A Day in the Life of a Spoken Word

A Day in the Life of a Spoken Word Nicolas Dumay and M. Gareth Gaskell (n.dumay/g.gaskell@psych.york.ac.uk) Department of Psychology, University of York York, YO10 5DD, UK Xiaojia Feng (fengxj@yorku.ca) Department of Psychology, York University 4700 Keele Street, Toronto, M3J 1P3, Canada involved in the lexical competition process, or in our terms, produce a lexical footprint . Adults were familiarized with made-up words that overlapped strongly with existing words (such as cathedruke for cathedral ), through repeated presentation in a phoneme-monitoring task. In one experiment, good explicit knowledge of the novel words was obtained after only one training session (i.e., 12 presentations of each item), whereas the inhibitory influence of these new competitors on the identification of existing words in a lexical decision task (LD) required three (successive) days of exposure to emerge. In another experiment, we disentangled the roles of time and level of exposure in the lexicalization process, using a single training session at a high exposure rate (i.e., 36 presentations). We also swapped LD with a more implicit test of lexical activity, the pause detection task. Here, participants made speeded decisions as to whether a short silence was present towards the offset of the existing words (e.g., cathedr_al ). As Mattys and Clark (2002) showed, pause detection latencies are positively correlated with the amount of lexical activity elicited by the portion of speech preceding the pause. They hypothesized that the activation of lexical candidates involves the use of processing resources that would otherwise be allocated to pause detection. Our experiment showed good explicit recognition of the novel items right after exposure. In contrast, an increase in lexical activity as indexed by longer pause detection latencies when a new competitor had been learnt was not immediately observed, but had emerged when re- tested a week later. So, in contrast to phonological storage, lexicalization is apparently not instantaneous and in fact may require a substantial amount of time, possibly to allow the consolidation of episodic traces (cf. O'Reilly & Norman, 2002). Nonetheless, on the basis of the above findings, it is not possible to tell how long it takes after a sufficient level of exposure has been reached for a newly learnt word to be lexically operational. Furthermore, in Gaskell and Dumay (2003) participants had to learn only the sound-form of the novel words in quite an artificial situation, i.e., phoneme monitoring. Therefore, whether these data give us a good picture of what happens in more normal circumstances when semantic and thematic information are usually available must be addressed. In particular, the delay observed in the emergence of lexical Abstract Two experiments tracked the emergence of lexical competition effects for newly learnt spoken words (e.g., cathedruke ). Experiment 1 compared form-only learning with learning in semantically rich sentence contexts. In both cases, although immediate explicit recognition of the novel words was good, lexical competition effects (e.g., cathedruke-cathedral ) emerged only after a delay of at least 24 hours. Experiment 2 evaluated the timecourse of learning in more detail and used embedding (rather than cohort) new competitors (e.g., shadowks ). Again results showed no evidence of lexicalization immediately after exposure, but clear lexical competition effects after 24 hours. Furthermore, recognition and free recall improved over time. These results are interpreted in terms of a consolidation process that integrates words into the mental lexicon over a relatively protracted period of time. 1. Introduction Our knowledge about what information is relevant for language acquisition has increased greatly in the last decade. Factors such as statistical properties of the input (Saffran, Aslin, & Newport, 1996) and current lexical knowledge (Dahan & Brent, 1999) have been shown to influence lexical development. However, less is known about exactly how new vocabulary items are integrated into one's mental lexicon, a process called lexicalization . The main reason for this state of affairs is that studies on word acquisition have typically used only direct measures of learning, such as the performance in familiarity judgment or recollection tasks. Yet, such measures only tell us about the strength of the traces left by exposure, not whether a new lexical entry per se has been created. A critical methodology for addressing the lexicalization issue looks at whether newly learnt words influence how the learner recognizes preexisting words. For models of spoken word recognition, a key feature of a lexical entry is its ability to be evoked when compatible with the input, and to compete with similar-sounding entities for identification (e.g., McClelland & Elman, 1986). Therefore, a strong test of whether a speech sequence has been lexicalized is whether it engages in lexical competition, and thereby affects the activity within the mental lexicon. In a recent study (Gaskell & Dumay, 2003), we began to explore how and when newly learnt spoken words become