Let’s look a little more closely at these surprising results.
Solving this problem requires people to literally think outside the box.
In other words, the “trick” was revealed in advance.
The second group was told that the solution required the lines to be drawn outside the imaginary box bordering the dot array.
The symmetry, the beautiful simplicity of the solution, and the fact that 80 percent of the participants were effectively blinded by the boundaries of the square led Guilford and the readers of his books to leap to the sweeping conclusion that creativity requires you to go outside the box.
The idea went viral (via 1970s-era media and word of mouth, of course).
In the 1970s, however, very few were even aware of its existence, even though it had been around for almost a century.
If you have tried solving this puzzle, you can confirm that your first attempts usually involve sketching lines inside the imaginary square.