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Purpose: This study investigated the effects of external feedback on perceptual learning of visual speech during lipreading training with sentence stimuli. The goal was to improve visual-only (VO) speech recognition and increase accuracy of audiovisual (AV) speech recognition in noise. The rationale was that spoken word recognition depends on the accuracy of sublexical (phonemic/phonetic) speech perception; effective feedback during training must support sublexical perceptual learning. Method: Normal-hearing (NH) adults were assigned to one of three types of feedback: Sentence feedback was the entire sentence printed after responding to the stimulus. Word feedback was the correct response words and perceptually near but incorrect response words. Consonant feedback was correct response words and consonants in incorrect but perceptually near response words. Six training sessions were given. Pre- and posttraining testing included an untrained control group. Test stimuli were disyllable nonsense words for forced-choice consonant identification, and isolated words and sentences for open-set identification. Words and sentences were VO, AV, and audio-only (AO) with the audio in speech-shaped noise. Results: Lipreading accuracy increased during training. Pre- and posttraining tests of consonant identification showed no improvement beyond test–retest increases obtained by untrained controls. Isolated word recognition with a talker not seen during training showed that the control group improved more than the sentence group. Tests of untrained sentences showed that the consonant group significantly improved in all of the stimulus conditions (VO, AO, and AV). Its mean words correct scores increased by 9.2 percentage points for VO, 3.4 percentage points for AO, and 9.8 percentage points for AV stimuli. Conclusions: Consonant feedback during training with sentences stimuli significantly increased perceptual learning. The training generalized to untrained VO, AO, and AV sentence stimuli. Lipreading training has potential to significantly improve adults' face-to-face communication in noisy settings in which the talker can be seen. |
