Interactive attention to amount and time information in intertemporal choice

The study of attention dynamics in decision making has been increasingly important in uncovering the cognitive principles of choice behavior, including intertemporal choice. Recently, empirical work on this topic has suggested that the two attributes involved in intertemporal choice (monetary amounts and time delays) have distinct and independent influences on the choice process, and that these attributes are additively aggregated in an evidence accumulation process. In this paper we outline theoretical problems with such an account, and argue that intertemporal choice processes necessarily includes interaction between the two attributes in order to generate reasonable choice behavior. Furthermore, we re-examine existing eye-tracking datasets of intertemporal choice using a Markov model of attentional dynamics. Our model assumes that the transitions between distinct attentional states (e.g. amounts and delays of the two options) depend on a large number of variables, including, crucially, the most recently attended attribute value. We estimate model parameters within a hierarchical Bayesian framework and find that high values of currently sampled information lead to more frequent transitions to the other attribute within the same option. Thus, for example, participants are more likely to sample the time delay of an option when the monetary amount is high, relative to when the amount is low (and vice versa). This corresponds to interdependent and interactive attention dynamics during decision making. We conclude by examining how such an interactive attentional process can combine with an attention-based evidence accumulation process to generate observed patterns in intertemporal choice behavior.