Theories of early language acquisition

What features of brain processing and neural development support linguistic development in young children? To what extent is the profile and timing of linguistic development in young children determined by a pre-ordained genetic programme? Does the environment play a crucial role in determining the patterns of change observed in children growing up? Recent experimental, neuroimaging and computational studies of developmental change in children promise to contribute to a deeper understanding of how the brain becomes wired up for language. In this review, the muttidisciplinary perspectives of cognitive neuroscience, experimental psycholinguistics and neural network modelling are brought to bear on four distinct areas in the study of language acquisition: early speech perception, word recognition, word learning and the acquisition of grammatical inflections. It is suggested that each area demonstrates how linguistic development can be driven by the interaction of general learning mechanisms, highly sensitive to particular statistical regularities in the input, with a richly structured environment which provides the necessary ingredients for the emergence of linguistic representations that support mature language processing. Similar epigenetic principles, guiding the emergence of linguistic structure, apply to all these domains, offering insights into phenomena ranging from the precocity of young infant's sensitivity to speech contrasts to the complexities of the problem facing the young child learning the arabic plural.     

Words and possible words in early language acquisition

In order to acquire language, infants must extract its building blocks—words—and master the rules governing their legal combinations from speech. These two problems are not independent, however: words also have internal structure. Thus, infants must extract two kinds of information from the same speech input. They must find the actual words of their language. Furthermore, they must identify its possible words, that is, the sequences of sounds that, being morphologically well formed, could be words. Here, we show that infants’ sensitivity to possible words appears to be more primitive and fundamental than their ability to find actual words. We expose 12- and 18-month-old infants to an artificial language containing a conflict between statistically coherent and structurally coherent items. We show that 18-month-olds can extract possible words when the familiarization stream contains marks of segmentation, but cannot do so when the stream is continuous. Yet, they can find actual words from a continuous stream by computing statistical relationships among syllables. By contrast, 12-month-olds can find possible words when familiarized with a segmented stream, but seem unable to extract statistically coherent items from a continuous stream that contains minimal conflicts between statistical and structural information. These results suggest that sensitivity to word structure is in place earlier than the ability to analyze distributional information. The ability to compute nontrivial statistical relationships becomes fully effective relatively late in development, when infants have already acquired a considerable amount of linguistic knowledge. Thus, mechanisms for structure extraction that do not rely on extensive sampling of the input are likely to have a much larger role in language acquisition than general-purpose statistical abilities.     

Neurophysiological markers of early language acquisition: from syllables to sentences

Recently, there have been several reports of the neurophysiological correlates of language acquisition. These indicate that the infant's brain is able to discriminate different phonemes within the first 2 months of life, that knowledge about stress patterns and phonotactic rules is established between 5-12 months, and that phonotactic knowledge begins to interact with lexical-semantic processes between 12-14 months. Electrophysiological markers for lexical-semantic processes indicate that semantic processing of words in picture contexts is present at 14 months and for words in sentential contexts around 30 months. At 32 months, children demonstrate an adult-like electrophysiological response pattern to syntactic violations. The similarities between the brain response patterns observed in children and adults support the view that language develops in a continuous manner.     

Mechanisms of aural encoding: VI. Consonants and vowels are remembered as subsets of distinctive features

An attempt was made to examine the manner in which consonants and vowels are coded in short-term memory. under identical recall conditions. Ss were presented with sequences of consonant-vowel digrams for serial recall. Sequences were composed of randomly presented consonants paired with/a/ or randomly presented vowels paired with /d/. Halle’s distinctive feature system was used to generate predictions concerning the frequency of intrusion errors. among phonemes. These predictions were based on the assumption that phonemes are discriminated in memory in terms of their component distinctive features, so that intrusions should most frequently occur between phonemes sharing similar distinctive features. The analysis of intrusion errors revealed that each consonant and vowel phoneme was coded m short-term memory by a particular combination of distinctive features which differed from one phoneme to another. A given phoneme was coded by the same set of distinctive features regardless of the number of syllables in the sequence. However, distinctive feature theories were not able to predict the frequency of intrusion errors for phonemes presented in the middle serial positions of a sequence with 100% accuracy. The results of the experiment support the notion that consonant and vowel phonemes are coded in a similar manner in STM and that this coding involves the retention of a specific set of distinctive features for each phoneme.     

The relationship between temperamental dimensions and inhibitory control in early childhood: Implications for language acquisition

The present study investigates the latent organization of inhibitory control in children aged between 2;3 and 3;0 years. In addition, it explores the relationships between temperament dimensions - social orientation, motor activity, and attention -, inhibitory control and language. One-hundred-twelve typically developing children were evaluated with tasks for inhibitory control and lexical skills, while ratings of temperament and language were collected from their caregivers. A Confirmatory Factor Analysis reveals that inhibitory control seems to be best described by a unitary dimension. A Structural Equation Model suggests that 78 % of the variance in vocabulary is explained by a model considering the language observed measures, the three temperamental dimensions, and inhibitory control and in which both temperamental attention and the latent dimension of inhibitory control are significantly related to vocabulary. In addition, inhibitory control does not mediate the relationship between temperament and language.     

