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Measuring Intelligibility in Children: Why and How

Measuring Intelligibility in Children: Why and How. Peter Flipsen Jr., PhD, S-LP(C), CCC-SLP Idaho State University flippete@isu.edu. Intelligibility. Making yourself understood. The ultimate goal of human communication. Usually the long-term goal for most clients we work with.

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Measuring Intelligibility in Children: Why and How

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  1. Measuring Intelligibility in Children: Why and How ASHA 2010 Philadelphia, PA Peter Flipsen Jr., PhD, S-LP(C), CCC-SLP Idaho State University flippete@isu.edu

  2. Intelligibility • Making yourself understood. • The ultimate goal of human communication. • Usually the long-term goal for most clients we work with. • IF IT’S THE GOAL, LET’S MEASURE IT! • Measure it at baseline to know where we start. • Measure it regularly to monitor progress. ASHA 2010 Philadelphia, PA

  3. Intelligibility and Accuracy • Related but NOT THE SAME THING. • Typically-developing 4 year old is fully intelligible (100%). • But still makes some speech sound errors. • Many children with SSD present with much reduced intelligibility. • But they may have enough sounds correct in single words that they DON’T qualify for services. ASHA 2010 Philadelphia, PA

  4. Being intelligible • Means: • Choosing the best words to convey intentions • Formulating the syntax correctly • Knowing the correct sounds to produce • Including the appropriate prosody • Staying on topic • Having the physical skill to produce the entire message fluently. ASHA 2010 Philadelphia, PA

  5. intelligibility • More than just speech sound accuracy! • Can NOT be adequately measured with an articulation test! • Ertmer (2010) and others have shown that single word artic scores rarely account for more than 25% of the variability. • Need to measure it directly by asking: • “how much can be understood?” ASHA 2010 Philadelphia, PA

  6. Measuring intelligibility • If you want to know how well someone is being understood, • YOU HAVE TO MEASURE HOW MUCH IS BEING UNDERSTOOD DIRECTLY! ASHA 2010 Philadelphia, PA

  7. Measuring intelligibility • How do we do it? • Many clinicians make informal estimates. • Demo– clinicians listened to a sample and rated. ASHA 2010 Philadelphia, PA

  8. Informal estimates? • Here’s a sampling of values the clinicians came up with: • 20%, 65%, 45%, 40%, 55%, 35%, 15%, 70%, 60%, 40%, 40%, 50%, 30%, 65%, 15%, 55%, 25%, 45%, 60%, 35% • Probably no better than pulling numbers out of a hat. • Highly variable across listeners. • Rely on memory. • Not valid for monitoring progress as SLP becomes a “more familiar listener”. • Calibration changes over time. ASHA 2010 Philadelphia, PA

  9. Rating scales – an alternative? • Many available. For example: • 1. completely intelligible • 2. mostly intelligible • 3. somewhat intelligible • 4. mostly unintelligible • 5. completely unintelligible • Schiavetti (1992) identified several problems: • 1. listeners don’t treat all parts of the scale equally. • 2. high variability in scores across listeners especially in the middle of the scale. • 3. they don’t allow us to identify possible sources of intelligibility breakdowns. ASHA 2010 Philadelphia, PA

  10. Rating scales – practical problems • 1. How much change does it take to move from one level to the next? • Not clear. • Not consistent across points on the scale. • 2. Such scales are NOT sensitive enough to track change in individuals over time. ASHA 2010 Philadelphia, PA

  11. Write-down procedures • Generally considered the best approach. • Listener tries to identify exactly what the intended message was. • We calculate actual % understood. ASHA 2010 Philadelphia, PA

  12. Write-down procedures • Possible at several linguistic levels. • 1. Single words. • Spontaneous or imitated. • 2. Sentences. • Spontaneous or imitated. • 3. Conversation. ASHA 2010 Philadelphia, PA

  13. Write-down procedures • Which level to use? • Speakers with less than perfect speech likely to perform differently at different levels. • Milder cases do better in connected speech because context helps listener to “fill in the blanks”. • More severe cases do better in single words because high level of errors overwhelm the listener. • Ideally do more than one level. ASHA 2010 Philadelphia, PA

  14. Single word procedures • Several possible approaches. • Most flexible procedure available is: • Children’s Speech Intelligibility Measure (CSIM) • By Wilcox and Morris • Published by Psych Corp in 1999. ASHA 2010 Philadelphia, PA

