Once a week or so, a message like the following appears on some musical USENET newsgroup or listserv:
My buddies and I have a long standing controversy about whether a Satanic message is backwards masked on Stairway to Heaven.
I happened to respond to that message on ALLMUSIC, and (always recycle) here's my response:
Many years ago I was a psych major (they'd probably call it cog sci these days -- heavy on the psychobiology, perception, psychophysics, rat-running and math; hold the ab psych).
Anyhow, "backward masking" describes a visual phenomenon. When you use a tachistoscope (like a slide projector that flashes stuff on a screen really, really fast) and you present a pattern like the following for a few mSec:
ABCDEFGHI JKLMNOPQR STUVWXYZA BCDEFGHIJ KLMNOPQRS
then you flash a pattern like the following (the Xs representing solid black squares):
X X X X X X X X X X X X X XXXXX XXXXXXXXX
a hundred or so mSec later, it turns out that where the black squares were on the latter picture, you can't read the letters on the former picture. The black squares seem to mask the letters from your visual perception BACKWARDS IN TIME! OoooEEEEEooooo!
This led Ulrich Niesser to hypothesize an "iconic storage" mechanism that precedes short-term memory which, together with J.J. Gibson's work (and a dash of E.O. Hebb), constitutes the standard model of visual perception these days. Unless I've dozed off again and they've come up with something better.
All very interesting if you like that sort of thing, and it was kind of exciting at the time, but what the hell does this have to do with Led Zeppelin?
Actually nothing at all, were it not for some fundies who decided they could make a buck or two scaring people by playing records backward.
Incidentally, we who were teenagers in the age of vinyl had been playing Beatles records and such backwards for a couple of decades before the guys in the shiny polyester suits caught on, on account of there were (and are) some things on records that actually were recorded backwards on purpose to enrich the sonic stew. And of course to reveal the truth about Paul's death ;-)
But these fundies (whose education is in Bible "Colleges" and who never had a physiology and psychology of perception course in their lives -- but that's OK, neither have their victims) decided to appropriate the term "backward masking" from visual perception and misapply it to a different phenomenon in auditory perception.
By doing this, they attempted to be scientific, at least in the eyes of those even more ignorant than they -- and there's nothing some fundies want more than to be thought of as scientific.
Needless to say, perceptual scientists (and their poor subjects) have been subjected to endless experimentation attempting to show that it's possible to understand verbal material that's played backwards. All negative, of course. In fact, virtually every model of auditory perception relies on time in such a deep way that hundreds of other experiments would be thrown into serious doubt (unlikely in itself) if you really could hear stuff backwards.
But that didn't bother the guys with the vinyl haircuts -- they're out to save your soul (and line their pockets) and a few pesky facts will never deter them from their mission. Even a negative result that's close to positive (e.g., one of 20 experiments shows significance at the .05 level -- you have to have had a little statistics to understand this joke) leads these psychobozos to proclaim that "The effect might be subliminal," thereby pushing another one of my hot buttons.
Just for the record, there's a mathematical reason why even mentioning the word "subliminal" marks you as an ignoramus. Can you say "ROC curve," boys and girls? I knew you could.
But when the snake-oil salesmen stole and misapplied a legitimate cog sci term like "backward masking", they gave themselves the power to point their present and future dupes at all the psychological literature about backward masking and say, "See, there must be something to it."
And there is some "evidence" to back them up that they can bring out in their traveling shows: when you play certain words or sentences backwards, you can sometimes hear words or even short sentences (not related to the content of the actual sentence, of course). The human ear hears sounds which, from their timbre, appear to be a human voice. It attempts to resolve those sounds into speech. Duh! It would be miraculous if the human auditory perception mechanism didn't do that!
But to the guys in the blue suits with the odd posture and the spooky grins, that's all it takes to convince their prey that there's "something to it."
Since you used the term the way these folks wanted you to, it seems to have worked, at least in your case.
You know, a lot of people take great pains to keep away from folks who try to fool them. Some don't. You gotta decide which you're gonna be.
There's more on this subject (thanks to Malinda McCall for the reference) in Big Secrets. William Poundstone, ISBN# 0-688-04830-7. William Morrow and Company, Inc., 105 Madison Ave., New York, NY 10016. Here is the relevant quote, and thanks to Malinda for her marathon typing.
I was depressed but not surprised to read there a proposed bill in the U.S. House that uses both the term "backward masking" and the word "subliminal" and attempts to purge this evil that's poisoning the minds of our youth. Sigh. -- Bob