Another illustration of this:
"Another effective [debugging] technique is to explain your code to
someone else. This will often cause you to explain the bug to yourself.
Sometimes it takes no more than a few sentences, followed by an
embarrassed "Never mind, I see what's wrong. Sorry to bother you." This
works remarkably well; you can even use non-programmers as listeners.
One university computer center kept a teddy bear near the help desk.
Students with mysterious bugs were required to explain them to the bear
before they could speak to a human counselor."