A hypothesis raised for no evidential reason receives the attention due to a candidate, and the effort spent examining it is mistaken for grounds to consider it.
The illustration is a detective who names one resident of a city as a murder suspect with no evidence, and then investigates. Even honest investigation now spends its effort on a hypothesis selected at random from millions. The general lesson is that the expensive step is promotion to consideration, and it usually happens without anyone noticing it was a step.
In practice
- A board that spends an hour on the one option somebody named has let the naming do the work of a shortlist.
- A diagnosis considered because it was mentioned receives tests that the base rates do not justify.
- Standing
- Related to anchoring and to the availability heuristic, and distinct from both: the fault is in what got onto the list, not in how it was weighed.
- Subject
- Decision-making & Reasoning
- Essay
- The catalogue of predictable errors