©2018 by Samantha Carouso-Peck, Photography by Michael Goldstein.



Using Video to Manipulate Social Feedback

Although it has been demonstrated as a vocal learning mechanism in human infants, learning via active social feedback is considered rare and atypical among non-human animals.  We found the first evidence that song learning in the zebra finch (Taeniopygia guttata), the most common model species of vocal learning and development, utilizes socially guided vocal learning. We used a video playback paradigm to demonstrate experimentally that the songs of juvenile zebra finches are guided towards mature vocal forms by real-time visual feedback from adult females that is contingent on their early, immature vocalizations. We found that juvenile birds that received non-vocal female feedback contingently on their immature song learned significantly better and more accurate song than did yoked controls that received identical but non-contingent feedback.  Both contingent and non-contingent groups sang at similar rates. Non-imitative social learning is a crucial, potentially widespread mechanism of vocal development, and have established a foundational parallel between humans and our most ubiquitous animal model of vocal learning – the crucial role of social feedback to immature vocalizations in the development of communication. I am currently investigating the exact mechanisms driving this effect, by manipulating the timing and form of feedback, as well as using non-biological controls.

Manipulations of Organizational Nonapeptides Affect Social Behavior and Song Learning

Social interactions organize attention and enhance motivation to learn species-typical behavior. However, the neurobiological mechanisms connecting social motivation and vocal learning are unknown. Using zebra finches, we found that manipulations of nonapeptide hormones in the vasopressin family [arginine vasotocin (AVT)] early in development can promote or disrupt both song and social motivation. Young male zebra finches, like human infants, are socially gregarious and require interactive feedback from adult tutors to learn mature vocal forms. To investigate the role of social motivational mechanisms in song learning, we injected hatchling males with AVT or Manning Compound (MC, a nonapeptide receptor antagonist) on days 2-8 post-hatching and recorded song at maturity. AVT males produced adult song that was a better acoustic match to their tutor’s song, whereas MC males produced a worse match. AVT birds’ songs were of surprisingly high quality; they learned significantly better than controls. Furthermore, song similarity was correlated with several measures of social motivation throughout development. These findings provide the first evidence that nonapeptides are critical to the development of vocal learning.

Ecological Traits Predict Evolution of Socially Guided Vocal Learning

Despite their phylogenetic distance, humans, marmosets, orcas, cowbirds, and zebra finches share several traits that may have given rise to socially guided vocal learning as a solution to the problem of developing communicative competence.  For example, these species are all socially gregarious, ensuring developmental access to social feedback, and all use their learned vocalizations to facilitate and maintain social bonds. Early in development, each of these species can learn new vocal forms at the same time they are producing immature vocalizations, which may facilitate a role for social feedback in response to immature vocalizations as a means of influencing vocal learning. In order to investigate whether particular ecological traits may be predictive of the likelihood of a given songbird species to utilize a socially guided vocal learning strategy, we constructed an evolutionary model. Using 28 well-studied passerine species, we conducted a literature search for evidence of social influences on vocal learning, to use as an outcome measure of susceptibility to social influences on song ontogeny. We investigated a number of ecological, developmental, and reproductive traits (hereafter referred to as ‘traits’), to determine which are predictive of the likelihood of a given species to utilize socially guided vocal learning.

Naturalistic Behavioral Analysis of Development, Family Interactions, and Feedback Behaviors

While we have found evidence that videos of female feedback affect juvenile song learning, we do not know to what degree such feedback occurs in natural contexts, how live conspecific feedback impacts song learning, or how different individuals in a family or flock might affect song differently. We performed a longitudinal study of juveniles raised with their families to study the unique and combined contributions of the feedback of mothers, fathers, and siblings in shaping the songs of young males across ontogeny, and the development feedback behaviors of young females.

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