Denis Burnham

Universality and specificity in infant-directed speech : pitch modifications as a function of infant age and sex in a tonal and non-tonal language

The aim of this study was to investigate the prosodic characteristics of infant-directed speech (IDS) to boys and girls in a tonal (Thai) and non-tonal (Australian English) language. Speech was collected from mothers speaking to infants at birth, and 3, 6, 9, and 12 months, and also to another adult. Mean-F0, pitch range, and utterance slope-F0 were extracted, and the integrity of the tonal information in Thai investigated. The age trends across the two languages differed for each of these measures but Australian English IDS was generally more exaggerated than Thai IDS. With respect to sex differences, Australian English mothers used higher mean-F0, pitch range, and more rising utterances for girls than boys, but Thai mothers used more subdued mean-F0 and more falling utterances for girls than boys. Despite variations in pitch modifications by Thai and Australian English mothers, overall IDS is more exaggerated than adult-directed speech (ADS) in both languages. Furthermore, tonal information in Thai was only slightly less identifiable in Thai IDS than Thai ADS. The universal features and language-specific differences in IDS are discussed in terms of facilitating infant socialization at younger ages, and language acquisition later in infancy.

Development of Categorical Identification of Native and Non-Native Bilabial Stops: Infants, Children, and Adults.

Using an infant speech identification (ISI) procedure, English language environment infants, two- and six-year-old children, and adults were tested for their identification of sounds on a native (voiced/voiceless bilabial stop) and a non-native (prevoiced/voiced bilabial stop) speech continuum. Categorical perception of the two contrasts diverged as a function of age, increasing for the native contrast and decreasing for the non-native between two and six years. In Experiment 2, subjects of the same four ages were tested for their identification of a continuum of harmonic tones varying in pitch. Comparison of the results of Experiment 1 with the essentially continuous perception of this pitch continuum supports the view that the perception of the native contrast becomes more categorical with age, while perception of the non-native contrast becomes less categorical, especially at six years. Experiment 3, in which adults were tested on the three continua with a multi-trial open set procedure, demonstrated that results with the ISI procedure in Experiments 1 and 2 are comparable to results with more traditional methods. The results of the three experiments are discussed in terms of the role of specific linguistic experience in the development of categorical speech perception.

Language Specific Speech Perception and the Onset of Reading.

In two studies the relationship between theonset of reading and language specific speechperception, the degree to which native speechperception is superior to non-native speechperception, was investigated. In Experiment 1with children of 4, 6, and 8 years, languagespecific speech perception occurred maximallyat 6 years and was positively related toreading ability for age and languagecomprehension level. In Experiment 2, with anexpanded range of ages and various stimulus andtask changes, the relationship between readingand language specific speech perception stillheld, and maximal language specific speechperception occurred around the onset of readinginstruction for three different sets of speechcontrasts, but not for a control set ofnon-speech contrasts. The results show thatlanguage specific speech perception is alinguistic rather than an acoustic phenomenon.Results are discussed in terms of early speechperception abilities, experience with oralcommunication, cognitive ability, readingability, alphabetic versus logographiclanguages, phonics versus whole word readinginstruction, and the effect of age versusinstruction.

Congenital Amusia (or Tone-Deafness) Interferes with Pitch Processing in Tone Languages

Congenital amusia is a neurogenetic disorder that affects music processing and that is ascribed to a deficit in pitch processing. We investigated whether this deficit extended to pitch processing in speech, notably the pitch changes used to contrast lexical tones in tonal languages. Congenital amusics and matched controls, all non-tonal language speakers, were tested for lexical tone discrimination in Mandarin Chinese (Experiment 1) and in Thai (Experiment 2). Tones were presented in pairs and participants were required to make same/different judgments. Experiment 2 additionally included musical analogs of Thai tones for comparison. Performance of congenital amusics was inferior to that of controls for all materials, suggesting a domain-general pitch-processing deficit. The pitch deficit of amusia is thus not limited to music, but may compromise the ability to process and learn tonal languages. Combined with acoustic analyses of the tone material, the present findings provide new insights into the nature of the pitch-processing deficit exhibited by amusics.

Emotional prosodic processing in auditory hallucinations

Deficits in emotional prosodic processing, the expression of emotions in voice, have been widely reported in patients with schizophrenia, not only in comprehending emotional prosody but also expressing it. Given that prosodic cues are important in memory for voice and speaker identity, Cutting has proposed that prosodic deficits may contribute to the misattribution that appears to occur in auditory hallucinations in psychosis. The present study compared hallucinating patients with schizophrenia, non-hallucinating patients and normal controls on an emotional prosodic processing task. It was hypothesised that hallucinators would demonstrate greater deficits in emotional prosodic processing than non-hallucinators and normal controls. Participants were 67 patients with a diagnosis of schizophrenia or schizoaffective disorder (hallucinating=38, non-hallucinating=29) and 31 normal controls. The prosodic processing task used in this study comprised a series of semantically neutral sentences expressed in happy, sad and neutral voices which were rated on a 7-point Likert scale from sad (-3) through neutral (0) to happy (+3). Significant deficits in the prosodic processing tasks were found in hallucinating patients compared to non-hallucinating patients and normal controls. No significant differences were observed between non-hallucinating patients and normal controls. In the present study, patients experiencing auditory hallucinations were not as successful in recognising and using prosodic cues as the non-hallucinating patients. These results are consistent with Cuttings hypothesis, that prosodic dysfunction may mediate the misattribution of auditory hallucinations.

