The law draws a line between being a minor and adulthood at 18 years of age in several ways. Voter registration, marriage without parental consent, and serving in juries are some examples. In 2005, the same distinction was made to juveniles facing trial for capital murder after the Rover v. Simmons case. In this case, the Court found that juveniles lack sufficient culpability and deterability to permit execution consistent with the Eighth Amendment (from Winick 2008).
How does the 18-year-old line compare to what we know about neurodevelopment and decision-making? There is ongoing research on neurodevelopment, especially now that MRI imaging techniques allow neuroscientists to peer into the human skull non-invasively. The research of Dr. Jay Giedd at the National Institute of Mental Health in Bethseda, Md., for example, looked at the brains of 145 healthy children at two-year intervals. One particular finding from this research is that the area of the brain called the prefrontal cortex (PFC) begins growing again before puberty.
The PFC is important in regulating behavior, controlling and regulating mood, planning, and organization. This role is known as the ‘executive function’ of the PFC and it might be helpful to understand that the PFC acts as the CEO of the brain. This area of the brain is still growing in teenagers (referenced in Spinck). In fact, the PFC is usually fully developed by age 25.
What does it mean for the PFC to be ‘under construction'? From the physiological perspective, this is the phase where synapses are pruned and consolidated. Gray matter is lost as some connections are enhanced and stabilized by an increase white matter. What can we say about the effects of this development on behavior? It is currently impossible to predict behavior or function from brain structure. As this research progresses, more will be known about how neurodevelopment may influence behavior.
Will these findings cross over to the legal system? The answer is problematic. It is unlikely that everyone’s brain will reach mature development at the same age. Some might mature at a much slower pace, and should this affect their legal status? The answer will be complicated, but there are some positive applications of these findings. For example, since the teenage brain undergoes a ‘growth-spurt’ just before puberty, and continues to develop until the early twenties, there may be many possibilities for rehabilitation. A better understanding of such development would help cognitive neuroscientists understand how to approach teens that exhibit antisocial or criminal behavior to maximize chances of improvement in their futures.