Set-Fit Effects in Choice

In 4 experiments, we investigate how the fit of an item with a set of similar items affects choice. We find that people have a notion of a set that fits together--one where all items are the same, or all items differ, on salient attributes. One consequence of this notion is that in addition to preferences over the set's individual items, choice reflects set-fit. This leads to predictable shifts in preferences, sometimes even resulting in people choosing normatively inferior options over superior ones.