Although the word-frequency effect is one of the most established findings in spoken-word recognition, the precise processing locus of this effect is still a topic of debate. In this study, we used event-related potentials (ERPs) to track the time course of the word-frequency effect. In addition, the neighborhood density effect, which is known to reflect mechanisms involved in word identification, was also examined. The ERP data showed a clear frequency effect as early as 350 ms from word onset on the P350, followed by a later effect at word offset on the late N400. A neighborhood density effect was also found at an early stage of spoken-word processing on the PMN, and at word offset on the late N400. Overall, our ERP differences for word frequency suggest that frequency affects the core processes of word identification starting from the initial phase of lexical activation and including target word selection. They thus rule out any interpretation of the word frequency effect that is limited to a purely decisional locus after word identification has been completed.
This study investigates the specificity of predictive coding in spoken word comprehension using event-related potentials (ERPs). We measured word-evoked ERPs in Catalan speakers listening to semantically constraining sentences produced in their native regional accent (experiment 1) or in a non-native accent (experiment 2). Semantically anomalous words produced long-lasting negative shift (N400) starting as early as 250 ms, thus reflecting phonological as well as semantic mismatch. Semantically expected but phonologically unexpected (non-native forms embedded in a native context) produced only an early (∼250 ms) negative difference. In contrast, this phonological expectancy effect failed for native albeit phonologically unexpected target words embedded in a non-native context. These results suggest phonologically precise expectations when operating over native input, whilst phonologically less specified expectations in a non-native context. Our findings shed light on contextual influence during word recognition, suggesting that word form prediction based on context is sensitive and adaptive to phonological variability.
Audiovisual speech perception has been frequently studied considering phoneme, syllable and word processing levels. Here, we examined the constraints that visual speech information might exert during the recognition of words embedded in a natural sentence context. We recorded event-related potentials (ERPs) to words that could be either strongly or weakly predictable on the basis of the prior semantic sentential context and, whose initial phoneme varied in the degree of visual saliency from lip movements. When the sentences were presented audio-visually (Experiment 1), words weakly predicted from semantic context elicited a larger long-lasting N400, compared to strongly predictable words. This semantic effect interacted with the degree of visual saliency over a late part of the N400. When comparing audio-visual versus auditory alone presentation (Experiment 2), the typical amplitude-reduction effect over the auditory-evoked N100 response was observed in the audiovisual modality. Interestingly, a specific benefit of high- versus low-visual saliency constraints occurred over the early N100 response and at the late N400 time window, confirming the result of Experiment 1. Taken together, our results indicate that the saliency of visual speech can exert an influence over both auditory processing and word recognition at relatively late stages, and thus suggest strong interactivity between audio-visual integration and other (arguably higher) stages of information processing during natural speech comprehension.
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