The lesson is modest. Build for the person who exists, not the one in the model. Consider the empty diary. It is a small thing, and small things are where habits live. The evidence here is thinner than the confident commentary suggests, and the honest position is a shrug with a direction of travel. If you want to see memory at work, watch a queue form where there is no reason for one.
What it gets right
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. A pattern this consistent is not a character flaw. It is a design feature, and design features can be worked with. We describe the departure from the model as an error. We might equally describe the model as a hopeful guess about us. The textbook treats memory as a preference to be revealed. In practice it is a story we tell ourselves after the fact.
