Covert contrast and covert errors in persistent velar fronting.
Acoustic and articulatory studies demonstrate covert contrast in perceptually neutralised phonemic contrasts in both typical children and children with speech disorders. These covert contrasts are thought to be relatively common and symptomatic of phonetic speech disorders. However, clinicians in the speech therapy clinic have had no easy way of identifying this covertness. This study uses ultrasound tongue imaging to compare tongue contours for /t/and /k/in seven children with persistent velar fronting. We present a method of overlaying tongue contours to identify covert contrast at the articulatory level. Results show that all seven children, contrary to expectations, produced both /t/and /k/with near-identical tongue shapes showing no evidence of covert contrast. However, further analysis of one of the participants showed highly variable tongue shapes for /t/and /k/, including retroflex productions of both. Although not phonologically conditioned, this covert error is evidence of speech disorder at the phonetic level.
a Psychological Sciences and Health , University of Strathclyde , Glasgow , Scotland , UK.
Joanne
J
Cleland
b Clinical Audiology, Speech & Language Research Centre , Queen Margaret University , Musselburgh , Scotland , UK.
James M
JM
Scobbie
b Clinical Audiology, Speech & Language Research Centre , Queen Margaret University , Musselburgh , Scotland , UK.
Cornelia
C
Heyde
b Clinical Audiology, Speech & Language Research Centre , Queen Margaret University , Musselburgh , Scotland , UK.
Zoe
Z
Roxburgh
c Articulate Instruments Ltd. , Queen Margaret University , Musselburgh , Scotland , UK.
Alan A
AA
Wrench
D002648:Child; D002657:Child Development; D005260:Female; D006801:Humans; D008297:Male; D013061:Speech Acoustics; D013064:Speech Disorders; D013068:Speech Production Measurement / Q000379:methods; D014059:Tongue / Q000000981:diagnostic imaging*; D014463:Ultrasonography / Q000379:methods*
Covert contrast; covert error; speech sound disorders; ultrasound; velar fronting