Valter Ciocca

Enhanced Pure-Tone Pitch Discrimination among Persons with Autism but not Asperger Syndrome.

Persons with Autism spectrum disorders (ASD) display atypical perceptual processing in visual and auditory tasks. In vision, Bertone, Mottron, Jelenic, and Faubert (2005) found that enhanced and diminished visual processing is linked to the level of neural complexity required to process stimuli, as proposed in the neural complexity hypothesis. Based on these findings, Samson, Mottron, Jemel, Belin, and Ciocca (2006) proposed to extend the neural complexity hypothesis to the auditory modality. They hypothesized that persons with ASD should display enhanced performance for simple tones that are processed in primary auditory cortical regions, but diminished performance for complex tones that require additional processing in associative auditory regions, in comparison to typically developing individuals. To assess this hypothesis, we designed four auditory discrimination experiments targeting pitch, non-vocal and vocal timbre, and loudness. Stimuli consisted of spectro-temporally simple and complex tones. The participants were adolescents and young adults with autism, Asperger syndrome, and typical developmental histories, all with IQs in the normal range. Consistent with the neural complexity hypothesis and enhanced perceptual functioning model of ASD (Mottron, Dawson, Soulières, Hubert, & Burack, 2006), the participants with autism, but not with Asperger syndrome, displayed enhanced pitch discrimination for simple tones. However, no discrimination-thresholds differences were found between the participants with ASD and the typically developing persons across spectrally and temporally complex conditions. These findings indicate that enhanced pure-tone pitch discrimination may be a cognitive correlate of speech-delay among persons with ASD. However, auditory discrimination among this group does not appear to be directly contingent on the spectro-temporal complexity of the stimuli.

The perception of Cantonese lexical tones by early-deafened cochlear implantees

This study investigated whether cochlear implant users can identify Cantonese lexical tones, which differ primarily in their F0 pattern. Seventeen early-deafened deaf children (age= 4 years, 6 months to 8 years, 11 months; postoperative period= 11-41 months) took part in the study. Sixteen children were fitted with the Nucleus 24 cochlear implant system; one child was fitted with a Nucleus 22 implant. Participants completed a 2AFC picture identification task in which they identified one of the six contrastive Cantonese tones produced on the monosyllabic target word /ji/. Each target stimulus represented a concrete object and was presented within a carrier phrase in sentence-medial position. Group performance was significantly above chance for three contrasts. However, the cochlear implant listeners performed much worse than a 6 1/2-year-old, moderately hearing impaired control listener who was tested on the same task. These findings suggest that this group of cochlear implant users had great difficulty in extracting the pitch information needed to accurately identify Cantonese lexical tones.

On the (non)categorical perception of lexical tones

Identification and discrimination of lexical tones in Cantonese were compared in the context of a traditional categorical perception paradigm. Three lexical tone continua were used: one ranging from low level to high level, one from high rising to high level, and one from low falling to high rising. Identification data showed steep slopes at category boundaries, suggesting that lexical tones are perceived categorically. In contrast, discrimination curves generally showed much weaker evidence for categorical perception. Subsequent investigation showed that the presence of a tonal context played a strong role in the identification of target tones and less of a role in discrimination. The results are consistent with the hypothesis that tonal category boundaries are determined by a combination of regions of natural auditory sensitivity and the influence of linguistic experience.

Perceptual correlates of Cantonese tones

Abstract This study investigated measurements related to average f0 level and f0 change over eight consecutive sections of the whole vocalic segment, for their roles as both acoustic and perceptual correlates of Cantonese lexical tones. Twenty-four CV Cantonese words, making up four sets of words that minimally contrasted in the six Cantonese tones (tones 55, 25, 33, 21, 23, and 22) were read by 10 speakers once in random order. Ten expert listeners and twenty naive listeners were asked to identify the words. Discriminant analysis showed that, in both production and perception, direction and magnitude of f0 change over the later part (6th and 7th sections) of the vocalic segment were important correlates of tone identity. f0 change provided separation both between contour tones (tones 25, 23, 21) and level tones (tones 55, 33, 22) as well as among contour tones. Average f0 provided separation among the level tones. Findings correspond well with description of tones based on Wangs phonological features of ‘rising’, ‘contour’, ‘falling’, and ‘height’.

The development of the perception of Cantonese lexical tones

This study investigated the development of Cantonese tone perception. Fifteen listeners were tested for each of four age groups: 4, 6 and 10 years old and adults. The stimuli were the six contrastive Cantonese tones produced with the monosyllabic target word /ji/, for which each tone represented a concrete object. The six target words were produced by a male native speaker of Cantonese within a carrier phrase. Listeners had to identify the target words, presented within the carrier phrase, by selecting one of two pictures. These pictures represented one of eight minimal pair contrasts: High Level v - v Mid Level; High Level v - v Low Level; Mid Level v - v Low Level; High Level v - v High Rising; High Rising v - v Low Rising; Low Rising v - v Low Level; Low Falling v - v Low Rising; Low Falling v - v Low Level. Overall, performance improved from age 4;0 to age 6;0, and from age 6;0 to age 10;0. By 10 years of age, children performed as accurately as adults. The Mid Level v - v Low Level and the High Rising v - v Low Rising contrasts were perceived with lower overall accuracy than all other contrasts. The differences in the relative level of difficulty among contrasts was explained in terms of the similarity in the fundamental frequency contour and range between the members of tone pairs. The results support the idea that the perception of lexical tones achieves adult performance at about 10 years of age.

