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Time and time again, I hear the term the social brain when people talk about social cognition. It’s a catchy phrase that captures how important social behavior is to the brains of social species, like us. However, this catchy terminology can also be misleading.
I try not to use it, but sometimes I give in to its efficiency in communicating that a vital function of the brain in social species is regulating social behavior. Essentially, the social brain suggests that there is a set of specialized brain regions for computing socially relevant information. In this blog post, I’ll unpack this and along the way hopefully convince you that this term can easily create and maintain a distorted view of how the brain computes social cognition.
The main concept underlying the social brain initially came from observing that lesioning certain areas of the brain leads to substantial impairments in social behavior. This concept has since been reinforced by many functional neuroimaging (fMRI) studies in people. The social brain has become a popular term to capture the important involvement of several of these brain regions in mediating social behavior. Largely, the social brain generally refers to the temporal parietal junction, posterior superior temporal sulcus, medial prefrontal cortex, anterior cingulate cortex, amygdala, and other regions implicated in social functions. These brain areas are reliably engaged (more so than other areas) when we are thinking about others, interacting with them, putting ourselves in their shoes, deciding to help them, cooperating or competing with them, and so on. Basically, these are the basic elements of being human.
However, the imprecision of the term is paramount. The mere fact that these brain areas are consistently activated when we interact socially does not mean that they are really specialized for social behavior. Instead, it is just as likely that these brain areas are driven by complex cognitive operations, such as inferential reasoning, predictive thinking, and reward valuation, that also happen to underlie core aspects of social functions. If one were to examine how nerve cells convey information by emitting electrical signals in one of these brain areas during social and non-social behaviors, we would likely find an immensely wide range of neural signals, ranging from non-social to social information, and everything in between.
Moreover, establishing the selectivity of a brain region to social over non-social computations is inherently complicated by the method used. For example, if we were to identify brain areas that show greater activation for social (compared to non-social) events, certain areas might appear to be selective to social functions. But if we were to zoom in to the level of ion channels necessary for nerve cells to send electrical signals in one of these brain areas, it would be humorous to consider whether such ion channels are selective to social functions – they’re not. Labeling brain areas as selective to social stimuli, then, would essentially mean ignoring the fact that the molecular and cellular, and sometimes even circuit-level building blocks of these brain areas are commonly shared in both social and non-social domains. How, then, could we claim functional specialization of these areas to social functions?
So, what is the real value, if any, in using the expression the social brain when we talk about social cognition in the brain? I think the merit behind this term is the emphasis on the importance of social interaction in our daily lives. Many central cognitive functions of the brain, such as valuation of rewards, emotion, and executive control, frequently take place in social contexts. In highly social species, the most common environment in which our brain does its work is a social environment. I would argue that the brains of highly social primate species, like us, are built to navigate and increase survival fitness in their social environments. Many brain regions may belong to the social brain by virtue of our brains being fine-tuned over evolution to operate in social settings. This point references Dr. Robin Dunbar’s famous Social Brain Hypothesis, where the term “social brain” is used to associate brain size with social complexity in primates and signifies the importance of social engagement in shaping primate brain evolution. Perhaps it really is true that one cannot understand the brain without taking into account its long evolutionary history.
