Infant speech perception develops within the context of specific language experience. While there is a corpus of empirical evidence concerning infants' perception of linguistic and prosodic information in speech, few studies have explored the interaction of the two. The present investigation was designed to combine what is known about infants' perception of nonnative phonemes (linguistic information) with what is known about infant preferences for ID speech (prosodic information). In particular, the purpose of this series of studies was to examine infant preferences for ID speech within the timeline of the phonemic perceptual reorganization that occurs at the end of the first postnatal year. In Experiment 1, 20 Native-English 10- to 11-month-old infants were tested in an infant-controlled preference procedure for attention to ID speech in their native language versus ID speech in a foreign language. The results showed that infants significantly preferred the ID-native speech. In Experiment 2, the preferred prosodic information (ID speech) was separated from the preferred linguistic information (native speech), as a means of discerning the relative perceptual draw of these types of speech characteristics. Specifically, a second group of 20 10- to 11-month-old infants was tested for a preference between ID speech in a foreign language and AD speech in their native language. In this case the infants exhibited a significant preference for ID-foreign speech, suggesting that prosodic information in speech has more perceptual weight than linguistic information. This pattern of results suggests that infants attend to linguistic-level information by 10- to 11-months of age, and that ID speech may play a role in the native-language tuning process by directing infants' attention to linguistic specifics in speech. / Master of Science