Since the experiments of Saffran et al. (1996a), there has been a great deal of interest in the question of how statistical regularities in the speech stream might be used by infants to begin to identify individual words. In this work, we use computational modeling to explore the effects of different assumptions the learner might make regarding the nature of words – in particular, how these assumptions affect the kinds of words that are segmented from a corpus of transcribed child-directed speech. We develop several models within a Bayesian ideal observer framework, and use them to examine the consequences of assuming either that words are independent units, or units that help to predict other units. We show through empirical and theoretical results that the assumption of independence causes the learner to undersegment the corpus, with many two- and three-word sequences (e.g. what’s that, do you, in the house) misidentified as individual words. In contrast, when the learner assumes that words are predictive, the resulting segmentation is far more accurate. These results indicate that taking context into account is important for a statistical word segmentation strategy to be successful, and raise the possibility that even young infants may be able to exploit more subtle statistical patterns than have usually been considered. 1

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Prior research suggests that stress cues are particularly important for English-hearing infants ’ detection of word boundaries. It is unclear, though, how infants learn to attend to stress as a cue to word segmentation. This series of experiments was designed to explore infants ’ attention to conflicting cues at different ages. Experiment 1 replicated previous findings: When stress and statistical cues indicated different word boundaries, 9-month-old infants used syllable stress as a cue to segmentation while ignoring statistical cues. However, in Experiment 2, 7-month-old infants attended more to statistical cues than to stress cues. These results raise the possibility that infants use their statistical learning abilities to locate words in speech and use those words to discover the regular pattern of stress cues in English. Infants at different ages may deploy different segmentation strategies as a function of their current linguistic experience. To achieve mastery of their native language, infants must identify and learn words. Identifying words in an unfamiliar language is no simple task. Unlike the white spaces that mark the boundaries between words in a written text, speakers do not consistently place silent pauses between words when speaking (e.g., Cole & Jakimik,

How do infants learn the sound patterns of their native language? By the end of the 1st year, infants have acquired detailed aspects of the phonology and phonotactics of their input language. However, the structure of the learning mechanisms underlying this process is largely unknown. In this study, 9-month-old infants were given the opportunity to induce specific phonological patterns in 3 experiments in which syllable structure, consonant voicing position, and segmental position were manipulated. Infants were then familiarized with fluent speech containing words that either fit or violated these patterns. Subsequent testing revealed that infants rapidly extracted new phonological regularities and that this process was constrained such that some regularities were easier to acquire than others. Months before infants speak their first words, they have acquired extensive and detailed knowledge about the sound patterns of their native language. Indeed, sounds are the infant’s entrance point into spoken language acquisition, beginning with the rhythmic patterns of the infant’s language—knowledge acquired before birth (e.g., Mehler et al., 1988)—and extending during the 1st year to include language-typical phonological patterns such as lexical

To learn a language, the learners must first learn its words, the essential building blocks for utterances. The difficulty in learning words lies in the unavailability of explicit word boundaries in speech input. The learners have to infer lexical items with some innately endowed learning mechanism(s) for regularity detection- regularities in the speech normally indicate word patterns. With respect to Zipf's least-effort principle and Chomsky's thoughts on the minimality of grammar for human language, we hypothesise a cognitive mechanism underlying language learning that seeks for the least-effort representation for input data. Accordingly, lexical learning is to infer the minimal-cost representation for the input under the constraint of permissible representation for lexical items. The main theme of this thesis is to examine how far this learning mechanism can go in unsupervised lexical learning from real language data without any pre-defined (e.g., prosodic and phonotactic) cues, but entirely resting on statistical induction of structural patterns for the most economic representation for the data. We first review

In this chapter we present the initial stages of work that attempts to assess the ‘psychological reality ’ of one of the more subtle grammatical principles of Optimality Theory (‘OT’; Prince and Smolensky 1993), Richness of the Base. Within the OT competence theory, we develop several of this principle’s empirical predictions concerning the grammar’s final state (Section 1) and initial state (Section 2). We also formulate linking hypotheses which allow these predictions concerning competence to yield predictions addressing performance. We then report and discuss the results of experimental work testing these performance predictions with respect to linguistic processing in infants (Section 3) and adults (Section 4). 1.

Speech rhythm has long been claimed to be a useful bootstrapping cue in the very first steps of language acquisition. Previous studies have suggested that newborn infants do categorize varieties of speech rhythm, as demonstrated by their ability to discriminate between certain languages. However, the existing evidence is not unequivocal: in previous studies, stimuli discriminated by newborns always contained additional speech cues on top of rhythm. Here, we conducted a series of experiments assessing discrimination between Dutch and Japanese by newborn infants, using a speech resynthesis technique to progressively degrade non-rhythmical properties of the sentences. When the stimuli are resynthesized using identical phonemes and artificial intonation contours for the two languages, thereby preserving only their rhythmic and broad phonotactic structure, newborns still seem to be able to discriminate between the two languages, but the effect is weaker than when intonation is present. This leaves open the possibility that the temporal correlation between intonational and rhythmic cues might actually facilitate the processing of speech rhythm. Key-words: newborn speech perception language discrimination rhythm intonation prosody bootstrapping.

Four experiments examined effects of lexical stress on lexical access for recently learned words. Participants learned artificial lexicons (48 words) containing phonologically similar items and were tested on their knowledge in a 4-alternative forced-choice (4AFC) referent-selection task. Lexical stress differences did not reduce confusions between cohort items: KAdazu and kaDAzeI were confused with one another in a 4AFC task and in gaze fixations as often as BOsapeI and BOsapaI. However, lexical stress did affect the relative likelihood of stress-initial confusions when words were embedded in running nonsense speech. Words with medial stress, regardless of initial vowel quality, were more prone to confusions than words with initial stress. The authors concluded that noninitial stress, particularly when word segmentation is difficult, may serve as “noise ” that alters lexical learning and lexical access.

this paper is to expose the `external observer' point of view, which goes as follows. (1) Both the exact locus and the nature of the phonological deficit remain to be explicitly defined. (2) It may seem surprising that the vast body of knowledge available in phonology is seldom brought to bear on hypotheses about the phonological deficit. Paying more attention to what phonology has to offer may therefore help in refining and testing the phonological deficit hypothesis

tening to an unfamiliar language we no longer experience sequences of discrete words, but rather hear a continuous stream of speech with boundaries separating individual sentences or utterances. Examination of the physical form of speech confirms the impression given by listening to foreign languages. Speech does not contain gaps or other unambiguous markers of word boundaries -- there is no auditory analog of the spaces between words in printed text (Lehiste, 1960). Thus the perceptual experience of native speakers reflects language- Matt Davis Lexical segmentation and vocabulary acquisition 3 specific knowledge of ways in which to divide speech into words. An important set of questions, therefore, concern the sources of information that are used for segmentation and how infants learn to segment the speech stream in order to learn their first words. The continuous nature of speech might not be a problem for infants learning language if they were `spoon-fed' with sin