In an unusually reflective mood, Harry stepped onto the open field surrounded by a small crowd of gawking onlookers. He remembered the gregarious old gentleman who had first encouraged him to try this strange art for himself. Now, as he loosely gripped the short end of an L-shaped rod in each hand, making sure the long ends were perfectly level and pointing straight ahead, he remembered how those long ends had swung about in aimless, uncoordinated fashion for only a few seconds back then before he was able to get them under proper mysterious control. From then on it was like riding a bicycle. Why, if there was no water around, he could probably walk for miles almost in his sleep without the rods deviating from parallel by more than a barely perceptible wiggle. No question about it, Harry was a natural. It was really only a hobby for him, but perhaps he should be charging more for his services!
Of course, Harry knew that the true explanation for dowsing had nothing to do with spirits, in spite of that awful name some people had for it. “Water witching”—please! We are not medieval simpletons! We understand that it is our own hands that determine the movement of the rods, and that the purpose of the rods is simply to amplify the tiny motions of our hands into something more visible. That is precisely why it is so important to hold the rods just at the edge of equilibrium, where they are so free to move that the tiniest variation in the position of our hands will make them change direction. Just how the human body is able to sense the location of underground water and subconsciously transmit that sensation into a movement of our hands is admittedly not yet understood, but that is all part of the wonder of our craft.
As he walked back and forth across the field in a semi-random pattern, Harry sensed that some of the onlookers were beginning to lose interest. Nothing seemed to be happening. But there was nearly always water somewhere, so Harry knew it was just a matter of time before he would find it. Where would it turn out to be? You couldn’t help wondering. Well, the rods would eventually tell. Maybe they were on to something already. Was that slight wiggle an indication? No, they’re still pointing straight ahead. Oh, wait, how about this little movement? It seems to be a tad more pronounced than usual. Perhaps we’re getting close!
The next step and the rods not only wiggled but positively started to point inwards. It was only by an inch or two, but Harry had enough experience to know what this meant. Another step and his suspicion was confirmed. Aha! Now they were almost crossing. One more step ought to do it, he thought, and sure enough, there they were, exactly 90 degrees from the straight-ahead position where they had started. He took a step backward, more to show off to his audience than to confirm anything in his own mind, since he already knew the rods would move right back to where they had been, and he was right. A step forward, and there they were again, proving beyond all doubt the legitimacy of this exercise. Yes, he thought, perhaps I will charge a little more next time.
The preceding was a fictional account, of course. I don’t have any direct experience with dowsing myself. I just made up a story about it to illustrate how easily people can be deluded even by what turn out to be very silly beliefs. There’s really nothing mysterious about dowsing once we understand the power of positive feedback in our beliefs. What is positive feedback? The most commonly-recognized example would probably be when the microphone gets too close to the speakers in a public-address sound system. The background noise or other sound detected by the microphone is then amplified and sent to the speakers, so that a louder version of it is in turn picked up by the microphone and amplified yet more. This goes back to the speakers and is again picked up by the microphone and amplified, and so on in an infinite loop. The result is an annoying, maximum-volume squeal that can only be silenced by breaking the loop in some way, such as by repositioning the microphone so that it doesn’t pick up the sound from the speakers, or by temporarily turning the volume control almost all the way down.
In the case of dowsing, the feedback loop does not involve sound but rather the dowser’s belief about where the water is located. To understand how this works we need to first recognize a phenomenon called the ideo-motor effect. This is something that we all make use of every day just by standing or walking, but a more illustrative example would be that of riding a bicycle. When you think about it, the ease with which even a child can keep a bicycle perfectly balanced is pretty amazing. If we tried to do this by simply finding the exact balance point and holding our bodies rock-steady at that point, most of us would fall in a second. The human body is simply not so adept at holding itself in a perfectly fixed position like this. We cannot keep our muscles from constantly moving, even if only in tiny, almost imperceptible amounts. So how do we manage to keep a bicycle balanced? The answer is that we don’t do it statically, but dynamically. We continuously make tiny corrections to the position of our bodies and to the bicycle’s steering as we ride, corrections so small that an onlooker cannot even perceive them, but just big enough to compensate for the direction in which we sense the bicycle would otherwise fall. With just a little practice, these corrections become so smooth and natural that we are no longer even consciously aware of the process ourselves. We don’t try to make the bicycle stay balanced; our bodies just seem to do it automatically. At that point we say the required adjustments are controlled by the ideo-motor effect.
