How our decisions change with age
The brain changes at different stages of life, and the way we weigh the pros and cons of our decisions changes with it.
One thing we don't need science to prove: nobody over 40 will ever understand the decision-making process of a teenager.
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The reason comes down to more than just lack of intelligence or experience on the part of the teenager. The juvenile brain is fundamentally different from older brains, and those differences show up in the kinds of decisions teenagers make.
During adolescence, the front part of the brain – where higher thinking takes place – goes through dramatic changes. "Cells that are being used less die," said Kathleen Fitzpatrick, assistant professor of psychiatry and behavioral sciences."Then cells that are being used more often have a huge proliferation.
"The new brain connections come with new behaviors. "You can watch kids try things on," Fitzpatrick said.
During this time of brain circuit upheaval, adolescents weigh the pros and cons of decisions differently from adults. They overestimate the rewards of a decision (Fun! Friends!) but don't accurately estimate possible risks (grounding, police).
As adolescents try out new behaviors, the results actually influence the circuits that are retained into adulthood, Fitzpatrick said. Behaviors that reap rewards strengthen new connections so that the behaviors are available in the future. For behaviors that aren't rewarded the associated neurons wither, leaving that behavior as a mere embarrassing memory.
This altered balance of perceived risk and reward shows up not just in puzzling behaviors but also in brain scans. Brains of teenagers activate the risk/reward circuitry in different ways than adults when carrying out the same decision-making tasks.
As we age and our brain wiring becomes more stable, the craving for all things new and rewarding mellows and we become better able to consider consequences. We start saving money. We drive closer to the speed limit. We turn down the last drink of the night. We act old.
But the changes don't stop there.
Brian Knutson, associate professor of psychiatry and neuroscience and a member of Stanford Bio-X, and his former graduate student Gregory Samanez-Larkin recently reviewed what's known about decision-making in the aging brain in Nature Reviews Neuroscience.
They found that as older adults grow less able to hold on to multiple thoughts, they have a harder time making decisions that require considering multiple options. However, decisions that require established knowledge remain strong well into old age.
The results did point toward something to look forward to: brain scans of older people show that they are less concerned about the threat of bad outcomes, and they retain their youthful excitement about the possibility of good outcomes from their decisions.
Those older people might not be able to remember much or understand teenagers, but they are more sanguine about the possibility of their decisions not going well.