Vocal imitation is an essential component of early language acquisition in human infants. It occurs intensively during infancy, but is much less efficient later in life. A similar phenomenon occurs in songbirds: a zebra finch can accurately imitate a series of complex sounds during a sensitive period of its ontogeny, but as the bird grows up, it gradually loses the ability to imitate. During the current project period, we examined how individual syllables are learned during development. Trajectories of vocal change were traced from the early subsong to the mature song revealing the specific methods the bird uses for mastering a syllable. The proposed continuation will study how the order of sounds (syntax) changes during vocal learning until it matches the target. This process has interesting parallels with speech development, but it has not been analyzed quantitatively, largely due to a paucity of data. New techniques have overcome this problem, allowing the recording of all the songs during development, their automatic partitioning and the categorization of sounds. It is now possible to analyze the entire ontogenetic sequence and identify the emergence of each syllable type and the syntax rules that relate them. Research proposed here will examine if song syntax develops in identifiable stages. Song syntax will be characterized within and across narrow developmental windows using simple statistical models. We propose to compare syntax development between isolates versus trained birds, and between species with different song syntax complexity. Our previous research examined the effect of age on vocal learning. Data showed that delaying the onset of training results in fragmented imitation despite obvious signs that the birds were motivated to learn. The proposed research will attempt to improve vocal learning in older birds using approaches that have been successful in other forms of developmental plasticity e.g., gradual shifting of auditory-visual maps in barn owls (Linkenhoker & Knudsen, 2002). In particular, we will test whether vocal learning can be guided by providing the bird with clues that will direct the birds towards mastering certain sounds and towards assembling the appropriate syntax. In addition, we have discovered natural daily fluctuations in vocal learning that may be related to sleep. Proposed research will explore the nature of these fluctuations. The results may help relate brain mechanisms (e.g., song-like neural activity during sleep) to natural behavior. Finally, technology developed in the course of this research and used in a number of laboratories will be further enhanced and generalized to allow integration of vocal learning analysis across behavioral and neural levels. This work may facilitate a broader understanding of the acquisition of arbitrary sequences of behavior, and, as such, may be relevant to disorders in language acquisition in children. [unreadable] [unreadable]