Early Sensory Evidence Shapes Multichoice Confidence Bias: A Registered Report

Everyday decision making often involves choosing between multiple alternatives, and developing unified theories for this process would benefit broad disciplines of behavioral science. A key challenge lies in explaining behavioral irrationalities that arise specifically in multialternative decisions. This study, based on preregistered procedures, investigated such nonnormative behaviors in a three-choice dot numerosity discrimination task. We systematically manipulated the value of the lowest numerosity alternative (the dud stimulus) and quantified its effects on choice, response time, and confidence. We then explained observed behaviors with a sequential evidence accumulation model featuring a “max versus next” decision algorithm. This pseudo-optimal decision-making rule naturally accounted for a well-known nonnormative choice pattern: the violation of the independence of irrelevant alternatives. Our model also explained a multichoice metacognitive bias, known as the dud-alternative confidence boost, by identifying two critical time windows in confidence constructions: Confidence is based on sensory evidence collected shortly after stimulus presentation and evidence gathered right after decision making. These findings represent a significant advancement in understanding the dynamics underlying multichoice irrationalities.