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Event-related potentials associated with cognitive mechanisms underlying lexical-semantic processing in monolingual and bilingual 18-month-old children
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.
... 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). ...
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). ...
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). ...
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.
A number of studies have shown that from an early age, bilinguals outperform their monolingual peers on executive control tasks. We previously found that bilingual children and adults also display greater attention to unexpected language switches within speech. Here, we investigated the effect of a bilingual upbringing on speech perception in one language. We recorded monolingual and bilingual toddlers' event-related potentials (ERPs) to spoken words preceded by pictures. Words matching the picture prime elicited an early frontal positivity in bilingual participants only, whereas later ERP amplitudes associated with semantic processing did not differ between groups. These results add to the growing body of evidence that bilingualism increases overall attention during speech perception whilst semantic integration is unaffected.
Copyright © 2015 Elsevier Inc. All rights reserved.
Abstract The purpose of the present study was to examine patterns of neural activity relevant to language processing in 20-month-old infants, and to determine whether or not changes in cerebral organization occur as a function of specific changes in language development. Event-related potentials (ERPs) were recorded as children listened to a series of words whose meaning was understood by the child, words whose meaning the child did not understand, and backward words. The results showed that specific and different ERP components discriminated comprehended words from unknown and from backward words. Distinct lateral and anterior-posterior specializations were apparent in EW responsiveness to the different types of words. Moreover, the results suggested that increasing language abilities were associated with increasing cerebral specialization for language processing over the temporal and parietal regions of the left hemisphere.
Do infants learn their early words in semantic isolation? Or do they integrate new words into an inter-connected semantic system? In an infant-friendly adaptation of the adult lexical priming paradigm, infants at 18 and 24 months-of-age heard two words in quick succession. The noun-pairs were either related or unrelated. Following the onset of the target word, two pictures were presented, one of which depicted the target. Eye movements revealed that both age groups comprehended the target word. In addition, 24-month-olds demonstrated primed picture looking in two measures of comprehension: Named target pictures preceded by a related word pair took longer to disengage from and attracted more looking overall. The finding of enhanced target recognition demonstrates the emergence of semantic organisation by the end of the second year.
Infants improve substantially in language ability during their 2nd year. Research on the early development of speech production shows that vocabulary begins to expand rapidly around the age of 18 months. During this period, infants also make impressive gains in understanding spoken language. We examined the time course of word recognition in infants from ages 15 to 24 months, tracking their eye movements as they looked at pictures in response to familiar spoken words. The speed and efficiency of verbal processing increased dramatically over the 2nd year. Although 15-month-old infants did not orient to the correct picture until after the target word was spoken, 24-month-olds were significantly faster, shifting their gaze to the correct picture before the end of the spoken word. By 2 years of age, children are progressing toward the highly efficient performance of adults, making decisions about words based on incomplete acoustic information.
The interconnectedness of bilingual memory remains a topic of great debate. Semantic priming provides a powerful methodological tool with which to investigate this issue in early bilingual toddlers. Semantic priming effects were investigated in 21 bilingual toddlers (2.5 years) within and across each of their languages. Results revealed the first evidence of cross-language and within-language semantic priming in bilingual toddlers. However, priming effects were only observed when the prime was presented in the dominant language and were comparable in magnitude within and across languages. Findings point to high interconnectivity across languages; however, there appear to be strong influences of language dominance on semantic facilitation. Findings serve to inform and refine developmental models of bilingual memory.
