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Event-related potentials associated with cognitive mechanisms underlying lexical-semantic processing in monolingual and bilingual 18-month-old children

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Abstract

Prior to their second birthday, children are sensitive to the semantic relatedness between spoken words. Yet, it remains unclear whether simultaneous second language acquisition affects this sensitivity. Here, we investigated the influence of early acquisition of two languages on the event-related potentials (ERPs) associated with lexical-semantic processing of spoken words in 18-month-old monolingual and bilingual children. Children were exposed to an auditory semantic priming task in French, while their ERPs were recorded. Word pairs were either semantically related (e.g., train-bike) or unrelated (e.g., chicken-bike), and they were presented at two stimulus onset asynchronies (SOA). The results revealed that only monolingual children exhibited a semantic priming effect at the short SOA while at the long SOA condition, both monolingual and bilingual children exhibited more pronounced ERPs in response to unrelated compared with related target words. This finding suggests that both language groups are sensitive to taxonomic relations between words but activation of sematic network might be less automatized or slower in bilingual children.

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... Interference effects on word recognition are either indexed by longer response times to fixate the target or reduced fixations to the target when the target label is preceded by a related prime relative to an unrelated prime. This priming adaptation has recently been combined with automated eye tracking (see Delle-Luche, Durrant, Poltrock, & Floccia, 2015;Golinkoff, Ma, Song, & Hirsh-Pasek, 2013, for methodological reviews) and event-related potential data (e.g., Rämä, Sirri, & Goyet, 2018;Rämä, Sirri, & Serres, 2013;Torkildsen, Syversen, Moen, Simonsen, & Lindgren, 2007). ...
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Studies on lexical development in young children often suggest that the organization of the early lexicon may vary with age and increasing vocabulary size. In the current study, we explicitly examined this suggestion in further detail using a longitudinal study of the development of phonological and semantic priming effects in the same group of toddlers at three different ages. In particular, our longitudinal design allows us to disentangle effects of increasing age and vocabulary size on priming and the extent to which vocabulary size may predict later priming effects. We tested phonological and semantic priming effects in monolingual German infants at 18, 21, and 24 months of age. We used the intermodal preferential looking paradigm combined with eye tracking to measure the influence of phonologically and semantic related/unrelated primes on target recognition. We found that phonological priming effects were predicted by participants’ current vocabulary size even after controlling for participants’ age and participants’ early vocabulary size. Semantic priming effects were, in contrast, not predicted by vocabulary size. Finally, we also found a relationship between early phonological priming effects and later semantic priming effects as well as between early semantic priming effects and later phonological priming effects, potentially suggesting (limited) consistency in lexical structure across development. Taken together, these results highlight the important role of vocabulary size in the development of priming effects in early childhood.
... One study tested semantic priming effects in 18-month-old French monolinguals and French/mixed other language bilinguals and found an increased ERP response to unrelated in comparison to related words in both populations, compatible with the notion that semantic acquisition is not delayed in bilingual as compared to monolingual infants. However, the results further suggested that, at that age, semantic activation in the bilinguals was less automatized or slower than in monolinguals (Rämä, Sirri & Goyet, 2018). Another study tested the sensitivity of 7-month-old bilingual infants learning one language with Verb-Object order (English) and another language with Object-Verb word order (such as e.g., Japanese and Turkish), to the link between prosodic information and word order (Gervain & Werker, 2013). ...
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Many human infants grow up learning more than one language simultaneously but only recently has research started to study early language acquisition in this population more systematically. The paper gives an overview on findings on early language acquisition in bilingual infants during the first two years of life and compares these findings to current knowledge on early language acquisition in monolingual infants. Given the state of the research, the overview focuses on research on phonological and early lexical development in the first two years of life. We will show that the developmental trajectory of early language acquisition in these areas is very similar in mono- and bilingual infants suggesting that these early steps into language are guided by mechanisms that are rather robust against the differences in the conditions of language exposure that mono- and bilingual infants typically experience.
