The social brain and how it works to make first impression connections
By Kaeci Charles UA’26 and Jim Stellar
We previously wrote a blog about first impressions using the metaphor of thin slicing by Malcom Gladwell. Now we want to discuss how that might work in the brain, particularly the social brain.
First, what is the social brain? Research on this topic has been a long standing interest of scientists, but one place to begin is with the Dunbar number. This number was proposed by a British anthropologist, Robin Dumbar in a paper in 1992, that suggested a relationship between the size of the cerebral cortex and the size of a social group that species can manage. The basic idea was to sort out who was a free-rider and who was helpful (a reciprocal altruist) on an individual group member basis and keep track of all the individuals in the group. So, obviously, a bigger group required a bigger brain (i.e. neocortex).
The result is that social behavior is considered perhaps a driver of the evolution of expanded brain size and the neural mechanisms that also underlie the social brain. The social brain allows us to operate and process social information like first impressions, fear, and empathy. Dunbar and Shultz later pointed out how we instinctively use the term “bondedness” simply because we experience it ourselves. However we find ourselves unable to fully describe in words how these bonds form in good part because the mechanisms for forming those bonds are likely in the limbic system, which transmits value information to the planning neocortex, but does not (or cannot) transmit the calculations used to determine that value judgement. The value judgment, like a bonding, is an endpoint not a process. It is not like a recipe for making blueberry pie that can even be handed down through the generations. It is just how the brain is built according to Gary Marcus in his book Kluge, and it requires cognitive reflection and insight to understand that value information to our planning.
One mechanism that is thought to be involved in forming bonds through social behavior is the mirror neuron system. These are motor command neurons that fire when the organism (e.g. monkey or human) sees another do a behavior it might do, like pick up a raison and put it in their mouth. This mechanism is thought to allow that organism to put itself in another’s place, maybe even understanding their actions and emotions of others. This mirror mechanism is thought to resemble a tuning fork where the vibrations of a ringing tuning fork can lead another tuning fork to also vibrate. Mirroring is said to be a sign of trust, portraying that people are in synchrony, resulting in an increase in bondedness between one another. With this we can say that the mirror mechanism is a part of the social brain as it can explain one of the ways we internally bond without realising it.
During first impressions neural pathways in the parietal-frontal network, Broca’s area, and the anterior cingulate cortex can fire mirror neurons. The frontoparietal network is a key player in cognitive control, ones voluntary goal-driven behavior. Within the frontoparietal network, the anterior cingulate cortex processes an individual’s actions, and works to decide what the next course of action should be. One 2004 paper looked at the anterior cingulate’s role in conflict monitoring, which allows one to assess a situation of potential conflict and facilitate a possible resolution. In a situation of conflict, one of the brain’s goals is to look at someone else’s actions, and act accordingly to maintain cognitive control. During first impressions, the goal of the interaction is to bond, so the anterior cingulate will assess an individual’s actions, and mirror them as the maintenance action needed for bonding to occur.
One of the ways neuroscientists have approached this issue is through the use of something called fMRI hyperscanning where two or more people are brain-scanned simultaneously while they are interacting. Now given the nature of a brain-scanner today by big machines, the social interactions are limited to on a screen and not face-to-face and certainly without the mobility to which we are accustomed in the real-world. However, it is still very interesting and allows the researchers to look at whether there is some neural synchrony in brain activity that goes along with social interactions, perhaps when those interactions are empathetic. One study using near-infrared hyperscanning implicated the dorsolateral prefrontal cortex. But it is much more likely that brain networks will be involved such as the default mode network and its interaction with other brain networks such as its interaction with the task-positive network. Some of this understanding may depend upon knowing the individual well from repeated scans, called precision fMRI.
Summary and Conclusion: Mirror neurons can help us further understand the neural mechanics of bond formation. Mirror neurons working synonymously with the frontoparietal network are key players in one’s ability to form bonds with others. Now of course other factors may come into play when deciding who to bond with based on certain criteria. Nevertheless, there is an innate, almost subconscious way that bonds can form quickly during things like first impressions, interviews, first dates, etc. The social brain has an amazing ability to use human interaction to determine the likelihood of bondedness between two individuals.
With this knowledge, we can take a look at individuals who have difficulties bonding with others and understand the neural mechanisms that may be compromised. When considering individuals with autism, the mirror neuron mechanism may operate in a different way compared to someone without autism. This could explain why some individuals with autism struggle with social cues. In an individual without autism, reading social cues subconsciously can work with the mirror neurons to help boost the bond between two people. Deviations within the mirror neuron system could be one of the reasons why people with autism struggle with social and nonverbal cues when communicating with others.
This work is complex and subtle and we intend to come back to it.
