Current State of Knowledge: Perceptual Processing by Children with Hearing Impairment

Emotional prosodic expression of children with hearing aids or cochlear implants, rated by adults and peers

OBJECTIVE

The emotional prosodic expression potential of children with cochlear implants is poorer than that of normal hearing peers. Though little is known about children with hearing aids.

DESIGN

This study was set up to generate a better understanding of hearing aid users' prosodic identifiability compared to cochlear implant users and peers without hearing loss.

STUDY SAMPLE

Emotional utterances of 75 Dutch speaking children (7 - 12 yr; 26 CHA, 23 CCI, 26 CNH) were gathered. Utterances were evaluated blindly by normal hearing Dutch listeners: 22 children and 9 adults (17 - 24 yrs) for resemblance to three emotions (happiness, sadness, anger).

RESULTS

Emotions were more accurately recognised by adults than by children. Both children and adults correctly judged happiness significantly less often in CCI than in CNH. Also, adult listeners confused happiness with sadness more often in both CHA and CCI than in CNH.

CONCLUSIONS

Children and adults are able to accurately evaluate the emotions expressed through speech by children with varying degrees of hearing loss, ranging from mild to profound, nearly as well as they can with typically hearing children. The favourable outcomes emphasise the resilience of children with hearing loss in developing effective emotional communication skills.

Self-concept of children and adolescents with cochlear implants

OBJECTIVES

Communicative disorders can complicate social interactions and may be detrimental for one's self-concept. This study aims to assess the self-concept of children with Cochlear Implants (CI). Results of educational peer groups (special needs or typical) were compared. Correlations amongst speech perception, language comprehension, self-concept and other study variables are determined.

METHODS

This retrospectively patient file study contained 53 CI participants with a mean age of 14.2 (SD = 2.8). Self-concept was measured with the Dutch language version of the Self-Perception Profile for Children and Adolescents. Proportions of low, normal and high competence scores were compared to a normative sample. Outcomes were analyzed for the total CI group and for the two educational peer groups.

RESULTS

In the Scholastic Competence, Athletic Competence, Physical Appearance and Behavioral Conduct domains larger proportions of high perceived competence levels were found in the CI Total group compared to the hearing normative sample. Children with CIs in the Mainstream educational subgroup were found to have larger proportions of high levels on these domains. Remarkably, children with CI in the Special hearing impaired educational subgroup reported comparable self-concept scores as their hearing peers. Speech perception and language comprehension were positively correlated to Scholastic Competence.

CONCLUSION

This study has shown that self-concept levels of profoundly hearing impaired children with CI are comparable to those of hearing peers. They are generally satisfied with their functioning in various domains. Better speech perception and language comprehension levels are related to higher outcomes in the Scholastic Competence domain.

Voice Emotion Recognition by Children With Mild-to-Moderate Hearing Loss

OBJECTIVES

Emotional communication is important in children's social development. Previous studies have shown deficits in voice emotion recognition by children with moderate-to-severe hearing loss or with cochlear implants. Little, however, is known about emotion recognition in children with mild-to-moderate hearing loss. The objective of this study was to compare voice emotion recognition by children with mild-to-moderate hearing loss relative to their peers with normal hearing, under conditions in which the emotional prosody was either more or less exaggerated (child-directed or adult-directed speech, respectively). We hypothesized that the performance of children with mild-to-moderate hearing loss would be comparable to their normally hearing peers when tested with child-directed materials but would show significant deficits in emotion recognition when tested with adult-directed materials, which have reduced prosodic cues.

DESIGN

Nineteen school-aged children (8 to 14 years of age) with mild-to-moderate hearing loss and 20 children with normal hearing aged 6 to 17 years participated in the study. A group of 11 young, normally hearing adults was also tested. Stimuli comprised sentences spoken in one of five emotions (angry, happy, sad, neutral, and scared), either in a child-directed or in an adult-directed manner. The task was a single-interval, five-alternative forced-choice paradigm, in which the participants heard each sentence in turn and indicated which of the five emotions was associated with that sentence. Reaction time was also recorded as a measure of cognitive load.

