Cohen @ Psychonomics

Reversing the Similarity Effect: The Influence of Presentation Format.

ANDREA CATALDO and ANDREW L. COHEN

University of Massachusetts, Amherst

(Presented by Andrew Cohen) — When a similar, competitive alternative is added to a choice set, the new alternative tends to take a disproportionate choice proportion from similar alternatives. This similarity effect has been used as a key benchmark for models of multi-alternative, multi-attribute choice. Recent work, however, suggests that this effect depends on factors such as the order in which information is gathered. The current experiment kept information constant across conditions, but encouraged different comparisons by changing presentation format. Each choice set consisted of three alternatives with two separable attributes, displayed as a bar length. In the by-alternative condition, the bars were grouped by alternative. The standard similarity effect was replicated. In the experimental by-attribute condition, the bars were grouped by attribute. The similarity effect reversed, i.e., the relative choice proportion of the similar alternative increased. These results have implications for models of choice and highlight the need to consider variations in stimulus presentation.