Single Talker Research Articles

Frequencies in Perception and Production Differentially Affect Child Speech.

Frequent sounds and frequent words are both acquired at an earlier age and are produced by children more accurately. Recent research suggests that frequency is not always a facilitative concept, however. Interactions between input frequency in perception and practice frequency in production may limit or inhibit growth. In this study, we consider how a range of input frequencies affect production accuracy and referent identification. Thirty-three typically developing 3- and 4-year-olds participated in a novel word-learning task. In the initial test block, participants heard nonwords 1, 3, 6, or 10 times-produced either by a single talker or by multiple talkers-and then produced them immediately. In a posttest, participants heard all nonwords just once and then produced them. Referent identification was probed in between the test and posttest. Production accuracy was most clearly facilitated by an input frequency of 3 during the test block. Input frequency interacted with production practice, and the facilitative effect of input frequency did not carry over to the posttest. Talker variability did not affect accuracy, regardless of input frequency. The referent identification results did not favor talker variability or a particular input frequency value, but participants were able to learn the words at better than chance levels. The results confirm that the input can be facilitative, but input frequency and production practice interact in ways that limit input-based learning, and more input is not always better. Future research on this interaction may allow clinicians to optimize various types of frequency commonly used during therapy.

The role of speech rate for Italian-speaking cochlear implant users: insights for everyday speech perception

This study investigated the effect of speech rate for Italian-speaking cochlear implant (CI) users with the aim of gaining insight into everyday listening situations where speaker’s rate may vary considerably together with speech level in fluctuating background noise. The test material was prepared by processing the Italian STARR test with temporal compression of sentence material. Twelve adult CI users were divided into two subgroups based on their STARR performance: good and poor performers. The effect of varying speech rate was remarkable for both subgroups. Good performers showed significant performance deterioration for the faster speech rate, whereas outcomes for poor performers improved significantly for the slower speech rate. Background noise is inevitable during daily life and CI users face a variety of speakers, so must cope with changes in both speech level and rate. Traditional tests with a single talker speaking very clearly while using a moderate to low speech rate may overestimate everyday speech perception for CI users. The use of tests that mimic everyday perception is of great importance and should become a routine part of audiometric measures for hearing impaired people.

Talker and Acoustic Variability in Learning to Produce Nonnative Sounds: Evidence from Articulatory Training

AbstractCompared to low‐variability training, high‐variability training leads to better learning outcomes and supports generalization of learning. However, it is unclear whether the learning advantage is driven by multiple talkers or by enhanced acoustic variability across target sounds. The current study addressed this issue in nonnative production learning. Spanish speakers were trained to produce the French /e/–/ɛ/ vowel contrast. The stimuli were recorded by five native French talkers for the multiple‐talker (MT) group or by one talker for the single‐talker (ST) group, but acoustic dispersion of the vowels and context were matched between the two groups. Both training paradigms improved production accuracy, with slightly greater improvement in the ST group. However, only MT training enhanced the compactness of vowel categories and generalized to the production of sounds elicited by an unfamiliar speaker. This suggests that talker variability supports the establishment of abstract phonemic categories in production.

Looking Behavior and Audiovisual Speech Understanding in Children With Normal Hearing and Children With Mild Bilateral or Unilateral Hearing Loss.

Visual information from talkers facilitates speech intelligibility for listeners when audibility is challenged by environmental noise and hearing loss. Less is known about how listeners actively process and attend to visual information from different talkers in complex multi-talker environments. This study tracked looking behavior in children with normal hearing (NH), mild bilateral hearing loss (MBHL), and unilateral hearing loss (UHL) in a complex multi-talker environment to examine the extent to which children look at talkers and whether looking patterns relate to performance on a speech-understanding task. It was hypothesized that performance would decrease as perceptual complexity increased and that children with hearing loss would perform more poorly than their peers with NH. Children with MBHL or UHL were expected to demonstrate greater attention to individual talkers during multi-talker exchanges, indicating that they were more likely to attempt to use visual information from talkers to assist in speech understanding in adverse acoustics. It also was of interest to examine whether MBHL, versus UHL, would differentially affect performance and looking behavior. Eighteen children with NH, eight children with MBHL, and 10 children with UHL participated (8-12 years). They followed audiovisual instructions for placing objects on a mat under three conditions: a single talker providing instructions via a video monitor, four possible talkers alternately providing instructions on separate monitors in front of the listener, and the same four talkers providing both target and nontarget information. Multi-talker background noise was presented at a 5 dB signal-to-noise ratio during testing. An eye tracker monitored looking behavior while children performed the experimental task. Behavioral task performance was higher for children with NH than for either group of children with hearing loss. There were no differences in performance between children with UHL and children with MBHL. Eye-tracker analysis revealed that children with NH looked more at the screens overall than did children with MBHL or UHL, though individual differences were greater in the groups with hearing loss. Listeners in all groups spent a small proportion of time looking at relevant screens as talkers spoke. Although looking was distributed across all screens, there was a bias toward the right side of the display. There was no relationship between overall looking behavior and performance on the task. The present study examined the processing of audiovisual speech in the context of a naturalistic task. Results demonstrated that children distributed their looking to a variety of sources during the task, but that children with NH were more likely to look at screens than were those with MBHL/UHL. However, all groups looked at the relevant talkers as they were speaking only a small proportion of the time. Despite variability in looking behavior, listeners were able to follow the audiovisual instructions and children with NH demonstrated better performance than children with MBHL/UHL. These results suggest that performance on some challenging multi-talker audiovisual tasks is not dependent on visual fixation to relevant talkers for children with NH or with MBHL/UHL.