... One study tested semantic priming effects in 18-month-old French monolinguals and French/mixed other language bilinguals and found an increased ERP response to unrelated in comparison to related words in both populations, compatible with the notion that semantic acquisition is not delayed in bilingual as compared to monolingual infants. However, the results further suggested that, at that age, semantic activation in the bilinguals was less automatized or slower than in monolinguals (Rämä, Sirri & Goyet, 2018). Another study tested the sensitivity of 7-month-old bilingual infants learning one language with Verb-Object order (English) and another language with Object-Verb word order (such as e.g., Japanese and Turkish), to the link between prosodic information and word order (Gervain & Werker, 2013). ...
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While the N400 component in adults is sensitive to both semantic incongruity and semantic relatedness between stimulus items, the N400 in toddlers has only been shown as an incongruity effect so far. The present event-related potential (ERP) study aimed to investigate whether the N400 in toddlers also indexes semantic relatedness between single words. To address this issue, we developed a unimodal auditory experiment with semantically related and unrelated word pairs, comparable to behavioral semantic priming tasks used with adults. In 24-month-old children, target words which were preceded by a semantically unrelated word elicited a broadly distributed N400-like effect compared to target words which were primed by a semantically related word. For related words, toddlers displayed a negativity in the 200-400 ms interval, indicating facilitated lexical-phonological processing. Results of the present study suggest that the N400 in toddlers is functionally equivalent to the adult component in indexing relatedness as well as semantic incongruity between stimulus items. Moreover, the study demonstrates an instrument for investigating semantic relatedness priming in young children, for whom behavioral tasks are often inappropriate.
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Several authors have contended that the N400 is a reflection of a post-lexical event such as that proposed by Neely and Keefe [J.H. Neely, D.E. Keefe, Semantic context effects on visual word processing: a hybrid prospective/retrospective processing theory, in: G.H. Bower (Ed.), The Psychology of Learning and Motivation: Advances in Research and Theory, Vol. 23, Academic Press, New York, 1989, pp. 207–248.], whereby the subject compares the word on the current trial to the “context” provided by the word on the preceding trial [M. Besson, M. Kutas, The many facets of repetition: A cued-recall and event-related potential analysis of repeating words in same versus different sentence contexts, Journal of Experimental Psychology: Learning, Memory and Cognition, 19 (5) (1993), 1115-1133; C. Brown, P. Hagoort, The processing nature of the N400: Evidence from masked priming. Journal of Cognitive Neuroscience, 5(1) (1993), 34–44; P.J. Holcomb, Semantic priming and stimulus degradation: Implications for the role of the N400 in language processing, Psychophysiology 30 (1993), 47–61; M.D. Rugg, M.C. Doyle, Event-related potentials and stimulus repetition in indirect and direct tests of memory, in: H. Heinze, T. Munte, G.R. Mangun (Eds), Cognitive Electrophysiology, Birkhauser Boston, Cambridge, MA, 1994]. A study which used masked primes to directly test this possibility has been reported by Brown and Hagoort [C. Brown, P. Hagoort, The processing nature of the N400: evidence from masked priming. Journal of Cognitive Neuroscience, 5(1) (1993), 34–44]. When the primes were masked, no priming effect was observed on the N400. When behavioral data were collected in the same paradigm, from another group of subjects, the usual priming effect on RT was obtained. Considered together, the data from the two groups of subjects indicated that activation of semantic representations had occurred without conscious awareness. As no N400 priming effect was observed, it was suggested that N400 must reflect a post-lexical process. This interpretation, however, is at odds with the findings of other studies which have reported N400 priming effects under conditions where post-lexical processes would not be thought to operate[J. Anderson, P. Holcomb, Auditory and visual semantic priming using different stimulus onset asynchronies: an event-related brain potential study. Psychophysiology 32 (1995), 177–190; J. Boddy, Event-related potentials in chronometric analysis of primed word recognition with different stimulus onset asynchronies, Psychophysiology 23 (1986), 232–245; D. Deacon, T. Uhm, W. Ritter, S. Hewitt, The lifetime of automatic priming effects may exceed two seconds, Cognitive Brain Research 7 (1999), 465–472; P.J. Holcomb, Automatic and attentional process: an event-related brain potential analysis of semantic priming. Brain and Language 35 (1998) 66–85]. The present study replicated Brown and Hagoort using a repeated measures design, a shorter SOA (stimulus onset asynchrony), and a slightly different threshold setting procedure. Significant priming effects were obtained on the mean amplitude of the N400 regardless of whether the words were masked or unmasked. The findings imply that the processing subserving the N400 is not postlexical, since the N400 was manipulated without the subjects being aware of the identity of the words.
