Management consultants in the 1970s and 1980s even used this puzzle when making sales pitches to prospective clients.
They are much more common than you probably think.*From Inside the Box: A Proven System of Creativity for Breakthrough Results Copyright 2014 Drew Boyd There are many theories of creativity.
The second group was told that the solution required the lines to be drawn outside the imaginary box bordering the dot array.
In other words, the “trick” was revealed in advance.
Today many people are familiar with this puzzle and its solution.
In the 1970s, however, very few were even aware of its existence, even though it had been around for almost a century.