Ann Bradlow, Ph.D. - US grants

The long-term goal of this project is to examine neural plasticity and auditory-perceptual learning in school-aged children with auditory-based learning disabilities. It is estimated that 5-9 percent of school-aged children in the United States have some kind of diagnosed learning disorder, and that an additional 3-5 percent have a diagnosed attention deficit disorder. Furthermore, it is common for children to qualify for both diagnoses. Previous research has established that many of these children exhibit perceptual deficits in response to auditory stimuli, suggesting that an auditory-perceptual deficit may underlie their learning disabilities. A separate line of research has focused on developing effective computer-based procedures for training the perception of difficult foreign language contrasts by monolingual adults. This work has identified several general principles of perceptual learning that are critical for achieving enhanced sensitivity to perceptually difficult acoustic-phonetic contrasts, the most important of which is exposure to a range of stimulus variability in the training set. In view of the fact that second-language learners and children with auditory-based learning disabilities both display diminished sensitivity to certain speech sounds, successful training approaches for one population may hold great promise for the other. Accordingly, this study will draw on findings from these two lines of research in an attempt to develop laboratory-based training procedures for children with auditory-based learning disorders. An important aspect of the design of the proposed study is that the battery of tests used to assess performance before and after training incorporates a wide range of auditory-perceptual tasks, ranging from a non-speech auditory discrimination task using simple tones and noise to ore complex spoken word recognition tasks. Thus, data from the proposed study will provide important information regarding the relationships between performance on a variety of auditory and speech perception tasks within individual subjects, as well as providing the means for investigating the effects of various training paradigms on performance on a range of relevant tasks. Further, using well-established electrophtsiologic techniques, we will examine the neurophysiologic changes that underlie auditory-perceptual learning. In this manner, we hope to shed light of the underlying sensory-perceptual deficit, as well as make advances towards the development of training procedures of these children.

DESCRIPTION (provided by applicant): The major objective of the proposed research is to identify some of the talker and listener characteristics that contribute to variation in speech intelligibility. The study consists of an extensive examination of the production and perception of "clear speech," a distinct speaking style that talkers adopt when the listener has speech perception difficulties due to a hearing loss, background noise, or a different native language. To the extent that clear speech is more intelligible than "conversational speech," an acoustic-phonetic comparison of these two speaking styles provides unique information about factors that affect speech intelligibility. The proposed studies will test the hypothesis that naturally produced clear speech reflects an interaction of universal, auditory-perceptual factors, which serve to enhance the overall acoustic salience of the speech signal such that it is more resistant to the adverse effects of environmental noise or listener-related perceptual deficits, and 1anguage-specific structural factors, which serve t o e enhance t he realization of phonologically important contrasts. Two important predictions of this hypothesis are (a) clear speech production will show predictable and systematic similarities and differences across languages, and (b) the intelligibility benefit of naturally produced clear speech will be greater for listeners with well-entrenched knowledge of the sound structure of the target language than for listeners with limited experience with the sound structure of the target language. In order to test these predictions two projects are proposed. Project 1 will investigate variability in clear speech production by comparing the conversational-to-clear speech transformations in English and Spanish. Project 2 will investigate variability in clear speech perception by comparing the clear speech intelligibility benefit across listeners that vary with respect to their experience with the sound structure of the target language (native vs. non-native listeners, adults vs. children).

Project Summary The long-term objective of the proposed work is to understand variability in speech intelligibility, with the ultimate goal of developing speech intelligibility enhancement techniques for a wide range of talkers, listeners and communicative situations. The current objective is to explore variability in speech intelligibility through both listener adaptation to the talker and talker adaptation to the listener. In particular, we focus on the special case of speech communication between all possible combinations of native and non-native English talkers. This focus is in-line with current national and global trends towards increasing contact between native and non- native English speakers, and therefore stands to make both theoretical and practical contributions. Our central claim is that variability in overall speech intelligibility is a function of talker-listener sound structure alignment, which can be adjusted in a bi-directional, dynamic manner according to the current communicative conditions. We hypothesize that a mismatch of language background between interlocutors is a bi-directional source of speech intelligibility variability, as well as of cognitive-linguistic innovation. Two predictions of this hypothesis are: (1) variability in intelligibility is related to talker-listener alignment rather than a simple function of talker and/or listener target language proficiency (bi-directional intelligibility variability), and (2) both native and non-native speakers exhibit speech perception and production changes in response to exposure to native and non-native speech (bi-directional innovation). The specific aims are: Aim 1: To develop a large corpus of speech produced by native and non-native speakers of English that includes both scripted and spontaneous, dialogue-based speech samples. The speakers will be carefully selected to cover a range of native language backgrounds and levels of English proficiency. Moreover, in the dialogue portion of the corpus, talkers will be paired in a principled manner, covering 4 different conversation pair types: 2 native talkers, 1 native and 1 non-native talker, 2 non-native talkers from the same language background, and 2 non-native talkers from different language backgrounds. The corpus will be fully transcribed and partially phonetically aligned, creating a valuable resource for the speech research community. Aim 2: To use this corpus to examine bi-directional talker-listener alignment at the level of speech production and perception. In a series of 3 planned experiments we will (i) examine foreign-accented speech intelligibility in relation to inter- and intra-talker acoustic-phonetic variability, (ii) compare overall communicative efficiency across all 4 types of conversation pairs, and (iii) compare the direction and extent of phonetic convergence in dialogues between conversation partners that vary with respect to their proficiency in the target language (English) and in terms of their native language background.

PROJECT SUMMARY (See instaictions): The primary purpose of this Research Core Center is to promote advancements in the science and understanding of communication by fostering a collaborative environment among a diverse group of investigators. A key element of this purpose is a shared commitment across the participating Pis to data sharing and standardization of research methodologies across laboratories. An Executive Committee, consisting of the Program Director, Program Co-Director, and each of the three Core Directors, will administer the center operations and make key management and strategic decisions. Core 1 will hire personnel to recruit specific populations of hard-to-reach subjects such as children with autism, young children, adolescents and elderly adults, and to administer routine and standardized screening tests. Core 2 will develop centralized and standardized tools for human subject management and data gathering, and will establish a research participant registry and relational database that will facilitate the secure storage and retrieval of information pertaining to subject groups and screening profiles. Finally, Core 3 will undertake the development and dissemination to research laboratories of broadly applicable tools for the analysis and integration of complex data. The Executive Committee will work with individual staff members and investigators to improve functionality of each core. The Executive Committee will work with individual investigators to make suggestions on how to leverage achievements in data sharing and experimental tool upgrading and standardization towards the establishment of new and innovative cross-laboratory collaborations. It will have regular meetings to discuss problems and strategies for solutions to problems that develop between the constituent cores and for problems within cores that are unable to be resolved within the core itself. The Director will have overall decision-making authority in the event that problems are not resolved by action of the committee. The committee will review applications for employment of staff personnel, will review the performance of staff members and will make decisions on hiring and dismissal. The committee will also evaluate yearly progress in relation to the goals of increasing collaborative research, enhancement of research productivity, strengths and weaknesses of the Center's operations, effective use of facilities and staff, and will review recommendations from Pis for improvement of the Center's operation.