Teenage Recklessness Gives Adolescent Humans and Monkeys a Leg Up

"For this pattern to have endured millions of years of evolution, it must confer some benefit."

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Teens like to experiment — sometimes in creative ways that earn them millions of followers on TikTok. Other times, that pattern is more destructive and may involve Tide Pods. As two scientists argue in a paper published Tuesday in Trends in Neurosciences, risk-taking behaviors pervade across humans and monkeys, suggesting that being a reckless teen has advantages that have allowed the behavior to persist in modern primates.

In this paper, neuroscientists reviewed past studies on maturing human brains, as well as those of non-human primates — mostly macaques, a genus of monkeys. For both groups, they saw a clear trend in maturity and impulse control over the course of a lifetime.

Christos Constantinidis, Ph.D., a professor of neurobiology and anatomy at Wake Forest School of Medicine and one of the study’s co-authors, tells Inverse that in humans, impulsiveness tends to follow a “u-curve” that peaks in adolescence. In the paper, he and his co-author Beatriz Luna, Ph.D., who studies neurocognitive development at the University of Pittsburgh, show that macaques also behave impulsively as teens.

That parallel, Constantinidis explains, points to an evolutionary reason that behaving like a reckless teen has not died out in either humans or macaques.

“Sensation seeking and risk taking may go as far as to compromise an adolescent’s survival, he says. “For this pattern to have endured millions of years of evolution, it must confer some benefit. It is likely that the experiences gained in adolescence are critical for survival later in life.”

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Teens tend to perform worse than adults do on inhibitory control tasks, but there are developmental upsides to not thinking through all your actions. 

Traditionally, we think of adolescence as a time when seem unable to stop ourselves from acting on impulse, explains Constantinidis. To show this, he and Luna looked into a series of past studies on how both people and primates perform on antisaccade tasks, in which you’re supposed to look away from (not towards) an object on a screen.

As humans mature from childhood to adulthood, they get better at fighting the urge to look towards the object on the screen, processing the instructions telling them to look away and executing that plan. Macaques, too, show a similar trajectory. Macaques mature three times faster than humans do, and adult macaques’ performance on that task was “greatly improved” compared to the performance of the teen macaques.

These improvements were also mirrored in the brain activity of both the macaques and the humans. Specifically, adult humans showed greater activation in the prefrontal cortex — an area of the brain involved in planning behaviors — than teens did. In macaques, the team points to similar studies showing that as they get older, their prefrontal cortices get reorganized, which makes that brain region more interconnected.

Taken with the behavioral findings, this points to the idea that both human and macaque teenagers are operating with impulse-related circuitry that’s not fully online yet. Instead, they’re going through the same tumultuous process of learning to rein in their instincts, pause, and make better decisions.

In the paper, they argue that since both humans and macaques have this long, impulsive period when teens are making questionable decisions, there must be some benefit. And in a statement, Luna described one of those benefits.

“You don’t have this perfect inhibitory control system in adolescence, but that’s happening for a reason. It has survived evolution because it’s actually allowing for new experiences to provide information about the environment that is critical for optimal specialization of the brain to occur,” she said.

Essentially, this period of high impulsivity allows us to experience new things, and once our full inhibition control circuitry is online, we can use those experience to make even better choices.

In other words, humans (and non-human primates) have a lot to gain during those teen years, when the impulses that tell us not to snort condoms are still offline.

Abstract:

Inhibitory control matures through adolescence and into early adulthood, impacting decision-making. Impairments in inhibitory control are associated with various psychopathologies, many of which emerge during adolescence. In this review, we examine the neural basis of developmental improvements in inhibitory control by integrating findings from humans and non-human primates, identifying the structural and functional specialization of executive brain systems that mediates cognitive maturation. Behavioral manifestations of response inhibition suggest that adolescents are capable of producing adult level responses on occasion, but lack the ability to engage systems mediating response inhibition in a consistent fashion. Maturation is associated with changes in structural anatomy as well as local and systems-level connectivity. Functional changes revealed by neuroimaging and neurophysiology indicate that maturation of inhibitory control is achieved through improvements in response preparation, error processing, and planned responses.