IMPACT OF VISUAL SALIENCE AND REWARD UNDERSTOOD USING NEURAL EVIDENCE ACCUMULATION

Abstract

Object representation in lateral occipital cortex (LO) is a dynamic process involving evidence (or information) accumulation over time. Evidence accumulation in cognitive science involves applications of paradigms that mathematically model behavioral data, broadly referred to as drift diffusion or sequential sampling. The parameters used by these models to describe the dynamics of a decision are the decision threshold (amount of information necessary to make a decision), drift rate (rate of accumulation of evidence over time, influenced by the quality of the evidence), and the non-decision time (accumulation onset latency). Substantial research exists supporting the application of neural evidence accumulation models to visual cortex (specifically LO), but the way stimulus characteristics alter neural evidence accumulation, and the contribution of the interaction of reward information and visual stimulus characteristics is not well characterized. In three experiments, salience was varied in ways that produced changes in the three accumulation parameters. Experiment One examined exogenous visual salience (object “popout”), rather than endogenous salience. Popout stimuli were more quickly identified, which was related to neural evidence accumulation by shortening accumulation onset latency. In the second study, individuated stimulus sets varying the endogenous, or learned, salience (reward) of the stimulus cues – a new technique developed here that allowed participants to select their own stimuli – demonstrated that endogenous salience (reward) influenced visual orienting and object representations. Experiment Three explored the neural basis of endogenous salience, and the impact this had on decisions about consuming individuated alcohol stimuli in various contexts vi (e.g. risky). Valence of endogenous salience (positive vs neutral) impacted the decision threshold of neural evidence accumulation, whereas context and endogenous salience impacted the drift rate, which reflected the quality of evidence retrieved from the object representation. Together, the three experiments advance understanding of visual mechanisms underlying the influence of endogenous and exogenous salience on decision making