Effect Of Social Influences On Developmental Processes In Songbirds

"Interactions with other individuals can greatly influence behavioral development. For example, infants and children demonstrate minimal speech and language learning following passive exposure to speech, and social interactions with adults enhance the acquisition and production of phonemes (Goldstein et al. 2003; Goldstein & Schwade 2008; Kuhl et al. 2003). Similarly, in social animals such as songbirds, social interactions with conspecifics can dramatically influence developmental processes and adult behaviors. In my thesis, I describe two sets of studies aimed at revealing the influence of social interactions on the development of song learning and preferences in songbirds.Previous studies have investigated the role of social interactions with conspecifics on song development, but such studies did not effectively control for the amount and type of song exposure, factors that significantly affect vocal learning. Here, I use a yoked paradigm that controls for the amount and type of song exposure to demonstrate that social interactions with adults significantly enhance vocal learning. I document that social influences on attention to song appear central to the social enhancement of learning since variation in attentiveness and in the social modulation of attention significantly predicted variation in learning. I also discovered that adult tutors alter the structure of their songs when directing them towards pupils in manners similar to how humans change their vocalizations when speaking to infants. These changes to song are distinct from the changes that occur when males sing female-directed courtship songs, suggesting that these vocal motor changes by tutors could promote song learning in juveniles. Furthermore, I also reveal that social interactions that rapidly enhance learning also increase the activity of norepinephrine- and dopamine-synthesizing neurons in the locus coeruleus and ventral tegmental area, suggesting a contribution of these areas to the social enhancement of song learning. Just as social experiences affect the developmental acquisition of song, early auditory song experiences can also shape female song preferences in adulthood. Females that associate with both parents throughout development show a significant preference for their father's song over other males' songs (Miller 1979). Furthermore, normally reared females prefer courtship songs over non-courtship songs and demonstrate different levels of neural activity in response to these songs (Woolley & Doupe 2008). While social interactions have been shown to affect song preference for different males, little is known about the role of early auditory experiences in the formation of preferences for courtship songs. I show that neural responses in higher order auditory processing areas to courtship and non-courtship songs are not affected by developmental experiences, suggesting that they arise independently of early auditory experience.Taken together, the studies described in this thesis reveal strong parallels between processes of vocal learning in humans and zebra finches, inherent biases in the zebra finch auditory system, and how developmental processes are critically shaped by social interactions in zebra finches." --