Position Effects in Choice from Simultaneous Displays: A Conundrum Solved

From drop-down computer menus to department-store aisles, people in everyday life often choose from simultaneous displays of products or options. Studies of position effects in such choices show seemingly inconsistent results. For example, in restaurant choice, items enjoy an advantage when placed at the beginning or end of the menu listings, but in multiple-choice tests, answers are more popular when placed in the middle of the offered list. When reaching for a bottle on a supermarket shelf, bottles in the middle of the display are more popular. But on voting ballots, first is the most advantageous position. Some of the effects are quite sensible, while others are harder to justify and can aptly be regarded as biases. This paper attempts to put position effects into a unified and coherent framework, and to account for them simply, using a small number of familiar psychological principles.