The mechanism of the einstellung (set) effect: a pervasive source of cognitive bias

The eye movements of expert players trying to solve a chess problem show that the first idea that comes to mind directs attention toward sources of information consistent with it and away from inconsistent information. This bias continues unconsciously even when players believe they are looking for alternatives. The result is that alternatives to the first idea are ignored. This mechanism for biasing attention ensures a speedy response in familiar situations, but it can lead to errors when the first thought that comes to mind is not appropriate. We propose that this mechanism is the source of many cognitive biases, from phenomena in problem solving and reasoning to perceptual errors and failures in memory.