WHAT do you do if, when you get to a subway platform, you see that it is already packed with people? Do you join the throngs to wait for the train, or do you shake your head and seek an alternative way to get where you’re going?

If you go the first route, you probably think that the crowd means there must not have been a train for some time and that one is imminent. If you choose the second, you’ve come to the opposite conclusion: It’s crowded, a train hasn’t come in a while, so it’s likely there’s some sort of problem — and who knows how long you’ll end up waiting. Better cut your losses and split.

When we think of self-control, we don’t normally see it in these terms — a reasoned decision to wait or not. In fact, the ability to delay gratification has traditionally been seen in large part as an issue of willpower: Do you have what it takes to wait it out, to choose a later — and, presumably, better — reward over an immediate, though not quite as good one? Can you forgo a brownie in service of the larger reward of losing weight, give up ready cash in favor of a later investment payoff? The immediate option is hot; you can taste it, smell it, feel it. The long-term choice is far cooler; it’s hard to picture it with quite as much color or power.

In psychological terms, the difference is typically seen as a dual-system trade-off: On one hand, you have the deliberative, reflective, cool system; on the other, the intuitive, reflexive, hot system. The less self-control you have, the further off and cooler the future becomes and the hotter the immediate present grows. Brownie? Yum.