Absolute brain size predicts dog breed differences in executive function
Large-scale phylogenetic studies of animal cognition have revealed robust links between absolute brain volume and species differences in executive function. However, past comparative samples have been composed largely of primates, which are characterized by evolutionarily derived neural scaling rules. Therefore, it is currently unknown whether positive associations between brain volume and executive function reflect a broad-scale evolutionary phenomenon, or alternatively, a unique consequence of primate brain evolution. Domestic dogs provide a powerful opportunity for investigating this question due to their close genetic relatedness, but vast intraspecific variation. Using citizen science data on more than 7000 purebred dogs from 74 breeds, and controlling for genetic relatedness between breeds, we identify strong relationships between estimated absolute brain weight and breed differences in cognition. Specifically, larger-brained breeds performed significantly better on measures of short-term memory and self-control. However, the relationships between estimated brain weight and other cognitive measures varied widely, supporting domain-specific accounts of cognitive evolution. Our results suggest that evolutionary increases in brain size are positively associated with taxonomic differences in executive function, even in the absence of primate-like neuroanatomy. These findings also suggest that variation between dog breeds may present a powerful model for investigating correlated changes in neuroanatomy and cognition among closely related taxa.
KeywordsCognitive evolution Brain evolution Brain size Executive function Breed differences Citizen science
We thank Laurie Santos, Richard Wrangham, David Ivy, Eliot Cohen, Kip Frey, and all other members of the Dognition.com team for their help in the creation of Dognition.com; Adam Boyko, Martin Schmidt, and James Serpell for sharing data used in this project; Stacey Tecot and David Raichlen for valuable feedback on previous drafts; and especially all of the dog owners who participated in Dognition.com experiments as citizen scientists.
BH, JC, JK, ÁM, and ELM conceived and designed the experiments. DJH and ELM analyzed the data. DJH, BH, JC, JK, ÁM, and ELM wrote the paper.
DJH was supported by an Emil W. Haury Fellowship from the School of Anthropology at the University of Arizona, and a Graduate Access Fellowship from the Graduate College at the University of Arizona. ÁM was supported by the Hungarian Academy of Sciences (MTA-ELTE Comparative Ethology Research Group, MTA 01 031).
Compliance with ethical standards
Conflict of interest
BH is a founder of Dognition.com and a member of its Scientific Advisory Board. JC, JK, and ÁM are also members of the Dognition.com Scientific Advisory Board.
Data are available as electronic supplementary material.
All animals included in this study were pet dogs tested by citizen scientists in their own homes. The use of third-party data from Dognition.com was approved by Duke University IACUC protocol A138-11-06 and data were collected in accordance with relevant guidelines and regulations.
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