How to make bad decisions: Assume everyone is equally competent

People are incredibly bad at taking differences in competence into account when making group decisions. — Bahador Bahrami

Over the past few decades, researchers have uncovered a long and growing list of cognitive biases that get in the way of good group decision making. The shared-ness bias trips up groups frequently, for example: groups will give higher weight to shared information (information known to many in the group) when in fact information known to few may be more …