Yes. Specifically, the prefrontal cortex, a region of the brain located above the eyes, is larger the greater the number of friends we have, according to a British study published in the journal 'Proceedings of the Royal Society B'.
Research suggests that to maintain a number of friends we need to use a cognitive skill called "mentalization", and that the ability to understand what another person is thinking and their mental state is defined from their behavior. This ability is crucial to manage our complex social world, even to converse with others (friends or acquaintances). And it increases the larger the size of the prefrontal cortex , according to neuroimaging techniques used by Robin Dunbar and his colleagues at the Institute of Evolutionary and Cognitive Anthropology at the University of Oxford (UK).
"Perhaps this helps us understand why humans have larger brains than other primates," Dunbar suggests.
