Preference Shifts During Multi-Attribute Value-Based Decisions

When choosing between options with multiple attributes, do we decide by integrating all of the attributes into a unified measure for comparison, or does the comparison occur at the level of each attribute, involving independent competitive processes that can dynamically influence each other? What happens when independent sensory features all carry information about the same decision factor, such as reward value? To investigate these questions, we asked human participants to perform a two-alternative forced choice task in which the reward value of a target was indicated by two independent visual attributes – its brightness (“bottom-up” feature) and its orientation (“top-down” feature). If decisions always occur after integration of both features, there should be no difference in the reaction time (RT) distribution regardless of the attribute combinations that drove the choice. Counter to that prediction, almost two-thirds of the participants exhibited RT differences that depended on the attribute combinations of given targets. The RT was shortest when both attributes were congruent or when the choice was based on the bottom-up feature, and longer when the attributes were in conflict (favoring opposite options), especially when choosing the option favored by the top-down feature. We also observed mid-reach changes-of-mind in a subset of conflict trials, mostly changing from the bottom-up to the top-down-favored target. These data suggest that multi-attribute value-based decisions are better explained by a distributed competition among different features than by a competition based on a single, integrated estimate of choice value.