Functional Morphemes and Early Language Acquisition

Acquisition of a new language: an enriched case study documents language growth without external input in a young Korean child's acquisition of English

This paper explores a case of suspension of data input during the acquisition of a second language by a young Korean child acquiring English in an English-only nursery school in the United States. Data suspension occurred naturally when the child returned to Korea for a summer where only Korean was spoken. Systematic investigations using an enriched case study methodology which assessed the nature of the child's English target language acquisition both before and after the Korean Summer revealed significant advances in his English after the Korean Summer despite the absence of English input during this time. Several hypotheses regarding the nature and explanation of this advance are tested. It is argued that significant internal linguistic integration leading to systematization of linguistic knowledge occurred in the absence of synchronous language data input, demonstrating the significance of internal computational processes over and above language data input in the language acquisition process. Results have implications for understanding the fundamental nature of language acquisition.

Wordform variability in infants' language environment and its effects on early word learning

Most research regarding early word learning in English tends to make the simplifying assumption that there exists a one-to-one mapping between concrete objects and their labels. In the current work, we provide evidence that runs counter to this assumption, aligning English with more morphologically-rich languages. We suggest that even in a morphologically-poor language like English, real world language input to infants does not provide tidy 1-to-1 mappings. Instead, infants encounter many variant wordforms for familiar nouns (e.g. dog∼doggy∼dogs). We explore this wordform variability in 44 English-learning infants' naturalistic environments using a longitudinal corpus of infant-available speech. We look at both the frequency and composition of wordform variability. We find two broad categories of variability: referent-changing alterations, where words were pluralized or compounded (e.g. coat∼raincoats); and wordplay, where words changed form without a notable change in referent (e.g. bird∼birdie). We further find that wordplay occurs with a limited number of lemmas that are usually early-learned, high-frequency, and shorter. When looking at all wordform variability, we find that individual words with higher levels of wordform variability are learned earlier than words with fewer wordforms, over and above the effect of frequency.

Six-month-old infants' perception of structural regularities in speech

In order to acquire grammar, infants need to extract regularities from the linguistic input. From birth, infants can detect regularities in speech based on identity relations, and show strong neural activation to syllable sequences containing adjacent repetitions of identical syllables (e.g. ABB: mubaba). Meanwhile, newborns' neural responses to sequences of different syllables (e.g. ABC: mubage, i.e. diversity-based relations) do not differ from baseline. However, this latter ability needs to emerge during development, as most linguistic units, such as words, are composed of highly variable sequences. As infants begin to learn their first word forms at 6 months, we hypothesize that the ability to represent sequences of different syllables might become important for them at this age. Using near-infrared spectroscopy (NIRS), we measured 6-month-old infants' brain responses to repetition- and diversity-based sequences in the bilateral temporal, parietal and frontal areas. We found that 6-month-olds discriminated the repetition- and diversity-based structures in frontal and parietal regions, and exhibited equally strong activation to both grammars as compared to baseline. These results show that by 6 months of age, infants encode sequences with diversity-based structures. They thus provide the earliest evidence that prelexical infants represent difference in speech stimuli, which behavioral studies first attest at 11 months of age.

The role of Function Words to build syntactic knowledge in French-speaking children

The question of how children learn Function Words (FWs) is still a matter of debate among child language researchers. Are early multiword utterances based on lexically specific patterns or rather abstract grammatical relations? In this corpus study, we analyzed FWs having a highly predictable distribution in relation to Mean Length Utterance (MLU) an index of syntactic complexity in a large naturalistic sample of 315 monolingual French children aged 2 to 4 year-old. The data was annotated with a Part Of Speech Tagger (POS-T), belonging to computational tools from CHILDES. While eighteen FWs strongly correlated with MLU expressed either in word or in morpheme, stepwise regression analyses showed that subject pronouns predicted MLU. Factor analysis yielded a bifactor hierarchical model: The first factor loaded sixteen FWs among which eight had a strong developmental weight (third person singular verbs, subject pronouns, articles, auxiliary verbs, prepositions, modals, demonstrative pronouns and plural markers), whereas the second factor loaded complex FWs (possessive verbs and object pronouns). These findings challenge the lexicalist account and support the view that children learn grammatical forms as a complex system based on early instead of late structure building. Children may acquire FWs as combining words and build syntactic knowledge as a complex abstract system which is not innate but learned from multiple word input sentences context. Notably, FWs were found to predict syntactic development and sentence complexity. These results open up new perspectives for clinical assessment and intervention.