Article
In ERP studies of adults, semantic incongruities elicit a late negative response called the N400. Recently it was demonstrated that the amplitude of the N400 is sensitive to the organization of semantic categories in memory. The present study sought to investigate whether a similar incongruity response can be identified in children in their second year of life and whether this response is sensitive to category relationships at this early stage of lexical acquisition.In a picture–word mismatch paradigm with basic-level words, 20-month-olds displayed an N400-like incongruity effect. The incongruity response was earlier and larger for between-category violations than for within-category violations when each of the two violation types was compared to a control condition. This suggests that the N400 component is already sensitive to the semantic organization of the mental lexicon in toddlers, and may serve as a useful tool in the study of phenomena in lexical development such as overextension.Some behavioral studies have suggested that toddler's overextensions of basic-level words result from oversized conceptual categories. This is at odds with the present finding of incongruity responses even to within-category violations.
Article
The relation between the maturation of brain mechanisms responsible for the N400 elicitation in the event-related brain potential (ERP) and the development of behavioral language skills was investigated in 12-month-old infants. ERPs to words presented in a picture-word priming paradigm were analyzed according to the infants' production and comprehension skills as rated by their parents. Infants with high early word production displayed an N400 semantic priming effect already at 12 months. Infants with low early word production did not show this effect, not even for those words that parents rated to be comprehended by their child. The results suggest that the very early functioning of the neural mechanisms underlying N400 generation is related to the infants' state of behavioral language development. The possible functional relation of the N400 neural mechanisms and the infant's word learning ability is discussed.
Article
A dual-task paradigm was used to assess attentional processing demands during visual word recognition. By manipulating the difficulty of each task, it is argued that the procedure estimates the attention demands of the memory-access component of word recognition. Specifically, the the complexity of the secondary task was varied from a simple reaction time task to a choice reaction time task, and the difficulty of a lexical decision (word vs. nonword) primary task was varied by manipulating word frequency. A comparison of the effect of secondary task complexity across levels of word frequency showed that the difference between the two secondary tasks was larger for low-frequency words than for high-frequency words. This result, supported by other characteristics of the data, suggests that the memory-access processing in one type of word recognition task does demand attention.
A new off-line procedure for dealing with ocular artifacts in ERP recording is described. The procedure (EMCP) uses EOG and EEG records for individual trials in an experimental session to estimate a propagation factor which describes the relationship between the EOG and EEG traces. The propagation factor is computed after stimulus-linked variability in both traces has been removed. Different propagation factors are computed for blinks and eye movements. Tests are presented which demonstrate the validity and reliability of the procedure. ERPs derived from trials corrected by EMCP are more similar to a 'true' ERP than are ERPs derived from either uncorrected or randomly corrected trials. The procedure also reduces the difference between ERPs which are based on trials with different degrees of EOG variance. Furthermore, variability at each time point, across trials, is reduced following correction. The propagation factor decreases from frontal to parietal electrodes, and is larger for saccades than blinks. It is more consistent within experimental sessions than between sessions. The major advantage of the procedure is that it permits retention of all trials in an ERP experiment, irrespective of ocular artifact. Thus, studies of populations characterized by a high degree of artifact, and those requiring eye movements as part of the experimental task, are made possible. Furthermore, there is no need to require subjects to restrict eye movement activity. In comparison to procedures suggested by others, EMCP also has the advantage that separate correction factors are computed for blinks and movements and that these factors are based on data from the experimental session itself rather than from a separate calibration session.
Article
In a sentence reading task, words that occurred out of context were associated with specific types of event-related brain potentials. Words that were physically aberrant (larger than normal) elecited a late positive series of potentials, whereas semantically inappropriate words elicited a late negative wave (N400). The N400 wave may be an electrophysiological sign of the "reprocessing" of semantically anomalous information.
