Faculty of Humanities
School of Professional Social Sciences
Department of Communication Pathology
Selected Highlights from Research Findings
The aims of this study were to determine if second language speech production will differentiate between normal speaking adults and adult speakers with speech level neurogenic disorders due to acquired brain damage and also between two subgroups with speech level neurogenic disorders. The two subgroups were speakers with apraxia of speech, a motor planning disorder, and speakers with phonemic paraphasias, a phonological planning disorder. Although the underlying problems in these two populations seem quite distinct, the overlap of some features complicates the differentiation between these disorders. The effect of first language (L1) speech production versus second language (L2) speech production on vowel duration, utterance duration, utterance onset duration and voice onset time were determined with acoustic analyses. Five normal speaking participants, three participants with apraxia of speech and three participants with phonemic paraphasias took part in the study. The three participants with apraxia of speech and two with phonemic paraphasias seemed to be influenced by speaking in L2 to a greater extent than the normal speakers and one participant with phonemic paraphasias. The results of the study, conducted in partnership with Dr Karen Theron, confirmed that L2 speech production is more complex than L1 speech production and also that all speakers with apraxia of speech exhibit a motor based problem. On the other hand not all speakers with phonemic paraphasias show greater difficulty with L2 speech production than normal speakers do. This result argues against a motor based problem in all speakers with phonemic paraphasias.
Contact person: Prof A van der Merwe.
Contact person: Prof A van der Merwe.
The aim of this project is to determine the status of early detection of early hearing loss and intervention services in the public healthcare sector of South Africa. Early detection of hearing loss within the first 3 months of life provides a window of opportunity for implementation of early intervention. The earlier intervention commences the better the chances for these children to develop speech and language comparable to their hearing peers. Unfortunately there is a dearth of such services in South Africa and currently there is no information regarding the availability of early detection and intervention services for infant hearing loss. Subsequently, a national survey was initiated to determine the current status of newborn/infant hearing screening systems in public sector hospitals throughout South Africa by means of a descriptive survey. Data on current screening practices and protocols as well as available resources was gathered by means of a self-administered postal questionnaire. The questionnaire was sent to speech therapy and audiology departments within public sector hospitals throughout South Africa. Preliminary enquiries revealed that there are approximately ninety public healthcare hospitals in South Africa that have speech therapy and audiology departments but there are very few systematic screening programmes in place. The major challenges thus far reported are staff shortages and lack of necessary equipment. The findings of this study will make a valuable contribution to the field of early hearing loss detection and intervention by providing an indication of the current status of such services in South Africa. This information serves as a baseline for the development and structuring of early hearing detection and intervention services as a priority in the public healthcare sector.
Contact person: Dr DCD Swanepoel.
The Four-Level Framework of Speech Sensorimotor Control (Van der Merwe, 1997) complicates the traditional view of dysarthria - a collective term for a group of neurologic speech disorders - as a purely motor execution disorder. According to this model, hypokinetic, hyperkinetic and ataxic dysarthria are programming-execution dysarthrias, while flaccid dysarthria is the only pure execution dysarthria. Acoustic and physiological investigations have suggested that in communicatively impaired individuals, disruptions in temporal control reflect a disrupted motor control system. This study aimed to differentiate programming-execution dysarthria from execution dysarthria by examining variability of the temporal control of speech. Temporal aspects of speech include voice onset time, vowel duration, vowel steady state duration and vowel formant transition duration. Six participants and five paired control participants repeated 15 stimulus words ten times. Voice onset time, vowel duration, vowel steady state duration and vowel formant transition duration were measured acoustically. The coefficient of variation of the temporal parameters, and the correlation coefficient between the durational parameters, were calculated and analysed using descriptive statistics. The coefficient of variation revealed that the speakers with dysarthria were more variable than the control speakers. All participants, except those with flaccid dysarthria, showed similar trends in intra-subject variability. Those with flaccid dysarthria exhibited greater intra-subject variability of voice onset time than of the durational parameters. The correlation analysis did not reveal differences between dysarthria types, or between the dysarthric speakers and the controls. Differences in the trends in variability may support the hypothesis that the nature and level of breakdown in programming-execution dysarthria differs from the nature and level of breakdown in execution dysarthria. Further research in this field is necessary. This study was published in the South African Journal of Communication Disorders in 2007.
Contact person: Prof A van der Merwe.
The Four-Level Framework of Speech Sensorimotor Control (Van der Merwe, 1997) complicates the traditional view of dysarthria - a collective term for a group of neurologic speech disorders - as a purely motor execution disorder. According to this model, hypokinetic, hyperkinetic and ataxic dysarthria are programming-execution dysarthrias, while flaccid dysarthria is the only pure execution dysarthria. Acoustic and physiological investigations have suggested that in communicatively impaired individuals, disruptions in temporal control reflect a disrupted motor control system. This study aimed to differentiate programming-execution dysarthria from execution dysarthria by examining variability of the temporal control of speech. Temporal aspects of speech include voice onset time, vowel duration, vowel steady state duration and vowel formant transition duration. Six participants and five paired control participants repeated 15 stimulus words ten times. Voice onset time, vowel duration, vowel steady state duration and vowel formant transition duration were measured acoustically. The coefficient of variation of the temporal parameters, and the correlation coefficient between the durational parameters, were calculated and analysed using descriptive statistics. The coefficient of variation revealed that the speakers with dysarthria were more variable than the control speakers. All participants, except those with flaccid dysarthria, showed similar trends in intra-subject variability. Those with flaccid dysarthria exhibited greater intra-subject variability of voice onset time than of the durational parameters. The correlation analysis did not reveal differences between dysarthria types, or between the dysarthric speakers and the controls. Differences in the trends in variability may support the hypothesis that the nature and level of breakdown in programming-execution dysarthria differs from the nature and level of breakdown in execution dysarthria. Further research in this field is necessary. This study was published in the South African Journal of Communication Disorders in 2007.
Contact person: Mrs AM Stipinovich.
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