How Adolescent Neuroscience Has Transformed the Law

“I would there were no age between ten and three-and-twenty, or that youth would sleep out the rest; for there is nothing in the between but getting wenches with child, wronging the ancientry, stealing, fighting.” - Shakespeare, The Winter’s Tale, 1623

One constant in all recorded human societies is the recognized period of ambiguity that bifurcates childhood and adulthood. Long before the advent of fMRI and other brain scan technologies, observers have noted (and often derided as an era of “storm and stress”) the unique period of adolescence.

More than a century of behavioral research has shown that the psychosocial capacity of adolescents remains significantly underdeveloped as compared to adults (for review, see Steinberg, 2014). This psychosocial immaturity causes adolescents to be more vulnerable to peer pressure, increases their desire towards "sensation-seeking," undermines their ability to control impulses, and reduces their aversion to risk.

More recently—within the last decade or so—the burgeoning field of neuroscience has begun mapping the adolescent brain and linking past behavioral findings to the unique morphology and function of adolescent neural systems. In doing so, researchers have identified a troublesome mismatch: The brain's "pleasure center" is firing at all-time highs while the "control center" remains underdeveloped. Like muscle cars without breaks, adolescent brains are geared to seek out pleasure but lack the control mechanisms needed to keep emotional impulses in check.

The Unique Adolescent Brain: A Recipe for Trouble

More so than at any other time in the lifespan, adolescent brains experience significant dopaminergic activity in the limbic system—a region associated with emotion, sensation-seeking, and reward (Steinberg, 2009). Given its status as the chief neurotransmitter responsible for the experience of pleasure, dopamine plays a critical role in affective and motivational regulation. Put simply, increased dopaminergic activity in the limbic system results in a heightened motivation to experience new sensations and pleasurable stimuli.

While dopaminergic activity is at its peak in the limbic system, the pre-frontal cortex remains underdeveloped. Regularly referred to as the "control center of the brain," the pre-frontal cortex is responsible for rational thought, planning, decision-making, and the moderation of social behavior. During adolescence, this critical brain region is only just beginning to develop. Research has confirmed that the pre-frontal cortex does not completely mature until around age 25 (Sharma et al., 2013). Several clever studies utilizing fMRI brain scans have shown that adolescents engage their limbic system in response to certain tasks, such as navigating interpersonal interactions, reading others' emotions, making difficult decisions, and assessing risk, whereas adults engage primarily their pre-frontal cortex (e.g., Somerville et al., 2011). Without a fully developed pre-frontal cortex to moderate the effects of high dopaminergic activity in the limbic system, adolescents are neurologically predisposed to seek out new and exciting stimuli, discount risk, demonstrate poor impulse control, and fall prey to peer pressure.

By offering new insights into the inner workings of the adolescent brain, neuroscience has completely transformed and revolutionized how developmental scientists view this unique period of life. Interestingly, it's not just scientists who are taking note; attorneys, judges, and lawmakers have also started looking to neuroscience research when enacting serious change within our legal system (particularly the juvenile system).

How Adolescent Neuroscience Has Changed Our Laws: Three Seminal Supreme Court Cases

In 1993, 17-year-old Christopher Simmons was convicted of robbing and murdering Shirley Crook by tying her up and throwing her off a bridge into a river below. He was later sentenced to the death penalty. After more than a decade of legal appeals (capital punishment cases are often extremely long and protracted), Simmons' case found its way to the Supreme Court in Roper v. Simmons, 543 U.S. 551 (2005).

Attorneys for Simmons argued that executing a juvenile amounted to cruel and unusual punishment in violation of the Eighth Amendment. The Court agreed and summarily banned the death penalty for juveniles nationwide. Interestingly, the Court's opinion actually relied heavily on neuroscientific research showing that adolescents have less impulse control, increased susceptibility to peer influence, and immature reasoning skills. Several studies from Dr. Laurence Steinberg, one of the leading developmental psychologists in the nation, were cited heavily in the Court's opinion.

In 2010, the Supreme Court was once again tasked with deciding to what extent juvenile offenders should be punished. In Graham v. Florida, 560 U.S. 48 (2010), 16-year-old Terrance Graham pleaded guilty to charges of attempted armed robbery and armed burglary after he tried to rob a barbecue restaurant in Jacksonville, Florida. Although initially just sentenced to probation, Graham was soon arrested again for a home invasion robbery, which violated his probation agreement. In response, the judge in his case sentenced to him to life in prison without the possibility of parole.

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Given the severity of this sentence, significant national attention was paid to Graham's case, and it was appealed all the way to the Supreme Court. Once more, the Court looked to neuroscience to aid in its decision-making process. In writing his opinion for the Court, Justice Kennedy explicitly noted that "developments in psychology and brain science continue to show fundamental differences between juvenile and adult minds. For example, parts of the brain involved in behavior control continue to mature through late adolescence." Ultimately, the Court ruled that sentencing juveniles to life without parole for any offense other than murder amounted to cruel and unusual punishment in violation of the Eighth Amendment.

Just two years after Graham was decided, the Supreme Court heard the case of Miller v. Alabama, 567 U.S. 460 (2012). Here, Evan Miller, a 14-year-old from Alabama, was convicted of murder after he beat a victim with a baseball bat and then set fire to the trailer where the victim laid unconscious inside. Under Alabama law, Miller's gruesome murder triggered a mandatory life sentence without parole. Extending its previous Graham decision, the Supreme Court ruled that any mandatory life sentences for juveniles, even in cases of murder, violated the Eighth Amendment. In authoring the Court's opinion, Justin Kagan explicitly cited to an amicus brief submitted by the American Psychological Association. (Amicus briefs are formal reports from individuals or organizations that offer information, expertise, or insights that might be useful to a court.) Kagan referred to several studies highlighted in the APA's brief, and noted that the science supporting the neurological differences between adolescents and adults had only grown stronger since they last examined in the issue in Graham.

The three Supreme Court rulings discussed above have changed the legal landscape for countless adolescent defendants. In placing an emphasis on findings from adolescent neuroscience, the Supreme Court (and lower courts throughout the country) have essentially determined that adolescents, by virtue of their neurological hardwiring for pleasure without the control mechanisms needed to moderate their behavior, are less culpable than adult offenders. As stated by Justice Kennedy in Roper:

"The susceptibility of juveniles to immature and irresponsible behavior means their irresponsible conduct is not as morally reprehensible as that of an adult. Their own vulnerability and comparative lack of control over their immediate surroundings mean juveniles have a greater claim than adults to be forgiven for failing to escape negative influences in their whole environment."

Additionally, given that the pre-frontal cortex of the adolescent brain still has significant time to develop, the law views adolescents as having a greater chance at being rehabilitated than adults. Rehabilitation is a core tenet of our criminal system. Judges are not keen to lock up an offender and "throw away the key" if there is a chance that they can one day mature and become a productive member of society.

Overall, as new lessons from neuroscience continue to infiltrate the justice system, there is no doubt that significant changes will be seen in the future. Most most legal scholars agree that neuroscience has only just begun to make waves. Numerous areas of inquiry remain to be addressed, such as the criminal culpability of those with mental disorders, traumatic brain injuries, and even low IQ or genetic predisposition to aggression.