Learning Through Processing: Toward an Integrated Approach to Early Word Learning

Children's linguistic knowledge and the learning mechanisms by which they acquire it grow substantially in infancy and toddlerhood, yet theories of word learning largely fail to incorporate these shifts. Moreover, researchers' often-siloed focus on either familiar word recognition or novel word learning limits the critical consideration of how these two relate. As a step toward a mechanistic theory of language acquisition, we present a framework of "learning through processing" and relate it to the prevailing methods used to assess children's early knowledge of words. Incorporating recent empirical work, we posit a specific, testable timeline of qualitative changes in the learning process in this interval. We conclude with several challenges and avenues for building a comprehensive theory of early word learning: better characterization of the input, reconciling results across approaches, and treating lexical knowledge in the nascent grammar with sufficient sophistication to ensure generalizability across languages and development.

The Acquisition of Noun and Verb Categories by Bootstrapping From a Few Known Words: A Computational Model

While many studies have shown that toddlers are able to detect syntactic regularities in speech, the learning mechanism allowing them to do this is still largely unclear. In this article, we use computational modeling to assess the plausibility of a context-based learning mechanism for the acquisition of nouns and verbs. We hypothesize that infants can assign basic semantic features, such as “is-an-object” and/or “is-an-action,” to the very first words they learn, then use these words, the semantic seed, to ground proto-categories of nouns and verbs. The contexts in which these words occur, would then be exploited to bootstrap the noun and verb categories: unknown words are attributed to the class that has been observed most frequently in the corresponding context. To test our hypothesis, we designed a series of computational experiments which used French corpora of child-directed speech and different sizes of semantic seed. We partitioned these corpora in training and test sets: the model extracted the two-word contexts of the seed from the training sets, then used them to predict the syntactic category of content words from the test sets. This very simple algorithm demonstrated to be highly efficient in a categorization task: even the smallest semantic seed (only 8 nouns and 1 verb known) yields a very high precision (~90% of new nouns; ~80% of new verbs). Recall, in contrast, was low for small seeds, and increased with the seed size. Interestingly, we observed that the contexts used most often by the model featured function words, which is in line with what we know about infants' language development. Crucially, for the learning method we evaluated here, all initialization hypotheses are plausible and fit the developmental literature (semantic seed and ability to analyse contexts). While this experiment cannot prove that this learning mechanism is indeed used by infants, it demonstrates the feasibility of a realistic learning hypothesis, by using an algorithm that relies on very little computational and memory resources. Altogether, this supports the idea that a probabilistic, context-based mechanism can be very efficient for the acquisition of syntactic categories in infants.

Looking for Wugs in all the Right Places: Children's Use of Prepositions in Word Learning

To help infer the meanings of novel words, children frequently capitalize on their current linguistic knowledge to constrain the hypothesis space. Children's syntactic knowledge of function words has been shown to be especially useful in helping to infer the meanings of novel words, with most previous research focusing on how children use preceding determiners and pronouns/auxiliary to infer whether a novel word refers to an entity or an action, respectively. In the current visual world experiment, we examined whether 28- to 32-month-olds could exploit their lexical semantic knowledge of an additional class of function words-prepositions-to learn novel nouns. During the experiment, children were tested on their ability to use the prepositions in, on, under, and next to to identify novel creatures displayed on a screen (e.g., The wug is on the table), as well as their ability to later identify the creature without accompanying prepositions (e.g., Look at the wug). Children overall demonstrated understanding of all the prepositions but next to and were able to use their knowledge of prepositions to learn the associations between novel words and their intended referents, as shown by greater-than chance looks to the target referent when no prepositional phrase was provided.

