Comparison, grouping, and preference

How does the attractiveness of a particular option depend on comparisons dr awn between it and other alternatives? We observe that in many cases, compa risons hurt: When the options being compared have both meaningful advantage s and meaningful disadvantages, comparison between options makes each optio n less attractive. The effects of comparison are crucial in choice problems involving grouped options, because the way in which options are grouped in fluences which comparisons are likely to be made. In particular we propose that grouping focuses comparison, making within-group comparisons moi-e lik ely than between-group comparisons. This line of reasoning suggests that gr ouping should hurt, and we observe that it does: An option is more likely t o be chosen when alone than when part of a group.