The Origin of the phrase "Thinking Outside The Box"

There is a famous puzzle. 9 dots arranged in a square, like this

Your job is to connect all of the dots using only 4 straight lines without lifting your hand off the paper, crossing each dot only once. The only way to do it is to extend at least one of the lines beyond the perimeter of the "box". 

This solution never occurs to most people. They see a box, and their thinking is limited by that.

Thinking outside the box is a metaphor that means to think differently, unconventionally, or from a new perspective. This phrase often refers to novel or creative thinking. The term is thought to derive from management consultants in the 1970s and 1980s challenging their clients to solve the "nine dots" puzzle, whose solution requires some lateral thinking. This phrase can also be found commonly in dance, as encouragement to move creatively, beyond simple, geometric box steps and their basic variations, to literally step outside the box into more complex patterns of expression.

The catchphrase, or cliché, has become widely used in business environments, especially by management consultants and executive coaches, and has been referenced in a number of advertising slogans. To think outside the box is to look further and to try not thinking of the obvious things, but to try thinking of the things beyond them.