Presentations

Abstract

Listening, in any language, involves processing the phone¬mic content of spoken input in order to identify the words of which utterances are made up. Models of spoken-word recognition agree that deriving the correct word sequence from speech input is a process in which multiple candidate words are considered in parallel, and in which words com¬pete with one another where they separately lay claim on the same input. In ideal speech situations, the phonemic sequence of each spoken word would be fully instantiated in the speech signal, listeners would correctly identify every one of these uttered phonemes, and listeners stored lexical representations would exactly match with the form in which the words are encoun¬tered in speech. In the real world, with which this workshop is concerned, none of these propositions is guaranteed to hold. This presentation addresses the particular case of lis¬tening in a second language (L2), and the potential effects on the word recognition process of misidentifying a pho¬neme in the input. The misidentification of L2 phonemes is a notorious source of listening difficulty. Contrary to many L2 users’ intuitions, however, the most serious problem is not lexical indistinguishability (‘write’ heard as ‘light’, etc.). There are two reasons for this: Spurious homophones such as ‘light/write’ would contribute only a trivial increase to the signif¬icant number of real homophones in the lexicon, and the number of fully indistinguishable words is massively out¬weighed by the set of temporarily indistinguishable words, which nevertheless add to the amount of lexical competition that a L2 listener experiences. The relevant lexical statistics will be presented in support of this claim. Exacerbating the increase in lexical competition in L2 is the curious situation whereby an L2 user’s lexical represen¬tations can encode phonemic distinctions which are not reli¬ably perceived by the same person in spoken input. This com¬bination of lexical accuracy with perceptual inaccuracy, now repeatedly established in listening experiments, is fatal in the competition situation. As will be illustrated in simulations with a computationally implemented spoken-word recog¬nition model, the combination inevitably results in compe¬tition which is more persistent than the competition from accurately perceived words. Word recognition experiments with L2 listeners confirm that this extra-persistent compe¬tition is indeed observed. The real world of the second-lan¬guage listener is more competition-prone than the world of the native-language listener, ideal or real.

Abstract

The speech infants hear, in the first year of life before they themselves begin to speak, is mainly multi-word utterances, without clear pauses between the words. Thus to construct the initial vocabulary they need to begin speaking themselves, infants need to learn how to segment words from speech. Indeed, there is evidence that segmentation ability in the first year of life correlates positively with vocabulary size at two years. This evidence has come principally from studies of segmentation using the behavioralheadturn-preference procedure. If infants first hear words in isolation, and then recognise these familiarised words when they occur later in sentences, they have shown that they can segment individual words out of multi-word utterances. An electrophysiological analogue to this behavioralprocedure, measuring Event-Related Potentials (ERPs) was however later developed by Kooijman. This allowed, for the first time, an online assessment of infants’ word segmentation. Kooijmantested seven-and ten-month-olds; the ten-month-olds showed a clear recognition response (in the form of a left negativity) for familiarised words heard later in sentences, relative to unfamiliar words. This showed that the ten-month-olds indeed had the ability to segment speech. Such segmentation behaviorwas not, however, consistently present in the seven-month-olds. We here report three studies relating this ERP measure of speech segmentation to later language development. First, we divided the seven-month-old infants tested by Kooijmaninto two sub-groups: those with an ERP effect similar to the 10-month-olds’ pattern, and those without such an effect. When re-tested at three years of age, the former group displayed significantly higher language scores than the latter group. Second, we examined whether ten-month-olds can recognize words that have previously been presented just once, within an utterance. Recognition was again indicated by a left-frontal negativity, and presence and size of this response proved in later testing to be related to vocabulary size, both at 12 and at 24 months. Third, we conducted a study in which both familiarization and test phases consisted of continuous sentences. Again we observed the same recognition response in the infant brain, and the patterning of this response was once more related to later performance, this time in a test of recognition of known words at 16 months. Hence, with a variety of measures, we see that a consistently observed ERP effect of word segmentation serves as a direct predictor of the degree of later language development.

Abstract

Speech is a continuous stream. Listeners can only make sense of speech by identifying the components that comprise it - words. Segmenting speech into words is an operation which has to be learned very early, since it is how infants compile even their initial vocabulary. Infants' relative success at achieving speech segmentation in fact turns out to be a direct predictor of language skills during later development. Adult listeners segment speech so efficiently, however, that they are virtually never aware of the operation of segmentation. In part they achieve this level of efficiency by exploiting accrued knowledge of relevant structure in the native language. Amassing this language-specific knowledge also starts in infancy. However, some relevant features call on more advanced levels of language processing ability; the continuous refinement of segmentation skills is apparent in that these structural features are exploited for segmentation too, even when applying them means overturning otherwise universal constraints available in infancy.

