Life is full of consequential decisions: How should you invest your savings? Is it OK to trust the person on the phone who asks for money? Should you have surgery, start a new medication, get a COVID-19 vaccine? The strategies we use to make these decisions evolve over time. A large body of research shows that as we age, we draw more on prior experiences, take fewer risks, and make decisions more quickly, to take a few examples.
Building on decades of animal research on the cells and circuits involved in decision-making, neuroscientists are now starting to explore the age-related changes in the brain that may be responsible for that shifting behavior. A better understanding of these changes and how they manifest both cognitively and neurologically could have practical consequences, helping people avoid scams, better manage retirement savings, and navigate health care, experts say.
The research is also challenging long-standing stereotypes about cognitive decline. “Many age-related differences in behavior and learning capacity may arise not from neurodegeneration, but from active remodeling of neural circuits,” says Michael Ryan, a postdoctoral fellow in neuroscientist Anne Churchland’s lab at the University of California, Los Angeles. Ryan, Churchland and collaborators are testing this hypothesis as part of a collaboration funded by the Simons Collaboration on Plasticity and the Aging Brain, with studies zeroing in on the cortex, the striatum and the dopamine system.
Decision patterns over the life span
Decision-making involves many steps, each requiring complex processes in the brain. To buy a car, for example, you first need to recognize that your old car is past its prime and that it’s time to buy a new one, wrote Corinna Löckenhoff, a life span developmental psychologist, in a 2017 review published in Gerontology. If you choose to move forward, you will likely collect information, assess which sources you can trust, and then compare the benefits and risks of your options. Finally, you’ll need to purchase the car and, ultimately, evaluate that decision and form memories of your opinions in ways that will inform future decisions.
Over the last two decades, laboratory studies have documented a variety of ways that decision-making behavior changes with age, some of them detrimental and others beneficial. Compared with younger adults, for example, older adults are more likely to delegate, defer, or avoid making decisions. They are less likely to exhaustively search for information and less able to remember where information comes from. They prefer to consider information that is important or familiar to them, and they use simpler strategies, like considering only one trait or picking the first option that seems good enough. They tend to tap into emotions to make decisions, focusing in particular on positive information, even as they become less willing to take risks. They look back on their previous decisions with more satisfaction and less regret.
Older people can also be more patient in their decision-making. They are less likely to practice a phenomenon called temporal discounting, which is the tendency to put more value on a more imminent reward. That means they’ll wait longer for a larger payout — choosing five dollars tomorrow over one dollar today, for example. On the flip side, research suggests that decision-making becomes less flexible with age. In lab studies where the rules for the task change spontaneously — the rewarded choice changes without warning, for example — researchers find that older people take longer to switch their selection to the newly optimal choice.
As researchers have documented behavior changes over the life span, neuroscientists have begun to map out some of the basic neural circuitry that supports decision-making. This complex cognitive process involves a number of functions, such as processing rewards, estimating value and navigating uncertainties. These functions are distributed across the brain. Two regions that seem to be particularly important are the cortex and the striatum, Churchland says. In studies in rodents, perturbing or disrupting neural circuits in those areas alters the decisions animals make.
These regions change with age. Brain imaging studies in humans have revealed that the volume of gray matter in frontal and parietal regions of the cortex, which are important for making decisions, becomes vulnerable to shrinkage from neuron deterioration over time, says Nichole Lighthall, a cognitive neuroscientist at the University of Central Florida in Orlando who wrote a 2020 review on the neural mechanisms of decision-making changes in aging. And both human and animal studies show that connections between the cortex and the striatum weaken with age.
Some studies have begun to link age-related changes in parts of the cortex to differences in decision-making. In one paper published in 2021, more than 100 people, ranging in age from 17 to 54, completed a gambling task before undergoing a structural MRI. Participants became increasingly willing to take risks up to about age 35, at which point their aversion to losses grew. Imaging showed that people who were most loss averse when they got older had the thinnest posterior cingulate cortex, a region that has been linked to emotional processing, reward signaling, focus and other decision-related processes.
Researchers are now taking a deeper look at age-related changes in decision-making circuits, for example exploring how evolving connectivity in the prefrontal cortex influences decision-making throughout the life span. In early life, the number of synapses in the brain grows rapidly, followed by a period of intense pruning. Some pruning continues in adulthood, but not with the same level of reorganization as in early development. The refined circuits of the adult brain allow animals to make more consistent decisions in response to inputs, and modeling research suggests that adults use previous experience to inform decisions more than young people do, says Kevin Mastro, a postdoctoral fellow in the labs of Bernardo Sabatini and Beth Stevens at Harvard Medical School.
Based on his prior work studying brain development in adolescence, Mastro is starting to look at how synapses change late in life. If another dramatic period of synapse loss accompanies old age, that could explain why flexibility declines, making it harder for individuals to switch their behavior in some circumstances. Another reorganization at that point wouldn’t be surprising, he says, considering the oxidative stress, protein misfolding and other processes that accelerate in the aging brain. Unveiling structural changes could lead to new insights into why behaviors change over time. “If we can understand how structure is changing, then it could help us understand behavioral changes,” he says.
Scientists are also looking at neurotransmitters for clues to how the brain alters its decision-making strategies with age. Dopamine in particular appears to be a key player — growing evidence suggests that, for some people, a decline in the binding of dopamine in multiple regions contributes to decision-making changes by altering how we assess value and process rewards.