RESULTS

Acoustic analyses confirmed the exaggerated prosodic cues in the child-directed materials relative to the adult-directed materials. Results showed significant effects of age, specific emotion (happy, sad, etc.), and test materials (better performance with child-directed materials) in both groups of children, as well as susceptibility to talker variability. Contrary to our hypothesis, no significant differences were observed between the 2 groups of children in either emotion recognition (percent correct or d' values) or in reaction time, with either child- or adult-directed materials. Among children with hearing loss, degree of hearing loss (mild or moderate) did not predict performance. In children with hearing loss, interactions between vocabulary, materials, and age were observed, such that older children with stronger vocabulary showed better performance with child-directed speech. Such interactions were not observed in children with normal hearing. The pattern of results was broadly consistent across the different measures of accuracy, d', and reaction time.

CONCLUSIONS

Children with mild-to-moderate hearing loss do not have significant deficits in overall voice emotion recognition compared with their normally hearing peers, but mechanisms involved may be different between the 2 groups. The results suggest a stronger role for linguistic ability in emotion recognition by children with normal hearing than by children with hearing loss.

Impaired frequency selectivity and sensitivity to temporal fine structure, but not envelope cues, in children with mild-to-moderate sensorineural hearing loss

Psychophysical thresholds were measured for 8-16 year-old children with mild-to-moderate sensorineural hearing loss (MMHL; N = 46) on a battery of auditory processing tasks that included measures designed to be dependent upon frequency selectivity and sensitivity to temporal fine structure (TFS) or envelope cues. Children with MMHL who wore hearing aids were tested in both unaided and aided conditions, and all were compared to a group of normally hearing (NH) age-matched controls. Children with MMHL performed more poorly than NH controls on tasks considered to be dependent upon frequency selectivity, sensitivity to TFS, and speech discrimination (/bɑ/-/dɑ/), but not on tasks measuring sensitivity to envelope cues. Auditory processing deficits remained regardless of age, were observed in both unaided and aided conditions, and could not be attributed to differences in nonverbal IQ or attention between groups. However, better auditory processing in children with MMHL was predicted by better audiometric thresholds and, for aided tasks only, higher levels of maternal education. These results suggest that, as for adults with MMHL, children with MMHL may show deficits in frequency selectivity and sensitivity to TFS, but sensitivity to the envelope may remain intact.

Time-Gated Word Recognition in Children: Effects of Auditory Access, Age, and Semantic Context

Purpose We employed a time-gated word recognition task to investigate how children who are hard of hearing (CHH) and children with normal hearing (CNH) combine cognitive-linguistic abilities and acoustic-phonetic cues to recognize words in sentence-final position. Method The current study included 40 CHH and 30 CNH in 1st or 3rd grade. Participants completed vocabulary and working memory tests and a time-gated word recognition task consisting of 14 high- and 14 low-predictability sentences. A time-to-event model was used to evaluate the effect of the independent variables (age, hearing status, predictability) on word recognition. Mediation models were used to examine the associations between the independent variables (vocabulary size and working memory), aided audibility, and word recognition. Results Gated words were identified significantly earlier for high-predictability than low-predictability sentences. First-grade CHH and CNH showed no significant difference in performance. Third-grade CHH needed more information than CNH to identify final words. Aided audibility was associated with word recognition. This association was fully mediated by vocabulary size but not working memory. Conclusions Both CHH and CNH benefited from the addition of semantic context. Interventions that focus on consistent aided audibility and vocabulary may enhance children's ability to fill in gaps in incoming messages.

Speech perception in children with cochlear implants for continua varying in formant transition duration

PURPOSE

To examine the developmental course of labial and alveolar manner of articulation contrasts, and to determine how that course may be different for typically developing (TD) children with cochlear implants (CI).

METHOD

Eight young adults, eight TD 5-8 year-old children, and seven 5-8 year-old children with CIs participated. Labial /ba/-/wa/ and alveolar /da/-/ja/ continua stimuli were presented, with each continuum consisting of nine synthetic stimuli varying in F2 and F3 transition duration. Participants were asked to label the stimuli as either a stop or glide, and responses were analysed for phonetic boundaries and slopes.

RESULT

For the /ba/-/wa/ contrast, children with CIs required longer transition durations compared to TD children or adults to cross from one phoneme category to another. The children with CIs demonstrated less confidence in labelling the stimuli (i.e. less steep slopes) than the TD children or the adults. For the /da/-/ja/ contrast, the children with CIs showed less steep slope values than adults.

CONCLUSION

These results suggest that there are differences in the way TD children and children with CIs develop and maintain phonetic categories, perhaps differences in phonetic representation or in linking acoustic and phonetic representations.

