Why Simple Answers Are So Hard to Kill

A stereotype has several advantages over a good model. It is short, it does not require you to specify the country, the generation, the social class and the design of the law, it does not ask you to distinguish a group average from the probability of a single outcome, and it delivers a cause immediately, sometimes together with a culprit. A good explanation behaves worse: it pins down age, city, the purpose of meeting, the cost of refusal, the available set of options, whether the interaction repeats and the reputational price of cheating. By that time the folk formula has already produced a finished answer — but those details decide which rule will apply.

One mechanism can switch sign under different conditions. A high cost of leaving can protect long-term investments and keep people inside a destructive union; a wide choice expands opportunity but can reduce attention to each option; specialisation raises current efficiency and creates future dependence. A stereotype usually remembers one side. On top of that, many formulas were reasonable in a world that has since disappeared. When property passed through legal heirs and biological paternity could not be established, sexual fidelity had both personal and property significance. When a woman could barely earn on her own, a well-off husband was not a symbol of some special female pull towards status but access to housing and safety. History shows which part of behaviour changes along with institutions.