The mind that evolved for small groups and immediate dangers is now asked to manage a pension. It does its best. Consider the tip jar. It is a small thing, and small things are where habits live. Every one of us runs the same shortcut, and every one of us believes we are the exception. In the studies we have, the effect is modest, reliable and almost entirely ignored by the people it describes.
The ordinary case
Nobody sets out to be governed by the tip jar, yet it shapes an astonishing share of the ordinary day. The point is not that people are foolish. The point is that patience is expensive, and we economise on it like everything else. Put a number on patience and it becomes a target; put a target on it and the number stops meaning what it meant. The lesson is modest. Build for the person who exists, not the one in the model.
