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Large-scale phylogenetic studies of animal cognition have revealed robust links between 6 absolute brain volume and species differences in executive function. However, past comparative 7 samples have been composed largely of primates, which are characterized by evolutionarily 8 derived neural scaling rules. Therefore, it is currently unknown whether positive associations 9 between brain volume and executive function reflect a broad-scale evolutionary phenomenon, or 10 alternatively, a unique consequence of primate brain evolution. Domestic dogs provide a powerful 11 opportunity for investigating this question due to their close genetic relatedness, but vast 12 intraspecific variation. Using citizen science data on more than 7,000 purebred dogs from 74 13 breeds, and controlling for genetic relatedness between breeds, we identify strong relationships 14 between estimated absolute brain weight and breed differences in cognition. Specifically, largerbrained 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.

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