Benefits of simultaneous bilateral cochlear implantation on verbal reasoning skills in prelingually deaf children

BACKGROUND

Impaired auditory speech perception abilities in deaf children with hearing aids compromised their verbal intelligence enormously. The availability of unilateral cochlear implantation (CI) auditory speech perception and spoken vocabulary enabled them to reach near ageappropriate levels. This holds especially for children in spoken language environments. However, speech perception in complex listening situations and the acquisition of complex verbal skills remains difficult. Bilateral CI was expected to enhance the acquisition of verbal intelligence by improved understanding of speech in noise.

METHODS

This study examined the effect of bilateral CI on verbal intelligence of 49 deaf children (3;5-8;0 years). Relations between speech perception in noise, auditory short-term memory and verbal intelligence were analysed with multiple linear regressions. In addition, the interaction of educational setting, mainstream or special, on these relations was analysed.

RESULTS

Children with bilateral CI obtained higher scores on verbal intelligence. Significant associations were present between speech perception in noise, auditory short-term memory and verbal intelligence.

CONCLUSION

Children with simultaneous bilateral CIs showed better speech perception in noise than children with unilateral CIs, which mediated by the auditory short-term memory capacity, enhanced the ability to acquire more complex verbal skills for BICI children in mainstream education.

Speech Recognition and Parent Ratings From Auditory Development Questionnaires in Children Who Are Hard of Hearing

OBJECTIVES

Progress has been made in recent years in the provision of amplification and early intervention for children who are hard of hearing. However, children who use hearing aids (HAs) may have inconsistent access to their auditory environment due to limitations in speech audibility through their HAs or limited HA use. The effects of variability in children's auditory experience on parent-reported auditory skills questionnaires and on speech recognition in quiet and in noise were examined for a large group of children who were followed as part of the Outcomes of Children with Hearing Loss study.

DESIGN

Parent ratings on auditory development questionnaires and children's speech recognition were assessed for 306 children who are hard of hearing. Children ranged in age from 12 months to 9 years. Three questionnaires involving parent ratings of auditory skill development and behavior were used, including the LittlEARS Auditory Questionnaire, Parents Evaluation of Oral/Aural Performance in Children rating scale, and an adaptation of the Speech, Spatial, and Qualities of Hearing scale. Speech recognition in quiet was assessed using the Open- and Closed-Set Test, Early Speech Perception test, Lexical Neighborhood Test, and Phonetically Balanced Kindergarten word lists. Speech recognition in noise was assessed using the Computer-Assisted Speech Perception Assessment. Children who are hard of hearing were compared with peers with normal hearing matched for age, maternal educational level, and nonverbal intelligence. The effects of aided audibility, HA use, and language ability on parent responses to auditory development questionnaires and on children's speech recognition were also examined.

RESULTS

Children who are hard of hearing had poorer performance than peers with normal hearing on parent ratings of auditory skills and had poorer speech recognition. Significant individual variability among children who are hard of hearing was observed. Children with greater aided audibility through their HAs, more hours of HA use, and better language abilities generally had higher parent ratings of auditory skills and better speech-recognition abilities in quiet and in noise than peers with less audibility, more limited HA use, or poorer language abilities. In addition to the auditory and language factors that were predictive for speech recognition in quiet, phonological working memory was also a positive predictor for word recognition abilities in noise.

CONCLUSIONS

Children who are hard of hearing continue to experience delays in auditory skill development and speech-recognition abilities compared with peers with normal hearing. However, significant improvements in these domains have occurred in comparison to similar data reported before the adoption of universal newborn hearing screening and early intervention programs for children who are hard of hearing. Increasing the audibility of speech has a direct positive effect on auditory skill development and speech-recognition abilities and also may enhance these skills by improving language abilities in children who are hard of hearing. Greater number of hours of HA use also had a significant positive impact on parent ratings of auditory skills and children's speech recognition.

Consonant discrimination by Mandarin-speaking children with prelingual hearing impairment

OBJECTIVES

Little is known about the consonant discrimination ability of Mandarin-speaking children with prelingual hearing impairment (HI) and fitted with hearing aids (HAs). The present study aimed to evaluate Mandarin consonant discrimination ability in children with HI, and explore the effects of unaided and aided hearing threshold, the age of first HA fitting and the duration of HA use on consonant discrimination ability.