A dowser is similarly actively engaged in a delicate balancing act that is controlled at the subconscious level by the same ideo-motor effect. He keeps the dowsing rods as close as possible to the equilibrium point, where they are almost free to swing around. But this is a dynamic process, not a static one. No human being can hold the rods precisely at the equilibrium point in a rock-steady manner, especially not while walking or chewing gum at the same time. Instead, the dowser must make continuous adjustments to the position of his hands to compensate for the tiny wiggles he senses in the rods, even though he is not aware of the process. That is the only reason the rods stay pointed straight ahead when the dowser thinks they ought to be pointed straight ahead. And that is the reason the rods cross exactly where the dowser believes there is water, even though he does not consciously try to make them do this.
This is only half the story, however. I’m not suggesting that the dowser subconsciously moves his hands to make the rods cross at a spot he had preselected as to where he believed water would most likely be found. That may be true in some cases, but I suspect the vast majority of dowsers probably do indeed begin the procedure without any idea whatsoever where the rods will cross. And this is where the positive feedback loop comes into play.
The sophisticated dowser’s theory that the rods amplify the subconscious movements of his hands is right as far as it goes. But what he fails to realize is that this subconscious movement of his hands is not controlled by some mysterious extra-sensory perception, but simply by the everyday ideo-motor effect operating in accordance with his desires and therefore beliefs. And his belief about where the water is located is caused by positive feedback. It may start out as just the slightest hunch triggered by his observation of a tiny wiggle in the dowsing rods. But that hunch is fed back into the position of his hands to make the rods move a little more. This in turn strengthens the hunch into a tentative opinion, which makes him subconsciously move the rods even more in response, and upon seeing this, his tentative belief in turn becomes a positive conviction. So his belief is caused by the “evidence” of the movement of the rods, but the movement of the rods is also caused by his belief. This is the essence of the positive feedback loop, and this is why the dowsing rods appear to be so mysteriously controlled.
What the example of dowsing primarily shows is how positive feedback can obscure the otherwise very conspicuous weaknesses in our structures of belief. The dowser’s belief that he has found water at a certain location seems quite reasonable to him, being built on many lower-level beliefs that are almost indisputably true. These would include the belief that the rods move outside his conscious control, for example, and that they always cross in the same spot when he backs away and moves forward again. If he realized that this was all ultimately caused by just a wiggle and a hunch, the game would be over.
Perhaps the only really surprising thing about dowsing is how many people fail to understand this and are instead convinced that it really locates water. But this, too, is primarily the result of a positive feedback mechanism of sorts. This second kind of positive feedback mechanism has to do with our natural tendency to color and filter the evidence in accordance with our beliefs.
When a well is dug at a location picked by a dowser it frequently hits water. This is not surprising, since when a well is dug at random it also frequently hits water. But what often happens is that a person who already believes in dowsing to some degree will tend to look only for confirmation of his belief, not contradiction. This phenomenon is called confirmation bias.
