Psychologists have known about the so-called Einstellung effect since the 1940s. Now researchers are developing a solid understanding of how the phenomenon works.

"Our brain generally prefers a familiar, trusted solution, rather than exploring alternatives", Merim Bilalić (Department of Psychology) explains. This phenomenon has been known since 1942, when the American psychologist Abraham Luchins conducted experiments with water jugs, each with a different capacity. Participants in the experiments were asked to work out how to transfer liquid between the jugs so that they would end up with 100 units of water in one container. The solution to this task involved three steps. When they were subsequently given simpler tasks to solve, they continued to apply the more complicated three-step solution.

"Researchers have conducted similar experiments with chess players", Bilalić goes on to say. In his experiments, expert chess players were presented with a situation where they could use a well-known five-step sequence ("smothered mate"). The players also had the option to win the game by applying a less familiar sequence, involving only three steps. Most players chose the familiar sequence. During the interviews conducted subsequently, it was not possible to determine why they had disregarded the (simpler) alternative.

Bilalić and his colleagues decided to track the players' eye movements with an infrared camera. "We were able to establish that they were, quite literally, blind to the alternative, better solutions", the psychologist reports. The players' gaze did not shift away from the squares that they had identified as part of the "smothered mate" sequence, even though they insisted that they had looked for alternative solutions. The alternatives they did explore were clearly only variations of the already established five-step sequence.

According to Bilalić, this bias presents a problem in many areas. What makes the Einstellung effect particularly difficult is that most are simply not aware of the phenomenon. "We believe that we generally approach problems with an open mind. However, the brain unconsciously steers our attention towards previously stored knowledge. Any information that does not match the solution or the theory we have already internalized, tends to be ignored or masked." This may lead doctors to make erroneous diagnoses, and judges to form judgements in line with earlier cases. Bilalić therefore concludes: "We must be aware of our errors, if we genuinely want to improve our thinking."