METHODS

Subjects were Mandarin-speaking children aged 5;4-12;6 years with profound HI (n=41), children aged 6;1-12;4 years with severe HI (n=26), and children aged 5;0-11;9 years with moderate HI (n=9). The Mandarin Consonant Discrimination Test was administered in six test conditions: -10, -5, 0, 5 and 10dB signal to noise ratios (S/Ns) and quiet. HAs were in the usual user's settings, adjusted to match the manufacturer prescribed settings and individual preferences, and the volume was set to comfortable listening level.

RESULTS

The results revealed that /p(h)/-/t(h)/, /ts/-/tʂ/ and /ʐ/-/l/ were the most difficult and /p/-/p(h)/, /t/-/t(h)/, /tɕ/-/tɕ(h)/ and /k/-/k(h)/ were the easiest consonant minimal pairs to discriminate in quiet both for children with profound HI and those with moderate to severe HI. In noise, no significant difference in performance was found among all consonant minimal pairs. A backward elimination stepwise multiple linear regressions revealed that unaided hearing level accounted for 25.4% of the variance in consonant discrimination performance in noise at 10dB S/N and 30.4% in quiet. However, aided hearing threshold, the age of first HA fitting and the duration of HA use did not significantly predict consonant discrimination ability both in quiet and in noise.

CONCLUSIONS

Consonant discrimination performance of children with profound HI was poorer than those with moderate to severe HI. The ability to discriminate consonant pairs seems to depend on age of acquisition of the consonants. Although the age of first HA fitting and the duration of HA use were not correlated with consonant discrimination outcomes, this finding does not preclude the importance of early HA fitting.

Listening effort and perceived clarity for normal-hearing children with the use of digital noise reduction

OBJECTIVES

The goal of this study was to evaluate how digital noise reduction (DNR) impacts listening effort and judgment of sound clarity in children with normal hearing. It was hypothesized that when two DNR algorithms differing in signal-to-noise ratio (SNR) output are compared, the algorithm that provides the greatest improvement in overall output SNR will reduce listening effort and receive a better clarity rating from child listeners. A secondary goal was to evaluate the relation between the inversion method measurements and listening effort with DNR processing.

DESIGN

Twenty-four children with normal hearing (ages 7 to 12 years) participated in a speech recognition task in which consonant-vowel-consonant nonwords were presented in broadband background noise. Test stimuli were recorded through two hearing aids with DNR off and DNR on at 0 dB and +5 dB input SNR. Stimuli were presented to listeners and verbal response time (VRT) and phoneme recognition scores were measured. The underlying assumption was that an increase in VRT reflects an increase in listening effort. Children rated the sound clarity for each condition. The two commercially available HAs were chosen based on: (1) an inversion technique, which was used to quantify the magnitude of change in SNR with the activation of DNR, and (2) a measure of magnitude-squared coherence, which was used to ensure that DNR in both devices preserved the spectrum.

RESULTS

One device provided a greater improvement in overall output SNR than the other. Both DNR algorithms resulted in minimal spectral distortion as measured using coherence. For both devices, VRT decreased for the DNR-on condition, suggesting that listening effort decreased with DNR in both devices. Clarity ratings were also better in the DNR-on condition for both devices. The device showing the greatest improvement in output SNR with DNR engaged improved phoneme recognition scores. The magnitude of this improved phoneme recognition was not accurately predicted with measurements of output SNR. Measured output SNR varied in the ability to predict other outcomes.

CONCLUSIONS

Overall, results suggest that DNR effectively reduces listening effort and improves subjective clarity ratings in children with normal hearing but that these improvements are not necessarily related to the output SNR improvements or preserved speech spectra provided by the DNR.

The effects of limited bandwidth and noise on verbal processing time and word recall in normal-hearing children

OBJECTIVES

Understanding speech in acoustically degraded environments can place significant cognitive demands on school-age children who are developing the cognitive and linguistic skills needed to support this process. Previous studies suggest the speech understanding, word learning, and academic performance can be negatively impacted by background noise, but the effect of limited audibility on cognitive processes in children has not been directly studied. The aim of the present study was to evaluate the impact of limited audibility on speech understanding and working memory tasks in school-age children with normal hearing.

DESIGN

Seventeen children with normal hearing between 6 and 12 years of age participated in the present study. Repetition of nonword consonant-vowel-consonant stimuli was measured under conditions with combinations of two different signal to noise ratios (SNRs; 3 and 9 dB) and two low-pass filter settings (3.2 and 5.6 kHz). Verbal processing time was calculated based on the time from the onset of the stimulus to the onset of the child's response. Monosyllabic word repetition and recall were also measured in conditions with a full bandwidth and 5.6 kHz low-pass cutoff.

