I know that this is an oooolllddd subject and isn't technology, but the Skeptoid podcast had an episode on Reverse Speech and pareidolia last month. Pareidolia is a very good scientific explanation of the Law of Fives.
http://skeptoid.com/episodes/4105
QuotePareidolia is the perceptual phenomenon by which we perceive familiar patterns in disorder. It is the brain's incredible computing power that lets us recognize people, understand language, and read handwriting. For the brain to have this capability, it necessarily results in the ability to perceive patterns where none in fact exists. Most of us can say "Hey, that tree bark looks like Ernest Borgnine," without actually concluding that Ernest Borgnine has somehow become a tree. Our intelligence allows us to not make that mistake. But sometimes a horse might see a garden hose on the ground; its pareidolia tells it that it's a snake, but it lacks sufficient intelligence to overcome the instinctive recognition. I'm not saying that reverse speech believers lack intelligence, only that they lack critical thinking skills; because there is a genuine gray area where it's hard to tell if a pattern is accidental or deliberate. But speech is a deliberate speaking action, so the reverse speech advocates do have a point they can make. It's not an accident of nature like the tree bark, speech is the deliberate result of a speaker's brain communicating. What the reverse speech advocates are missing is that the well-known, well-understood, and well-evidenced phenomenon of pareidolia is a much more reasonable, simple, and probable explanation for why we can often perceive patterns in meaningless noise, in this case reverse speech.