Labels and object categorization in six- and nine-month-olds: tracking labels across varying carrier phrases

Language shapes object categorization in infants. This starts as a general enhanced attentional effect of language, which narrows to a specific link between labels and categories by twelve months. The current experiments examined this narrowing effect by investigating when infants track a consistent label across varied input. Six-month-old infants (N = 48) were familiarized to category exemplars, each presented with the exact same labeling phrase or the same label in different phrases. Evidence of object categorization at test was only found with the same phrase, suggesting that infants were not tracking the label's consistency, but rather that of the entire input. Nine-month-olds (N = 24) did show evidence of categorization across the varied phrases, suggesting that they were tracking the consistent label across the varied input.

Learning word order: early beginnings

We examine the beginning of the acquisition of the relative order of function and content words, a fundamental but cross-linguistically highly variable aspect of grammar. A review of the existing empirical literature shows that infants as young as 8 months of age can distinguish between functors and content words, and have a rudimentary knowledge of the order of these two universal lexical categories in their native language. Furthermore, human adults and non-human animals such as rodents process the same linguistic information differently from infants, emphasizing the developmental relevance of bootstrapping function/content word order from surface cues available in the input. We discuss the implications of these findings for a synergistic view of language acquisition, considering how grammar acquisition interacts with word learning.

Meaning before grammar: A review of ERP experiments on the neurodevelopmental origins of semantic processing

According to traditional linguistic theories, the construction of complex meanings relies firmly on syntactic structure-building operations. Recently, however, new models have been proposed in which semantics is viewed as being partly autonomous from syntax. In this paper, we discuss some of the developmental implications of syntax-based and autonomous models of semantics. We review event-related brain potential (ERP) studies on semantic processing in infants and toddlers, focusing on experiments reporting modulations of N400 amplitudes using visual or auditory stimuli and different temporal structures of trials. Our review suggests that infants can relate or integrate semantic information from temporally overlapping stimuli across modalities by 6 months of age. The ability to relate or integrate semantic information over time, within and across modalities, emerges by 9 months. The capacity to relate or integrate information from spoken words in sequences and sentences appears by 18 months. We also review behavioral and ERP studies showing that grammatical and syntactic processing skills develop only later, between 18 and 32 months. These results provide preliminary evidence for the availability of some semantic processes prior to the full developmental emergence of syntax: non-syntactic meaning-building operations are available to infants, albeit in restricted ways, months before the abstract machinery of grammar is in place. We discuss this hypothesis in light of research on early language acquisition and human brain development.

Is prosodic information alone sufficient for guiding early grammatical acquisition?

An infant perceptual experiment investigated the role of prosody. All-nonsense-word sentences (e.g., Guin felli crale vur ti gosine), each in structure 1 ([[Determiner + Adjective + Noun] [Verb + Determiner + Noun]]) and structure 2 ([[Determiner + Noun] [Verb + Preposition + Determiner + Noun]]), were recorded (by mimicking real-word French sentences) with disambiguating prosodic groupings matching the two major constituents. French-learning 20- and 24-month-olds were familiarized with either structure 1 or structure 2. All infants were tested with noun-use trials (e.g., Le crale "the crale-Noun") versus verb-use trials (Tu crales "You crale-Verb"). Structure-2-familiarized infants, but not structure-1-familiarized infants, discriminated the test trials, demonstrating that prosody alone guides verb categorization. Noun categorization requires determiners, as shown in earlier work [S. Massicotte-Laforge and R. Shi, J. Acoust. Soc. Am. 138(4), EL441-EL446 (2015)].

Studying the Real-Time Interpretation of Novel Noun and Verb Meanings in Young Children

