Now for sure or later with a risk? Modeling risky intertemporal choice as accumulated preference.

Research on risky and inter-temporal decision-making often focuses on descriptive models of choice. This class of models sometimes lack a psychological process account of how different cognitive processes give rise to choice behavior. Here, we attempt to decompose these processes using sequential accumulator modeling (i.e., the Linear Ballistic Accumulator model; LBA). Participants were presented with pairs of gambles that either involve different levels of probability or delay (Experiment 1) or a combination of these dimensions (both probability and delay; Experiment 2). Response times (RTs) were recorded as a measure of preferential strength. We then combined choice data and response times, and utilized variants of the LBA to explore different assumptions about how preferences are formed. Specifically we show that a model which allows for the subjective evaluation of a fixed now/certain option to change as a function of the delayed/risky option with which it is paired provides the best account of the combined choice and RT data. The work highlights the advantages of using cognitive process models in risky and inter–temporal choice, and points towards a common framework for understanding how people evaluate time and probability.