Even when we get the big decisions directionally right, we’re not guaranteed to get the results we want.

We don’t think of ordinary moments as decisions. No one taps us on the shoulder as we react to a comment by a coworker to tell us that we’re about to pour gasoline or water onto this flame.

1.5. The Inertia Default

The inertia default pushes us to maintain the status quo. Starting something is hard but so too is stopping something. We resist change even when change is for the best.

The Latin word inertia means literally “inertness”: that is, laziness or idleness. In physics, “inertia” refers to an object resisting change in its state of motion. Hence, a popular way of stating Newton’s first law of motion— the law of inertia— is this: “A body in motion tends to stay in motion, and a body at rest tends to stay at rest.

The physicist Leonard Mlodinow sums it up this way: “Once our minds are set in a direction, they tend to continue in that direction unless acted upon by some outside force.” This cognitive inertia is why changing our minds is hard.

It’s easy to underestimate the role ease plays in decision-making. Since behaviour follows the path of least resistance, a surprisingly successful approach is to add friction where you find yourself doing things you don’t want to do.

Sometimes adults do too. Perhaps it’s because we have to make a choice so quickly that we don’t have time to evaluate the options. Or maybe it’s because we let habit choose for us, the inertia of past choices carrying us through the present moment without exploring our options. Or maybe it’s just that we let our emotions make choices without even realizing it— momentary anger, fear, or desire preempting evaluation and pushing us to act without thinking or reason.