Auditory Processing of Acoustic Cues for Prosodic Recognition

The variations of voice pitch (fundamental frequency, or F0) in human speech convey important emotional and linguistic information to the listener. For infants and young children, these prosodic cues are critical in the earliest stages of language acquisition. During the prolonged development of the auditory system from infancy to the teenage years children’s processing of prosodic information is likely to become more sophisticated as well. For children speaking a tonal language, the voice pitch changes of lexical tones are phonemic and are thus even more critical in oral communication. Given that prosodic information has the greatest ecological validity for the youngest children, we hypothesize that neural plasticity most strongly impacts the processing of prosodic cues in the earliest stages of development. Today, many young children and even infants who are profoundly hearing impaired or deaf are receiving cochlear implants (CIs) early in life. Studies have shown that earlier implantation provides children with an advantage over those who were implanted later. It seems clear that auditory stimulation and brain plasticity during the critical period are important for shaping the responsiveness of the auditory system to various aspects of speech and language. Although CIs do not transmit complex voice pitch cues with sufficient spectral resolution, the greater neural plasticity in the critical period may help early implanted CI children to overcome device limitations and maximize their reception of F0-related information. This may be achieved by i) enhanced sensitivity to the available (temporal envelope-based) cues for pitch and/or ii) improved ability to trade spectral pitch cues for other co-varying acoustic cues (“cue-weighting”). There is a dearth of knowledge about children’s psychophysical sensitivity to acoustic cues in general. In particular, few studies have rigorously quantified school-aged children’s ability to discriminate between different complex pitches. Little is known about children’s ability to use subtle differences in acoustic cues such as pitch, duration, or intensity in order to identify speech intonation or lexical tones. Even less is known about CI children’s abilities in these areas. Experiments proposed here represent a first attempt at addressing some of these gaps in the knowledge-base. The purposes of this proposed study is to determine school-aged NH children’s cue-weighting strategies for lexical tone recognition of spectrally intact vs. degraded speech, and compare with CI children’s cue-weighting strategies for spectrally intact lexical tones. Children with NH will be assessed for their reliance on F0 and duration cues to identify Mandarin lexical tone contrasts, using both spectrally intact and spectrally-degraded stimuli.