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.
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.
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.
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.