Different time courses of maturation for learning and generalization following auditory training in children.

OBJECTIVE: We recently demonstrated that learning abilities among school-age children vary following frequency discrimination (FD) training, with some exhibiting mature adult-like learning while others performing poorly (non-adult-like learners). This study tested the hypothesis that children's post-training generalisation is related to their learning maturity. Additionally, it investigated how training duration influences children's generalisation, considering the observed decrease with increased training in adults. DESIGN: Generalisation to the untrained ear and untrained 2000 Hz frequency was assessed following single-session or nine-session 1000 Hz FD training, using an adaptive forced-choice procedure. Two additional groups served as controls for the untrained frequency. STUDY SAMPLE: Fifty-four children aged 7-9 years and 59 adults aged 18-30 years. RESULTS: (1) Only adult-like learners generalised their learning gains across frequency or ear, albeit less efficiently than adults; (2) As training duration increased children experienced reduced generalisation, similar to adults; (3) Children's performance in the untrained tasks correlated strongly with their trained task performance after the first training session. CONCLUSIONS: Auditory skill learning and its generalisation do not necessarily mature contemporaneously, although mature learning is a prerequisite for mature generalisation. Furthermore, in children, as in adults, more practice makes rather specific experts. These findings should be considered when designing training programs.

Long-Term Training-Induced Gains of an Auditory Skill in School-Age Children As Compared With Adults.

The few studies that compared auditory skill learning between children and adults found variable results, with only some children reaching adult-like thresholds following training. The present study aimed to assess auditory skill learning in children as compared with adults during single- and multisession training. It was of interest to ascertain whether children who do not reach adult-like performance following a single training session simply require additional training, or whether different mechanisms underlying skill learning need to reach maturity in order to become adult-like performers. Forty children (7-9 years) and 45 young adults (18-35 years) trained in a single session. Of them, 20 children and 24 adults continued training for eight additional sessions. Each session included six frequency discrimination thresholds at 1000 Hz using adaptive forced-choice procedure. Retention of the learning-gains was tested 6 to 8 months posttraining. Results showed that (a) over half of the children presented similar performance and time course of learning as the adults. These children had better nonverbal reasoning and working memory abilities than their non-adult-like peers. (b) The best predicting factor for the outcomes of multisession training was a child's performance following one training session. (c) Performance gains were retained for all children with the non-adult-like children further improving, 6 to 8 months posttraining. Results suggest that mature auditory skill learning can emerge before puberty, provided that task-related cognitive mechanisms and task-specific sensory processing are already mature. Short-term training is sufficient, however, to reflect the maturity of these mechanisms, allowing the prediction of the efficiency of a prolonged training for a given child.

Auditory backward masking and the effect of training in normal hearing adults.

Recent renewed interest in auditory backward masking has stemmed from studies of children with language impairments who were found to have significant, elevated thresholds for this paradigm, compared to normal cohorts. There are, however, many unresolved theoretical and procedural issues. The present study was conducted to investigate some of these issues. Specific purposes were: 1) To establish the differences between backward masking and simultaneous masking in normal hearing subjects; 2) To investigate the effect of listening conditions, i.e., monaural versus binaural; 3) To measure the effect of training on the performance of a backward masking paradigm; and 4) To measure generalization of the trained condition to untrained conditions. Two experiments were conducted: In experiment I, we compared the performance of 10 normal-hearing adult subjects for backward masking and simultaneous masking paradigms in both monaural and binaural modes of presentation. Stimuli consisted of a 1000 Hz pure-tone and bandpass masker (600-1400 Hz). Tone thresholds for backward masking were significantly lower than those of the simultaneous masking. The binaural mode of presentation yielded lower thresholds than those of the monaural mode only for the backward masking condition. A significantly large inter- and intra-subject variability was observed in the backward masking paradigm. Experiment II was conducted to measure the effects of training and generalization. Two groups of subjects were included: a trained group and a control group of six and eight normal hearing adults, respectively. The trained group received 10 sessions of backward masking training with feedback. The control group was tested only twice, with a 2-week interval between testing. Only the trained group showed a significant improvement in backward masking thresholds, which amounted to an average of 10.7 dB. No significant improvement was observed in the non-trained group. A nonsignificant trend of generalization occurred for the trained task to the untrained ear. No generalization was evident in the untrained condition (simultaneous masking). The data have important clinical and theoretical implications regarding the ability to train for auditory tasks in general, and for backward masking in particular.

Pitch discrimination: are professional musicians better than non-musicians?

