Discriminating Children with Speech Sound Disorders from Children with Typically Developing Speech Using the Motor Speech Hierarchy Probe Words: A Preliminary Analysis

The Motor Speech Hierarchy (MSH) Probe Words (PW) have yet to be validated as an effective tool to discriminate between impaired and typically developing speech motor control. The first purpose of this preliminary study was, therefore, to examine the effectiveness of the mandibular control subtest of the MSH-PW in classifying typically developing (TD) and speech sound disordered (SSD) children aged between 3 years 0 months and 3 years 6 months. Secondly, we compared automatically derived kinematic measures of jaw range and control with MSH-PW consensus scoring to assist in identifying deficits in mandibular control. Methods: Forty-one children with TD speech and 13 with SSD produced the 10 words of the mandibular stage of the MSH-PW. A consensus team of speech pathologists observed video recordings of the words to score motor speech control and phonetic accuracy, as detailed in the MSH-PW scoring criteria. Specific measures of jaw and lip movements during speech were also extracted to derive the objective measurements, with agreement between the perceptual and objective measures of jaw range and jaw control evaluated. Results: A significant difference between TD and SSD groups was found for jaw range (p = .004), voicing transitions (p = .005) and total mandibular scores (p = .015). SSD and TD discrim-ination was significant (at alpha = 0.01) with a balanced classification accuracy of 0.79. Initial analysis indicates objective kinematic measures using facial tracking show good agreement with perceptual judgements of jaw range and jaw control. Conclusions: Preliminary data indicate the MSH-PW can discriminate TD speech from SSD at the level of mandibular control and can be used by clinicians to assess speech motor control. Further investigation of objective measures to support perceptual scoring is indicated.