RESULTS

Nonword repetition scores decreased as audibility decreased. Verbal processing time increased as audibility decreased, consistent with predictions based on increased listening effort. Although monosyllabic word repetition did not vary between the full bandwidth and 5.6 kHz low-pass filter condition, recall was significantly poorer in the condition with limited bandwidth (low pass at 5.6 kHz). Age and expressive language scores predicted performance on word recall tasks, but did not predict nonword repetition accuracy or verbal processing time.

CONCLUSIONS

Decreased audibility was associated with reduced accuracy for nonword repetition and increased verbal processing time in children with normal hearing. Deficits in free recall were observed even under conditions where word repetition was not affected. The negative effects of reduced audibility may occur even under conditions where speech repetition is not impacted. Limited stimulus audibility may result in greater cognitive effort for verbal rehearsal in working memory and may limit the availability of cognitive resources to allocate to working memory and other processes.

Perceptual development of nasal consonants in children with normal hearing and in children who use cochlear implants

PURPOSE

This study was conducted to determine whether the perceptions of nasal consonants in children with normal hearing and children with cochlear implants were predicted by the discontinuity hypothesis. Methods Four groups participated: 8 adults, 8 children with normal hearing (ages 5-7 years), 8 children with normal hearing (ages 3.5-4 years), and 5 children with cochlear implants (ages 5-7 years). Stimuli were 128 nasal consonant + vowel (/m/ /n/ + /i/ /æ/ /u/ //) syllables produced by a male adult. Each syllable production was edited into 4 segment types: (a) 50-ms murmur, (b) 25-ms murmur + 25-ms transition, (c) 50-ms transition, and (d) full syllable.

RESULTS

Developmental effects were observed across listener groups. The children performed better in the 25-ms murmur + 25-ms transition condition, which suggests that they benefit from an integrated perceptual cue. The children wearing cochlear implants performed poorer than children with normal hearing on all segments.

CONCLUSIONS

Developmental differences in perception of nasal consonants were evident. Children wearing cochlear implants showed weaker integration and perception abilities compared to younger children with normal hearing. As predicted by the discontinuity hypothesis, the segment with the spectral discontinuity provided the strongest perceptual cues to place of articulation of nasals in children with normal hearing.

Auditory training of speech recognition with interrupted and continuous noise maskers by children with hearing impairment

Previous studies have indicated that individuals with normal hearing (NH) experience a perceptual advantage for speech recognition in interrupted noise compared to continuous noise. In contrast, adults with hearing impairment (HI) and younger children with NH receive a minimal benefit. The objective of this investigation was to assess whether auditory training in interrupted noise would improve speech recognition in noise for children with HI and perhaps enhance their utilization of glimpsing skills. A partially-repeated measures design was used to evaluate the effectiveness of seven 1-h sessions of auditory training in interrupted and continuous noise. Speech recognition scores in interrupted and continuous noise were obtained from pre-, post-, and 3 months post-training from 24 children with moderate-to-severe hearing loss. Children who participated in auditory training in interrupted noise demonstrated a significantly greater improvement in speech recognition compared to those who trained in continuous noise. Those who trained in interrupted noise demonstrated similar improvements in both noise conditions while those who trained in continuous noise only showed modest improvements in the interrupted noise condition. This study presents direct evidence that auditory training in interrupted noise can be beneficial in improving speech recognition in noise for children with HI.

Use of acoustic cues by children with cochlear implants

PURPOSE

This study examined the use of different acoustic cues in auditory perception of consonant and vowel contrasts by profoundly deaf children with a cochlear implant (CI) in comparison to age-matched children and young adults with normal hearing.

METHOD

A speech sound categorization task in an XAB format was administered to 15 children ages 5-6 with a CI (mean age at implant: 1;8 [years;months]), 20 normal-hearing age-matched children, and 21 normal-hearing adults. Four contrasts were examined: //-/a/, /i/-/i/, /bu/-/pu/, and /fu/-/su/. Measures included phoneme endpoint identification, individual cue reliance, cue weighting, and classification slope.

