"But it’s just possible that the creaky machinery of an aging brain might make a president better at the job...."

"[Neuroscientist Gregory Samanez-Larki] and his colleagues... recently found evidence that older adults are better at keeping their emotions and impulses in check.... 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.... The more presidents slow down, the more decisions get made by other people.... 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.... 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...."

From "The Upside to Having an Old President/As presidents slow down, more decisions get made by other people" by Graeme Woode (in The Atlantic).