Perceptual expectations, attention, and speech recognition.

Research has demonstrated substantial plasticity in the adult speech perceiver. When listeners receive feedback about the classification of a speech signal, this feedback can shape attention affecting phoneme perception. This demonstrates that it is possible to shape perceptual attention prospectively changing subsequent speech perception. These changes can also reduce the cognitive load of speech perception. The effect of expectations on speech perception has been reported for a wide range of studies from sinewave speech perception to phonetic categorization and effects of talker variability. Neural changes occurring during learning and the neural effects of expectations both appear to involve regions of motor cortex implicated in speech production. These neural changes suggest a model of speech perception similar to analysis-by-synthesis in which sensory processes are tuned by activity within the speech motor system. Although such sensory-motor interactions have been implicated in speech perception due to coarticulation and the encoding of speech into sound, the role of expectations in speech perception may extend beyond segmental perception. We consider evidence that the interpretation of prosodic signals also depends on perceptual expectations, suggesting that the role of expectations may be to constrain recognition given the many-to-many relationship that holds broadly in speech.