A particular network of brain areas was bigger in dominant animals, while other regions were bigger in subordinates.
The study suggests that primate brains, including ours, can be specialised for life at either end of the hierarchy.
The differences might reflect inherited tendencies toward leading or following, or the brain adapting to an animal's role in life - or a little of both.
Neuroscientists made the discovery, which appears in the journal Plos Biology, by comparing brain scans from 25 macaque monkeys that were already "on file" as part of ongoing research at the University of Oxford.