We are faced with the need to make decisions every day.  Should we bring product A or B to market?  Which marketing strategy should we use?  Of the choices that we have available, who is the best person to hire or who would make the best partner? In each case, we try to rely on as many facts as we can so that we can make a reasonable estimation of the best path to follow.  At first glance, the approach of weighing the evidence rationally seems perfectly reasonable.  Yet, in so many instances, rational predictions fail.  Why is that? And what can we do about it?