Fixedness - Abraham Luchins

Fixedness can also be defined as the Einstellung effect, first described by Abraham Luchins in 1942. It occurs when a person is presented with a problem or situation similar to one they have worked through in the past. The person will likely provide that same response without giving the problem too much thought, even though a more appropriate response may be available.

Essentially, the Einstellung effect is one of the human brain’s ways of finding a solution as efficiently as possible, even though it might not be the most appropriate solution.

In a 1942 experiment, Luchins gave his subjects 3 water jars with the capacity of 21 units (A), 127 units (B) and 3 units (C), and asked them to measure out exactly 100 units.

Luchins 1

The solution was to fill the B -127 units jar, then pour out enough to fill the A -21 units jar and twice the C -3 unit jar. 100 units = B-(A+2C).


Next the subjects were given another 3 water jars – 18 units, 48 units and 4 units, and asked to measure out exactly 22 units as quickly as possible.

Luchins 2

The result? Most subjects used the same solution B-(A+2C) as opposed to the shorter A+C solution. However, a second group of subjects who weren’t exposed to the first test all chose the A+C solution immediately. When the first group were told about the Einstellung effect half immediately saw that A+C was an easier solution.

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