  15. CSIM • 50 item test. • NOT norm-referenced. • Can be administered multiple times because unique test is created each time. • Each item has 12 “similar sounding” words. • E.g., tall, stall, wall, shawl, call, all, fall, ball, hall, crawl, mall, Paul • E.g., Tanner, planner, matter, manner, mother, banner, mother, brother, sander, bother, batter, other ASHA 2010 Philadelphia, PA

  16. Csim • Pick 1 item at random before administering. • Child imitates examiner saying the word (can read it if they are old enough). • Record child’s productions and give to unfamiliar listeners (preferably at least 2). • Listener either writes word down with no reference or circles word on blank test form (multiple choice option). ASHA 2010 Philadelphia, PA

  17. Sentence level procedures • Several possible have been proposed. • For very young or very unintelligible children one quite flexible one is: • The Beginner’s Intelligibility Test (BIT). • Originally designed for the hearing impaired but can be used with any population. • Osberger, M. J., Robbins, A. M., Todd, S. L., & Riley, A. I. (1994). Speech intelligibility of children with cochlear implants. The Volta Review, 96(5), 169-180. ASHA 2010 Philadelphia, PA

  18. BIT • NOT norm-referenced. • 4 sets of 2-5 word sentences. • E.g., • 1. The bear sleeps. • 2. Mommy sits. • 3. The rabbit hops. • 4. The cowboy jumps. • 5. Grandma falls. • 6. That is a black hat. • 7. The boy is under the table. • 8. My airplane is small. • 9. He is painting the chair. • 10. She is cooking dinner. ASHA 2010 Philadelphia, PA

  19. Bit • Use one set each time so it can be administered at regular intervals. • Child imitates or reads the sentences which are recorded. • Give recording to 2 unfamiliar listeners who write down what they hear. • Calculate % of words correctly identified. ASHA 2010 Philadelphia, PA

  20. For older children (7 years +) • Could use sentence portion of: • Assessment of the Intelligibility of Dysarthric Speech. • By Yorkston & Beukelman. Published by Pro-Ed. • NOT norm-referenced. • Select 5 sentences from each list of 5-8 word sentences (20 total sentences, 130 total words). • Child imitates or reads the sentences which are recorded. • Give recording to 2 unfamiliar listeners who write down what they hear. • Calculate % of words correctly identified. ASHA 2010 Philadelphia, PA

  21. conversation • Most ecologically valid approach (i.e., this is what we do most of the time). • Record true interaction. • Avoid narratives as they may induce abnormal prosody which may influence scores. • Have unfamiliar listeners transcribe what they hear (regular spelling!). • % understood = words understood • ------------------------- • (words understood + words not understood) ASHA 2010 Philadelphia, PA

  22. Conversation – big challenge • Unlike CSIM or BIT we won’t know what the intended targets are. • How many words are present in the parts we don’t understand? • With occasional unintelligible parts, listeners can easily guess how many words are there. • They use context to help. ASHA 2010 Philadelphia, PA

  23. Conversation – big challenge • With longer stretches no context to help. • Listeners can count syllables! • Each syllable contains a vowel and vowels are louder. • Have them put X down for each syllable heard. • Use the syllable counts to estimate the number of unknown words. • For most young children about 75% of words are 1 syllable long. Most of the rest are 2 syllables long. • 3:1 ratio = 1.25 syllables per word on average. • Count syllables heard. Divide by 1.25 to get words not understood. ASHA 2010 Philadelphia, PA

  24. Who should be Judges? • Unfamiliar = best test. • Don’t do it yourself because you will become familiar very quickly (and biased!). • Preferably use inexperienced listeners but use colleagues who don’t know the child if necessary. • Do it for each other to spread the work around. ASHA 2010 Philadelphia, PA

  25. Who should be Judges? • Don’t use parents or siblings. • Tend to be highly familiar so you get over-estimate of intelligibility. • Reference: Flipsen, P., Jr. (1995). Speaker-listener familiarity: Parents as judges of delayed speech intelligibility. Journal of Communication Disorders 28(1), 3-19. ASHA 2010 Philadelphia, PA

  26. Clinical decisions:How intelligible? What criteria? • No known valid norms available. • Too many variables involved to develop such norms. • Best index = • age in years / 4 = % understood in conversation. • 2 years old = 2/4 or 50% • 3 years old = 3/4 or 75% • 4 years old = 4/4 or 100% * • * speech sound errors still quite possible. • Reference: Coplan, J., & Gleason, J. R. (1988). Unclear speech: Recognition and significance of unintelligible speech in preschool children. Pediatrics, 82, 447–452. ASHA 2010 Philadelphia, PA

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