I think it makes perfect sense to talk about the social brain, but I strongly agree with the proposition by Lockwood et al. that it is crucial to distinguish the aspects of this question on Marr’s three levels of explanation. There are some fascinating human evolutionary questions that I don’t find mentioned in these two papers, for instance, the distinction between biological and cultural evolution. What kind of “social brain” is required for the ability for complex cultural transmission, as displayed in human communities, but not other animals? Lockwood et al. propose that the best candidate for a clearly socially specific algorithm is theory of mind processing. Strikingly, this is an ability that is commonly only attributed to humans. How are the two abilities – ToM and cultural transmission — related?
Other animals clearly also display social behaviours to varying degrees. Some findings in primates and dogs at least stretch the boundaries of insisting on very human-specific interpretations of both of these abilities. In light of biological evolutionary trajectories, the most sensible conception of social brain abilities would consist of a gradual continuum, rather than sharp, discrete boundaries. But perhaps on a certain level of explanation, especially if we’re looking at abilities such as ToM and cultural transmission, there is indeed some more discrete kind of leap that corresponds to the uniqueness of human “social brains”.
On another note, perhaps our difficulty to explain social behaviours in scientific models without implicating these two abilities stems from our own perpetual reliance on them throughout our everyday lives. Perhaps there is also something to gain from trying to come up with models of the social brain without necessarily involving these two highly human-specific abilities.