Dissociable mechanisms govern when and how strongly reward attributes affect decisions

Abstract

Rewards usually have multiple attributes that are relevant for behavior. For instance, even apparently simple choices between liquid or food rewards involve comparisons of at least two attributes, flavor and amount. Thus, in order to make the best choice, an organism will need to take multiple attributes into account. Theories and models of decision making usually focus on how strongly different attributes are weighted in choice, e.g., as a function of their importance or salience to the decision-maker. However, when different attributes impact on the decision process is a question that has received far less attention. Although one may intuitively assume a systematic relationship between the weighting strength and the timing with which different attributes impact on the final choice, this relationship is untested. Here, we investigate whether attribute timing has a unique influence on decision making using a time-varying sequential sampling model (tSSM) and data from four separate experiments. Contrary to expectations, we find only a modest correlation between how strongly and how quickly reward attributes impact on choice. Experimental manipulations of attention and neural activity demonstrate that we can dissociate at the cognitive and neural levels the processes that determine the relative weighting strength and timing of attribute consideration. Our findings demonstrate that processes determining either the weighting strengths or the timing of attributes in decision making can adapt independently to changes in the environment or goals. Moreover, they show that a tSSM incorporating separable influences of these two sets of processes on choice improves understanding and predictions of individual differences in basic decision behavior and self-control.