A bilingual upbringing has been shown to enhance executive control, but the neural mechanisms underpinning such effect are essentially unknown. Here, we investigated whether monolingual and bilingual toddlers differ in semantic processing efficiency and their allocation of attention to expected and unexpected visual stimuli. We simultaneously recorded event-related brain potentials (ERPs) and pupil size in monolingual and bilingual toddlers presented with (spoken) word-picture pairs. Although ERP effects elicited by semantic relatedness were indistinguishable between the two children groups, pictures unrelated to the preceding word evoked greater pupil dilation than related pictures in bilinguals, but not in monolinguals. Furthermore, increasing pupil dilation to unrelated pictures was associated with decreasing N400 amplitude in bilinguals, whereas the monolingual toddlers showed the opposite association. Hence, attention to unexpected stimuli seems to hamper semantic integration in monolinguals, but to facilitate semantic integration in bilinguals, suggesting that bilingual toddlers are more tolerant to variation in word-referent mappings. Given the link between pupil dilation and norepinephrine-driven cognitive efficiency, correlations between ERP amplitude and concurrent pupil dilation provide new insights into the neural bases of the bilingual cognitive advantage.
Koriat (1981) demonstrated that an association from the target to a preceding prime, in the absence of an association from the prime to the target, facilitates lexical decision and referred to this effect as “backward priming”. Backward priming is of relevance, because it can provide information about the mechanism underlying semantic priming effects. Following Neely (1991), we distinguish three mechanisms of priming: spreading activation, expectancy, and semantic matching/ integration. The goal was to determine which of these mechanisms causes backward priming, by assessing effects of backward priming on a language-relevant ERP component, the N400, and reaction time (RT). Based on previous work, we propose that the N400 priming effect reflects expectancy and semantic matching/ integration, but in contrast with RT does not reflect spreading activation. Experiment 1 shows a backward priming effect that is qualitatively similar for the N400 and RT in a lexical decision task. This effect was not modulated by an ISI manipulation. Experiment 2 clarifies that the N400 backward priming effect reflects genuine changes in N400 amplitude and cannot be ascribed to other factors. We will argue that these backward priming effects cannot be due to expectancy but are best accounted for in terms of semantic matching/integration.
Prior to each target letter string presented visually to 120 university students in a speeded word–nonword classification task, either {bird, body, building,} or {xxx} appeared as a priming event. Five types of word-prime/word-target trials were used: bird-robin, bird-arm, body-door, body-sparrow, and body-heart. The stimulus onset asynchrony (SOA) between prime and target letter string varied between 250 and 2,000 msec. At 2,000-msec SOA, reaction times (RTs) on bird-robin type trials were faster than on xxx-prime trials (facilitation), whereas RTs on bird-arm type trials were slower than on xxx-prime (inhibition). As SOA decreased, the facilitation effect on bird-robin trials remained constant, but the inhibition effect on bird-arm decreased until, at 250-msec SOA, there was no inhibition. For Shift conditions at 2,000-msec SOA, facilitation was obtained on body-door type trials and inhibition was obtained on body-sparrow type. These effects decreased as SOA decreased until there was no facilitation or inhibition. On body-heart type trials, there was an inhibition effect at 2,000 msec SOA, which decreased as SOA decreased until, at 250-msec SOA, it became a facilitation effect. Results support the theory of M. I. Posner and S. R. Snyder (1975) that postulated 2 distinct components of attention: a fast automatic inhibitionless spreading-activation process and a slow limited-capacity conscious-attention mechanism. (27 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Tested the 2-process theory of detection, search, and attention presented by the current authors (1977) in a series of experiments. The studies (a) demonstrate the qualitative difference between 2 modes of information processing: automatic detection and controlled search; (b) trace the course of the learning of automatic detection, of categories, and of automatic-attention responses; and (c) show the dependence of automatic detection on attending responses and demonstrate how such responses interrupt controlled processing and interfere with the focusing of attention. The learning of categories is shown to improve controlled search performance. A general framework for human information processing is proposed. The framework emphasizes the roles of automatic and controlled processing. The theory is compared to and contrasted with extant models of search and attention. (31/2 p ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Presents a spreading-activation theory of human semantic processing,
which can be applied to a wide range of recent experimental results.
The theory is based on M. R. Quillian's (1967) theory of semantic
memory search and semantic preparation, or priming. In conjunction
with this, several misconceptions concerning Quillian's theory are
discussed. A number of additional assumptions are proposed for his
theory to apply it to recent experiments. The present paper shows
how the extended theory can account for results of several production
experiments by E. F. Loftus, J. F. Juola and R. C. Atkinson's (1971)
multiple-category experiment, C. Conrad's (1972) sentence-verification
experiments, and several categorization experiments on the effect
of semantic relatedness and typicality by K. J. Holyoak and A. L.