Better-ear glimpsing with symmetrically-placed interferers in bilateral cochlear implant users.

For a frontal target in spatially symmetrically placed interferers, normal hearing (NH) listeners can use "better-ear glimpsing" to select time-frequency segments with favorable signal-to-noise ratio in either ear. With an ideal monaural better-ear mask (IMBM) processing, some studies showed that NH listeners can reach similar performance as in the natural binaural listening condition, although interaural phase differences at low frequencies can further improve performance. In principle, bilateral cochlear implant (BiCI) listeners could use the same better-ear glimpsing, albeit without exploiting interaural phase differences. Speech reception thresholds of NH and BiCI listeners were measured in three interferers (speech-shaped stationary noise, nonsense speech, or single talker) either co-located with the target, symmetrically placed at ±60°, or independently presented to each ear, with and without IMBM processing. Furthermore, a bilateral noise vocoder based on the BiCI electrodogram was used in the same NH listeners. Headphone presentation and direct stimulation with head-related transfer functions for spatialization were used in NH and BiCI listeners, respectively. Compared to NH listeners, both NH listeners with vocoder and BiCI listeners showed strongly reduced binaural benefit from spatial separation. However, both groups greatly benefited from IMBM processing as part of the stimulation strategy.

Impact of talker adaptation on speech processing and working memory

Talker adaptation is known to facilitate immediate speech recognition. However, it is unclear whether and how talker adaptation also facilitates working memory for speech. Using electroencephalography (EEG) during a delayed recall of digit span task, we investigated whether talker adaptation facilitates working memory performance. We also investigated whether neural alpha oscillatory power reflects facilitatory effects of talker adaptation. Listeners encoded sequences of seven randomly ordered digits, recalling them after a 5-s retention. Digit sequences were spoken by either a single talker or multiple talkers, and were presented at either faster or slower speech rates (0-ms vs. 500-ms inter-digit intervals). Overall, listeners responded faster and more accurately for single-talker sequences compared to multiple-talker sequences. Especially for the faster presentation rate, listeners were more efficient (faster and more accurate) in recalling sequences spoken by a single talker. For the faster presentation rate, processing digit sequences spoken by single vs. multiple talkers also elicited reduced alpha power during both speech encoding and working memory retention. These results suggest that talker adaptation reduces cognitive effort during both speech encoding and memory retention, thereby producing more efficient working memory for speech information, especially when listeners process speech rapidly.

The irrelevant speech effect in multi-talker environments: Applications to open-plan offices

Irrelevant speech from co-workers has consistently been listed as one of the major nuisances within open-plan work environments. To explore the psychoacoustic basis of the so-called irrelevant speech effect (ISE; which causes cognitive decline and increases acoustic distraction) within a multi-talker context, a series of laboratory-based experiments were run. These experiments used room acoustical simulations of various open-plan office environments within a climate-controlled chamber to test several factors relevant to the ISE. These factors included the number of simultaneously active talkers, their spatial arrangements, sound pressure levels and the semanticity of speech. The main findings thus far indicate that multi-talker speech lead to a stronger ISE than speech from a single talker, which further interacts with the overall sound level, semanticity, etc., to exhibit a more complicated effect than what has been proposed in previous studies. The effect of the number of active talkers alone suggests reconsiderations of some assumptions in the ISO 3382-3. More generally, the perception of speech “babble” seems to be affected by multiple factors in a realistic working environment. Some of our research is directly related to characterising speech babble and its function as a beneficial sound masker in multi-talker environments.Irrelevant speech from co-workers has consistently been listed as one of the major nuisances within open-plan work environments. To explore the psychoacoustic basis of the so-called irrelevant speech effect (ISE; which causes cognitive decline and increases acoustic distraction) within a multi-talker context, a series of laboratory-based experiments were run. These experiments used room acoustical simulations of various open-plan office environments within a climate-controlled chamber to test several factors relevant to the ISE. These factors included the number of simultaneously active talkers, their spatial arrangements, sound pressure levels and the semanticity of speech. The main findings thus far indicate that multi-talker speech lead to a stronger ISE than speech from a single talker, which further interacts with the overall sound level, semanticity, etc., to exhibit a more complicated effect than what has been proposed in previous studies. The effect of the number of active talkers alone suggests r...

