# 49. Manipulation of bias and heuristics in decision making ## 49.5. Methodology/Refinements/Sub-species ### 49.5.51. Pessimism bias This is the tendency for some people, especially those suffering from depression, to overestimate the likelihood of negative things happening to them. A manipulator can use this bias to persuade a victim to act in a certain way, buying unnecessary insurance for instance, or selling stocks or property at a loss when convinced of impending economic doom around the corner. This is a favorite of equity market manipulators, who force a market down in order to buy stock at low prices.