Glass (1975), L. J. Rips et al (1973), and E. Rosch (1973). The paper
also provides a critique of the Rips et al model for categorization
judgments.
The extant literature includes conflicting assertions regarding the influence of bilingualism on the rate of language development. The present study compared the language development of equivalently high-SES samples of bilingually and monolingually developing children from 1 ; 10 to 2 ; 6. The monolingually developing children were significantly more advanced than the bilingually developing children on measures of both vocabulary and grammar in single language comparisons, but they were comparable on a measure of total vocabulary. Within the bilingually developing sample, all measures of vocabulary and grammar were related to the relative amount of input in that language. Implications for theories of language acquisition and for understanding bilingual development are discussed.
When and how do infants develop a semantic system of words that are related to each other? We investigated word-word associations in early lexical development using an adaptation of the inter-modal preferential looking task where word pairs (as opposed to single target words) were used to direct infants' attention towards a target picture. Two words (prime and target) were presented in quick succession after which infants were presented with a picture pair (target and distracter). Prime-target word pairs were either semantically and associatively related or unrelated; the targets were either named or unnamed. Experiment 1 demonstrated a lexical-semantic priming effect for 21-month olds but not for 18-month olds: unrelated prime words interfered with linguistic target identification for 21-month olds. Follow-up experiments confirmed the interfering effects of unrelated prime words and identified the existence of repetition priming effects as young as 18 months of age. The results of these experiments indicate that infants have begun to develop semantic-associative links between lexical items as early as 21 months of age.
Research using online comprehension measures with monolingual children shows that speed and accuracy of spoken word recognition are correlated with lexical development. Here we examined speech processing efficiency in relation to vocabulary development in bilingual children learning both Spanish and English (n=26 ; 2 ; 6). Between-language associations were weak: vocabulary size in Spanish was uncorrelated with vocabulary in English, and children's facility in online comprehension in Spanish was unrelated to their facility in English. Instead, efficiency of online processing in one language was significantly related to vocabulary size in that language, after controlling for processing speed and vocabulary size in the other language. These links between efficiency of lexical access and vocabulary knowledge in bilinguals parallel those previously reported for Spanish and English monolinguals, suggesting that children's ability to abstract information from the input in building a working lexicon relates fundamentally to mechanisms underlying the construction of language.
Presented 2 strings of letters simultaneously, with 1 string displayed visually above the other, to high school students (n = 24). In exp. I, ss responded "yes" if both strings were words, otherwise responding "no." in exp. Ii, ss responded "same" if the 2 strings were either both words or both nonwords, otherwise responding "different." "yes" responses and "same" responses were faster for pairs of commonly associated words than for pairs of unassociated words. "same" responses were slowest for pairs of nonwords. "no" responses were faster when the top string in the display was a nonword, whereas "different" responses were faster when the top string was a word. Results support a retrieval model involving a dependence between separate successive decisions about whether each of the 2 strings is a word. Possible mechanisms that underlie this dependence are discussed. (19 ref.) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The study of bilingualism has often focused on two contradictory possibilities: that the learning of two languages may produce deficits of performance in each language by comparison with performance of monolingual individuals, or on the contrary, that the learning of two languages may produce linguistic or cognitive advantages with regard to the monolingual learning experience. The work reported here addressed the possibility that the very early bilingual experience of infancy may affect the unfolding of vocal precursors to speech. The results of longitudinal research with 73 infants aged 0;4 to 1;6 in monolingual and bilingual environments provided no support for either a bilingual deficit hypothesis nor for its opposite, a bilingual advantage hypothesis. Infants reared in bilingual and monolingual environments manifested similar ages of onset for canonical babbling (production of well-formed syllables), an event known to be fundamentally related to speech development. Further, quantitative measures of vocal performance (proportion of usage of well-formed syllables and vowel-like sounds) showed additional similarities between monolingual and bilingual infants. The similarities applied to infants of middle and low socio-economic status and to infants that were born at term or prematurely. The results suggest that vocal development in the first year of life is robust with respect to conditions of rearing. The biological foundations of speech appear to be such as to resist modifications in the natural schedule of vocal development.
