Speech perception abilities are modified by linguistic experience to maximize sensitivity to acoustic contrasts that are important for one's linguistic community, while reducing sensitivity to other acoustic cues. Although some of these changes may be irreversible, in other cases adults may learn to perceive non-native speech sounds in a linguistically meaningful manner with limited perceptual training. The present study investigates the possibility of using a technique based on perceptual fading to train Canadian francophone adults to distinguish the voiced and voiceless "th" sounds of English: Ifj/, as in "the," versus 19/, as in "theta." Following a pretest to measure identification and discrimination performance with both natural and synthetic speech tokens, 10 subjects were trained using synthetic stimuli. Approximately 90 min ofthis training improved performance with both natural and synthetic tokens relative to that of untrained control subjects. The results suggest that there is a much higher degree of plasticity in these acoustic/linguistic categories than would be inferred from the normal performance of Canadian francophones who learn English as adults. The nature of the training technique is discussed in relation to other training paradigms. Linguistic experience produces major and very durable changes in the perception of some speech sounds. For example, English speakers place the phonetic boundary separating Ibl and Ipl at approximately +25 msec voiceonset time (VOT; see Lisker & Abramson, 1970; Williams, 1977, 1979), whereas Spanish speakers place this boundary at approximately 0 to-5 msec VOT (see Williams, 1977). Similarly, speakers of Canadian French place the voicedlvoicelesscategorical boundary at a shorter VOT value than do unilingual English or bilingual FrenchlEnglish speakers (see Carmazza, Yeni-Komshian, Zurif, & Carbone, 1973). One consequence of such subtle language-specific distinctions is that adults who learn a second language often have special difficulty with the perception and production of sounds that are distinct in the new language but allophonic in their native language. The example considered in this paper is one aspect of the voicedlvoiceless distinction between the En-This work was supported by grants from the Alberta Heritage Foundation for Medical Research, the National Health Research Development Program of Health and Welfare Canada, and the Natural Sciences and Engineering Research Council to D.GJ. and by an AHFMR Scholarship to D.E.M. We are grateful to Eleanor Rogers for providing testing facilities in Kingston and for helping to obtain subjects, to Carol McDermid for her assistance in providing subjects at Calgary, and to Fred Wightman and Terry Dolan for their hospitality at the Waisman Center, University of Wisconsin, where this work was completed while D.G.J. was a Visiting Fellow. Special thanks are due to Meg Cheesman, Terry Nearey, Curtis Ponton, and Mike Procter for advice and assistance throughout this project. Requests for reprints should be directed to

There is a growing trend for hearing aids to incorporate wide dynamic range compression. The input/output (I/O) hearing aid formula, presented in this report, is a general frequency-specific mathematical approach which describes the relationship between the input level of a signal delivered to a hearing aid and the output level produced by the hearing aid. The I/O formula relates basic psychoacoustic parameters, including hearing threshold level and uncomfortable listening level, to the electroacoustic characteristics of hearing aids. The main design goal of the I/O formula was to fit the acoustic region corresponding to the "extended" normal auditory dynamic range into the hearing-impaired individual's residual auditory dynamic range. The I/O approach can be used to fit hearing aids utilizing linear gain, linear compression or curvilinear compression to a hearing-impaired individual's residual auditory area.

The auditory temporal resolving power of young children was measured using an adaptive forced-choice psychophysical paradigm that was disguised as a video game. 20 children between 3 and 7 years of age and 5 adults were asked to detect the presence of a temporal gap in a burst of half-octave-band noise at band center frequencies of 400 and 2,000 Hz. The minimum detectable gap (gap threshold) was estimated adaptively in 20-trial runs. The mean gap thresholds in the 400-Hz condition were higher for the younger children than for the adults, with the 3-year-old children producing the highest thresholds. Gap thresholds in the 2,000-Hz condition were generally lower than in the 400-Hz condition and showed a similar age effect. All the individual adaptive runs were "adult-like," suggesting that the children were generally attentive to the task during each run. However, the variability of threshold estimates from run to run was substantial, especially in the 3-5-year-old children. Computer simulations suggested that this large within-subjects variability could have resulted from frequent, momentary lapses of attention, which would lead to "guessing" on a substantial portion of the trials.

Acoustical measures of vocal function are routinely used in the assessments of disordered voice, and for monitoring the patient's progress over the course of voice therapy. Typically, acoustic measures are extracted from sustained vowel stimuli where short-term and long-term perturbations in fundamental frequency and intensity, and the level of "glottal noise" are used to characterize the vocal function. However, acoustic measures extracted from continuous speech samples may well be required for accurate prediction of abnormal voice quality that is relevant to the client's "real world" experience. In contrast with sustained vowel research, there is relatively sparse literature on the effectiveness of acoustic measures extracted from continuous speech samples. This is partially due to the challenge of segmenting the speech signal into voiced, unvoiced, and silence periods before features can be extracted for vocal function characterization. In this paper we propose a joint time-frequency approach for classifying pathological voices using continuous speech signals that obviates the need for such segmentation. The speech signals were decomposed using an adaptive time-frequency transform algorithm, and several features such as the octave max, octave mean, energy ratio, length ratio, and frequency ratio were extracted from the decomposition parameters and analyzed using statistical pattern classification techniques. Experiments with a database consisting of continuous speech samples from 51 normal and 161 pathological talkers yielded a classification accuracy of 93.4%.

Two experiments investigating the effect of the direction of a relational judgment on the speed of the judgment are reported. In both experiments, college students required more time to select the smaller of a pair of large animals than to select the larger. Conversely, the smaller of a pair of small animals was selected more quickly than was the larger. The magnitude of this "cross-over effect" was fully graded, increasing regularly with extremity, but the variability of the response times in each direction was unrelated to extremity. Individual animals were classified as "small" or "large" with almost perfect consistency. This pattern of results is used to evaluate several models of relational judgment; of these, the congruency model is shown to be inconsistent with these data.The time required for subjects to make a comparative judgment reflects the relation between the direction of the judgment and the position of the to-be-compared stimuli on the judged dimension. Shipley, Coffin, and Hadsell (1945), for example, observed that more time was required to select the more preferred of a pair of colors when the pair was relatively nonpreferred than when the pair was highly preferred. Shipley, Norris, and Roberts (1946) showed that the opposite effect obtained when subjects were required to select the less preferred color: now highly preferred colors were associated with slower responding than were non preferred colors. The interaction between the location of the judged pair on the underlying dimension and the direction of judgment, which the papers, taken together, demonstrate, has been named the "cross-over effect"