Dopamine changes might be region-specific, Ryan says, with neurons showing many different patterns of activity that then affect various parts of the brain. One 2021 study found that, depending on what kinds of decisions mice are making, patterns of dopamine transmission differ in the striatum, a subcortical region that helps us process the consequences of our actions and adapt to changes in the environment. To better understand how and where dopamine mediates age-related decision changes, such as the shift to making more past-looking decisions in later life, Ryan and colleagues are now using imaging to look at dopamine transmission across the cortex during decision-making and how those patterns change as animals age.
Changes in both connectivity and dopamine function likely contribute to age-related changes in decision-making. For instance, younger people tend to consider what will provide the most benefit in the future when they make decisions, while older people tend to make choices based on how past decisions panned out. That shift likely reflects reduced connectivity between the prefrontal and limbic cortices and the striatum, Ryan says, as well as a decline in systems like dopamine that allow us to assess the value of our actions and make the kind of prospective decisions that older people struggle to make, among other major shifts. “They are more willing to just continue to do what they were doing in the past, because at one point, it did work,” Ryan says. “There are clearly changes that are occurring in the brain, which lead us to rely more so on this sort of retrospective strategy as opposed to a prospective one.”
Getting at the links between dopamine, decisions and age will require a clearer understanding of exactly what roles the neurotransmitter plays in the process of thinking through choices at any age. “We know the cortex is important for decision-making, and we know that dopamine has some modulation over that,” Ryan says. “But we really don’t have a clear idea, at a very large circuit level, how dopamine might be guiding this balance in decision-making, and we also don’t really have a great foothold, at the cellular level, how dopamine in a particular cortical region is changing the computations that are necessary to make decisions either based on the past or the future.”
Rethinking age-related changes
Although stereotypes portray the aging brain as one that gets worse in all areas, including its ability to make good decisions, universal decline does not appear to be inevitable, Löckenhoff says. Often, studies show, neurological changes and psychological shifts reflect new strategies for navigating life choices that may be different but not necessarily worse. In some ways, older brains may compensate for age-related changes to maintain or even improve on decision-making tasks and make better decisions.
Working memory and processing speed tend to decline in the aging brain, for example. But studies also show that older people use broader brain networks compared with younger adults. Older people may draw from a larger pool of experience and knowledge to make decisions more efficiently. “The field is moving towards an increasingly differentiated understanding of how people are using limited resources in adaptive ways across the life span,” Löckenhoff says.
In the real world, where decision-making is more complex than in lab studies, brain changes can lead to behavioral choices whose consequences can be positive or negative, says Alan Castel, a cognitive psychologist at UCLA. There might be downsides to age-related changes if, for instance, older people skip past excessive details to get to the gist of a financial document or vacation deal. But the shift in strategy toward quicker and more experience-based decision-making might help keep people from getting bogged down by irrelevant details. “As you get older, you’re not just getting worse but getting different,” he says.
Even if we do end up making more mistakes as we age, those mistakes might be a useful part of the strategy-shifting process, Churchland says. In a series of formative experiments, she says, people sat in a dark room before being told to press a lever when they saw a flash. As obvious as the light was, both people would sometimes fail to report it. Scientists have always thought of these lapses as little screw-ups.
To learn more about what’s behind these mistakes, Churchland and colleagues trained mice to associate visual flashes and auditory clicks with ports that would give them rewards. As the intervals between stimuli changed, the mice had to make more complicated decisions about where to go for their rewards. Sometimes, the team reported in a 2021 study, they made mistakes even when the decisions should have been easy.
But analyses showed that mistakes were more common when there was some uncertainty in the task. This suggests that what seemed like a screw-up was actually a form of exploration as the mice tried to understand the environment, figure out what they were supposed to do, and decipher relationships between uncertain situations and rewards. In a 2022 study, Churchland and collaborators found evidence that mice also switch their decision-making strategies over the course of an hour, so that they are sometimes engaged and sometimes disengaged. When we see lapses occur in older people, Churchland says, those mistakes might also reflect the aging brain’s attempt to adapt to a new way of decision-making that accommodates other aging-related brain changes. “Sometimes, we think of aging like it’s just everything’s getting worse and you’re making more mistakes, but maybe that’s not really the whole story,” Churchland says. Mistakes that happen with age “might just be a signature of a new kind of strategy that the brain is adopting.”
That complexity suggests the need to look at aging and decision research with a critical eye, Löckenhoff says, especially as lab studies don’t always reflect what’s happening in the real world. When people feel they are being judged by stereotypes, she says, like a belief that older people are worse at cognitive tasks, studies show they actually do worse, complicating findings that assess decision-making changes over the life span. “If people feel that they potentially look like ‘an old dog who can’t learn new tricks,’ they may actually take longer before they give an answer,” she says. “They may be as accurate as younger adults, but they take longer to get there — not necessarily because they don’t have the cognitive resources, but because they consciously decided to double-check to make sure that the answers are actually right.”
There is also a bias in the field toward publishing studies that show age-related effects and discarding those that show “quote-unquote no effects,” she says.
Eventually, understanding the behavioral shifts that happen with age, the way goals and priorities change over time, and the brain regions and circuits that change to affect decision-making could lead to interventions that facilitate better decision-making into old age, experts say. Older people might benefit from behavioral approaches that teach them how to make sound choices, Löckenhoff says, as well as efforts to present information in a way that’s better suited to their needs and preferences and to combat stereotypes among health care providers.
To develop useful interventions, the field will also need to consider individual variability, Mastro says. Understanding why one older person is still very flexible in making decisions may eventually help someone else who is not, he says. “There’s not one type of way of being an aged individual, and we have to start to take that into consideration.”