Musicians are typically considered to exhibit exceptional auditory skills. Only few studies, however, have substantiated this in basic psychoacoustic tasks. The purpose of the present investigation was to expand our knowledge on basic auditory abilities of musicians compared to non-musicians. Specific goals were: (1) to compare frequency discrimination thresholds (difference limen for frequency [DLF]) of non-musical pure tones in controlled groups of professional musicians and non-musicians; (2) to relate DLF performance to musical background; and (3) to compare DLF thresholds obtained with two threshold estimation procedures: 2- and 3- interval forced choice procedures (2IFC and 3IFC). Subjects were 16 professional musicians and 14 non-musicians. DLFs were obtained for three frequencies (0.25, 1 and 1.5 kHz) using the 3IFC adaptive procedure, and for one frequency (1 kHz) also using the 2IFC. Three threshold estimates were obtained for each frequency, procedure and subject. The results of the present study support five major findings: (a) mean DLFs for musicians were approximately half the values of the non-musicians; (b) significant learning for both groups during the three threshold estimations; (c) classical musicians performed better than those with contemporary musical background; (d) performance was influenced by years of musical experience; and (e) both groups showed better DLF in a 2IFC paradigm compared to the 3IFC. These data highlight the importance of short-term training on an auditory task, auditory memory and factors related to musical background (such as musical genre and years of experience) on auditory performance.

Speech perception results--the first 10 years of a cochlear implant program.

Long-term speech perception test results for prelingually deaf children were compared with those of postlingually deafened adults, both groups having undergone cochlear implant at our Center. Average open-set score results of adults were similar to those of the children. However, some qualitative differences were demonstrated on the perception of phonological contrasts between the groups.

A test of the overconfidence phenomenon using audio signals.

The existence of the overconfidence phenomenon was examined using a signal detection paradigm. Fifty-five participants were asked to decide whether they heard a signal or noise only, and to rate how certain they were of their decisions. The results confirmed the existence of overconfidence as well as the "hard-easy" effect.

Speech perception test for Arabic-speaking children.

The high incidence of hearing impairment in the Arabic-speaking population in Israel, as well as the use of advanced aural rehabilitation devices, motivated the development of Arabic speech assessment tests for this population. The purpose of this paper is twofold. The first goal is to describe features that are unique to the Arabic language and that need to be considered when developing such speech tests. These include Arabic diglossia (i.e., the sharp dichotomy between Literary and Colloquial Arabic), emphatization, and a simple vowel system. The second goal is to describe a new analytic speech test that assesses the perception of significant phonological contrasts in the Colloquial Arabic variety used in Israel. The perception of voicing, place, and manner of articulation, in both initial and final word positions, was tested at four sensation levels in 10 normally-hearing subjects using a binary forced-choice paradigm. Results show a relationship between percent correct and presentation level that is in keeping with articulation curves obtained with Saudi Arabic and English monosyllabic words. Furthermore, different contrasts yielded different articulation curves: emphatization was the easiest to perceive whereas place of articulation was the most difficult. The results can be explained by the specific acoustical features of Arabic.

Identification of the relative onset time of a two-tone complex: auditory sensitivity or language based?

Categorical perception occurs when equal physical differences on a continuum sometimes cause no changes in the identification of a stimulus, while at other points on the same continuum, that difference causes an abrupt change in perception. One of the unresolved issues regarding this phenomenon is what determines categorical perception: a special speech mode or "natural" psychophysical boundaries. One way to answer this question is by investigating categorical perception with non-speech stimuli. An example is the identification of the relative onset of a two-tone complex (TOT) analogous to voice-onset time (VOT), the acoustic cue to voicing in initial position. Studies in English found similar category boundaries for TOT and VOT (at +20 ms) supporting the non-speech specific theory. The purpose of this study was to investigate TOT in Hebrew-speaking listeners whose language uses very different VOT values from those reported in English. Twenty Hebrew-speaking young adults participated in this study. Stimuli consisted of a two-tone complex that varied in the relative onset time of the lower tone from a lead of -50 ms to a lag of +50 ms in 10 ms steps. Results show that: (1) All subjects were able to identify the lag conditions from the simultaneous ones but only half of them were also able to identify the lead from the simultaneous ones. This was explained in terms of prominent pitch cues available when shifting from simultaneous to lagging stimuli. (2) Hebrew category boundaries (CBs) for TOT are shorter than those of VOT, and both are shorter than the respective English ones. Nonetheless, all CBs fell into the range of 10 to 30 ms. The data support the hypothesis that "natural" psychophysical boundaries determine categorical perception but behavioral measures may be influenced by speech.

Age-related changes in the visual perception of phonologically significant contrasts.

The purpose of the present study was to determine whether the ability to speechread phonological contrasts is influenced by age. Forty-eight subjects were equally represented in three age groups: 8-9 years, 11-12 years and adults (20-29 years). The Hebrew version of the Speech Pattern Contrast (HeSPAC) test was administered by speechreading alone. Results showed that: age influenced performance; performance was contrast-dependent (place contrasts highly visible, manner and vowel height partially visible and voicing contrast invisible); hierarchy of contrast performance was similar for all age groups; Hebrew and English differ in the visual accessibility to speech contrasts in final voicing only; and females were found to be poorer speechreaders than males for the partially visible contrasts. The results suggest that speechreading at the phonological level follows a developmental course. The implications of these findings extend to recommendations provided to children in noisy listening conditions, speechreading training in hearing-impaired children and those with central auditory processing disorders (CAPD), and to the design of sensory aids.

The effect of partially restored hearing on speech production of postlingually deafened adults with multichannel cochlear implants.

