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.
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.
The correct solution, however, requires you to draw lines that extend beyond the area defined by the dots.
At the first stages, all the participants in Guilford’s original study censored their own thinking by limiting the possible solutions to those within the imaginary square (even those who eventually solved the puzzle).
Because they hadn’t, they were obviously not as creative or smart as they had previously thought, and needed to call in creative experts. The nine-dot puzzle and the phrase “thinking outside the box” became metaphors for creativity and spread like wildfire in marketing, management, psychology, the creative arts, engineering, and personal improvement circles.There seemed to be no end to the insights that could be offered under the banner of thinking outside the box.Speakers, trainers, training program developers, organizational consultants, and university professors all had much to say about the vast benefits of outside-the-box thinking.Even though they weren’t instructed to restrain themselves from considering such a solution, they were unable to “see” the white space beyond the square’s boundaries.Only 20 percent managed to break out of the illusory confinement and continue their lines in the white space surrounding the dots.Let’s look a little more closely at these surprising results.Solving this problem requires people to literally think outside the box.It was an appealing and apparently convincing message.Indeed, the concept enjoyed such strong popularity and intuitive appeal that no one bothered to check the facts.No one, that is, before two different research teams—Clarke Burnham with Kenneth Davis, and Joseph Alba with Robert Weisberg—ran another experiment using the same puzzle but a different research procedure.Both teams followed the same protocol of dividing participants into two groups.