Individual differences in the perceptual learning of degraded speech: implications for cochlear implant aural rehabilitation

In the noise and commotion of daily life, people achieve effective communication partly because spoken messages are replete with redundant information. Listeners exploit available contextual, linguistic, phonemic, and prosodic cues to decipher degraded speech. When other cues are absent or ambiguous, phonemic and prosodic cues are particularly important because they help identify word boundaries, a process known as lexical segmentation. Individuals vary in the degree to which they rely on phonemic or prosodic cues for lexical segmentation in degraded conditions.

Deafened individuals who use a cochlear implant have diminished access to fine frequency information in the speech signal, and show resulting difficulty perceiving phonemic and prosodic cues. Auditory training on phonemic elements improves word recognition for some listeners. Little is known, however, about the potential benefits of prosodic training, or the degree to which individual differences in cue use affect outcomes.

The present study used simulated cochlear implant stimulation to examine the effects of phonemic and prosodic training on lexical segmentation. Participants completed targeted training with either phonemic or prosodic cues, and received passive exposure to the non-targeted cue. Results show that acuity to the targeted cue improved after training. In addition, both targeted attention and passive exposure to prosodic features led to increased use of these cues for lexical segmentation. Individual differences in degree and source of benefit point to the importance of personalizing clinical intervention to increase flexible use of a range of perceptual strategies for understanding speech.