What to choose? Goals determine the effect of set value on the speed of value-based decisions
Romy Froemer1, Carolyn K. Dean Wolf1, Amitai Shenhav1; 1Brown University
All else being equal, people are faster to choose between higher value options compared to lower value options. This finding is often attributed to the value of the options themselves (e.g., that higher reward invigorates a faster response). Here we propose an alternative hypothesis, that responses are facilitated by the congruence of a choice set with the task goal, which is always to choose the best option. We tested this hypothesis in two studies: In Study 1, participants chose the worst of 4 items. As predicted, we reversed the standard effect: participants were slower, not faster, with increasing choice set value. In Study 2, participants chose the best item on half of the trials and chose the worst item on the other half. We observed a significant interaction of goal with set value: RTs decreased with increasing set value for choose-best, but increased for choose-worst. To better understand the mechanism underlying this effect, we fit our data with a hierarchical drift diffusion model. We compared three alternative models, testing whether the interaction of set value with goal was driven by changes in (a) drift rate, (b) response threshold or (c) non-decision time. The threshold and non-decision time models outperformed the drift rate model, suggesting that goal-congruent set values drive faster responses without also improving choice accuracy. Our findings suggest that the influence of set value on the speed of value-based decisions is a function of its ability to facilitate one’s choice goal, rather than how much reward it promises.
Topic Area: THINKING: Decision making