Older adults show impaired modulation of attentional alpha oscillations: Evidence from dichotic listening.

Auditory attention is critical for selectively listening to speech from a single talker in a multitalker environment (e.g., Cherry, 1953). Listening in such situations is notoriously more difficult and more poorly encoded to long-term memory in older than in young adults (Tun, O'Kane, & Wingfield, 2002). Recent work by Payne, Rogers, Wingfield, and Sekuler (2017) in young adults demonstrated a neural correlate of auditory attention in the directed dichotic listening task (DDLT), where listeners attend to one ear while ignoring the other. Measured using electroencephalography, differences in alpha band power (8-14 Hz) between left and right hemisphere parietal regions mark the direction to which auditory attention is focused. Little prior research has been conducted on alpha power modulations in older adults, particularly with regard to auditory attention directed toward speech stimuli. In the current study, an older adult sample was administered the DDLT and delayed recognition procedures used by Payne et al. (2017). Compared to young adults, older adults showed reduced selective attention in the DDLT, evidenced by a higher rate of intrusions from the unattended ear. Moreover, older adults did not exhibit attention-related alpha modulation evidenced by young adults, nor did their event-related potentials (ERPs) to recognition probes differentiate between attended or unattended probes. Older adults' delayed recognition did not reveal a pattern of suppression of unattended items evidenced by young adults. These results serve as evidence for an age-related decline in selective auditory attention, potentially mediated by age-related decline in the ability to modulate alpha oscillations. (PsycINFO Database Record

Using high variability phonetic training to train non-tonal listeners with no musical background to perceive lexical tones

Previous research has not extensively investigated whether High Variability Phonetic Training (HVPT) is effective in training listeners with no musical background and no prior experience with a tone language in their identification of non-native lexical tones. In this study, it was investigated whether HVPT is applicable to the acquisition of non-native tones by such listeners. Twenty-one speakers of American English were trained in eight sessions using the HVPT approach to identify Mandarin tones in monosyllabic words. Ten of the participants were exposed to words produced by multiple talkers (MT condition), and eleven participants were exposed to words produced by a single talker (ST condition). The listeners’ identification accuracy revealed an average 44% increase from the pretest to the posttest for the MT condition and an average 30% increase for the ST condition. The improvement also generalized to new monosyllabic words produced by a familiar talker and those produced by two unfamiliar talkers. The learning however did not generalize to novel disyllabic words produced either by a familiar talker or an unfamiliar talker. Comparisons between two groups further revealed that the improvement of the listeners in the MT condition was significantly higher than that of the listeners in the ST condition.

Varying acoustic-phonemic ambiguity reveals that talker normalization is obligatory in speech processing.

The nondeterministic relationship between speech acoustics and abstract phonemic representations imposes a challenge for listeners to maintain perceptual constancy despite the highly variable acoustic realization of speech. Talker normalization facilitates speech processing by reducing the degrees of freedom for mapping between encountered speech and phonemic representations. While this process has been proposed to facilitate the perception of ambiguous speech sounds, it is currently unknown whether talker normalization is affected by the degree of potential ambiguity in acoustic-phonemic mapping. We explored the effects of talker normalization on speech processing in a series of speeded classification paradigms, parametrically manipulating the potential for inconsistent acoustic-phonemic relationships across talkers for both consonants and vowels. Listeners identified words with varying potential acoustic-phonemic ambiguity across talkers (e.g., beet/boat vs. boot/boat) spoken by single or mixed talkers. Auditory categorization of words was always slower when listening to mixed talkers compared to a single talker, even when there was no potential acoustic ambiguity between target sounds. Moreover, the processing cost imposed by mixed talkers was greatest when words had the most potential acoustic-phonemic overlap across talkers. Models of acoustic dissimilarity between target speech sounds did not account for the pattern of results. These results suggest (a) that talker normalization incurs the greatest processing cost when disambiguating highly confusable sounds and (b) that talker normalization appears to be an obligatory component of speech perception, taking place even when the acoustic-phonemic relationships across sounds are unambiguous.