Article
Semantic priming effects (behavioral and electrophysiological) were compared in the visual and auditory modalities across three stimulus onset asynchronies (SOAs; 0, 200, and 800 ms). When both prime and target were presented in the visual modality (the prime just to the left of a fixation point and the target to the right), there were N400 priming effects present across the three SOAs. However, the N400 in the 0-ms SOA condition extended longer in time (800 vs. 500 ms) than in the other SOAs. When both the prime and target were presented in the auditory modality (the prime to the right ear and the target to the left), the largest priming effects were found for the 800-ms SOA. Moreover, there was a relatively early priming effect present in the 0- and 800-ms SOA conditions but not in the 200-ms condition. The results are discussed in terms of modality differences in the time course of word comprehension processes.
Article
The physical energy that we refer to as a word, whether in isolation or embedded in sentences, takes its meaning from the knowledge stored in our brains through a lifetime of experience. Much empirical evidence indicates that, although this knowledge can be used fairly flexibly, it is functionally organized in 'semantic memory' along a number of dimensions, including similarity and association. Here, we review recent findings using an electrophysiological brain component, the N400, that reveal the nature and timing of semantic memory use during language comprehension. These findings show that the organization of semantic memory has an inherent impact on sentence processing. The left hemisphere, in particular, seems to capitalize on the organization of semantic memory to pre-activate the meaning of forthcoming words, even if this strategy fails at times. In addition, these electrophysiological results support a view of memory in which world knowledge is distributed across multiple, plastic-yet-structured, largely modality-specific processing areas, and in which meaning is an emergent, temporally extended process, influenced by experience, context, and the nature of the brain itself.
Article
The capacity of human infants to discriminate contrasting speech sounds specializes to the native language by the end of the first year of life, when the first signs of word recognition have also been found, using behavioural measures. The extent of voluntary attentional involvement in such word recognition has not been explored, however, nor do we know what its neural time-course may be. Here we demonstrate that 11-month-old children shift their attention automatically to familiar words within 250 ms of presentation onset by measuring event-related potentials elicited by familiar and unfamiliar words. A significant modulation of the first negative peak (N200), known to index implicit change detection in adults, was induced by word familiarity in the infants.
Article
To understand mechanisms of early language acquisition, it is important to know whether the child's brain acts in an adult-like manner when processing words in meaningful contexts. The N400, a negative component in the eventrelated potential (ERP) of adults, is a sensitive index of semantic processing reflecting neural mechanisms of semantic integration into context. In the present study, we investigated whether the mechanisms indexed by the N400 are already working during early language acquisition. While 19-month-olds were looking at sequentially presented pictures, they were acoustically presented with words that were either congruous or incongruous to the picture content. The ERP averaged across the group of 55 children revealed an N400-like semantic incongruity effect in addition to an early phonological-lexical priming effect. The results suggest that both lexical expectations facilitating early phonological processing and mechanisms of semantic priming facilitating integration into semantic context are already present in 19-month-olds. The child's specific comprehension abilities are reflected in strength, latency, and hemispheric differences of the semantic incongruity effect. Spatio-temporal differences in that effect, thus, indicate changes in the organization of brain activity correlated with the child's behavioral development.
Article
This study investigates by means of the event-related brain potential whether mechanisms of lexical priming and semantic integration are already developed in 14-month-olds. While looking at coloured pictures of known objects children were presented with basic-level words that were either congruous or incongruous to the pictures. The event-related potential of 14-month-olds revealed an early negativity in the lateral frontal brain region for congruous words, and a later N400-like negativity for incongruous words. These results indicate that both lexical priming and semantic integration are already present as early as 14 months.
