The aim of this research proposal is to determine whether children use amplitude comodulation (AM) as a grouping cue in the formation of auditory objects. Specifically, auditory object formation refers to the ability to separate the auditory foreground from the background. This project will examine whether children's ability to use AM as a grouping cue is different from adults and whether this ability changes with development. Although researchers are currently studying auditory object formation in adults, little is known about the development of this phenomenon in children. Because the study of auditory grouping in speech perception is complicated by the fact that speech contains numerous acoustic characteristics, time varying sinusoidal (TVS) speech will be used. These stimuli do not contain typical acoustic characteristics of speech and have been used in previous studies to examine auditory grouping in adults. New stimuli will be developed based on age-appropriate sentences. This project will examine the ability of adults and children to use AM as an auditory grouping cue in the perception of TVS sentences. Speech recognition of TVS sentences (unmodulated and AM at four frequencies) will be obtained. It is hypothesized that children are less able than adults to use AM as an auditory grouping cue and that children's ability to use this information improves with age. The results of this study will enhance our knowledge of the process of auditory object formation in children's speech perception.