Apparent-talker height is influenced by Mandarin lexical tone

Apparent-talker height is determined by a talker's fundamental frequency (f0) and spectral information, typically indexed using formant frequencies (FFs). Barreda [(2017b). J. Acoust. Soc. Am. 141, 4781-4792] reports that the apparent height of a talker can be influenced by vowel-specific variation in the f0 or FFs of a sound. In this experiment, native speakers of Mandarin were presented with a series of syllables produced by talkers of different apparent heights. Results indicate that there is substantial variability in the estimated height of a single talker based on lexical tone, as well as the inherent f0 and FFs of vowel phonemes.

Effects of attention on the speech reception threshold and pupil response of people with impaired and normal hearing

For people with hearing difficulties, following a conversation in a noisy environment requires substantial cognitive processing, which is often perceived as effortful. Recent studies with normal hearing (NH) listeners showed that the pupil dilation response, a measure of cognitive processing load, is affected by ‘attention related’ processes. How these processes affect the pupil dilation response for hearing impaired (HI) listeners remains unknown. Therefore, the current study investigated the effect of auditory attention on various pupil response parameters for 15 NH adults (median age 51 yrs.) and 15 adults with mild to moderate sensorineural hearing loss (median age 52 yrs.). Both groups listened to two different sentences presented simultaneously, one to each ear and partially masked by stationary noise. Participants had to repeat either both sentences or only one, for which they had to divide or focus attention, respectively. When repeating one sentence, the target sentence location (left or right) was either randomized or blocked across trials, which in the latter case allowed for a better spatial focus of attention. The speech-to-noise ratio was adjusted to yield about 50% sentences correct for each task and condition. NH participants had lower (‘better’) speech reception thresholds (SRT) than HI participants. The pupil measures showed no between-group effects, with the exception of a shorter peak latency for HI participants, which indicated a shorter processing time. Both groups showed higher SRTs and a larger pupil dilation response when two sentences were processed instead of one. Additionally, SRTs were higher and dilation responses were larger for both groups when the target location was randomized instead of fixed. We conclude that although HI participants could cope with less noise than the NH group, their ability to focus attention on a single talker, thereby improving SRTs and lowering cognitive processing load, was preserved. Shorter peak latencies could indicate that HI listeners adapt their listening strategy by not processing some information, which reduces processing time and thereby listening effort.

Learning a Talker or Learning an Accent: Acoustic Similarity Constrains Generalization of Foreign Accent Adaptation to New Talkers.

Past research has revealed that native listeners use top-down information to adjust the mapping from speech sounds to phonetic categories. Such phonetic adjustments help listeners adapt to foreign-accented speech. However, the mechanism by which talker-specific adaptation generalizes to other talkers is poorly understood. Here we asked what conditions induce crosstalker generalization in talker accent adaptation. Native-English listeners were exposed to Mandarin-accented words, produced by a single talker or multiple talkers. Following exposure, adaptation to the accent was tested by recognition of novel words in a task that assesses online lexical access. Crucially, test words were novel words and were produced by a novel Mandarin-accented talker. Results indicated that regardless of exposure condition (single or multiple talker exposure), generalization was greatest when the talkers were acoustically similar to one another, suggesting that listeners were not developing an accent-wide schema for Mandarin talkers, but rather attuning to the specific acoustic-phonetic properties of the talkers. Implications for general mechanisms of talker generalization in speech adaptation are discussed.

Listener estimates of talker age in a single-talker, 50-year longitudinal sample

PurposeWhile many studies have shown that listeners make relatively accurate age judgments from hearing talkers’ voices, most have used just one age per talker. The present study evaluated listeners’ age estimation abilities for a longitudinal sample: a single talker recorded over nearly five decades. MethodWe extracted 60 samples from addresses given by a male talker over 48 years. For each sample, listeners gave a direct estimate of his age. We also asked listeners if they could identify the talker, who was known locally, from the recordings. ResultsWhile correlations between the talker’s chronological age and direct estimates of age were generally strong, the relationship was particularly strong when the talker was older than 68 years, although listeners underestimated chronological age by approximately 5 years. When the talker was between 49 and 68 years, direct age estimates were less accurate and less strongly correlated with chronological age. Additionally, direct age estimates were more accurate when listeners recognized the talker. ConclusionsCorroborating cross-sectional studies, our listeners overestimated the talker’s age when he was younger and underestimated it when he was older. However, the crossover between overestimation and underestimation, the point where estimated and chronological ages were equal, occurred at a later talker age for this longitudinal study than in previous cross-sectional studies. Additionally, listeners who recognized the talker made more accurate age estimates when the talker’s chronological age was near the age where they would have known him. We propose future studies explore the relationship between familiarity and estimated age.

