Karl Berg, Ph.D. - US grants

Vocal babbling occurs at a critical juncture in infant psychological and vocal development and can translate into important differences in intelligence later in life. However, it is unknown what causes some babies to babble more or differently than others in the first place. This project uses an animal model to examine one popular, yet un-tested, hypothesis that the quantity and quality of playmates stimulates cognitive development as displayed by more robust vocal babbling. Early social environment can have dramatic and lasting effects on behavior in highly intelligent animals, but most models of language learning have focused on adult-juvenile interactions; occur in captive or laboratory settings; suffer from small sample sizes; or lack crucial experimental evidence. Capitalizing on a long-term, pedigreed population of wild parrots, this project manipulates the number of sibling nest mates to examine later effects on vocal babbling. Research will also investigate how social play and stress hormones impact learning. Parrots are good models to examine social influences on language learning because they have the most sophisticated vocal imitative abilities of non-humans, they have long-term pair bonds, and an elaborate and elongated period of juvenile play. Results will provide a firmer foundation for exploring potential pathways involved in early human cognitive and vocal development. The project is based at a minority serving institution in an economically disadvantaged region of the U.S. long underrepresented in science and math and will provide hands-on scientific training to a large number of undergraduate and graduate students.

Songbirds have been the main model for research on the neurobiology and neuroendocrinology of vocal imitation. However, song differs from human spoken language in that the former is often restricted to males who learn during a brief sensitive phase in development, a masculinization process in the brain strongly influenced by gonadal steroids; later in adulthood, song is activated by the same androgenic steroids. In humans and parrots, individuals of both sexes use complex lingual articulation of sounds to learn new vocalizations throughout life, but little is known about how the endocrine system mediates vocal learning in both sexes. While a role for sex steroids cannot be ruled-out, stress steroids such as corticosterone tend to be more sex-neutral and can have a profound influence on neural substrates during early development. Work will: 1) quantify individual variation in the spectrographic structure of nestling vocal babbling as a function of brood size and hatching sequence; 2) quantify metrics of social networks and how these relate to patterns in 1; 3) measure adrenocortical responsiveness and any correlations with 1-2; 4) experiment through brood size and corticosterone manipulations to establish causal explanations for patterns found in 1-3; and 5) use path analysis to delineate developmental steps. Given the large variation in brood size (4-11 nestlings), this presents a unique opportunity to test if sibling social interactions foster learning processes indirectly, or directly through provisioning of vocal templates to younger siblings. Either scenario would represent novel learning strategies in birds and transform our view of early psychological development. Results will be disseminated via publications in peer-reviewed national and international journals and presentations at national and international meetings. Both undergraduate and graduate student research support is provided as well as international researcher involvement.