Jonathan Ernst / Reuters

The two elderly front-runners for the Democratic nomination share an improbable trait: Despite their advancing years, both men seem to have an energy level that I could not achieve if I spent all morning chugging coffee and gobbling amphetamines. That level of energy is, as generations of political observers have reminded us, what it takes to win the presidency. Whether it is a sustainable and permanent condition is another matter. Actuarial tables say that we can expect about nine more years out of Joe Biden and eight more years out of Bernie Sanders before they slow down significantly, due to their death. Of course, few people die at the height of their powers, whereas everyone experiences a gentle cognitive decline, and then a steep one if and when dementia sets in.

What happens when a president goes senile while in office? For good reason, we worry about this possibility—and whether the Twenty-Fifth Amendment, which governs the president’s incapacitation, is one of the parts of the legal system that still functions, or one of the parts that the Donald Trump era has exposed as a nullity. But it’s just possible that the creaky machinery of an aging brain might make a president better at the job.

True enough, an old president will not function with the acuity of a young one. Give him a set of arithmetic problems, and watch him fumble, while his neuronally gifted interns ace the test or, more likely, cheat with their smartphones. The decline in the ability to deal with most simple cognitive tasks is linear from young adulthood to very old age, says Gregory Samanez-Larkin, a neuroscientist at Duke University. Your mind declines no faster from 55 to 65 than it does from 35 to 45. (After 70, the decline becomes less predictable, mostly because those ages have been studied less.) If you have ever sat impatiently while watching an older relative try to find a television channel or use a remote control, that decline is what you witnessed.

But consider what that older relative witnessed: your impatience, and perhaps even your inability to tame your desire to flip channels like a madman. Samanez-Larkin and his colleagues Daisy Burr, Jaime Castrellon, and David Zald recently found evidence that older adults are better at keeping their emotions and impulses in check. Their results, published in Emotion, “provide unique evidence that emotional health and regulation improve with age.” Moreover, Samanez-Larkin says, the set of skills known as “decision making” does not decline in any predictable way during normal aging. The interns might be whizzes at a chalkboard, but faced with complex decisions—whether to buy a new TV, say, rather than how to use it adroitly once they have it—the fogies match and sometimes outperform them.

The question then becomes: Is being president more like having to do a lot of math problems, or more like having to contain one’s emotions and make difficult decisions? It might be both: Presidents need to have a spry brain, capable of assimilating new information and rapidly adding it to their cognitive repertoire. But the job is, most crucially, about making decisions—extremely difficult decisions that are, unlike arithmetic, matters of judgment and value. The rightness of a decision is often unknowable ex ante. In these treacherous exercises, the elderly do not do badly, and impetuous youngsters sometimes come very close to getting us all killed. When you travel to a country with lots of road deaths, you should choose an old taxi driver with a very slow car.

There is also the question of energy, which—unless Sanders (78) and Biden (77) really are on amphetamines—seems certain to decline, and probably within the four- or eight-year period during which they might hold office. (Compared with them, Trump is a spring chicken—a Rhode Island Red, judging by color—of 73.) The job of a president has, historically, been exhausting emotionally and physically, and we should prepare for the possibility of a president who, like Ronald Reagan in his later years in office, simply slows down.

This, too, might have some upsides. The more presidents slow down, the more decisions get made by other people. Call it the “Weekend at Bernie’s presidency,” though either Democratic candidate, or Trump, could graduate to this geriatric mode of administration. And perhaps we’d all be better served if other people—and not Biden, Sanders, or Trump—were making decisions. I see ample reason to question the soundness of the judgment of all three men.

Remember the joke about the diners who complain about a restaurant’s bad food, but also its small portions? A president who delegates lazily would be an ineffectual president, but one whose mistakes were blunted along with his successes. One diagnosis of the dysfunctions of the early Trump era is that the president did not know how to make things happen, so he flailed—occasionally making wild policy moves by tweet, without the interagency cooperation and feedback that allow desire to become fact. That feral incompetence has become less common as Trump has become familiar with his job, and I doubt anyone would prefer him to be feral and effective.

If the president took a Valium instead of a morning espresso, one possible outcome for the Weekend at Bernie’s presidency would be an administration that is simply muted in its effects, with no delegated official eager to initiate major change from the status quo. It would be, in that sense, a more conservative presidency. No doubt progressives would feel cheated by a President Sanders who hits snooze rather than waking up early to fight for systemic economic change. But systemic change comes slowly, and sudden policy decisions tend to be bad ones. A leader who is economical in his actions and laconic in his tweets does not sound all that unwelcome right now. Executive power wielded through sweeping policy changes and fiat is simply a bad way to use the presidency; the slow and laborious process of cooperative change is more effective, whether your goal is immigration reform or socialized medicine. (Granted, the risk of delegation is considerable too. Policy conducted in the president’s absence might just result in off-the-books shenanigans like the Iran-Contra affair.)

Samanez-Larkin says he welcomes the prospect of a really old president. Stigma against the elderly is worth fighting, he says, and cognitive decline could be balanced out by the wisdom of age. But he does have one warning. “The scariest thing is change,” he says. “If you see someone who is elderly changing suddenly, that is a very bad sign,” because dementia or another neurological disease could be taking over.

For now, though, enormous changes do not appear to be afflicting the candidates’ brains. Biden still loves Amtrak and himself. Sanders hasn’t changed his mind about anything, including the U.S.S.R., in 50 years. These foolish consistencies may be, as Ralph Waldo Emerson said, “the hobgoblins of little minds.” At least they are not signs of senile ones.

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