Switching Streams Across Ears to Evaluate Informational Masking of Speech-on-Speech.
Axelle Calcus, Tim Schoof, Stuart Rosen and 2 others
PMID 31107365WHAT IT FOUND
Switching speech streams between ears made a target sentence harder to hear than keeping them in opposite ears in young normal-hearing adults.
Fast periodic switching caused the most difficulty. Brief silent gaps unexpectedly made listening a little easier.
Key findings
01Switching target and masker speech across the ears made performance poorer than the dichotic condition, where target and masker were in opposite ears, by a mean difference of 5.9 dB.
02Periodic switching made performance poorer than switching at word boundaries, by about 8.8 dB.
03Silent gaps after switches made performance better than no gaps, by 2.3 dB on average.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study tested only young normal-hearing adults, so it does not show what happens in children or older adults, even though the discussion mentions those groups as potentially affected. The task used IEEE sentences with a female target and male masker, not everyday conversation. Switching improved performance relative to diotic presentation, so it did not fully reproduce the difficulty of two sounds in both ears. One participant could not reliably complete the periodic switching condition with silent gaps. The silent gaps produced the opposite of the predicted effect, and the authors say more work is needed to explain why. The study measured thresholds in a laboratory task, not functional communication or clinical outcomes.
The easy way to misread this
Do not read this as evidence that ear-switching speech causes everyday listening difficulty or that a therapy can be inferred from it. The study tested a laboratory method in young normal-hearing adults, and switching did not make performance as poor as when both sounds were in both ears.