The timed racing diffusion model of decision making

Many theories of decision making assume accumulation-to-threshold mechanisms. These thresholds almost always represent a criterion quantity on the 'evidence' or 'information' required to support a decision. We present a quantitative model that involves an additional accumulation-to-threshold mechanism where decisions can be triggered when a sufficient amount of time has been committed to the decision process. We show that a decision architecture composed of a competitive race with evidence-based and time-based thresholds provides a cohesive account of decision-making phenomena, including the speed-accuracy tradeoff. We show that it can also explain phenomena outside the domain of conventional evidence accumulation models, including simultaneously accounting for performance in decision and timing tasks. As a byproduct, the evidence-based vs time-based decision architecture eliminates the need for decision-to-decision variability parameters that are key elements of many accumulation-based theories of decision making.