RESULTS

The children with a CI used the spectral cues in the /fu/-/su/ contrast less effectively than the children with normal hearing, resulting in poorer phoneme endpoint identification and a shallower classification slope. Performance on the other 3 contrasts did not differ significantly. Adults consistently showed steeper classification slopes than the children, but similar cue-weighting patterns were observed in all 3 groups.

CONCLUSIONS

Despite their different auditory input, children with a CI appear to be able to use many acoustic cues effectively in speech perception. Most importantly, children with a CI and normal-hearing children were observed to use similar cue-weighting patterns.

Murine malaria is associated with significant hearing impairment

BACKGROUND

Plasmodium falciparum malaria has been suspected to cause hearing loss. Developmental, cognitive and language disorders have been observed in children, surviving cerebral malaria. This prospective study aims to evaluate whether malaria influences hearing in mice.

METHODS

Twenty mice were included in a standardized murine cerebral malaria model. Auditory evoked brainstem responses were assessed before infection and at the peak of the illness.

RESULTS

A significant hearing impairment could be demonstrated in mice with malaria, especially the cerebral form. The control group did not show any alterations. No therapy was used.

CONCLUSION

This suggests that malaria itself leads to a hearing impairment in mice.

Immediate and long-term effects of hearing loss on the speech perception of children

The purpose of the present study was to examine the immediate and long-term effects of hearing loss on the speech perception of children. Hearing loss was simulated in normally-hearing children and their performance was compared to that of children with hearing loss (long-term effects) as well as to their own performance in quiet (immediate effects). Eleven children with normal hearing (7-10 years) were matched to five children with mild to moderate sensorineural hearing loss (8-10 years). Frequency-shaped broadband noise was used to elevate the hearing thresholds of the children with normal hearing to those of their matched hearing-impaired peer. Meaningful and nonsense sentences were presented at five levels and quantified using an audibility index (AI). Comparison of the AI functions calculated for each group and listening condition revealed a significant, immediate effect of elevated hearing thresholds in the children with normal hearing but no long-term effects of hearing loss. The results of this study suggest that hearing loss affects speech perception adversely and that amplification does not fully compensate for those effects. However, the data suggest that over the long term children may develop compensatory strategies to reduce the effects of hearing loss.

Role of visual speech in phonological processing by children with hearing loss

PURPOSE

This research assessed the influence of visual speech on phonological processing by children with hearing loss (HL).

METHOD

Children with HL and children with normal hearing (NH) named pictures while attempting to ignore auditory or audiovisual speech distractors whose onsets relative to the pictures were either congruent, conflicting in place of articulation, or conflicting in voicing-for example, the picture "pizza" coupled with the distractors "peach," "teacher," or "beast," respectively. Speed of picture naming was measured.

RESULTS

The conflicting conditions slowed naming, and phonological processing by children with HL displayed the age-related shift in sensitivity to visual speech seen in children with NH, although with developmental delay. Younger children with HL exhibited a disproportionately large influence of visual speech and a negligible influence of auditory speech, whereas older children with HL showed a robust influence of auditory speech with no benefit to performance from adding visual speech. The congruent conditions did not speed naming in children with HL, nor did the addition of visual speech influence performance. Unexpectedly, the /wedge/-vowel congruent distractors slowed naming in children with HL and decreased articulatory proficiency.

CONCLUSIONS

Results for the conflicting conditions are consistent with the hypothesis that speech representations in children with HL (a) are initially disproportionally structured in terms of visual speech and (b) become better specified with age in terms of auditorily encoded information.

Use of auditory learning to manage listening problems in children

This paper reviews recent studies that have used adaptive auditory training to address communication problems experienced by some children in their everyday life. It considers the auditory contribution to developmental listening and language problems and the underlying principles of auditory learning that may drive further refinement of auditory learning applications. Following strong claims that language and listening skills in children could be improved by auditory learning, researchers have debated what aspect of training contributed to the improvement and even whether the claimed improvements reflect primarily a retest effect on the skill measures. Key to understanding this research have been more circumscribed studies of the transfer of learning and the use of multiple control groups to examine auditory and non-auditory contributions to the learning. Significant auditory learning can occur during relatively brief periods of training. As children mature, their ability to train improves, but the relation between the duration of training, amount of learning and benefit remains unclear. Individual differences in initial performance and amount of subsequent learning advocate tailoring training to individual learners. The mechanisms of learning remain obscure, especially in children, but it appears that the development of cognitive skills is of at least equal importance to the refinement of sensory processing. Promotion of retention and transfer of learning are major goals for further research.