To investigate whether the N400 effect is sensitive to automatic or controlled processes.
Two experiments were performed. In one experiment, directly related word pairs were used. In the other experiment, mediated-related word pairs were used. In order to reduce controlled processes, each experiment consisted of 3 tasks: Low- and high-proportion of related pairs, and single presentation lexical decision task.
In the first experiment, the amount of priming was equivalent for the 3 tasks. The N400 effect appeared in the high and low proportion of directly related words, but not in the single presentation task. In the second experiment, behavioral priming was also found in the 3 tasks. However, the N400 effect was observed only in the task with low proportion of related pairs.
These results suggest that the N400 effect may be related to controlled processes.
Divergent hypotheses exist concerning the types of knowledge underlying early bilingualism, with some portraying a troubled course marred by language delays and confusion, and others portraying one that is largely unremarkable. We studied the extraordinary case of bilingual acquisition across two modalities to examine these hypotheses. Three children acquiring Langues des Signes Québécoise and French, and three children acquiring French and English (ages at onset approximately 1;0, 2;6 and 3;6 per group) were videotaped regularly over one year while we empirically manipulated novel and familiar speakers of each child's two languages. The results revealed that both groups achieved their early linguistic milestones in each of their languages at the same time (and similarly to monolinguals), produced a substantial number of semantically corresponding words in each of their two languages from their very first words or signs (translation equivalents), and demonstrated sensitivity to the interlocutor's language by altering their language choices. Children did mix their languages to varying degrees, and some persisted in using a language that was not the primary language of the addressee, but the propensity to do both was directly related to their parents' mixing rates, in combination with their own developing language preference. The signing-speaking bilinguals did exploit the modality possibilities, and they did simultaneously mix their signs and speech, but in semantically principled and highly constrained ways. It is concluded that the capacity to differentiate between two languages is well in place prior to first words, and it is hypothesized that this capacity may result from biological mechanisms that permit the discovery of early phonological representations. Reasons why paradoxical views of bilingual acquisition have persisted are also offered.
It is a matter of debate whether the N400 component of the event-related brain potential (ERP) is sensitive to unconscious automatic priming mechanisms or to strategic mechanisms only. Recent studies demonstrated N400 modulation by masked primes at a short SOA supporting an automatic spreading activation account. However, it cannot be ruled out that strategic mechanisms based upon partial prime identification contributed to the observed priming effects. The present study was set up to substantiate masked N400 priming effects as an index of automatic spreading activation. It was assessed whether partial identification of the masked words due to backward priming could have supported strategic priming to occur. In experiment 1, ERPs were recorded while subjects performed lexical decisions on targets preceded by masked and unmasked primes at an SOA of 67 ms. Masked words, which were not consciously perceived, as well as visible words were shown to modulate the N400 to meaningfully related target words. Experiment 2 required subjects to perform decisions on visual, lexical and semantic features of masked words presented with or without semantically related context words. Subjects performed at chance in all tasks. Furthermore, the results exclude the possibility that backward priming has rendered the masked words partially visible. The present study therefore demonstrates that N400 priming effects can be reliably obtained from unconsciously perceived masked words at a very short SOA and strengthens the notion that the N400 is modulated by automatic spreading activation and not exclusively by strategic semantic processes.