Infant artificial language learning and language acquisition

The rapidity with which children acquire language is one of the mysteries of human cognition. A view held widely for the past 30 years is that children master language by means of a language-specific learning device. An earlier proposal, which has generated renewed interest, is that children make use of domain-general, associative learning mechanisms. However, our current lack of knowledge of the actual learning mechanisms involved during infancy makes it difficult to determine the relative contributions of innate and acquired knowledge. A recent approach to studying this problem exposes infants to artificial languages and assesses the resulting learning. In this article, we review studies using this paradigm that have led to a number of exciting discoveries regarding the learning mechanisms available during infancy. These studies raise important issues with respect to whether such mechanisms are general or specific to language, the extent to which they reflect statistical learning versus symbol manipulation, and the extent to which such mechanisms change with development. The fine-grained characterizations of infant learning mechanisms that this approach permits should result in a better understanding of the relative contributions of, and the dynamic between, innate and learned factors in language acquisition.     

Finding words in a language that allows words without vowels

Across many languages from unrelated families, spoken-word recognition is subject to a constraint whereby potential word candidates must contain a vowel. This constraint minimizes competition from embedded words (e.g., in English, disfavoring win in twin because t cannot be a word). However, the constraint would be counter-productive in certain languages that allow stand-alone vowelless open-class words. One such language is Berber (where t is indeed a word). Berber listeners here detected words affixed to nonsense contexts with or without vowels. Length effects seen in other languages replicated in Berber, but in contrast to prior findings, word detection was not hindered by vowelless contexts. When words can be vowelless, otherwise universal constraints disfavoring vowelless words do not feature in spoken-word recognition.     

Bootstrapping in miniature language acquisition

Given the difficulties in learning meanings of words by observing the referent, it has been suggested that children use the syntactic context of the word to predict part of its meaning, a hypothesis known as syntactic bootstrapping. Semantic bootstrapping is the opposite theory that the knowledge of semantics helps in acquiring syntax. While there is evidence that children can apply their knowledge of correlations between syntax and semantics to perform bootstrapping, it is not clear how they come to know about these correlations in the first place. Here, a connectionist network is presented that learns to comprehend a miniature language by associating sentences with the corresponding scenes. In doing so, it learns the syntactic/semantic correlations and exhibits bootstrapping behavior. It is argued that such specialized phenomena can emerge when general mechanisms are applied to a specific task, and it is not always necessary to endow the learner with pre-existing specialized mechanisms.     

Concept formation and language acquisition

Abstract.— Aspects of language acquisition (simulated) were studied in a concept formation situation with adult subjects. It was found that word meanings were acquired faster with complex than with simple stimulation, as detined by low and high variance distributions of attribute values. It was also demonstrated that stimulus and response choice strategies affect the acquisition of word meanings. Implicit hypotheses about the number of relevant stimulus dimensions were not found to influence concept formation. In a more general perspective, the outcome of the study is consistent with the assumption that the meaning of words is acquired by a concept formation process.     

The origin of language and relative roles of voice and gesture in early communication development

Both vocalization and gesture are universal modes of communication and fundamental features of language development. The gestural origins theory proposes that language evolved out of early gestural use. However, evidence reported here suggests vocalization is much more prominent in early human communication than gesture is. To our knowledge no prior research has investigated the rates of emergence of both gesture and vocalization across the first year in human infants. We evaluated the rates of gestures and speech-like vocalizations (protophones) in 10 infants at 4, 7, and 11 months of age using parent-infant laboratory recordings. We found that infant protophones outnumbered gestures substantially at all three ages, ranging from >35 times more protophones than gestures at 3 months, to >2.5 times more protophones than gestures at 11 months. The results suggest vocalization, not gesture, is the predominant mode of communication in human infants in the first year.     

Communicative Feedback in language acquisition

Children start to communicate and use language in social interactions from a very young age. This allows them to experiment with their developing linguistic knowledge and receive valuable feedback from their – often more knowledgeable – interlocutors. While research in language acquisition has focused a great deal on children's ability to learn from the linguistic input or social cues, little work, in comparison, has investigated the nature and role of Communicative Feedback, a process that results from children and caregivers trying to coordinate mutual understanding.In this work, we draw on insights from theories of communicative coordination to formalize a mechanism for language acquisition: We argue that children can improve their linguistic knowledge in conversation by leveraging explicit or implicit signals of communication success or failure. This new formalization provides a common framework for several lines of research in child development that have been pursued separately. Further, it points towards several gaps in the literature that, we believe, should be addressed in future research in order to achieve a more complete understanding of language acquisition within and through social interaction.     

