Because the solution is, in hindsight, deceptively simple, clients tended to admit they should have thought of it themselves.
If you have tried solving this puzzle, you can confirm that your first attempts usually involve sketching lines inside the imaginary square.
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.
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.The correct solution, however, requires you to draw lines that extend beyond the area defined by the dots.