Psychological impact of the Lidcombe Program of early stuttering intervention

The Lidcombe Program is an operant treatment for stuttering in preschool children for which favourable outcome and social validity data have been published. The treatment involves parental praise for stutter-free speech in childrens everyday speaking environments, and occasional correction of stuttered speech. Theoretical perspectives on the origins of stuttering have prompted suggestions that the Lidcombe Program may have an adverse psychological impact on children. The present preliminary investigation sought to identify any evidence of such a systematic, pernicious trend, which might justify statistically powerful investigations of the issue with large subject numbers. Subjects were eight preschool children who were successfully treated with the Lidcombe Program. The Child Behavior Checklist (CBCL) detected any post-treatment behavioural markers of changes in children such as anxiety, aggression, withdrawal or depression. The Attachment Q-Set (AQS) measured any changes in the quality of the attachment relationship between child and mother over the course of treatment. These case studies revealed no evidence of a systematic trend in either. In fact, CBCL data suggested improvements in the children after treatment. It is concluded that there is no reason to doubt that the Lidcombe Program is a safe treatment.

Perception of lexical tone across languages: evidence for a linguistic mode of processing

Pairs of Thai tones were presented for perceptual discrimination in three linguistic contexts [normal speech, low-pass filtered speech, and as musical (violin) sounds] to tonal language speakers, Thai and Cantonese, and non-tonal (English) language speakers. English speakers discriminated the tonal contrasts significantly better in the musical context than in filtered speech, and in filtered speech better than in full speech. On the other hand, both Thai and Cantonese speakers perceived the tonal contrasts equally well in all three contexts. Thus, developmental absence of exposure to lexical tone results in a linguistic mode of processing which involves the attenuation of a basic psychoacoustic ability, pitch discrimination.

Perception of the auditory‐visual illusion in speech perception by children with phonological disorders

An example of the auditory‐visual illusion in speech perception, first described by McGurk and MacDonald, is the perception of [ta] when listeners hear [pa] in synchrony with the lip movements for [ka]. One account of the illusion is that lip‐read and heard speech are combined in an articulatory code since people who mispronounce words respond differently from controls on lip‐reading tasks. A same‐different judgment task assessing perception of the illusion showed no difference in performance between controls and children with speech difficulties. Another experiment compared children with delayed and disordered speech on perception of the illusion. While neither group perceived many illusions, a significant interaction indicated that children with disordered phonology were strongly biased to the auditory component while the delayed groups response was more evenly split between the auditory and visual components of the illusion. These findings suggest that phonological processing, rather than articulation, supports lip‐reading ability.

Universality and language-specific experience in the perception of lexical tone and pitch

Two experiments focus on Thai tone perception by native speakers of tone languages (Thai, Cantonese, and Mandarin), a pitch–accent (Swedish), and a nontonal (English) language. In Experiment 1, there was better auditory-only and auditory–visual discrimination by tone and pitch–accent language speakers than by nontone language speakers. Conversely and counterintuitively, there was better visual-only discrimination by nontone language speakers than tone and pitch–accent language speakers. Nevertheless, visual augmentation of auditory tone perception in noise was evident for all five language groups. In Experiment 2, involving discrimination in three fundamental frequency equivalent auditory contexts, tone and pitch–accent language participants showed equivalent discrimination for normal Thai speech, filtered speech, and violin sounds. In contrast, nontone language listeners had significantly better discrimination for violin sounds than filtered speech and in turn speech. Together the results show that tone perception is determined by both auditory and visual information, by acoustic and linguistic contexts, and by universal and experiential factors.

Auditory-Visual Speech Perception as a Direct Process: The McGurk Effect in Infants and Across Languages

The McGurk effect, in which auditory [b] dubbed onto visual [g] is perceived as [d] or [D] (as in them), is used in two experiments on humans’ integration of auditory and visual speech information. In the first it was found that 4-month-old infants perceive the McGurk effect. In the second a group of English- and another of Thai-speaking adults were tested on the auditory [m] plus visual [N] (=[n]) version of the effect. Despite the phonological irrelevance of initial [N] in English, both groups perceived a [na] fusion to the same extent. Thus the McGurk effect transcends phonological constraints. The results suggest that auditory and visual speech information is integrated in a common metric which is unaffected by phonological experience.