Cognition gone wild: A test of the social intelligence hypothesis in wild birds
McCune, Kelsey Brenna
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Complex sociality evolved in many species across the animal kingdom, including humans. Species in complex social systems are likely adapted to not just the physical environmental niche (like climate and foraging resources), but also to social environmental pressures. Therefore, one consequence of complex sociality might be the evolution and development of complex cognitive abilities to enable successful navigation of social interactions for increased survival and fitness within the social group. The social intelligence hypothesis (SIH) posits that species exhibiting dynamic relationships and groups with larger sizes will also evolve increased cognitive abilities. However, previous research testing this hypothesis relied on broad proxy measures for both sociality and cognition to compare species across taxa. Studies that do experimentally assess cognition are conducted in tightly controlled, artificial lab environments. As a result, there is still extensive conflicting evidence for the effect of sociality on the evolution of cognition. In the research presented here I used social network analysis to directly quantify the sociality of two congeneric jay species, the social Mexican Jay (MEJA) and the relatively asocial California Scrub-Jay (CASJ). I conducted cognitive assessments on individuals from both species in the wild, and experimentally tested whether these subjects and a subset of these subjects who were tested in temporary captivity performed similarly. I also quantified whether sociality had a divergent effect on the behavioral response to a threatening stimuli in two boldness contexts. I found that naïve individuals from the social species did not imitate novel foraging behavior of knowledgeable conspecifics and did not significantly outperform CASJ. Instead, behavioral responses of individual MEJA to the novel foraging task and the two threat contexts were associated with a mechanism of social facilitation. In contrast, CASJ have higher quality social relationships with their mate, but showed no indication of an association between social context and behavioral responses to the foraging or threat tasks. By directly quantifying cognitive and behavioral performance on an ecologically relevant task in the social and physical environment in which selection is occurring, I found limited support for the SIH. Future research that expands on these methods by testing additional congeneric species pairs, and different socio-cognitive mechanisms like transitive inference will further increase our understanding of the effect of sociality on brain evolution and development.
- Psychology