BRAIN DIFFERENCE: SOMETIMES ADOLESCENTS JUST CAN'T RESIST
Don't get mad the next
time you catch your teenager texting when he promised to be studying. He simply
may not be able to resist
A University of Iowa
study found teenagers are far more sensitive than adults to the immediate
effect or reward of their behaviors. The findings may help explain, for
example, why the initial rush of texting may be more enticing for adolescents
than the long-term payoff of studying.
"The rewards have
a strong, perceptional draw and are more enticing to the teenager," says
Jatin Vaidya, a professor of psychiatry at the UI and corresponding author of
the study, which appeared online this week in the journal Psychological
Science. "Even when a behavior is no longer in a teenager's best
interest to continue, they will because the effect of the reward is still there
and lasts much longer in adolescents than in adults."
For parents, that
means limiting distractions so teenagers can make better choices. Take the
homework and social media dilemma: At 9 p.m., shut off everything except a
computer that has no access to Facebook or Twitter, the researchers advise.
"I'm not saying
they shouldn't be allowed access to technology," Vaidya says. "But
they need help in regulating their attention so they can develop those
impulse-control skills."
In their study,
"Value-Driven Attentional Capture in Adolescence," Vaidya and
co-authors Shaun Vecera, a professor of psychology, and Zachary Roper, a
graduate student in psychology, note researchers generally believe teenagers
are impulsive, make bad decisions, and engage in risky behavior because the
frontal lobes of their brains are not fully developed.
But the UI researchers
wondered whether something more fundamental was going on with adolescents to
trigger behaviors independent of higher-level reasoning.
"We wanted to try
to understand the brain's reward system and how it changes from childhood to
adulthood," says Vaidya, who adds the reward trait in the human brain is
much more primitive than decision-making. "We've been trying to understand
the reward process in adolescence and whether there is more to adolescent
behavior than an under-developed frontal lobe," he adds.
For their study, the
researchers recruited 40 adolescents, ages 13 and 16, and 40 adults, ages 20
and 35. First, participants were asked to find a red or green ring hidden
within an array of rings on a computer screen.
Once identified, they
reported whether the white line inside the ring was vertical or horizontal. If
they were right, they received a reward between 2 and 10 cents, depending on
the color. For some participants, the red ring paid the highest reward; for
others, it was the green. None was told which color would pay the most.
After 240 trials, the
participants were asked whether they noticed anything about the colors. Most
made no association between a color and reward, which researchers say proves
the ring exercise didn't involve high-level, decision-making.
In the next stage,
participants showed they had developed an intuitive association when they were
asked to find a diamond-shaped target. This time, the red and green rings were
used as decoys.
At first, the adolescents
and adults selected the color ring that garnered them the highest monetary
reward, the goal of the first trial. But in short order, the adults adjusted
and selected the diamond. The adolescents did not.
Even after 240 trials,
the adolescents were still more apt to pick the colored rings.
"Even though
you've told them, 'You have a new target,' the adolescents can't get rid of the
association they learned before," Vecera says. "It's as if that
association is much more potent for the adolescent than for the adult.
"If you give the
adolescent a reward, it will persist longer," he adds. "The fact that
the reward is gone doesn't matter. They will act as if the reward is still
there."
Researchers say that
inability to readily adjust behavior explains why, for example, a teenager may
continue to make inappropriate comments in class long after friends stopped
laughing.
In the future,
researchers hope to delve into the psychological and neurological aspects of
their results.
"Are there
certain brain regions or circuits that continue to develop from adolescence to
adulthood that play role in directing attention away from reward stimuli that
are not task relevant?" Vaidya asks. "Also, what sort of life
experiences and skill help to improve performance on this task?"
The study was funded
by the University of Iowa's Social Sciences Funding Program.
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