The early acquisition of verb meaning in German by normally developing and language impaired children

The research reported here focuses on the early acquisition of event structure in German. Based on longitudinal studies from 5 normally developing (ND) and 6 language-impaired (LI) children, a model of "event structural bootstrapping" is presented that spells out how ND children log into the verb lexicon. They project a target-consistent event tree, depicting the head-of-event of transitions. Young LI children, failing to employ this bootstrapping strategy, resort to radically underspecified event representations. The results from a truth-value judgment experiment with 16 ND and 16 LI children showed that ND children perform correctly on transitional verbs, while LI children perform at chance level on the same tasks. These findings are accounted for by the model of event structural bootstrapping to the extent that LI children lack an explicit representation of the head-of-event.     

Symbouki: a meta‐analysis on the emergence of sound symbolism in early language acquisition

Adults and toddlers systematically associate pseudowords such as “bouba” and “kiki” with round and spiky shapes, respectively, a sound symbolic phenomenon known as the “bouba‐kiki effect”. To date, whether this sound symbolic effect is a property of the infant brain present at birth or is a learned aspect of language perception remains unknown. Yet, solving this question is fundamental for our understanding of early language acquisition. Indeed, an early sensitivity to such sound symbolic associations could provide a powerful mechanism for language learning, playing a bootstrapping role in the establishment of novel sound–meaning associations. The aim of the present meta‐analysis (SymBouKi) is to provide a quantitative overview of the emergence of the bouba‐kiki effect in infancy and early childhood. It allows a high‐powered assessment of the true sound symbolic effect size by pooling over the entire set of 11 extant studies (six published, five unpublished), entailing data from 425 participants between 4 and 38 months of age. The quantitative data provide statistical support for a moderate, but significant, sound symbolic effect. Further analysis found a greater sensitivity to sound symbolism for bouba‐type pseudowords (i.e., round sound‐shape correspondences) than for kiki‐type pseudowords (i.e., spiky sound‐shape correspondences). For the kiki‐type pseudowords, the effect emerged with age. Such discrepancy challenges the view that sensitivity to sound symbolism is an innate language mechanism rooted in an exuberant interconnected brain. We propose alternative hypotheses where both innate and learned mechanisms are at play in the emergence of sensitivity to sound symbolic relationships.     

Developmental trends in auditory processing can provide early predictions of language acquisition in young infants

Auditory processing capabilities at the subcortical level have been hypothesized to impact an individual's development of both language and reading abilities. The present study examined whether auditory processing capabilities relate to language development in healthy 9‐month‐old infants. Participants were 71 infants (31 boys and 40 girls) with both Auditory Brainstem Response (ABR) and language assessments. At 6 weeks and/or 9 months of age, the infants underwent ABR testing using both a standard hearing screening protocol with 30 dB clicks and a second protocol using click pairs separated by 8, 16, and 64‐ms intervals presented at 80 dB. We evaluated the effects of interval duration on ABR latency and amplitude elicited by the second click. At 9 months, language development was assessed via parent report on the Chinese Communicative Development Inventory ‐ Putonghua version (CCDI‐P). Wave V latency z‐scores of the 64‐ms condition at 6 weeks showed strong direct relationships with Wave V latency in the same condition at 9 months. More importantly, shorter Wave V latencies at 9 months showed strong relationships with the CCDI‐P composite consisting of phrases understood, gestures, and words produced. Likewise, infants who had greater decreases in Wave V latencies from 6 weeks to 9 months had higher CCDI‐P composite scores. Females had higher language development scores and shorter Wave V latencies at both ages than males. Interestingly, when the ABR Wave V latencies at both ages were taken into account, the direct effects of gender on language disappeared. In conclusion, these results support the importance of low‐level auditory processing capabilities for early language acquisition in a population of typically developing young infants. Moreover, the auditory brainstem response in this paradigm shows promise as an electrophysiological marker to predict individual differences in language development in young children.     

Controversies about CP: a comparison of language acquisition and language impairments in Broca's aphasia

In both language acquisition research and the study of language impairments in Broca's aphasia there is an ongoing debate whether or not phrase-structure representations contain the Complementizer Phrase (CP) layer. To shed some light on this debate, I will provide data on German child language and on German agrammatic Broca's aphasia. Analyses of subordinate clauses, wh-questions, and verb placement indicate that early child grammars do not generate the CP layer yet, whereas the ability to project the CP layer is retained in agrammatism.     

Asynchronous language acquisition in developmental dysphasia

A longitudinal study was conducted to document and compare evolution of children with linguistic acquisition impairment. To determine whether development of the analytic mechanisms underlying linguistic processing occured in similar fashion, two children with mixed developmental dysphasia were assessed from 4 to 5:6 years of age with psycholinguistic tests at 6-months interval. Spontaneous speech and language production (consonant repertory in initial word position, MLU, and lexical diversity) were investigated in a standardized symbolic play context. The phonologic and lexico-morphologic evolution analyses revealed a marked improvement in motor control of phonology and in the application of morphosyntaxic rules in child 1, whereas child 2 was still impaired in phonology and morphosyntax. The singular developmental changes in spontaneous speech results indicate dynamic relationships between various language production facets and variability in the kind of deficit and lexical automation presented by these children. These contrasts in the evolution of language production profiles between child 1 and child 2 also underline the importance of longitudinal studies in the analysis of the atypical linguistic processing paths used by children with developmental dysphasia.