Understanding how reward and saliency affect overt attention and decisions

The ability to rapidly choose among multiple valuable targets embedded in a complex perceptual environment is key to survival in many animal species. Targets may differ both in their reward value as well as in their low-level perceptual properties (e.g., visual saliency). Previous studies investigated separately the impact of either value on decisions, or saliency on attention, thus it is not known how the brain combines these two variables to influence attention and decision-making. In this talk, I will describe how we addressed this question with three experiments in which human subjects attempted to maximize their monetary earnings by rapidly choosing items from a brief display. Each display contained several worthless items (distractors) as well as two targets, whose value and saliency were varied systematically. The resulting behavioral data was compared to the predictions of three computational models which assume that: (1) subjects seek the most valuable item in the display, (2) subjects seek the most easily detectable item (e.g., highest saliency), (3) subjects behave as an ideal Bayesian observer who combines both factors to maximize expected reward within each trial. We find that, regardless of the motor response used to express the choices, decisions are influenced by both value and feature-contrast in a way that is consistent with the ideal Bayesian observer. Thus, individuals are able to engage in optimal reward harvesting while seeking multiple relevant targets amidst clutter. I will describe ongoing studies on whether attention, like decisions, may also be influenced by value and saliency to optimize reward harvesting.