According to Wikipedia, a cognitive bias is a pattern of deviation in judgement that occurs in particular situations. In other words, sometimes people make wrong or irrational decisions based on selective use of information or misinterpretation of a situation. Well known examples include hindsight and bandwagons.

Our brains sometimes can’t be trusted to make the right decisions based on the available information. In fact, we don’t even make decisions based on an absolute (or “discrete” to use the maths term) concept of right or wrong but a fuzzy scale (see fuzzy logic) of more or less right or wrong. As we assimilate more information, our disposition to choose one or other of two option shifts on a scale and sometimes irrationally.

There are some decision making processes where this analogue approach is beneficial, hence the invention of artificial neural networks in computer science to try to model this behaviour using computers which are fundamentally digital.

This is pretty interesting and bears some thinking about. Why, in certain circumstances, are people predisposed to act in a way that doesn’t make logical sense?

For some interesting further reading, here’s a handy list of cognitive biases from Wikipedia.