Recent evidence demonstrates that lexical-semantic connections emerge over the second year of life for monolingual children. Yet, little is known about the developing lexical-semantic organization of children acquiring two languages simultaneously. Two- to 4 year-old French–Spanish bilingual children completed a within-language auditory semantic priming task in both of their languages, while event-related potentials (ERPs) were recorded. The results revealed that bilingual children exhibited sensitivity to taxonomic relationships between words in each of their languages, but the pattern of brain activity varied across the dominant (DL) and the non-dominant (NDL) languages. While the N2 occurred for both languages, the N400 appeared for target words in the DL only and the late anterior negativity for target words in the NDL only. These findings indicate that words are organized taxonomically in the bilinguals’ lexicons. However, the patterns of brain activity suggest that common and distinct neural resources underlie lexical-semantic processing in each language.
This study compares lexical access and expressive and receptive vocabulary development in monolingual and bilingual toddlers. More specifically, the link between vocabulary size, production of translation equivalents, and lexical access in bilingual infants was examined as well as the relationship between the Communicative Development Inventories and the Computerized Comprehension Task. Twenty-five bilingual and 18 monolingual infants aged 24 months participated in this study. The results revealed significant differences between monolingual and bilinguals' expressive vocabulary size in L1 but similar total vocabularies. Performance on the Computerized Comprehension Task revealed no differences between the two groups on measures of both reaction time and accuracy, and a strong convergent validity of the Computerized Comprehension Task with the Communicative Development Inventories was observed for both groups. Bilinguals with a higher proportion of translation equivalents in their expressive vocabulary showed faster access to words in the Computerized Comprehension Task.
A substantial body of evidence demonstrates that infants understand the meaning of spoken words from as early as 6 months. Yet little is known about their ability to do so in the absence of any visual referent, which would offer diagnostic evidence for an adult-like, symbolic interpretation of words and their use in language mediated thought. We used the head-turn preference procedure to examine whether infants can generate implicit meanings from word forms alone as early as 18 months of age, and whether they are sensitive to meaningful relationships between words. In one condition, toddlers were presented with lists of words taken from the same taxonomic category (e.g. animals or body parts). In a second condition, words taken from two other categories (e.g. clothes and food items) were interleaved within the same list. Listening times were found to be longer in the related-category condition than in the mixed-category condition, suggesting that infants extract the meaning of spoken words and are sensitive to the semantic relatedness between these words. Our results show that infants have begun to construct the rudiments of a semantic system based on taxonomic relations even before they enter a period of accelerated vocabulary growth.
Language learners rapidly acquire extensive semantic knowledge, but the development of this knowledge is difficult to study, in part because it is difficult to assess young children's lexical semantic representations. In our studies, we solved this problem by investigating lexical semantic knowledge in 24-month-olds using the Head-turn Preference Procedure. In Experiment 1, looking times to a repeating spoken word stimulus (e.g., kitty-kitty-kitty) were shorter for trials preceded by a semantically related word (e.g., dog-dog-dog) than trials preceded by an unrelated word (e.g., juice-juice-juice). Experiment 2 yielded similar results using a method in which pairs of words were presented on the same trial. The studies provide evidence that young children activate of lexical semantic knowledge, and critically, that they do so in the absence of visual referents or sentence contexts. Auditory lexical priming is a promising technique for studying the development and structure of semantic knowledge in young children.
Abstract The N400 is an endogenous event-related brain potential (ERP) that is sensitive to semantic processes during language comprehension. The general question we address in this paper is which aspects of the comprehension process are manifest in the N400. The focus is on the sensitivity of the N400 to the automatic process of lexical access, or to the controlled process of lexical integration. The former process is the reflex-like and effortless behavior of computing a form representation of the linguistic signal, and of mapping this representation onto corresponding entries in the mental lexicon. The latter process concerns the integration of a spoken or written word into a higher-order meaning representation of the context within which it occurs. ERPs and reaction times (RTs) were acquired to target words preceded by semantically related and unrelated prime words. The semantic relationship between a prime and its target has been shown to modulate the amplitude of the N400 to the target. This modulation can arise from lexical access processes, reflecting the automatic spread of activation between words related in meaning in the mental lexicon. Alternatively, the N400 effect can arise from lexical integration processes, reflecting the relative ease of meaning integration between the prime and the target. To assess the impact of automatic lexical access processes on the N400, we compared the effect of masked and unmasked presentations of a prime on the N400 to a following target. Masking prevents perceptual identification, and as such it is claimed to rule out effects from controlled processes. It therefore enables a stringent test of the possible impact of automatic lexical access processes on the N400. The RT study showed a significant semantic priming effect under both unmasked and masked presentations of the prime. The result for masked priming reflects the effect of automatic spreading of activation during the lexical access process. The ERP study showed a significant N400 effect for the unmasked presentation condition, but no such effect for the masked presentation condition. This indicates that the N400 is not a manifestation of lexical access processes, but reflects aspects of semantic integration processes.
