Confirmation Bias – The tendency for people to favor information that confirms their beliefs or ideas.  Investors and economists often fail to fully appreciate other views due to a narrow minded view of the world often resulting from what they think they already know.

Ingroup bias – the tendency to favor one’s own group.  In investing and economics we see this in ideologies and particular strategies.  Austrians favor those who believe their own thinking.  Chartists dislike value investors.  Often times, the strongest economists and investors are the ones who are able to move beyond this ingroup bias and explore the potential that other groups have something positive to contribute.

Gambler’s Fallacy – When an individual erroneously believes that the onset of a certain random event is less likely to happen following an event or a series of events.  We see this in trading all the time.  This is the belief that just because something has occurred in the past that it is more likely to occur in the future.  The “trend is your friend” and that sort of thing….

Post-Purchase Rationalization – When one rationalizes past purchases after the fact in an attempt to justify past actions.  Investors often learn about how a bad trade turns into an investment when they rationalize their past purchases.  If you’ve been in the business for a while you know how destructive this can be. (more…)