"Youth is a blunder; manhood a struggle; old age a regret," wrote 19th-century British Prime Minister Benjamin Disraeli in his political novel, Coningsby. Hyperbole aside, he may have mixed things up a bit. The latest research suggests that young people tend to fixate on their regrets, whereas older adults generally learn not to waste time wallowing in remorse about past circumstances they cannot change. A new study demonstrates that these cognitive differences manifest themselves in brain scans and physiological responses, revealing that, unlike healthy adults, both depressed adults and young people treat missed opportunities and genuine losses as equally regretful events—even if they were not directly responsible. Taming such ruefulness appears to be crucial to emotional stability and happiness in old age, and related therapies could help adults with depression. For the young, however, a little regret might be useful, motivating them to learn from their mistakes.

In their first set of experiments, Stefanie Brassen of the University Medical Center Hamburg-Eppendorf in Germany and her colleagues studied 20 healthy 20-somethings, as well as 20 healthy adults and 20 depressed adults around 65 years old. All the participants played a simple gambling game inside a magnetic resonance imaging (MRI) machine. A computer screen depicted a row of eight unopened wooden crates that the volunteers could open one at a time, from left to right. The participants knew that seven of the crates contained gold and that one contained a demon—a cartoonish red devil, pitchfork in hand, who would steal everything the participant had won and end the game if uncovered. Each step of the way, the participants had the chance to stop and walk away with their earnings or keep playing and risk unleashing the demon. If a participant decided to stop while they were ahead, the devil's position in the row of crates was revealed, showing the participant whether they had missed out on lots more gold or avoided a close call.

As the participants played the computer game inside the MRI machine, Brassen and her colleagues analyzed their brain activity. They focused on a part of the brain called the ventral striatum, which—to simplify things greatly—responds to rewards the way a game show clap-o-meter registers applause: When someone wins a reward, their ventral striatum becomes much more active than when they lose.

The brain-imaging results suggest that stronger spasms of regret rippled through the minds of young people and depressed adults than through those of healthy older adults. When the 20-somethings and depressed adults realized that they had bowed out too soon, neural activity in the ventral striatum dropped far below levels observed when participants left the game at the right time. In contrast, ventral striatum activity barely changed in healthy older adults, regardless of whether their decision to leave cost them mores gold. These adults only showed decreased activity in the ventral striatum when they accidentally released the demon, whereas the brains of young people and depressed adults treated uncovering the demon and leaving the game too soon as equally regretful outcomes.

Healthy older adults also seemed to more effectively suppress whatever regret they did feel. Many bands of neural tissue link the ventral striatum to the anterior cingulate cortex, a brain region known to regulate emotions. When healthy older adults left the game too soon or uncovered the devil, their anterior cingulate cortices were more active than those of 20-somethings and depressed people, suggesting that the older adults were dampening any negative feelings.

For a second round of experiments, Brassen recruited 30 new participants—15 healthy adults and 15 depressed adults—who also played the hidden-demon computer game. This time, however, Brassen measured her volunteers' heart rates as well as their skin's electrical conductivity, which increases the more someone sweats. Such physiological measurements reflect one's emotional state. The healthy adults did not show huge differences in heart rate or sweat production, regardless of how they fared in the game, but missed opportunities diminished the depressed adults' physiological responses—their heart rates slowed and they did not sweat as much, indicating feelings of dejection.

Brassen and her colleagues also asked the 30 new participants about their life regrets: How often did they think about them? How often did they lose sleep over them? Did their regrets impede their ability to enjoy their social life and leisure activities? Healthy adults reported less intrusive thoughts about their regrets and less sensitivity to them in everyday life. The findings appear online in the April 19 issue of Science.

Carsten Wrosch, a psychologist at Concordia University in Montreal, has studied how people's regrets change over their lifetimes. He says the new findings "converge quite substantially" with what he has found in his own research. "We argue in our work that regret can be a double-edged sword: it teaches us how to change, but it can also lead to depression," he says. "Older adults need to adjust how they cope with regret—if they react to regret like young adults, they are more likely to be depressed."

Although the new study does not offer direct experimental evidence to explain why healthy older adults in the study were less susceptible to regret, Brassen has a few ideas. She speculates that healthy older adults blame themselves less than depressed adults and young people, distinguishing between actions for which they are responsible and events they cannot control—such as when the devil in the game appeared. Brassen further proposes that disengaging from regret is a protective strategy that kicks in sometime in old age, preventing the elderly—who do not have as much time or opportunity to make amends—from needlessly feeling sorry about things they cannot realistically change. In contrast, young people have their whole lives ahead of them—plenty of time to repeat their mistakes if they do not learn from them.

Wrosch says he thinks about regret similarly: "If someone in their 70s regrets that they never had the education or job they wanted, there no going back to change life circumstances. But if a similar regret happens to someone in their early 20s, they can use that information to turn their life around."

Currently, Brassen and her colleagues plan to develop a therapeutic program that teaches middle-aged adults how to regulate regret through "external attribution"—blaming forces outside of one's control, rather than blaming oneself. "I'm sure we have a lot to learn from healthy older adults about managing regret," Brassen says.