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Category: Project

Description: Speech unfolds over time and the cues for even a single phoneme are rarely available simultaneously. Consequently, to recognize a single phoneme listeners must integrate material over several hundred milliseconds. Prior work contrasts two accounts: 1) a memory buffer account in which listeners accumulate auditory information in memory and only access higher level representations (i.e. lexical representations) when sufficient information has arrived; and 2) an immediate integration strategy in which lexical representations can be partially activated on the basis of early cues and then updated when more information arises. These studies have uniformly shown evidence for immediate integration for a variety of phonetic distinctions. We attempted to extend this to fricatives, a class of speech sounds which requires not only temporal integration of asynchronous cues (the frication, followed by the formant transitions 150-350 msec later), but also integration across different frequency bands, and compensation for contextual factors like coarticulation. Experiments employed eye-movements in the visual world paradigm and showed clear evidence for a memory buffer. Results were replicated in five experiments, ruling out methodological factors and tying the release of the buffer to the onset of the vowel. These findings support a general auditory account for speech by suggesting that the acoustic nature of particular speech sounds may have large effects on how they are processed. It also has major implications for theories of auditory and speech perception by raising the possibility of an encapsulated memory buffer in early auditory processing.