Arguably, all judgments and decisions are made in 1 (or some combination) of 2 basic evaluation modes—joint evaluation mode (JE), in which multiple options are presented simultaneously and evaluated comparatively, or separate evaluation mode (SE), in which options are presented in isolation and evaluated separately. This article reviews recent literature showing that people evaluate options differently and exhibit reversals of preferences for options between JE and SE. The authors propose an explanation for the JE/SE reversal based on a principle called the evaluability hypothesis. The hypothesis posits that it is more difficult to evaluate the desirability of values on some attributes than on others and that, compared with easy-to-evaluate attributes, difficult-to-evaluate attributes have a greater impact in JE than in SE.
Hsee, C. K., Loewenstein, G. F., Blount, S., &Bazerman, M. H. (1999). Preference reversals between joint and separate evaluations of options: a review and theoretical analysis. Psychological bulletin, 125(5), 576-590.