The effect of auditory feedback on speech production was investigated in five postlingually deafened adults implanted with the 22-channel Nucleus device. Changes in speech production were measured before implant and 1, 6, and 24 months postimplant. Acoustic measurements included: F1 and F2 of vowels in word-in-isolation and word-in-sentence context, voice-onset-time (VOT), spectral range of sibilants, fundamental frequency (F0) of word-in-isolation and word-in-sentence context, and word and sentence duration. Perceptual ratings of speech quality were done by ten listeners. The significant changes after cochlear implantation included: a decrease of F0, word and sentence duration, and F1 values, and an increase of voiced plosives' voicing lead (from positive to negative VOT values) and fricatives' spectral range. Significant changes occurred until 2 years postimplant when most measured values fell within Hebrew norms. Listeners were found to be sensitive to the acoustic changes in the speech from preimplant to 1, 6, and 24 months postimplant. Results suggest that when hearing is restored in postlingually deafened adults, calibration of speech is not immediate and occurs over time depending on the age-at-onset of deafness, years of deafness, and perception skills. The results also concur with hypothesis that the observed changes of some speech parameters are an indirect consequence of intentional changes in other articulatory parameters.

The perception of phonologically significant contrasts using speech envelope cues.

The observation that many cochlear implantees demonstrate high levels of speech recognition, despite limited or distorted spectral information, has motivated research on the importance of temporal information for the perception of speech. The purpose of this study was to measure the recognition of speech contrasts via only the speech envelope before and after training. Test stimuli consisted of eight segmental and two suprasegmental contrasts of the Hebrew Speech Pattern Contrast test using a binary forced-choice paradigm. Multiplying the speech waveform with white noise eliminated spectral information. Results show that stress, intonation and manner of articulation were very well perceived using only temporal information, whereas voicing and place of articulation were perceived above chance levels. Results also show that vowels were more susceptible to the removal of spectral information than consonants. These findings help to better understand speech perception performance of hearing-impaired individuals, including cochlear implant users. They may also have practical implications for aural rehabilitation and sensory aids design for the Hebrew speaking population.

Multisensory speech perception of young children with profound hearing loss.

The contribution of a two-channel vibrotactile aid (Trill VTA 2/3, AVR Communications LTD) to the audiovisual perception of speech was evaluated in four young children with profound hearing loss using words and speech pattern contrasts. An intensive, hierarchical, and systematic training program was provided. The results show that the addition of the tactile (T) modality to the auditory and visual (A+V) modalities enhanced speech perception performance significantly on all tests. Specifically, at the end of the training sessions, the tactile supplementation increased word recognition scores in a 44-word, closed-set task by 12 percentage points; detection of consonant in final position by 50 percentage points; detection of sibilant in final position by 30 percentage points; and detection of voicing in final position by 25 percentage points. Significant learning over time was evident for all test materials, in all modalities. As expected, fastest learning (i.e., smallest time constants) was found for the AVT condition. The results of this study provide further evidence that sensory information provided by the tactile modality can enhance speech perception in young children.

Speechreading enhancement: a comparison of spatial-tactile display of voice fundamental frequency (F0) with auditory F0.

In two experiments, subjects repeated video-recorded sentences presented via speechreading with and without enhancement by a sensory input derived from the acoustic speech signal. Enhancement was measured as percentage increase in recognized words. In experiment 1, tactile presentation of fundamental frequency (F0) provided, after training, for three of four postlingually deafened adults a mean enhancement of 11%. In experiment 2, using six hearing adults, the auditory presentation of F0 provided a mean enhancement of 50%. This value fell, but only to 37%, when the F0 signal was derived from the processor of the tactile aid used in experiment 1. From these experiments it can be concluded that the unexpectedly small enhancement found in experiment 1 is probably due both to the fact that this tactile aid was not providing effective access to all of the information available in the F0 contour and to limitations related to the tactile processing ability of the kinaesthetic system.

Voice fundamental frequency as an auditory supplement to the speechreading of sentences.

Recognition of words in conversational sentences of known topic was measured in nine normally hearing subjects by speechreading alone and by speechreading supplemented with auditory presentation of the output of an electroglottograph. Mean word recognition probability rose from 30% to 77% with the addition of the acoustic signal. When this signal was filtered to remove possible high-frequency spectral cues, the supplemented score fell, but only by a marginally significant 7 percentage points, supporting the conclusion that voice fundamental frequency was the principal source of enhancement. Enhancement occurred for all subjects, regardless of speechreading competence.

Tactile presentation of voice fundamental frequency as an aid to the perception of speech pattern contrasts.

The perception of initial consonant voicing, final consonant voicing, pitch change, and word stress, was measured in six normal subjects, by speechreading alone, by tactile transmission of fundamental voice frequency alone, and by the two in combination. Two tactile displays were used: a single-channel (temporal) display and a 16-channel (spatial) display. By speechreading alone, all contrasts except initial consonant voicing were partially perceptible. By both tactile aids alone, all four contrasts were partially perceptable. The addition of tactile input to speechreading provided better performance than that obtained by speechreading alone. The multichannel display was found to be significantly more effective than the single-channel for perception of pitch rise/fall only.