Hearing and voice are the principal instruments of human communication. Early auditory experience of our native language(s) shapes the way we hear for the rest of our lives. By 12 months of age, we have already developed auditory perceptual skills around the speech phonemes we hear in social environments. This early specialization of auditory processing facilitates sensorimotor integration as we learn to speak; accurate phoneme discrimination in the first year of life is correlated with language proficiency years later. An important goal in the pursuit to understand how we acquire and use speech and what goes wrong when we can't use speech is determining how developmental experience of vocal sounds shapes auditory processing and perception for successful communication. While it is clear that the optimal time in life for language development is limited to before puberty, we do not know why the young brain is particularly sensitive to auditory-vocal experience or how vocal learning shapes auditory circuits in the service of communication. We propose to integrate manipulations in vocal learning with measures of central auditory processing and behavior to determine how early auditory-vocal experience shapes development of the auditory cortex and perception in songbirds. The proposed experiments will identify neural mechanisms for experience-dependent development of vocal communication. The significance of the proposed research to the NIH mission is three-fold. First, this work will identify changes in auditory cortical processing that accompany milestones in normal vocal learning. Second, the work will test the impact of delayed and impaired vocal development on auditory processing and perception. Third, our results will provide insights into how experience manipulations and training can improve prevention, diagnosis and treatment of developmental speech impairments such as those observed in children with auditory spectrum disorders.