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bbcnews | Monkeys at the top and bottom of the social pecking order have physically different brains, research has found.
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.
"We were also looking at learning and memory
and decision-making, and the changes that are going on in your brain
when you're doing those things," explained Dr MaryAnn Noonan, the
study's first author.
The decision to look at the animals' social status produced an unexpectedly clear result, Dr Noonan said.
"It was surprising. All our monkeys were of different ages
and different genders - but with fMRI (functional magnetic resonance
imaging) you can control for all of that. And we were consistently
seeing these same networks coming out."
The monkeys live in groups of up to five, so the team
identified their social status by watching their behaviour, then
compared it to different aspects of the brain data.
In monkeys at the top of their social group, three particular
bits of the brain tended to be larger (specifically the amygdala, the
hypothalamus and the raphe nucleus). In subordinate monkeys, the
tendency was for a different cluster of regions to be bigger (all within
the striatum).
