Abstract
Recent studies have shown that during value-based decisions fixation durations at each alternative are directly related to the alternative's relative value and are predictive of choices. However, these studies have not determined to what extent bottom-up visual saliency affects these fixation durations. One recent study has shown that during two-alternative, value-based decisions, subjects' decisions can be biased towards more salient items at short latencies. It is currently unclear whether this occurs during multiple-alternative decisions and to what extent information about saliency and value are combined. Here, we measure eye movements and decisions from from ten human subjects performing a multiple-alternative, forced-choice task involving snack food items. After fasting, subjects viewed displays containing between four and twenty-eight different snack food items and chose which item they would most like to eat at the session's end. By controlling the display duration, we quantified the temporal dynamics of the influence of saliency and preference on fixation locations and final choices. Our results show three distinct effects of saliency on value-based decisions. First, fixation duration increases with increasing saliency of the item fixated and that this effect is strongest at short display durations. Second, as subjects visually explore the alternatives, the saliency of the items fixated decreases with increasing numbers of fixations while the preference of the items fixated increases. Finally, decisions made at very short latencies are more biased towards more salient items whereas decisions made at long latencies are more biased towards more preferred items. All of these results persist regardless of the number of alternatives. These results show that during multiple-alternative decision-making saliency has a large effect on value-based decisions when subjects are under time pressure, often causing them to pick the most salient item regardless of its value.
Meeting abstract presented at VSS 2012