Description) Across the world, adults exaggerate many of the prosodic and linguistic attributes of their speech when talking to infants. Such infant-directed (ID) speech is preferred by infants throughout the first postnatal year, compared to adult-directed (AD) speech. Several researchers in this area have speculated that ID speech is a powerful modulator of infant attention, leading it to be a primary candidate for affecting aspects of infant perceptual development. Outside of behavioral measures such as looking time, however, no psychophysiological measures of attention have been obtained from infants as they listen to ID speech. The goal of this application is to expand the behavioral paradigm used in the investigator's laboratory to include measurements of changes in autonomic nervous system activity as infants attend to speech. Specifically, both a visual attention measure (looking time) and a psychophysiological attention measure (heart rate activity) will be recorded in one and four month-olds as they listen to various recordings of female ID and AD speech. Separate groups of infants will be given the opportunity to control their exposure to one of two speech recordings. These contrasts will consist of either natural ID or AD utterances, or variations of ID speech in which the pitch, rate, or communicative intent of the utterances has been altered. Of primary interest is whether the patterns of attention will vary both as a function of infant age and type of speech to which they were listening. Generally, it is predicted that ID speech will produce greater heart rate decelerations and longer deceleratory periods, coupled with longer looking times as compared to those generated by AD speech in both age groups. However, the degree to which ID speech produces such behavioral and psychophysiological effects will vary as a function of age and its pitch and rate characteristics. In addition, the investigator predicts that naturally-produced ID utterances intended to maintain infant attention will produce similar effects as compared to those in response to ID utterances intended to elicit infant attention, but only at four months of age. This will be the first demonstration of heart rate activity related to the acoustic characteristics of ID speech, and will provide the foundation for a new avenue of research tht explores individual differences in infants' autonomic and behavioral responses to the natural language of their environments. For example, these poreliminary data will allow us to plan future studies which will explore whether the flat expressive affet shown by the infants of clinically depressed women is a correlate of diminished (or at least different) autonomic nervous system responsivity.
