exhibiting either a bimodal or unimodal frequency distribution. During the test phase, only infants in the bimodal condition discriminated tokens from the endpoints of the continuum. These results demonstrate that infants are sensitive to the statistical distribution of speech sounds in the input language, and that this sensitivity influences speech perception.

A cross-language comparison of /d/-/th/ perception: evidence for a new developmental pattern

Previous studies have shown that infants perceptually differentiate certain non-native contrasts at 6-8 months but not at 10-12 months of age, whereas differentiation is evident at both ages in infants for whom the test contrasts are native. These findings reveal a language-specific bias to be emerging during the first year of life. A developmental decline is not observed for all non-native contrasts, but it has been consistently reported for every contrast in which language effects are observed in adults, In the present study differentiation of English /d-th/ by English- and French-speaking adults and English- and French-learning infants at two ages (6-8 and 10-12 months) was compared using the conditioned headturn procedure. Two findings emerged. First, perceptual differentiation was unaffected by language experience in the first year of life, despite robust evidence of language effects in adulthood. Second, language experience had a facilitative effect on performance after 12 months, whereas performance remained unchanged in the absence of specific language experience. These data are clearly inconsistent with previous studies as well as predictions based on a conceptual framework proposed by Burnham [Appl. Psycholing. 7, 201-240 (1986)]. Factors contributing to these developmental patterns include the acoustic properties of /d-th/, the phonotactic uniqueness of English /th/, and the influence of lexical knowledge on phonetic processing.

Phonotactic cues for segmentation of fluent speech by infants

There is growing evidence that infants become sensitive to the probabilistic phonotactics of their ambient language sometime during the second half of their first year. The present study investigates whether 9-month-olds make use of phonotactic cues to segment words from fluent speech. Using the Headturn Preference Procedure, we found that infants listened to a CVC stimulus longer when the stimulus previously appeared in a sentential context with good phonotactic cues than when it appeared in one without such cues. The goodness of the phonotactic cues was estimated from the frequency with which the C.C clusters at the onset and offset of a CVC test stimulus (i.e. C.CVC.C) are found within and between words in child-directed speech, with high between-word probability associated with good cues to word boundaries. A similar segmentation result emerged when good phonotactic cues occurred only at the onset (i.e. C.CVC.C) or the offset (i.e. C.CVC.C) of the target words in the utterances. Together, the results suggest that 9-month-olds use probabilistic phonotactics to segment speech into words and that high-probability between-word clusters are interpreted as both word onsets and word offsets.

The beginnings of word segmentation in english-learning infants

A series of 15 experiments was conducted to explore English-learning infants' capacities to segment bisyllabic words from fluent speech. The studies in Part I focused on 7.5 month olds' abilities to segment words with strong/weak stress patterns from fluent speech. The infants demonstrated an ability to detect strong/weak target words in sentential contexts. Moreover, the findings indicated that the infants were responding to the whole words and not to just their strong syllables. In Part II, a parallel series of studies was conducted examining 7.5 month olds' abilities to segment words with weak/strong stress patterns. In contrast with the results for strong/weak words, 7.5 month olds appeared to missegment weak/strong words. They demonstrated a tendency to treat strong syllables as markers of word onsets. In addition, when weak/strong words co-occurred with a particular following weak syllable (e.g., "guitar is"), 7.5 month olds appeared to misperceive these as strong/weak words (e.g., "taris"). The studies in Part III examined the abilities of 10.5 month olds to segment weak/strong words from fluent speech. These older infants were able to segment weak/strong words correctly from the various contexts in which they appeared. Overall, the findings suggest that English learners may rely heavily on stress cues when they begin to segment words from fluent speech. However, within a few months time, infants learn to integrate multiple sources of information about the likely boundaries of words in fluent speech.

Phonotactic and prosodic effects on word segmentation in infants

This research examines the issue of speech segmentation in 9-month-old infants. Two cues known to carry probabilistic information about word boundaries were investigated: Phonotactic regularity and prosodic pattern. The stimuli used in four head turn preference experiments were bisyllabic CVC.CVC nonwords bearing primary stress in either the first or the second syllable (strong/weak vs. weak/strong). Stimuli also differed with respect to the phonotactic nature of their cross-syllabic C.C cluster. Clusters had either a low probability of occurring at a word juncture in fluent speech and a high probability of occurring inside of words ("within-word" clusters) or a high probability of occurring at a word juncture and a low probability of occurring inside of words ("between-word" clusters). Our results show that (1) 9-month-olds are sensitive to how phonotactic sequences typically align with word boundaries, (2) altering the stress pattern of the stimuli reverses infants' preference for phonotactic cluster types, (3) the prosodic cue to segmentation is more strongly relied upon than the phonotactic cue, and (4) a preference for high-probability between-word phonotactic sequences can be obtained either by placing stress on the second syllable of the stimuli or by inserting a pause between syllables. The implications of these results are discussed in light of an integrated multiple-cue approach to speech segmentation in infancy.

Artificial grammar learning by 1-year-olds leads to specific and abstract knowledge

Four experiments used the head-turn preference procedure to assess whether infants could extract and remember information from auditory strings produced by a miniature artificial grammar. In all four experiments, infants generalized to new structure by discriminating new grammatical strings from ungrammatical ones after less than 2 min exposure to the grammar. Infants acquired specific information about the grammar as demonstrated by the ability to discriminate new grammatical strings from those with illegal endpoints (Experiment 1). Infants also discriminated new grammatical strings from those with string-internal pairwise violations (Experiments 2 and 3). Infants in Experiment 4 abstracted beyond specific word order as demonstrated by the ability to discriminate new strings produced by their training grammar from strings produced by another grammar despite a change in vocabulary between training and test. We discuss the implications of these findings for the study of language acquisition.

INFLUENCES ON INFANT SPEECH PROCESSING: Toward a New Synthesis

To comprehend and produce language, we must be able to recognize the sound patterns of our language and the rules for how these sounds "map on" to meaning. Human infants are born with a remarkable array of perceptual sensitivities that allow them to detect the basic properties that are common to the world's languages. During the first year of life, these sensitivities undergo modification reflecting an exquisite tuning to just that phonological information that is needed to map sound to meaning in the native language. We review this transition from language-general to language-specific perceptual sensitivity that occurs during the first year of life and consider whether the changes propel the child into word learning. To account for the broad-based initial sensitivities and subsequent reorganizations, we offer an integrated transactional framework based on the notion of a specialized perceptual-motor system that has evolved to serve human speech, but which functions in concert with other developing abilities. In so doing, we highlight the links between infant speech perception, babbling, and word learning.