Lexically-guided perceptual learning in speech processing

During listening to spoken language, the perceptual system needs to adapt frequently to changes in talkers, and thus to considerable interindividual variability in the articulation of a given speech sound. This thesis investigated a learning process which allows listeners to use stored lexical representations to modify the interpretation of a speech sound when a talker's articulation of that sound is consistently unclear or ambiguous. The questions that were addressed in this research concerned the robustness of such perceptual learning, a potential role for sleep, and whether learning is specific to the speech of one talker or, alternatively, generalises to other talkers. A further study aimed to identify the underlying functional neuroanatomy by using magnetic resonance imaging methods. The picture that emerged for lexically-guided perceptual learning is that learning occurs very rapidly, is highly specific, and remains remarkably robust both over time and under exposure to speech from other talkers

Comparison of word-, sentence, and phoneme-based training strategies in improving the perception of spectrally-distorted speech

Purpose: To compare the effectiveness of three self-administered strategies for auditory training that might improve speech perception by adult users of cochlear implants. The strategies are based, respectively, on discriminating isolated words, words in sentences, and phonemes in nonsense syllables. Method: Participants were 18 normally-hearing adults who listened to speech processed by a noise-excited vocoder to simulate the information provided by a cochlear implant. They were assigned randomly to word-, sentence-, or phoneme-based training and underwent nine 20-minute training sessions on separate days over a 2-3-week period. The effectiveness of training was assessed as the improvement in accuracy of discriminating vowels and consonants, and identifying words in sentences, relative to participants’ best performance in repeated tests prior to training. Results: Word- and sentence-based training led to significant improvements in the ability to identify words in sentences that were significantly larger than the improvements produced by phoneme-based training. There were no significant differences between the effectiveness of word- and sentence-based training. No significant improvements in consonant or vowel discrimination were found for the sentence- or phoneme-based training groups, but some improvements were found for the word-based training group. Conclusions: The word- and sentence-based training strategies were more effective than the phoneme-based strategy at improving the perception of spectrally-distorted speech

The listening talker: A review of human and algorithmic context-induced modifications of speech

International audienceSpeech output technology is finding widespread application, including in scenarios where intelligibility might be compromised - at least for some listeners - by adverse conditions. Unlike most current algorithms, talkers continually adapt their speech patterns as a response to the immediate context of spoken communication, where the type of interlocutor and the environment are the dominant situational factors influencing speech production. Observations of talker behaviour can motivate the design of more robust speech output algorithms. Starting with a listener-oriented categorisation of possible goals for speech modification, this review article summarises the extensive set of behavioural findings related to human speech modification, identifies which factors appear to be beneficial, and goes on to examine previous computational attempts to improve intelligibility in noise. The review concludes by tabulating 46 speech modifications, many of which have yet to be perceptually or algorithmically evaluated. Consequently, the review provides a roadmap for future work in improving the robustness of speech output

The Relationship Between Phonemic Category Boundary Changes and Perceptual Adjustments to Natural Accents

published Online First October 21, 2019People often experience difficulties when they first hear a novel accent. Prior research has shown that relatively fast natural accent accommodation can occur. However, there has been little investigation of the underlying perceptual mechanism that drives the learning. The current study examines whether phonemic boundary changes play a central role in natural accent accommodation. Two well-established boundary shifting phenomena were used here—recalibration and selective adaptation—to index the flexibility of phonemic category boundaries. Natural accent accommodation was measured with a task in which listeners heard accented words and nonwords before and after listening to English sentences produced by one of two native Mandarin Chinese speakers with moderate accents. In two experiments, participants completed recalibration, selective adaptation, and natural accent accommodation tasks focusing on a consonant contrast that is difficult for native Chinese speakers to produce. We found that: (a) On the accent accommodation task, participants showed an increased endorsement of accented/ mispronounced words after exposure to a speaker’s accented speech, indicating a potential relaxation of criteria in the word recognition process; (b) There was no strong link between recalibrating phonemic boundaries and natural accent accommodation; (c) There was no significant correlation between recalibration and selective adaptation. These results suggest that recalibration of phonemic boundaries does not play a central role in natural accent accommodation. Instead, there is some evidence suggesting that natural accent accommodation involves a relaxation of phonemic categorization criteria.Support was provided by Ministerio de Ciencia E Innovacion, Grant PSI2017-82563-P, Centro de Excelencia Severo Ochoa, Grant SEV-2015- 0490, by the Basque Government through the BERC 2018–2021 program, and by the National Science Foundation under Grant IBSS-1519908

Building phonetic categories: an argument for the role of sleep

The current review provides specific predictions for the role of sleep-mediated memory consolidation in the formation of new speech sound representations. Specifically, this discussion will highlight selected literature on the different ideas concerning category representation in speech, followed by a broad overview of memory consolidation and how it relates to human behavior, as relevant to speech/perceptual learning. In combining behavioral and physiological accounts from animal models with insights from the human consolidation literature on auditory skill/word learning, we are in the early stages of understanding how the transfer of experiential information between brain structures during sleep manifests in changes to online perception. Arriving at the conclusion that this process is crucial in perceptual learning and the formation of novel categories, further speculation yields the adjacent claim that the habitual disruption in this process leads to impoverished quality in the representation of speech sounds

Cognitive factors in perception and imitation of Thai tones by Mandarin versus Vietnamese speakers

The thesis investigates how native language phonological and phonetic factors affect non-native lexical tone perception and imitation, and how cognitive factors, such as memory load and stimulus variability (talker and vowel context variability), bias listeners to a phonological versus phonetic mode of perception/imitation. Two perceptual experiments and one imitation experiment were conducted with Thai tones as the stimuli and with Mandarin and Vietnamese listeners, who had no experience with Thai (i.e., naive listeners/imitators). The results of the perceptual experiments (Chapters 5 and 6) showed phonological effects as reflected in assimilation types (Categorised vs. UnCategorised assimilation) and phonetic effects indicated by percent choice and goodness ratings in tone assimilation, largely in line with predictions based on the Perceptual Assimilation Model (PAM: Best, 1995). In addition, phonological assimilation types and phonological overlap of the contrasts affected their discrimination in line with predictions based on PAM. The thesis research has revealed the influence of cognitive factors on native language influences in perception and imitation of non-native lexical tones, which contribute differently to different tasks. The findings carry implications for current non-native speech perception theories. The fact that non-native tone imitation deviations can be traced back to native phonological and phonetic influences on perception supports and provides new insights about perception-production links in processing non-native tones. The findings uphold the extrapolation of PAM and ASP principles to non-native tone perception and imitation, indicating that both native language phonological and phonetic influences and their modulation by cognitive factors hold implications for non-native speech perception/learning theories, as well as for second language instruction

Toddlers recognize words in an unfamiliar accent after brief exposure

Both subjective impressions and previous research with monolingual listeners suggest that a foreign accent interferes with word recognition in infants, young children, and adults. However, because being exposed to multiple accents is likely to be an everyday occurrence in many societies, it is unexpected that such non-standard pronunciations would significantly impede language processing once the listener has experience with the relevant accent. Indeed, we report that 24-month-olds successfully accommodate an unfamiliar accent in rapid word learning after less than 2 minutes of accent exposure. These results underline the robustness of our speech perception mechanisms, which allow listeners to adapt even in the absence of extensive lexical knowledge and clear known-word referents