Listeners use lexical information to retune the mapping between the acoustic signal and speech sound representations, resulting in changes to phonetic category boundaries. Other research shows that phonetic categories have a rich internal structure; within-category variation is represented in a graded fashion. The current work examined whether lexically informed perceptual learning promotes a comprehensive reorganization of internal category structure. The results showed a reorganization of internal structure for one but not both of the examined categories, which may reflect an attenuation of learning for distributions with extensive category overlap. This finding points towards potential input-driven constraints on lexically guided phonetic retuning.
Listeners use lexical information to resolve ambiguity in the speech signal, resulting in the restructuring of speech sound categories. Recent findings suggest that lexically guided perceptual learning is attenuated when listeners use a perception-focused listening strategy (that directs attention towards surface variation) compared to when listeners use a comprehension-focused listening strategy (that directs attention towards higher-level linguistic information). However, previous investigations used the word position of the ambiguity to manipulate listening strategy, raising the possibility that attenuated learning reflected decreased strength of lexical recruitment instead of a perception-oriented listening strategy. The current work tests this hypothesis. Listeners completed an exposure phase followed by a test phase. During exposure, listeners heard an ambiguous fricative embedded in word-medial lexical contexts that supported realization of the ambiguity as /∫/. At test, listeners categorized members of an /ɑsi/-/ɑ∫i/ continuum. Listening strategy was manipulated via exposure task (experiment 1) and explicit acknowledgement of the ambiguity (experiment 2). Compared to control participants, listeners who were exposed to the ambiguity showed more /∫/ responses at the test; critically, the magnitude of learning did not differ across listening strategy conditions. These results suggest that given sufficient lexical context, lexically guided perceptual learning is robust to task-based changes in listening strategy.
This review examines the role of auditory training on speech adaptation for cochlear implant users. A current limitation of the existing evidence base is the failure to adequately account for wide variability in speech perception outcomes following implantation. While many preimplantation factors contribute to the variance observed in outcomes, formal auditory training has been proposed as a way to maximize speech comprehension benefits for cochlear implant users. We adopt an interdisciplinary perspective and focus on integrating the clinical rehabilitation literature with basic research examining perceptual learning of speech. We review findings on the role of auditory training for improving perception of degraded speech signals in normal hearing listeners, with emphasis on how lexically oriented training paradigms may facilitate speech comprehension when the acoustic input is diminished. We conclude with recommendations for future research that could foster translation of principles of speech learning in normal hearing listeners to aural rehabilitation protocols for cochlear implant patients.
A fundamental goal of research in the domain of speech perception has been to describe how listeners resolve the lack-of-invariance problem in order to achieve stable word recognition. Here we review work from our laboratory and others that has examined the representational nature of prelexical and lexical knowledge by considering the degree to which listeners customize the mapping from the acoustic signal to meaning on a talker-specific basis. One central finding is that while talker-specificity effects in speech perception are observed frequently, they are not absolute, and seem to be influenced by rich interactions within the cognitive and language architectures. We consider these findings with respect to their implications for abstract and episodic accounts of spoken word recognition.
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