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The emergence of lexical networks in the second year of life.

Sunday, October 02nd,   2011 [09:30 - 11:10]

SY_21. The emergence of lexical networks in the second year of life

Mayor, J.

Basque Center on Cognition, Brain and Language, Donostia, Spain

Recent evidence reveals that two-year-olds display effects of phonological, phono-semantic and semantic priming, similarly to adults. This symposium will provide converging evidence that lexico-semantic networks emerge between 19 months of age and 21 months of age. Natalia Arias-Trejo will present two semantic priming tasks with infants demonstrating evidence for lexico-semantic networks in 21- and 24-month old infants, and will discuss the absence of semantic priming effects in 18-month olds. She will suggest that entries in the 18-month old lexicon may be best characterised in terms of “lexical islands” that are not in competition with each other because they are unconnected. Nivedita Mani will report cascading phono-semantic priming effects at 24 months of age, a priming effect that can only derive from activation of words phonologically and semantically related to the prime label. This will show that hearing a word leads to the activation of related words during word recognition. This will expand on her previous results showing that 24-month olds' phonological priming effects are being modulated by the neighbourhood size of the target words, whereas no such evidence was found at 18 months of age. Julien Mayor will present simulations using the TRACE model of speech perception. Simulations of phonological priming results at 24 months of age will confirm the necessity of lexical competition from the modeling perspective so as to display an inhibitory priming effect. However, a re-analysis of White and Morgan's (2008) study, where 19-month olds show a graded sensitivity to the severity of word mispronunciations, will suggest that lexical competition must be absent at that age, an imbalance in cohort sizes across conditions otherwise interfering with the graded sensitivity effect. Kim Plunkett and Nuria Sebastian will discuss the implications of these findings for recent theories about first language acquisition and the formation of lexical networks.



SY_21.1 - Lexical Priming Effects between 18 and 24 Months of Age

Arias-Trejo, N. 1 & Plunkett, K. 2

1 Facultad de Psicologia, UNniversidad Nacional Autonoma de Mexico, UNAM
2 Dept. of Experimental Psychology, University of Oxford, United Kingdom

Exposure to prior related words facilitates subsequent word processing in school-age children and adults (Nation & Snowling, 1999; Neely, 1991). Infants are sensitive to word-world associations at least as early as their first birthday; however, virtually nothing is known about infants’ knowledge of word-word associations which eventually form the basis of the network of meanings underlying the adult semantic system. We investigated infants’ word associations using the Inter-modal Preferential Looking task. Experiment 1 measures 18- and 21-month-olds’ visual preferences for a target over a distracter object when exposed to pairs of semantically and associatively related or unrelated words. In order to evaluate the impact of the prime word itself, priming is also tested when the target object is not labelled. Experiment 2 compares two types of lexical-semantic relationship, associative and taxonomic at 21 and 24 months of age. The results indicated a semantic-associative priming effect for 21- but not for 18-month-olds. Eighteen-month-olds responded equally well to target names, regardless of their prior exposure to a related or an unrelated word. In contrast, 21-month-olds identified the target referent only in the condition in which they heard related-named pairs of words. Moreover, unrelated words interfered with linguistic target identification for 21-month-olds. Experiment 2 finds that both types of lexical relations, taxonomic and thematic, have been established at 24 months of age. These data indicate that words are associated in the early lexicon. Infants as early as 21 months of age establish a word-word relationship between semantic-associative word pairs. Furthermore, unrelated words inhibit referent identification. Older infants exhibited a priming effect in both associative and taxonomic conditions, pointing to the formation of lexical semantic networks driven by different relations. In conclusion, by their second birthday, infants have begun to construct a lexical-semantic system based on relations and have moved beyond an independent listing of lexical entries.

SY_21.2 - Automatic Cascaded Lexical Activation in Priming Tasks

Mani, N.