High or low? Comparing high and low-variability phonetic training in adult and child second language learners.

BackgroundHigh talker variability (i.e., multiple voices in the input) has been found effective in training nonnative phonetic contrasts in adults. A small number of studies suggest that children also benefit from high-variability phonetic training with some evidence that they show greater learning (more plasticity) than adults given matched input, although results are mixed. However, no study has directly compared the effectiveness of high versus low talker variability in children.MethodsNative Greek-speaking eight-year-olds (N = 52), and adults (N = 41) were exposed to the English /i/-/ɪ/ contrast in 10 training sessions through a computerized word-learning game. Pre- and post-training tests examined discrimination of the contrast as well as lexical learning. Participants were randomly assigned to high (four talkers) or low (one talker) variability training conditions.ResultsBoth age groups improved during training, and both improved more while trained with a single talker. Results of a three-interval oddity discrimination test did not show the predicted benefit of high-variability training in either age group. Instead, children showed an effect in the reverse direction—i.e., reliably greater improvements in discrimination following single talker training, even for untrained generalization items, although the result is qualified by (accidental) differences between participant groups at pre-test. Adults showed a numeric advantage for high-variability but were inconsistent with respect to voice and word novelty. In addition, no effect of variability was found for lexical learning. There was no evidence of greater plasticity for phonetic learning in child learners.DiscussionThis paper adds to the handful of studies demonstrating that, like adults, child learners can improve their discrimination of a phonetic contrast via computerized training. There was no evidence of a benefit of training with multiple talkers, either for discrimination or word learning. The results also do not support the findings of greater plasticity in child learners found in a previous paper (Giannakopoulou, Uther & Ylinen, 2013a). We discuss these results in terms of various differences between training and test tasks used in the current work compared with previous literature.

Impact of stimulus-related factors and hearing impairment on listening effort as indicated by pupil dilation

Previous research has reported effects of masker type and signal-to-noise ratio (SNR) on listening effort, as indicated by the peak pupil dilation (PPD) relative to baseline during speech recognition. At about 50% correct sentence recognition performance, increasing SNRs generally results in declining PPDs, indicating reduced effort. However, the decline in PPD over SNRs has been observed to be less pronounced for hearing-impaired (HI) compared to normal-hearing (NH) listeners. The presence of a competing talker during speech recognition generally resulted in larger PPDs as compared to the presence of a fluctuating or stationary background noise. The aim of the present study was to examine the interplay between hearing-status, a broad range of SNRs corresponding to sentence recognition performance varying from 0 to 100% correct, and different masker types (stationary noise and single-talker masker) on the PPD during speech perception. Twenty-five HI and 32 age-matched NH participants listened to sentences across a broad range of SNRs, masked with speech from a single talker (−25 dB to +15 dB SNR) or with stationary noise (−12 dB to +16 dB). Correct sentence recognition scores and pupil responses were recorded during stimulus presentation. With a stationary masker, NH listeners show maximum PPD across a relatively narrow range of low SNRs, while HI listeners show relatively large PPD across a wide range of ecological SNRs. With the single-talker masker, maximum PPD was observed in the mid-range of SNRs around 50% correct sentence recognition performance, while smaller PPDs were observed at lower and higher SNRs. Mixed-model ANOVAs revealed significant interactions between hearing-status and SNR on the PPD for both masker types. Our data show a different pattern of PPDs across SNRs between groups, which indicates that listening and the allocation of effort during listening in daily life environments may be different for NH and HI listeners.