The way confirmation bias works can be very subtle and gradual. For example, when the slight believer in dowsing hears of a case in which water is not found at the indicated location, he might properly acknowledge this as circumstantial evidence against his belief. But even so, he will likely still have a slight tendency to discount that evidence as less meaningful than the majority of cases he hears about in which water really is found, and which therefore strengthen and confirm his belief. Over time, he tends to forget about the cases that contradict his belief and remember the ones that confirm it. Additionally, it is likely that most of the cases he hears about will be relayed to him by other believers who also have a tendency to report only the successes and discount the failures. What he doesn’t realize is that his initial belief in the validity of dowsing is causing him to filter the data so that it only feeds back upon that belief in a positive way, thereby causing his belief to grow stronger over time, as he hears about or comes into contact with more cases. So although his belief in dowsing is now built on his inferences from the evidence, those inferences are not really reasonable, for they in turn hang on his belief in dowsing, or ultimately on just the very tenuous beliefs that caused him to suspect dowsing was valid in the first place, before he considered the evidence at all.
This form of positive feedback loop can be downright insidious. The filtering of evidence caused by confirmation bias and amplified by positive feedback is undoubtedly responsible for a great many of our most unreasonable beliefs. Homeopathy makes for another good illustration because its basic tenets are so patently absurd. Homeopathic elixirs are considered to have greater potency the more dilute they are. One common dilution is termed 30C, where the C stands for one part in 100 and the 30 indicates how many times this one percent dilution process is repeated. This means the final dilution has only one part in 1060 (that is, the numeral one with 60 zeros after it) of the original potion. As any high school chemistry student can calculate, a gallon of water contains “only” about 1026 molecules,[1] so the chances of a whole gallon of the final solution containing even one molecule from the original is only about one in 1034. If that’s not close enough to zero for you, you probably believe in the Easter bunny.
But suppose a person like Harry is not aware of all this. He may be sensible enough not to believe just anything he hears, but when a friend first tells him about this mysterious practice, his curiosity is still slightly piqued. Not enough to make him a believer, perhaps, but just enough to make him wonder if it might possibly work. And so he may be tempted to just give it a try the next time he is sick. After all, what could it hurt?
Unfortunately, of course, this very suspicion that prompts people to give homeopathy a try is usually also accompanied by a slight subconscious tendency to regard any improvement in their condition as evidence for its working. If such an improvement is in fact observed, even by chance, the positive feedback loop gains a toehold and will likely begin spiraling out of control. Over time, more and more supporting evidence will be amassed, along with a growing tendency to discount and forget anything opposed. After a few years of this sort of thing, a person’s belief in homeopathy might be so deeply felt that not even a chemistry lesson could break it.
The point in all this is not just to poke fun at incredible, wacky beliefs like dowsing and homeopathy, of course (though detached smugness is admittedly a rather enjoyable feeling), but rather to learn from them. I presume that most of my readers will be reasonable enough to see through the follies of people like Harry with relative ease. But the fact remains that even reasonable people arrive at very different conclusions to many questions, especially when it comes to evaluating the strengths and weaknesses of various ideological positions of a philosophical or political nature. Could one of the reasons be that that even we who truly value rational and scientific thinking are still infected on some level by the same kind of confirmation bias and positive feedback that I have just described?
I think honesty compels us to admit the answer is probably yes. Somewhat paradoxically, perhaps, even the fact that we take pride in our rationality can sometimes blind us to the very marks of irrationality we find so blatantly obvious in others. “So convenient a thing it is to be a reasonable creature,” quipped Benjamin Franklin about himself in his autobiography, “since it enables one to find or make a reason for everything one has a mind to do.”
For this problem I have no cure-all solution to present. I doubt if any one of us will ever be quite as objective as we like to think in regard to our reasons for belief. I think it will always be human nature to cheer for “our side” in any rational argument rather than to consider the evidence against it as honestly as we consider the evidence for it. But this doesn’t mean we should give up trying, of course. We must always fight the good fight. And that is why I suggest it is helpful to think about the peril of positive feedback in our beliefs, the more vigilantly to try to be on guard against it.
| [1] | 6.02×1023 molecules/mol ÷ 18 g/mol × 3785 g/gal = 1.26×1026 molecules/gal |
This page copyright © 2010-2014 Edward A. Morris. Created July 25, 2014. Last updated July 25, 2014.