Accuracy and variability of acoustic measures of voicing onset

Five commonly used methods for determining the onset of voicing of syllable-initial stop consonants were compared. The speech and glottal activity of 16 native speakers of Cantonese with normal voice quality were investigated during the production of consonant vowel (CV) syllables in Cantonese. Syllables consisted of the initial consonants /ph/, /th/, /kh/, /p/, /t/, and /k/ followed by the vowel /a/. All syllables had a high level tone, and were all real words in Cantonese. Measurements of voicing onset were made based on the onset of periodicity in the acoustic waveform, and on spectrographic measures of the onset of a voicing bar (f0), the onset of the first formant (F1), second formant (F2), and third formant (F3). These measurements were then compared against the onset of glottal opening as determined by electroglottography. Both accuracy and variability of each measure were calculated. Results suggest that the presence of aspiration in a syllable decreased the accuracy and increased the variability of spectrogram-based measurements, but did not strongly affect measurements made from the acoustic waveform. Overall, the acoustic waveform provided the most accurate estimate of voicing onset; measurements made from the amplitude waveform were also the least variable of the five measures. These results can be explained as a consequence of differences in spectral tilt of the voicing source in breathy versus modal phonation.

Effect of intonation on Cantonese lexical tones

In tonal languages, there are potential conflicts between the FO-based changes due to the coexistence of intonation and lexical tones. In the present study, the interaction of tone and intonation in Cantonese was examined using acoustic and perceptual analyses. The acoustic patterns of tones at the initial, medial, and final positions of questions and statements were measured. Results showed that intonation affects both the FO level and contour, while the duration of the six tones varied as a function of positions within intonation contexts. All six tones at the final position of questions showed rising FO contour, regardless of their canonical form. Listeners were overall more accurate in the identification of tones presented within the original carrier than of the same tones in isolation. However, a large proportion of tones 33, 21, 23, and 22 at the final position of questions were misperceived as tone 25 both within the original carrier and as isolated words. These results suggest that although the intonation context provided cues for correct tone identification, the intonation-induced changes in FO contour cannot always be perceptually compensated for, resulting in some erroneous perception of the identity of Cantonese tone.

Acoustic correlates of hypernasality

The aim of this study was to apply one‐third‐octave analysis for measuring an acoustic correlate of hypernasality in the speech of adults with a range of aetiologies (dysarthria, maxillectomy and cleft palate). Subjects included 12 speakers with hypernasality and 12 normal controls. The speech material was the vowel /i/ segmented from two Cantonese single words produced by each speaker. The results showed that speakers with hypernasality had significantly higher energy level for the one‐third‐octave bands centred at 630, 800 and 1000 Hz, and significantly lower amplitude for the band centred at 2500 Hz than speakers with normal resonance. These results are in general agreement with past findings about nasalization of vowels. This study showed that one‐third‐octave analysis has high intrajudge reliability and is applicable to the speech of adults with hypernasality due to different etiologies.

Effect of listener training on perceptual judgement of hypernasality

Reliable perceptual judgement is important for documenting the severity of hypernasality, but high reliability can be difficult to obtain. This study investigated the effect of practice and feedback on intra‐judge and inter‐judge reliability of hypernasality judgements. The judges were 36 speech‐language therapy students, who were randomly assigned to three groups for training: (1) Exposure (simple exposure to hypernasal speech samples), (2) Practice‐only (practice with hypernasality judgements without feedback), and (3) Practice‐Feedback (practice with hypernasality judgements with feedback). After training, the judges rated hypernasality in non‐nasal sentences produced by 20 speakers with hypernasality and two normal speakers, using direct magnitude estimation. Both practice groups showed fair‐to‐good inter‐judge reliability for rating the female samples: had more listeners who showed significant intra‐judge reliability, and had significantly larger range of hypernasality ratings than the exposure group. To conclude, practice (with or without feedback) is useful for improving the reliability of hypernasality ratings.

Speech errors in Cantonese speaking adults with cerebral palsy

The aim of this study was to characterize the speech errors made by Cantonese-speaking adults with dysarthria associated with cerebral palsy, using a perceptual-phonetic analysis. The subjects were 22 adult Cantonese speakers with cerebral palsy. Fifteen subjects had spastic-type cerebral palsy, five had athetoid-type and two mixed-type. Single words were transcribed phonetically and analysed by speech part for accuracy and error patterns. There were no significant differences in accuracy for type of cerebral palsy, gender or age. Speakers with athetosis had a significantly higher relative occurrence of diphthong reduction. The majority of error patterns could be explained by the neurological damage of cerebral palsy. However, several patterns were attributed to unique features of the Cantonese phonological system. Physiological explanations and language-specific contributions to speech disorder in this group of speakers were discussed.The aim of this study was to characterize the speech errors made by Cantonese-speaking adults with dysarthria associated with cerebral palsy, using a perceptual-phonetic analysis. The subjects were 22 adult Cantonese speakers with cerebral palsy. Fifteen subjects had spastic-type cerebral palsy, five had athetoid-type and two mixed-type. Single words were transcribed phonetically and analysed by speech part for accuracy and error patterns. There were no significant differences in accuracy for type of cerebral palsy, gender or age. Speakers with athetosis had a significantly higher relative occurrence of diphthong reduction. The majority of error patterns could be explained by the neurological damage of cerebral palsy. However, several patterns were attributed to unique features of the Cantonese phonological system. Physiological explanations and language-specific contributions to speech disorder in this group of speakers were discussed.