Assessing Speech Intelligibility and Severity What are some

Assessing Speech Intelligibility and Severity What are some standard procedures?

Are measures of intelligibility and severity the same? l l Although judgements about intelligibility and severity may be correlated, they represent two different indices about an individual’s speech For example, a child may have a severe resonance disorder, but his/her speech is still intelligible

Intelligibility Scales l l Typically a panel of 2 -5 listeners (expert ~ novice; familiar ~ unfamiliar) rate a taped (audio or video) segment of child’s speech Rank intelligibility of child’s speech compared to age peers Scales typically use 3 -point or 5 -point judgment scales (See Bleile) scores are averaged to derive a composite intelligibility rating score

Intelligibility Scales l Kent, Miolo, & Bloedel (1994) compared 19 intelligibility measures according to 5 categories that differed with regard to the emphasis of the analysis (phonetic ~ phonemic; word level ~ conversation)

Intelligibility Scales l Listed 8 factors that influence clinical evaluation of intelligibility: • • loss of phonological contrasts loss of contrasts in specific environments extent of homonymy amt of difference between target~realization frequency of occurrence in English consistency familiarity of listener with speaker context in which communication occurs

Intelligibility l Weston & Shriberg (1992) concluded that articulation variables alone cannot account for all the breakdowns that result in communication • other general contextual and linguistic variables are related to speech intelligibility

Severity l Similar to intelligibility rating scales, a panel of familiar or unfamiliar listeners judge a segment of a child’s recorded (audio or video-taped) speech (single word or connected speech)

Severity l Perceptual scales (see Bleile) or quantitative measures • 4 Point Clinical Judgement Scale of Severity • No disorder-Mild-Moderate-Severe • average score of 3. 5 often required to provide clinical services

Severity l Quantitative Measures • PCC (and 8 variations) • Hodson’s PDS • Edwards’ PDI

Comparison of PCC and PDS Severity Ratings PCC Mild >90% PDS Mild 1 -19 pts Mild-Mod 65 -85% Moderate 20 -39 Mod-Sev 50 -65% Severe Profound 60+ <50% 40 -59

Shriberg, Austin, Lewis, Mc. Sweeny, & Wilson (1997) 9 speech metrics PCC (based on conv speech) PCC-A (common clinical distortions scored correct) PCC-R ([un]common distortion scored correct) ACI (differentially weighs distortion ~ sub/omis) PCI (percentage of sounds mastered-early talkers) PVC (similar to PCC, but for vowels/diphthongs) PVC-R (similar to PCC-R, but for vowels/diphthongs) PPC (percentage to consonants/vowels correct) PPC-R (scores distortions correct)

Which metric is most appropriate? Depends on specific needs of the assessment • Interest limited to consonants • PCC, PCC-A, PCC-R, ACI • Young/severely delayed children • PCI • Interest in vowels/diphthongs • PVC, PVC-R • Interest in articulation competence on all speech sounds • PPC, PPC-R

Rafaat, Rvachew, & Russell (1995) l l l Purpose of study was to determine the percentage of agreement between SLPs in rating PI severity Adequate reliability for older children (4; 6+), but unreliable for children under 3; 6 Unable to reliably distinguish TD from mild delay

Why were SLPs less reliable on severity ratings of younger children?

What factors account for differences in reliability ratings?