The Development of the Social Brain

NeuroFluency PrinciplE: The brain develops in an experience-dependent manner.

Because the brain doesn’t develop in a linear fashion, we use our caretakers’ brains as adjuncts to our own early in life. Compare for example the fear circuits of the amygdala that are fully mature by birth with the cortical systems dedicated to regulating fear which take years to develop. During infancy and childhood, we rely on our caretakers to serve this yet to develop regulatory function.  The way in which our caretakers help us to deal with fear and anxiety shapes our own developing circuitry between our amygdala and prefrontal cortex. How this circuit is organized comes to reflect how we relate to others in the form of attachment schema. As our brains develop, our experiences shape the architecture of our neural circuitry, making our brains a living, three-dimensional expression of our histories.

There are also genetically timed bursts of neural growth called critical and sensitive periods that propel certain abilities to “come online” at specific times during development. Good examples are the emergence of stranger anxiety around eight months and the burst of language development at around 18 months. The challenges of childhood at home, school, and the community are mostly tailored to the adaptive skills of the age group they serve. Research has shown that these periods of enhanced growth must interact with exposure to specific challenges and stimuli in order to be fully taken advantage of. Children who are neglected or abused during early critical periods of attachment often have great difficulties in making up for the negative experiences during important developmental windows. 

The development of the teenage brain is characterized by the reorganization of networks involved in abstract thinking, emotional regulation, attachment, and reward.  This sensitive period is driven by the traditional social expectations that came along with adolescence to change your relationship with your family of origin, reorganize attachments in line with peer groups and mating, and take on the responsibilities of adulthood. Because modern Western society has postponed the timing of these challenges an extra decade, many adolescents are a poor fit for the ongoing dependency they must adapt to. They may gravitate to violent video games, challenging sports activities, and promiscuous sexual behavior in an attempt to fulfill the mandates of their genes and bodies. If this could be fully recognized by society, perhaps the timing of education could be modified and supplemented with activities and adventures more in line with brain development. Public work projects, archeological digs, exposure to other cultures would likely all be more successful than endless hours in classrooms for many adolescents.

As we mature into adulthood, the connectivity among neural regions increases as the white matter communication bundles continue to mature. There is also an increased ability to regulate our emotions because of the maturation of cortical-amygdala connections. These and many other changes parallel the demands placed on adults to do the consistent heavy lifting of the family and tribe and to employ sound judgment in the best interest of those who depend on them. This process continues into the later years of life as we shift to the roles and responsibilities of elders. Nurturing children and grandchildren, transmitting the stories, values and cultures of the tribe, and dealing with spiritual and complex social problems of the family and tribe. 

Some abilities, like remembering new information peak around age 25 and begins to slowly decline thereafter. This is likely due to the fact that through most of evolutionary history, there was not much new to learn after age 25, so the energy dedicated to those neural systems was diverted elsewhere. Others, like attachment, stay strong throughout life because of the necessity to nurture children, grandchildren, and new friends as old ones pass away. The primary developmental process during the last third of life is the increased participation of more areas of the brain in the service of complex problem-solving, especially in the areas of interpersonal dispute resolution and the appropriate allocation of resources. These were the high-level abstract skills necessary for the maintenance and survival of the tribe through many millions of years of primate/human evolution.

This is an excerpt from Dr. Cozolino’s book The Pocket Guide to Neuroscience for Clinicians.