Covert contrast and covert errors in persistent velar fronting

ABSTRACT

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.

KEYWORDS:

• Covert contrast
• covert error
• speech sound disorders
• ultrasound
• velar fronting

Acknowledgements

Thank you primarily to the children and their parents who attended weekly recording and therapy sessions. Thank you also to the Speech and Language Therapists who referred the children. Thank you to Steve Cowen for technical assistance with the ultrasound recordings.

Declaration of interest

The authors report no conflict of interest.

Funding

This work was funded by grants EP/I027696/1 (Engineering and Physical Sciences Research Council, UK) and ETM/402 (Chief Scientist Office, Scotland).

Additional information

Funding

This work was funded by grants EP/I027696/1 (Engineering and Physical Sciences Research Council, UK) and ETM/402 (Chief Scientist Office, Scotland).