How Should a Speech Recognizer Work?

Although researchers studying human speech recognition (HSR) and automatic speech recognition (ASR) share a common interest in how information processing systems (human or machine) recognize spoken language, there is little communication between the two disciplines. We suggest that this lack of communication follows largely from the fact that research in these related fields has focused on the mechanics of how speech can be recognized. In Marr's (1982) terms, emphasis has been on the algorithmic and implementational levels rather than on the computational level. In this article, we provide a computational-level analysis of the task of speech recognition, which reveals the close parallels between research concerned with HSR and ASR. We illustrate this relation by presenting a new computational model of human spoken-word recognition, built using techniques from the field of ASR that, in contrast to current existing models of HSR, recognizes words from real speech input.     

Short therapy of a child with Gilles de la Tourette's Syndrome*

This paper describes a three-hour intervention with a family whose younger son, aged four, was brought for consultation for Gilles de la Tourette's syndrome. The theoretical elaboration of the intervention is discussed so as to elucidate the therapeutic effect of the session leading to the lasting eradication of the symptoms.     

Discrimination and Puerto Rican children's and adolescents' mental health

Two studies of Puerto Rican youths' development on the U.S. mainland examined the consequences of perceived racial/ethnic discrimination on mental health. In Study I, children were found to have a low likelihood of perceiving discrimination, whereas in Study 2, nearly half of the adolescent sample reported perceiving racial/ethnic discrimination. Although both groups scored high on multiple indicators of mental health, perceiving discrimination and worrying about discrimination were negatively associated with some dimensions of self-esteem and positively associated with depression and stress. Adolescents were aware of negative stereotypes about Puerto Ricans, and nearly half of them related discriminatory instances. Results suggest that both perceiving discrimination and anxiety regarding discrimination can serve as risk factors for the mental health of this population.     

Audiovisual perception of noise vocoded speech in dyslexic and non-dyslexic adults: The role of low-frequency visual modulations

Visual speech inputs can enhance auditory speech information, particularly in noisy or degraded conditions. The natural statistics of audiovisual speech highlight the temporal correspondence between visual and auditory prosody, with lip, jaw, cheek and head movements conveying information about the speech envelope. Low-frequency spatial and temporal modulations in the 2–7 Hz range are of particular importance. Dyslexic individuals have specific problems in perceiving speech envelope cues. In the current study, we used an audiovisual noise-vocoded speech task to investigate the contribution of low-frequency visual information to intelligibility of 4-channel and 16-channel noise vocoded speech in participants with and without dyslexia. For the 4-channel speech, noise vocoding preserves amplitude information that is entirely congruent with dynamic visual information. All participants were significantly more accurate with 4-channel speech when visual information was present, even when this information was purely spatio-temporal (pixelated stimuli changing in luminance). Possible underlying mechanisms are discussed.     

Comparing lexically guided perceptual learning in younger and older listeners

Numerous studies have shown that younger adults engage in lexically guided perceptual learning in speech perception. Here, we investigated whether older listeners are also able to retune their phonetic category boundaries. More specifically, in this research we tried to answer two questions. First, do older adults show perceptual-learning effects of similar size to those of younger adults? Second, do differences in lexical behavior predict the strength of the perceptual-learning effect? An age group comparison revealed that older listeners do engage in lexically guided perceptual learning, but there were two age-related differences: Younger listeners had a stronger learning effect right after exposure than did older listeners, but the effect was more stable for older than for younger listeners. Moreover, a clear link was shown to exist between individuals’ lexical-decision performance during exposure and the magnitude of their perceptual-learning effects. A subsequent analysis on the results of the older participants revealed that, even within the older participant group, with increasing age the perceptual retuning effect became smaller but also more stable, mirroring the age group comparison results. These results could not be explained by differences in hearing loss. The age effect may be accounted for by decreased flexibility in the adjustment of phoneme categories or by age-related changes in the dynamics of spoken-word recognition, with older adults being more affected by competition from similar-sounding lexical competitors, resulting in less lexical guidance for perceptual retuning. In conclusion, our results clearly show that the speech perception system remains flexible over the life span.     

Composition and magnetic character of nanometre-size Cu precipitates in reactor pressure vessel steels: Implications for nuclear power plant lifetime extension

The sensitivity of positrons to nanometre-size Cu precipitates in Fe alloys has enabled us to apply a novel spin-polarized element-specific method to probe the composition and magnetic character of the precipitates responsible for reactor pressure vessel (RPV) steel embrittlement. The results clearly show that the precipitates are non-magnetic and place an upper limit of about 10at% on their Fe content. The practical implication of this result is that the Cu precipitate contribution to RPV steel embrittlement saturates is not expected to contribute further during lifetime extension. Our study demonstrates that polarized positrons can be used as a powerful probe of the magnetic character of nanoscale materials, even those embedded in a strongly magnetic host.     

Phonological abstraction without phonemes in speech perception

Recent evidence shows that listeners use abstract prelexical units in speech perception. Using the phenomenon of lexical retuning in speech processing, we ask whether those units are necessarily phonemic. Dutch listeners were exposed to a Dutch speaker producing ambiguous phones between the Dutch syllable-final allophones approximant [r] and dark [l]. These ambiguous phones replaced either final /r/ or final /l/ in words in a lexical-decision task. This differential exposure affected perception of ambiguous stimuli on the same allophone continuum in a subsequent phonetic-categorization test: Listeners exposed to ambiguous phones in /r/-final words were more likely to perceive test stimuli as /r/ than listeners with exposure in /l/-final words. This effect was not found for test stimuli on continua using other allophones of /r/ and /l/. These results confirm that listeners use phonological abstraction in speech perception. They also show that context-sensitive allophones can play a role in this process, and hence that context-insensitive phonemes are not necessary. We suggest there may be no one unit of perception.     

THE DUAL-FOCUS APPROACH TO CREATING BILINGUAL MEASURES

The dual-focus approach to creating bilingual research protocols requires a bilingual/bicultural research team, including indigenous researchers from the cultures being studied. The presence of indigenous researchers as full and equal members of the research team can guard against an unexamined exportation of ideas and methods developed in one culture to other cultural/linguistic communities. The team develops the research plan and a research protocol that express a given concept with equal clarity, affect, and level of usage simultaneously in two languages. The dual-focus method employs a concept-driven rather than a translation-driven approach to attain conceptual and linguistic equivalence. Examples of the application of this approach to creating new measures in Spanish and English, adapting existing measures, revising instructions to research participants, and correcting official translations are provided.