Assessing Speech Intelligibility and Severity What are some standard procedures?

Are measures of intelligibility and severity the same? 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 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 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 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 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 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 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 Quantitative Measures PCC (and 8 variations) Hodson’s PDS Edwards’ PDI

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

Shriberg, Austin, Lewis, McSweeny, & 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) 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?