The effects of sentential context and semantic memory structure during on-line sentence processing were examined by recording event-related brain potentials as individuals read pairs of sentences for comprehension. The first sentence established an expectation for a particular exemplar of a semantic category, while the second ended with (1) that expected exemplar, (2) an unexpected exemplar from the same (expected) category, or (3) an unexpected item from a different (unexpected) category. Expected endings elicited a positivity between 250 and 550 ms while all unexpected endings elicited an N400, which was significantly smaller to items from the expected category. This N400 reduction varied with the strength of the contextually induced expectation: unexpected, categorically related endings elicited smaller N400s in more constraining contexts, despite their poorer fit to context (lower plausibility). This pattern of effects is best explained as reflecting the impact of context-independent long-term memory structure on sentence processing. The results thus suggest that physical and functional similarities that hold between objects in the world—i.e., category structure—influence neural organization and, in turn, routine language comprehension processes.
The purpose of this study was to examine developmental changes in the organization of brain activity linked to comprehension of single words in 13‐ to 20‐month‐old infants. Event‐related potentials (ERPs) were recorded as children listened to a series of words whose meanings were understood by the child, words whose meanings the child did not understand, and backward words. The results were consistent with a previous study suggesting that ERPs differed as a function of word meaning within 200 ms after word onset. At 13 to 17 months, ERP differences between comprehended and unknown words were bilateral and broadly distributed over anterior and posterior regions. In contrast, at 20 months of age these effects were limited to temporal and parietal regions of the left hemisphere. The results are discussed in relation to the general effects of maturation, the maturation of language‐relevant brain systems, and the development of brain systems linked to level of ability independent of chronological age. We offer the working hypothesis that the neurophysiological changes that give rise to certain ERP effects reported here are linked to the remarkable changes in early lexical development that typically occur between 13 and 20 months, whereas others produce more general maturational effects.
The present paper summarizes research showing that bilingualism affects linguistic and cognitive performance across the lifespan. The effect on linguistic performance is generally seen as a deficit in which bilingual children control a smaller vocabulary than their monolingual peers and bilingual adults perform more poorly on rapid lexical retrieval tasks. The effect on cognitive performance is to enhance executive functioning and to protect against the decline of executive control in aging. These effects interact to produce a complex pattern regarding the effect of bilingualism on memory performance. Memory tasks based primarily on verbal recall are performed more poorly by bilinguals but memory tasks based primarily on executive control are performed better by bilinguals. Speculations regarding the mechanism responsible for these effects are described.
This study compares lexical development in a sample of 25 simultaneous bilingual and 35 monolingual children for whom semilongitudinal data were collected between the ages of 8 and 30 months. A standardized parent report form, the MacArthur Communicative Development Inventory (1989), was used to assess the children's receptive and productive vocabulary in English and/or Spanish. A methodology was devised to assess the degree of overlap between the bilingual children's lexical knowledge in one language and their knowledge in the other. Using the measures presented here, there was no statistical basis for concluding that the bilingual children were slower to develop early vocabulary than was the monolingual comparison group. The wide range of vocabulary sizes observed at these ages in normally developing children (Fenson et al., 1991) was observed in these bilingual children as well. The close correspondence of the pattern of the bilinguals' growth in two languages at once to monolinguals' growth in one suggests that norms for lexical development in bilinguals should be made with reference to the children's performance in two languages together.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.