Decades of research show that children rely on the linguistic context in which novel words occur to infer their meanings. However, because learning in these studies was assessed after children had heard numerous occurrences of a novel word in informative linguistic contexts, it is impossible to determine how much exposure would be needed for a child to learn from such information. This study investigated the speed with which French 20-month-olds and 3-to-4-year-olds exploit function words to determine the syntactic category of novel words and therefore infer their meanings. In a real-time preferential looking task, participants saw two videos side-by-side on a TV-screen: one showing a person performing a novel action, and the other a person passively holding a novel object. At the same time, participants heard only three occurrences of a novel word preceded either by a determiner (e.g., "Regarde! Une dase! - "Look! A dase!") or a pronoun (e.g., "Regarde! Elle dase!" - "Look! She's dasing!"). 3-to-4-year-olds exploited function words to categorize novel words and infer their meanings: they looked more to the novel action in the verb condition, while participants in the noun condition looked more to the novel object. 20-month-olds, however, did not show this difference. We discuss possible reasons for why 20-month-olds may have found it difficult to infer novel word meanings in our task. Given that 20-month-olds can use function words to learn word meanings in experiments providing many repetitions, we suspect that more repetitions might be needed to observe positive effects of learning in this age range in our task. Our study establishes nevertheless that before age 4, young children become able to exploit function words to infer the meanings of unknown words as soon as they occur. This ability to interpret speech in real-time and build interpretations about novel word meanings might be extremely useful for young children to map words to their possible referents and to boost their acquisition of word meanings.

Linking language and categorization in infancy

Language exerts a powerful influence on our concepts. We review evidence documenting the developmental origins of a precocious link between language and object categories in very young infants. This collection of studies documents a cascading process in which early links between language and cognition provide the foundation for later, more precise ones. We propose that, early in life, language promotes categorization at least in part through its status as a social, communicative signal. But over the first year, infants home in on the referential power of language and, by their second year, begin teasing apart distinct kinds of names (e.g. nouns, adjectives) and their relation to distinct kinds of concepts (e.g. object categories, properties). To complement this proposal, we also relate this evidence to several alternative accounts of language's effect on categorization, appealing to similarity ('labels-as-features'), familiarity ('auditory overshadowing'), and communicative biases ('natural pedagogy').

Learning word order at birth: A NIRS study

In language, the relative order of words in sentences carries important grammatical functions. However, the developmental origins and the neural correlates of the ability to track word order are to date poorly understood. The current study therefore investigates the origins of infants’ ability to learn about the sequential order of words, using near-infrared spectroscopy (NIRS) with newborn infants. We have conducted two experiments: one in which a word order change was implemented in 4-word sequences recorded with a list intonation (as if each word was a separate item in a list; list prosody condition, Experiment 1) and one in which the same 4-word sequences were recorded with a well-formed utterance-level prosodic contour (utterance prosody condition, Experiment 2). We found that newborns could detect the violation of the word order in the list prosody condition, but not in the utterance prosody condition. These results suggest that while newborns are already sensitive to word order in linguistic sequences, prosody appears to be a stronger cue than word order for the identification of linguistic units at birth.

'Form is easy, meaning is hard' revisited: (re) characterizing the strengths and weaknesses of language in children with autism spectrum disorder

Children with autism spectrum disorder (ASD) demonstrate impairments in social interaction and communication, and in repetitive/stereotypical behaviors. The degree to which children with ASD also manifest impairments in structural language-such as lexicon and grammar-is currently quite controversial. We reframe this controversy in terms of Naigles' (Naigles, Cognition 2002, 86: 157-199) 'form is easy, meaning is hard' thesis, and propose that the social difficulties of children with ASD will lead the meaning-related components of their language to be relatively more impaired than the form-related components. Our review of the extant literature supports this proposal, with studies (1) reporting that children with ASD demonstrate significant challenges in the areas of pragmatics and lexical/semantic organization and (2) highlighting their good performance on grammatical assessments ranging from wh-questions to reflexive pronouns. Studies on children with ASD who might have a co-morbid grammatical impairment are discussed in light of the absence of relevant lexical-semantic data from the same children. Most importantly, we present direct comparisons of assessments of lexical/semantic organization and grammatical knowledge from the same children from our laboratory, all of which find more children at a given age demonstrating grammatical knowledge than semantic organization. We conclude with a call for additional research in which in-depth grammatical knowledge and detailed semantic organization are assessed in the same children. WIREs Cogn Sci 2017, 8:e1438. doi: 10.1002/wcs.1438 This article is categorized under: Linguistics > Language Acquisition Linguistics > Language in Mind and Brain Neuroscience > Development.

