In this work, we sought to resolve a current debate on the influence of a third (distractor) option on the probability of choosing the better out of two other alternatives. One study reported that more valuable distractors make it more difficult to pick the best option (Louie et al., 2013, PNAS), but another study found just the opposite (Chau et al., 2014, Nature Neuroscience). In four experiments with a total of 147 participants, we used the paradigm of Chau and colleagues, added a specific set of trials, manipulated decision time, measured eye movements, and applied cognitive modeling to make sense of this controversy.

Remarkably, we neither found a positive nor a negative effect of the distractor’s value on the relative probability of choosing the best or the second-best option. Instead, better distractors were chosen more often themselves (even though participants were instructed not to pick them) and slowed down the choice process, thereby leading to longer response times and more failures to stay within the time limit. The best explanation for these effects was that the amount of attention spent on the distractor increased with its value. This was confirmed by eye-tracking data (see the figure): Participants looked more on high-value distractors (D), which made it more difficult for them to choose accurately. Finally, we analyzed the behavioral data of Chau and colleagues and found out that their effect resulted from a statistical artifact. Our study highlights the role of attention in speeded decision making as well as the importance of testing the robustness of previously published results.

Gluth, S.*, Spektor, M.S.*, & Rieskamp, J. (2018). Value-based attentional capture affects multi-alternative decision making. eLife, 7, e39659.