It's an interesting experiment, but the author's conclusion cannot possibly follow from the results of it.
your conclusion: that the second experiment disproves the theory that thinking outside the box is useful in solving problems, is itself a fallacy.
Because the solution is, in hindsight, deceptively simple, clients tended to admit they should have thought of it themselves.
That this advice is useless when actually trying to solve a problem involving a real box should effectively have killed off the much widely disseminated—and therefore, much more dangerous—metaphor that out-of-the-box thinking spurs creativity.
After all, with one simple yet brilliant experiment, researchers had proven that the conceptual link between thinking outside the box and creativity was a myth. But you will find numerous situations where a creative breakthrough is staring you in the face.
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.
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).Yet participants’ performance was not improved even when they were given specific instructions to do so.That is, direct and explicit instructions to think outside the box did not help.Let’s look a little more closely at these surprising results.Solving this problem requires people to literally think outside the box.The correct solution, however, requires you to draw lines that extend beyond the area defined by the dots.