# 49. Manipulation of bias and heuristics in decision making ## 49.5. Methodology/Refinements/Sub-species ### 49.5.49. Overconfidence effect This is the tendency towards excessive confidence in our answer to questions. For example, for certain types of exam questions, studies have shown that answers that people rate as 99% certain turn out to be wrong 40% of the time. Overconfidence has been called the most "pervasive and potentially catastrophic" of all the cognitive biases to which human beings fall victim \[Plous, S. (1993)\]. It has been blamed for lawsuits, strikes, wars, and stock market bubbles and crashes. A manipulator can trick an overconfident victim into an action or position which then turns out to be completely ill-judged - it could be an investment or a military action or a political strategy etc.