The lesson is modest. Build for the person who exists, not the one in the model. There is a version of this essay that ends with a policy prescription. This is not that version; the mechanism is interesting enough on its own. Every one of us runs the same shortcut, and every one of us believes we are the exception. Consider the commute. It is a small thing, and small things are where habits live.
The ordinary case
Every one of us runs the same shortcut, and every one of us believes we are the exception. Nobody sets out to be governed by the commute, yet it shapes an astonishing share of the ordinary day. The textbook treats loyalty as a preference to be revealed. In practice it is a story we tell ourselves after the fact. Understanding people turns out to be a more urgent task than changing them, and a great deal harder.
A better account of loyalty would begin with the ordinary case rather than the laboratory one. Every one of us runs the same shortcut, and every one of us believes we are the exception. It is tempting to call this irrational. It is more useful to ask what it is for. There is a version of this essay that ends with a policy prescription. This is not that version; the mechanism is interesting enough on its own.
