Treatment generalization from trained /ɹ/ to untrained /l/: a case study of persisting distortion errors.
Caitlin Raaz, Megan C Leece, Tara McAllister and 1 others
PMID 33530759WHAT IT FOUND
Treating one child's /ɹ/ distortion with ultrasound biofeedback also improved his untrained /l/ errors.
The child had a hidden acoustic difference between the two sounds before treatment, suggesting generalization may occur when this covert contrast exists.
Key findings
01Perceptual accuracy improved for both the treated /ɹ/ and the untreated /l/ sounds.
02Acoustic analysis showed a significant shift in formant values for /l/, indicating a move from a dark to a light production without direct cueing.
03Before treatment, the child produced a covert acoustic contrast between /ɹ/ and /l/ despite them sounding identical to listeners.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
This is a single case report, so findings cannot be generalized to all children with speech sound disorders. The study did not isolate which treatment component (ultrasound biofeedback, self-monitoring, or the covert contrast itself) caused the generalization. The child had average language and cognitive scores, which may not represent children with co-occurring language impairments.
Declared interests
The authors report no conflict of interest.
The easy way to misread this
Do not assume that treating /ɹ/ will automatically generalize to /l/ in all patients. This outcome occurred in one child who had a specific underlying acoustic difference (covert contrast) between the two sounds, which is not always present in clinical practice.