When you woke up this morning were you an expert water measurer? No? Well, you will be after reading this article. But that might not be a good thing: experts are sometimes worse off than regular Janes and Joes. To see why, first we need to wire your brain for expertise--read on.
Imagine you have three jars. One holds 4 units of water. Another holds 12 units. And the last holds 3. How can you measure exactly 2 units? (Hint: there's gotta be some subtraction here.)
Now check this out: Jar A holds 8 units, jar B holds 24 units, and jar C holds 6 units. How can you measure 4 units?
And finally: Jar A holds 12 units, jar B holds 36 units, and jar C holds 9 units. How can you measure exactly 6 units?
Congratulations! You're an expert!
Now the test: Jar A holds 6 units, jar B holds 78 units, and jar C holds 22 units. How can you measure 28 units?
Did you start with 78, subtract two-times-22, and then subtract another six (B-2C-A)? If so, congratulations again! You used the technique you learned to solve the tricky problem!
But check this out—there's another solution: just add 22 and 6 (A+C). Wow, that would've been easier, huh?
But don't feel bad. This water jar experiment by Abraham Luchins (1942) is a classic demonstration of the Einstellung effect: your previous experience makes the new problem more difficult.