Effects of many conflicting objectives on decision-makers’ cognitive burden and decision consistency

Practical planning and decision-making problems are often better and more accurately formulated with multiple conflicting objectives rather than a single objective. This study investigates a situation relevant for Multiple Criteria Decision Making (MCDM) as well as Evolutionary Multi-objective Optimization (EMO), where the decision-maker needs to make a series of choices between nondominated options characterized by multiple objectives. The cognitive capacity of humans is limited, which leads to cognitive burden that influences human decision-makers’ decisions. We measure how the varying number of objectives influences cognitive burden in a laboratory study, and the impacts that this burden has on the decision-makers’ behavior and the consistency of their decisions. We use psychophysiological, behavioral, and self-report methods. Our results suggest that a higher number of objectives (i) increases cognitive burden significantly, (ii) leads to adopting strategies in which only a limited number of objectives is considered, and (iii) decreases decision consistency. • Multiobjective decision support methods often consider a high number of objectives. • For decision-makers, this creates cognitive load that is experienced negatively. • To avoid this negative feeling, people only consider a few objectives out of many. • Ignoring objectives reduces decision consistency, indicating lower decision quality. • Limitations of human cognition should be considered when building decision models.