Article
In a previous semantic priming study, we found a semantic distance effect on the lexical-decision-related P300 when SOA was short (150 ms) only, but no different RT and N400 priming effects between short and long (700 ms) SOAs. To investigate this further, we separated priming from lexical decision, using a delayed lexical decision in the present study. In the short SOA only, primed targets evoked an early peaking (approximately 480 ms) P300-like component, probably because the subject detected the semantic relationship implicitly. We hypothesize that in tasks requiring an immediate lexical decision, this early P300 and the later lexical decision P300 (approximately 600 ms) are additive. Secondly, we found both a direct and an indirect priming effect for both SOAs for the ERP amplitude of the N400 time window. However the N400 component itself was considerably larger in the long SOA than in the short SOA. We interpreted this finding as an ERP correlate for deeper semantic processing in the long SOA, due to increased attention that was provoked by the use of pseudoword primes. In contrast, in the short SOA, subjects might have used a shallowed semantic processing. N400, P300, and RTs are sensitive to semantic priming-but the modulation patterns are not consistent. This raises the question as to which variable reflects an immediate physiological correlate of semantic priming, and which variable reflects co-occurring processes associated with semantic priming.
Article
During their first year of life, infants not only acquire probabilistic knowledge about the phonetic, prosodic, and phonotactic organization of their native language, but also begin to establish first lexical-semantic representations. The present study investigated the sensitivity to phonotactic regularities and its impact on semantic processing in 1-year-olds. We applied the method of event-related brain potentials to 12- and 19-month-old children and to an adult control group. While looking at pictures of known objects, subjects listened to spoken nonsense words that were phonotactically legal (pseudowords) or had phonotactically illegal word onsets (nonwords), or to real words that were either congruous or incongruous to the picture contents. In 19-month-olds and in adults, incongruous words and pseudowords, but not nonwords, elicited an N400 known to ref lect mechanisms of semantic integration. For congruous words, the N400 was attenuated by semantic priming. In contrast, 12-month-olds did not show an N400 difference, neither between pseudo- and nonwords nor between incongruous and congruous words. Both 1-year-old groups and adults additionally displayed a lexical priming effect for congruous words, that is, a negativity starting around 100 msec after words onset. One-year-olds, moreover, displayed a phonotactic familiarity effect, that is, a widely distributed negativity starting around 250 msec in 19-month-olds but occurring later in 12-month-olds. The results imply that both lexical priming and phonotactic familiarity already affect the processing of acoustic stimuli in children at 12 months of age. In 19-month-olds, adult-like mechanisms of semantic integration are present in response to phonotactically legal, but not to phonotactically illegal, nonsense words, indicating that children at this age treat pseudowords, but not nonwords, as potential word candidates.
Article
Infant bilingualism offers a unique opportunity to study the relative effects of language experience and maturation on brain development, with each child serving as his or her own control. Event-related potentials (ERPs) to words were examined in 19- to 22-month-old English-Spanish bilingual toddlers. The children's dominant vs. nondominant languages elicited different patterns of neural activity in the lateral asymmetry of an early positive component (P100), and the latencies and distributions of ERP differences to known vs. unknown words from 200-400 and 400-600 ms. ERP effects also differed for 'high' and 'low' vocabulary groups based on total conceptual vocabulary scores. The results indicate that the organization of language-relevant brain activity is linked to experience with language rather than brain maturation.
Article
Recent developmental research on word processing has shown that mechanisms of lexical priming are already present in 12-month-olds whereas mechanisms of semantic integration indexed by the N400 mature a few months later. In a longitudinal setting we investigated whether the occurrence of an N400 at 19 months is associated with the children's language skills later on. To this end children were retrospectively grouped according to their verbal performance in a language test at 30 months. Children with later age-adequate expressive language skills already displayed an N400 at 19 months. In contrast, children with later poor expressive language skills who have an enhanced risk for the development of specific language impairment (SLI) did not show an early N400. The results imply that children who have deficits in their expressive language at the age of 30 months are already impaired in their semantic development about one year earlier.
Article
The neural correlates of early language development and language impairment are described, with the adult language-related brain systems as a target model. Electrophysiological and hemodynamic studies indicate that language functions to be installed in the child's brain are similar to those of adults, with lateralization being present at birth, phonological processes during the first months, semantic processes at 12 months, and syntactic processes around 30 months. These findings support the view that the brain basis of language develops continuously over time. Discontinuities are observed in children with language impairment. Here, the observed functional abnormalities are accompanied by structural abnormalities in inferior frontal and temporal brain regions.