As you play this game Judging Black or White sheep, your mind is supposed to gradually slip into boredom and eventually sleep.
Counting sheep is a mental exercise that's well-known all over the world as a means of inducing sleep. Adults and children alike often suffer from insomnia, which is a sleep disorder characterized by difficulty falling asleep or staying asleep the whole night long. Any time someone mentions having trouble falling asleep, the suggestion to count sheep usually isn't far behind.