Georg-August Universität Göttingen, Germany

Does hearing a word lead to the activation of phonologically related words in the infant lexicon? Tests of lexical activation in adults and five-year-olds examines prime-target pairs that are phono-semantically related (cup (prime) - dog (target)) to each other. Here dog is semantically related to a cohort member of cup (cat). Since dog and cup do not share any sounds, the priming effects reported must derive from priming of words phonologically related to cup (cat, i.e., the sub-prime), and subsequent cascaded priming of words semantically related to cat. This paper investigates the patterns of phono-semantic priming displayed by younger children at 24-months of age. Twenty-four-month-olds were presented with a prime, followed by a standard target recognition task. During related trials, the target word was phono-semantically related to the prime. During unrelated trials, the target and the prime were not phonologically, semantically or phono-semantically related. Experiment 1 tested onset-overlapping phono-semantically related prime-target pairs (e.g., cup (prime) - [cat (sub-prime)] - dog (target)). Experiment 2 examined rhymo-semantically related prime-target pairs (hat (prime) - [cat (sub-prime)] - dog (target)) in order to examine the role of phonological overlap in driving lexical activation. In Experiment 1, infants looked longer at the target in unrelated trials compared to primed trials. When the phonological overlap between the prime and the sub-prime was increased in Experiment 2, infants now looked longer at the target in primed trials compared to unrelated trials. The contrast between Experiments 1 and 2 suggests an important role for phonological overlap (between the prime and the sub-prime) in driving the pattern of results. Furthermore, these effects can only derive from activation of words phonologically and semantically related to the prime label, providing evidence that hearing a word leads to the activation of related words during word recognition.

SY_21.3 - The emergence of lexical networks: Insights from TRACE simulations

Mayor, J.

Basque Center on Cognition, Brain and Language, Donostia, Spain

Recent evidence reveals that two-year-olds display effects of phonological priming (Mani and Plunkett, 2008), similarly to adults. When infants are primed with a picture whose name shares the same onset as the target (e.g., “bed” and “boot”) their looking time to the target is reduced, as opposed to when the prime is unrelated (e.g., “cat” and “boot”). This inhibition effect to be modulated by the neighbourhood size of the words tested, suggesting a lexical basis for the reported effects. In line with the successful comparison of TRACE with adults' looking behaviour described in Allopenna et al. (1998), we model phonological priming experiments in infancy. TRACE's mental lexicon was created by compiling typical lexicons for 24-month-olds from the British CDI, using token frequencies from the CHILDES database. In a first set of simulations, Mani and Plunkett's (2008) study is modelled successfully; priming effects interact with cohort sizes. In the presence of lexical competition, priming can be either facilitatory or inhibitory, depending on neighbouring size. In contrast, when lexical competition is removed, only facilitation can be observed. We argue that only inhibitory effects in phonological priming can be taken as evidence for lexical competition whereas facilitation effects can be driven by sub-lexical priming effects both with and without lexical competition. A second set of simulation captures White and Morgan's (2008) findings that 19 month-olds displayed a graded sensitivity to the severity of word mispronunciations. Crucially, TRACE only displays a graded sensitivity to mispronunciation severity, in absence of controlled cohort sizes, when lexical competition is suppressed.
Together, these simulations suggest that lexical competition is absent at 19 months of age whereas it is present from 24 months of age. Further re-analyses and simulations will aim at identifying more precisely the age at which words start competing for recognition.

SY_21.4 - Discussion

Plunkett, K. 1 & Sebastian-Galles, N. 2

1 Department of Psychology, University of Oxford
2 Universitat Pompeu Fabra, Barcelona

Kim Plunkett and Nuria Sebastian-Galles will discuss the implications of the symposium's contributions for recent theories about first language acquisition and the formation of lexical networks.

SY_21.5 - Bilingual phonological priming: An ERP study investigating interconnectivity of activation in the bilinguals’ two lexicons at different points in development

von Holzen, K. & Mani, N.

University of Göttingen, Germany

Phonological priming effects operate across a bilinguals’ two languages - words in one language can prime words in the other language (Van Wijnendaele and Brysbaert; 2002). These results point to the interconnectivity of the bilingual’s two lexicons. However, these results are based on studies which present subjects with orthographic or auditory stimuli from both languages (Phillips et al., 2006). It is unsurprising that words in both languages are activated. In contrast Wu and Thierry (2010) tested participants in only their second language, and found unconscious priming effects due to word relationships to the participants’ first language. The current study tests participants in their dominant language to demonstrate unconscious priming effects due to word relationships in the participants’ second language. Subjects were presented with images of name-known objects as primes followed by auditorily presented target words which were phonologically related, unrelated or identical to the label for the prime image. We studied adult German-English bilinguals and children in a German-English bilingual program. ERPs to targets were measured to determine differences in activation between the different conditions. In the rhyming conditions, phonological similarity between prime images and target labels was manipulated within (i.e. German prime, German target) and across (i.e. English prime, German target) languages. Importantly, since the prime is an image, and the targets were only German words for adults and English words for children, this study presents subjects with stimuli from only one language. Nevertheless, adult N400-like amplitude revealed no differences in activation from prime image-target labels that were related within and across languages. However, the N400-like amplitude of children showed a differentiation of the rhyming conditions, although both conditions differed from the unrelated condition. This provides strong evidence of interconnectivity of a bilingual’s two lexicons as it develops, despite presenting subjects with stimuli from only one language.

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