A preference reversal occurs when the same person, evaluating the exact same two options, gives contradictory answers depending purely on the format of the question — directly choosing between them versus separately pricing each one. This is a serious problem for the basic economic assumption that people have stable, well-defined preferences that simply get revealed differently depending on how you ask; a genuinely stable preference shouldn't flip based on question format alone.
The finding suggests something more unsettling than simple inconsistency: that a preference isn't always a fixed thing waiting to be measured, but can be partly constructed in the moment by the specific way a question is framed — which means the method used to elicit a preference (a direct choice versus a price) isn't a neutral measurement tool, it's itself shaping the answer.