Perceptual Adaptation to Noise-Vocoded Speech by Lip-Read Information: No Difference between Dyslexic and Typical Readers

Auditory speech can be difficult to understand but seeing the articulatory movements of a speaker can drastically improve spoken-word recognition and, on the longer-term, it helps listeners to adapt to acoustically distorted speech. Given that individuals with developmental dyslexia (DD) have sometimes been reported to rely less on lip-read speech than typical readers, we examined lip-read-driven adaptation to distorted speech in a group of adults with DD (N = 29) and a comparison group of typical readers (N = 29). Participants were presented with acoustically distorted Dutch words (six-channel noise-vocoded speech, NVS) in audiovisual training blocks (where the speaker could be seen) interspersed with audio-only test blocks. Results showed that words were more accurately recognized if the speaker could be seen (a lip-read advantage), and that performance steadily improved across subsequent auditory-only test blocks (adaptation). There were no group differences, suggesting that perceptual adaptation to disrupted spoken words is comparable for dyslexic and typical readers. These data open up a research avenue to investigate the degree to which lip-read-driven speech adaptation generalizes across different types of auditory degradation, and across dyslexic readers with decoding versus comprehension difficulties.