Information sources and congruency modulate preference-based decision-making processes

Preference-based decisions often need to combine multiple pieces of information. This study investigated how the number of information sources and information congruency affect decision performance. Participants made preference-based choices between two groups of food items. Increasing the number of items in each option led to slower and less accurate decisions. Drift-diffusion modelling showed that more information sources relate to a slower rate of evidence accumulation. Therefore, the additional information impeded rather than improved the decision accuracy. In Experiment 2, each choice option contained either fully congruent information or one piece of incongruent information. Decisions with incongruent information is associated with a lower drift rate than that with congruent information, leading to inferior behaviorual performance. Further model simulations support that the change in attention weighting over information sources leads to the observed effects of item numbers and item congruency. Our results suggest a bounded combination of information sources during preference-based decisions.