Abstract

Speech is a continuous stream. Listeners can only make sense of speech by identifying the components that comprise it - words. Segmenting speech into words is an operation which has to be learned very early, since it is how infants compile even their initial vocabulary. Evidence from new behavioural and electrophysiological studies of infant speech perception illustrates this learning process. Infants’ relative success at achieving speech segmentation in fact turns out to be a direct predictor of language skills during later development. Adult listeners segment speech so efficiently, however, that they are virtually never aware of the operation of segmentation. In part they achieve this level of efficiency by exploiting accrued knowledge of relevant structure in the native language. Amassing this language-specific knowledge also starts in infancy. However, some relevant features call on more advanced levels of language processing ability; the continuous refinement of segmentation efficiency is apparent in that (as revealed by adult listening studies across a dozen or so languages) these structural features are exploited for segmentation too, even if applying them means overturning constraints used, perhaps universally, by infants.

Abstract

What happens in the brain when infants are learning the meaning of words? Only a few studies (Torkildsen et al., 2008; Friedrich & Friederici, 2008) addressed this question, but they focused only on novel word learning, not on the acquisition of infant first words. From behavioral research we know that 12-month-olds can recognize novel exemplars of early typical word categories, but only after training them from nine months on (Schafer, 2005). What happens in the brain during such a training? With event-related potentials, we studied the effect of training context on word comprehension. We manipulated the type/token ratio of the training context (one versus six exemplars). 24 normal-developing Dutch nine-month-olds (+/- 14 days, 12 boys) participated. Twenty easily depictive words were chosen based on parental vocabulary reports for 15-months-olds. All trials consisted of a high-resolution photograph shown for 2200ms, with an acoustic label presented at 1000ms. Each training-test block contrasted two words that did not share initial phonemes or semantic class. The training phase started with six trials of one category, followed by six trials of the second category. Results show more negative responses for the more frequent pairings, consistent with word familiarization studies in older infants (Torkildsen et al., 2008; Friedrich & Friederici, 2008). This increase appears to be larger if the pictures changed. In the test phase we tested word comprehension for novel exemplars with the picture-word mismatch paradigm. Here, we observed a similar N400 as Mills et al. (2005) did for 13-month-olds. German 12-month-olds, however, did not show such an effect (Friedrich & Friederici, 2005). Our study makes it implausible that the latter is due to an immaturity of the N400 mechanism. The N400 was present in Dutch 9-month-olds, even though some parents judged their child not to understand most of the words. There was no interaction by training type, suggesting that type/token ratio does not affect infant word recognition of novel exemplars.

Abstract

How do infants learn words? Most studies focus on novel word learning to address this question. Only a few studies concentrate on the stage when infants learn their first words. Schafer (2005) showed that 12‐month‐olds can recognize novel exemplars of early typical word categories, but only after training them from nine months on. What happens in the brain during such a training? With event‐related potentials, we studied the effect of training context on word comprehension. 24 Normal‐developing Dutch nine‐month‐olds (± 14 days, 12 boys) participated. Twenty easily depictive words were chosen based on parental vocabulary reports for 15‐months‐olds. All trials consisted of a high‐resolution photograph shown for 2200ms, with an acoustic label presented at 1000ms. Each training‐test block contrasted two words that did not share initial phonemes or semantic class. The training phase started with six trials of one category, followed by six trials of the second category. We manipulated the type/token ratio of the training context (one versus six exemplars). Results show more negative responses for the more frequent pairings, consistent with word familiarization studies in older infants (Torkildsen et al., 2008; Friedrich & Friederici, 2008). This increase appears to be larger if the pictures changed. In the test phase we tested word comprehension for novel exemplars with the picture‐word mismatch paradigm. Here, we observed a similar N400 as Mills et al. (2005) did for 13‐month‐olds. German 12‐month‐olds, however, did not show such an effect (Friedrich & Friederici, 2005). Our study makes it implausible that the latter is due to an immaturity of the N400 mechanism. The N400 was present in Dutch 9‐month‐olds, even though some parents judged their child not to understand most of the words. There was no interaction by training type, suggesting that type/token ratio does not affect infants’ word recognition of novel exemplars.