ERP evidence for on-line syntactic computations in 2-year-olds

Syntax allows human beings to build an infinite number of sentences from a finite number of words. How this unique, productive power of human language unfolds over the course of language development is still hotly debated. When they listen to sentences comprising newly-learned words, do children generalize from their knowledge of the legal combinations of word categories or do they instead rely on strings of words stored in memory to detect syntactic errors? Using novel words taught in the lab, we recorded Evoked Response Potentials (ERPs) in two-year-olds and adults listening to grammatical and ungrammatical sentences containing syntactic contexts that had not been used during training. In toddlers, the ungrammatical use of words, even when they have been just learned, induced an early left anterior negativity (surfacing 100-400ms after target word onset) followed by a late posterior positivity (surfacing 700-900ms after target word onset) that was not observed in grammatical sentences. This late effect was remarkably similar to the P600 displayed by adults, suggesting that toddlers and adults perform similar syntactic computations. Our results thus show that toddlers build on-line expectations regarding the syntactic category of upcoming words in a sentence.

Where are the cookies? Two- and three-year-olds use number-marked verbs to anticipate upcoming nouns

We tested toddlers' and adults' predictive use of English subject-verb agreement. Participants saw pairs of pictures differing in number and kind (e.g., one apple, two cookies), and heard sentences with a target noun naming one of the pictures. The target noun was the subject of a preceding agreeing verb in informative trials (e.g., Wherearethe good cookies?), but not in uninformative trials (Do you see the good cookies?). In Experiment 1, 3-year-olds and adults were faster and more likely to shift their gaze from distractor to target upon hearing an informative agreeing verb. In Experiment 2, 2.5-year-olds were faster to shift their gaze from distractor to target in response to the noun in informative trials, and were more likely to be fixating the target already at noun onset. Thus, toddlers used agreeing verbs to predict number features of an upcoming noun. These data provide strong new evidence for the broad scope of predictive processing in online language comprehension.

The role of prosody in infants' early syntactic analysis and grammatical categorization

This study tested the hypothesis that phrasal prosody assists early syntactic acquisition. Stimulus-sentences consisting of French determiners and pseudo-lexical-words were ambiguous between two syntactic structures, e.g., [[TonDet felliAdj craleN]NP [vurV laDet gosineN]VP] versus [[TonDet felliN]NP [craleV vurPrep laDet gosineN]VP], which had distinct prosodic cues. French-learning 20-month-olds were familiarized with the sentences either in the prosody of one structure, or the other structure. All infants were tested with Det + N (e.g., LeDet craleN) versus Pron + V (e.g., TuPron cralesV) trials containing non-familiarized functors. Infants perceived the test-stimuli according to the familiarized structure. They used prosody to categorize words and interpret adjacent and non-adjacent syntactic dependencies.

Preschoolers use phrasal prosody online to constrain syntactic analysis

Two experiments were conducted to investigate whether young children are able to take into account phrasal prosody when computing the syntactic structure of a sentence. Pairs of French noun/verb homophones were selected to create locally ambiguous sentences ([la petite ferme] [est très jolie] 'the small farm is very nice' vs. [la petite] [ferme la fenêtre] 'the little girl closes the window'--brackets indicate prosodic boundaries). Although these sentences start with the same three words, ferme is a noun (farm) in the former but a verb (to close) in the latter case. The only difference between these sentence beginnings is the prosodic structure, that reflects the syntactic structure (with a prosodic boundary just before the critical word when it is a verb, and just after it when it is a noun). Crucially, all words following the homophone were masked, such that prosodic cues were the only disambiguating information. Children successfully exploited prosodic information to assign the appropriate syntactic category to the target word, in both an oral completion task (4.5-year-olds, Experiment 1) and in a preferential looking paradigm with an eye-tracker (3.5-year-olds and 4.5-year-olds, Experiment 2). These results show that both groups of children exploit the position of a word within the prosodic structure when computing its syntactic category. In other words, even younger children of 3.5 years old exploit phrasal prosody online to constrain their syntactic analysis. This ability to exploit phrasal prosody to compute syntactic structure may help children parse sentences containing unknown words, and facilitate the acquisition of word meanings.