Biases are human tendencies that lead us to follow a particular quasi-logical path, or form a certain perspective based on predetermined mental notions and beliefs. When investors act on a bias, they do not explore the full issue and can be ignorant to evidence that contradicts their initial opinions. Avoiding cognitive biases allows investors to reach impartial decision based solely on available data.


Some common psychological biases plaguing investors include: representative bias, cognitive dissonance, home bias, familiarity bias, mood and optimism, overconfidence bias, endowment effects, status quo bias, reference point & anchoring, law of small numbers, mental accounting, disposition effects, attachment bias, changing risk preference, media bias and internet information bias.