Evaluability (joint vs separate evaluation)
Attributes that are hard to judge in isolation only influence choice when options are seen side by side.
Where it applies
Three of the eight page areas.
How to use it
Three ways to put it to work.
- Put hard-to-judge specs on result tiles, where they can be judged against neighbours.
- Include hard-to-judge specs in compare tables.
- Add reference points so a spec means something on its own.
What the research found
Preferences reversed between side-by-side and one-at-a-time evaluation.
Preferences can reverse when options are seen side by side rather than one at a time.
Hsee found that preferences between options could reverse depending on whether people saw them side by side or one at a time, because hard-to-judge attributes only mattered in comparison. A Psychological Bulletin review by Hsee and colleagues collected many similar reversals. The studies were mostly hypothetical lab scenarios, not live shops. A preregistered replication by Vonasch and colleagues found the one-at-a-time result held, but the side-by-side reversal was weaker.
Key research
Three sources, each checked.
Last reviewed
Hsee (1996) The Evaluability Hypothesis: An Explanation for Preference Reversals between Joint and Separate Evaluations of Alternatives Organizational Behavior & Human Decision Processes Read the source Hsee, Loewenstein, Blount & Bazerman (1999) Preference reversals between joint and separate evaluations of options: A review and theoretical analysis Psychological Bulletin Read the source Vonasch, Hung, Leung, Nguyen, Chan, Cheng & Feldman (2023)Replication "Less Is Better" in Separate Evaluations Versus "More Is Better" in Joint Evaluations: Mostly Successful Close Replication and Extension of Hsee (1998) Collabra: Psychology Read the source