Here’s another astonishing tidbit along the same lines as the Joshua-Bell-in-the-Washington-subway fiasco. A couple of psychologists conducted an experiment a while ago in which researchers stopped random pedestrians and asked them for directions. Partway through the directions, a couple of “construction workers” carried a large wooden door between the pedestrian and the researcher—and while the door was between them, the researcher switched places with one of the construction workers.

About half of the people, believe it or not, continued with the directions where they had left off, not even noticing that they were talking to a completely and noticeably different person. Apparently it’s quite easy for people to miss a major change in their environment when they aren’t focused on what’s changing while the change is happening. In other words, if my red shirt suddenly becomes blue while you’re looking at me, you’re sure to notice unless you’re colorblind. But if you chat with me, turn aside for a minute to say something to a passerby, and when you turn back my red shirt has become blue, there’s a good chance you won’t notice. Your memory hasn’t bothered to store the color of my shirt (because what possible use could that information have?) and so you have no reason to suspect that something has changed.