This year’s presidential campaign offers a choice between 72-year old John McCain and 46-year old Barack Obama.  This large difference in age provoked Christopher Beam of Slate to review the scientific literature comparing the function of old brains versus younger brains.  Here are a few things to contemplate, assuming your brain is spry enough to carry out this contemplation:

As everyone with a grandparent knows, certain types of memory are affected by aging. Episodic memory—the ability to remember things that happened to you—declines. Same for prospective memory, or the ability to remember lists or agendas. You could argue these skills are less essential for a president, who has speechwriters to produce anecdotes and handlers to keep his schedule. But age also affects working memory, which we use to process, sort, and recall information on the fly. Mental arithmetic, for example, requires a good working memory. Fortunately, presidents have calculators. But working memory also translates into debating skills—the better your short-term retention, the better you can rebut your opponent’s arguments. Oldsters show fewer deficits in semantic memory, which includes vocabulary and general knowledge.

This straightforward Slate article presents many other effects of aging on the brain.