Auditory distraction in open-plan office environments: The effect of multi-talker acoustics

Within the soundscapes of open-plan offices, irrelevant speech has consistently been reported as the most distracting, and causing performance decrements for workers. Notwithstanding this generalization, the ‘babble’ created by multiple simultaneously active talkers can sometimes provide beneficial sound masking, but due to spatial release from masking (SRM), speech may still be sufficiently intelligible up to a certain number of talkers (estimated to be about four). This was explored within a highly-realistic office simulation, where the cognitive performance, and subjective distraction of participants were tested. The experimental design was a 4×2 factorial (4 talker numbers, 2 levels of broadband sound masking, as the factors). The results indicated that within lower sound pressure level (SPL) of broadband sound masking, multi-talker sound environments degraded cognitive tasks performance more than those with a single talker, suggesting SRM effects. For higher SPL broadband sound masking, the cognitive test scores were similar within the different talker numbers. The subjective distraction increased monotonically with the number of talkers, with higher distraction within lower SPL broadband sound masking. Overall, the results call into question the single talker assumption (being the most distracting) within the international standard for measuring open-plan office acoustic environments (ISO 3382-3:2012). Soundscapes with 4 simultaneous talkers were still not adequately providing beneficial ‘babble’ masking, and were more distracting than 1 active talker. In conclusion, it is suggested that the acoustics environment of open-plan offices needs better characterization by incorporating some of the complexity and psychoacoustics of multi-talker scenarios.

The Distribution of Talker Variability Impacts Infants' Word Learning.

Infants struggle to apply earlier-demonstrated sound-discrimination abilities to later word learning, attending to non-constrastive acoustic dimensions (e.g., Hay et al., 2015), and not always to contrastive dimensions (e.g., Stager & Werker, 1997). One hint about the nature of infants' difficulties comes from the observation that input from multiple talkers can improve word learning (Rost & McMurray, 2009). This may be because, when a single talker says both of the to-be-learned words, consistent talker's-voice characteristics make the acoustics of the two words more overlapping (Apfelbaum & McMurray, 2011). Here, we test that notion. We taught 14-month-old infants two similar-sounding words in the Switch habituation paradigm. The same amount of overall talker variability was present as in prior multiple-talker experiments, but male and female talkers said different words, creating a gender-word correlation. Under an acoustic-similarity account, correlated talker gender should help to separate words acoustically and facilitate learning. Instead, we found that correlated talker gender impaired learning of word-object pairings compared with uncorrelated talker gender-even when gender-word pairings were always maintained in test-casting doubt on one account of the beneficial effects of talker variability. We discuss several alternate potential explanations for this effect.

Better-ear glimpsing with symmetrically-placed interferers in bilateral cochlear implant users

For a frontal speaker in spatially symmetrically placed maskers, normal hearing (NH) listeners can use an optimal “better-ear glimpsing” strategy selecting time-frequency segments with favorable signal-to-noise ratio in either ear. It was shown that for a monaural signal, obtained by an ideal monaural better-ear mask (IMBM), NH listeners can reach similar performance as in the binaural condition, but interaural phase differences at low frequencies can further improve performance. In principle, bilateral cochlear implant (BiCI) users could use a glimpsing strategy; however, they cannot exploit (temporal fine structure) interaural phase differences. Here, speech reception thresholds of NH and BiCI listeners were measured in two symmetric maskers (±60°; speech-shaped stationaty noise, non-sense speech, single talker) using head-related transfer functions and headphone presentation or direct stimulation in BiCI listeners. Furthermore, a statistically independent masker in each ear, diotic presentation with IMBM processing, and a noise vocoder based on the BiCI electrodogram was used in NH. Results indicate that NH with vocoder and BiCI listeners show a strongly reduced binaural benefit in the ±60° condition relative to the co-located condition when compared to NH. However, both groups greatly benefit from IMBM processing (as part of the CI stimulation strategy). Individual differences are compared.

Task- and Talker-Specific Gains in Auditory Training.

This investigation focused on generalization of outcomes for auditory training by examining the effects of task and/or talker overlap between training and at test. Adults with hearing loss completed 12 hr of meaning-oriented auditory training and were placed in a group that trained on either multiple talkers or a single talker. A control group also completed 12 hr of training in American Sign Language. The experimental group's training included a 4-choice discrimination task but not an open-set sentence test. The assessment phase included the same 4-choice discrimination task and an open-set sentence test, the Iowa Sentences Test (Tyler, Preece, & Tye-Murray, 1986). Improvement on 4-choice discrimination was observed in the experimental group as compared with the control group. Gains were (a) highest when the task and talker were the same between training and assessment; (b) second highest when the task was the same but the talker only partially so; and (c) third highest when task and talker were different. The findings support applications of transfer-appropriate processing to auditory training and favor tailoring programs toward the specific needs of the individuals being trained for tasks, talkers, and perhaps, for stimuli, in addition to other factors.