Procedural invariance
Also known as: Procedure invariance
The principle — routinely violated — that the way you elicit a preference shouldn't change it.
What it means
Procedural invariance is the normative requirement that logically equivalent methods of eliciting a preference should yield the same preference ordering, so that whether you ask someone to choose, rank, or price options, the implied ranking is identical. It is one of two invariance principles underpinning rational choice, the other being description invariance, which framing effects violate. Procedural invariance is violated by preference reversals, by differences between choosing and rejecting, and by the gap between matching and choosing tasks. These failures imply that preferences are not pre-formed and stable but are constructed in the act of responding, shaped by which attributes a given procedure makes salient. The concept matters because survey design, valuation methods, and elicitation formats can manufacture the very preferences they claim merely to measure.
Examples
A respondent who, when choosing, prefers job A for its security will, when asked to state a salary that makes the jobs equal, reveal a ranking favoring job B.
Asked which holiday to book, people pick the vivid one with rich beaches and bad weather; asked which to cancel, they scrap that same holiday. Both tasks hunt for reasons.
A punter choosing between two scratchcards takes the safe one, then, asked what he would sell each for, prices the long shot higher — the same two cards, two rankings.
First described in Tversky, Sattath & Slovic (1988).