Sometimes I like to test whether I can actually construct or assemble a finished something in my mind from an inkling of a thought.

For example a few days ago I realized that I found it hard to reverse a word in my mind, even a simple one. Try for yourself, think of a word and then reverse it in your head with your eyes closed.

Some people might struggle with the above, some may find it doable in their heads, but most can agree that it's absurdly easy if you can externalize it to paper or a text editor at least.