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Artifacts in reasoning
Hidden persuaders make astrology work

Geoffrey Dean and Ivan W Kelly

Abstract -- Unaided human reasoning is subject to artifacts due to systematic errors (we call them hidden persuaders) that can fully explain why an astrology based on experience seems to work. Astrologers proudly and repeatedly claim that astrology is unassailable because it is based on experience, but they are mistaken -- what they see as its strength is actually its weakness. Here more than 30 hidden persuaders such as the Barnum effect are explained. Each will convince clients that astrology works, and all are in common use in astrology books and consulting rooms. They vary in effectiveness depending on situation, but all lead to client satisfaction, and none require that astrology be true. But if clients are going to be satisfied, astrologers can hardly fail to believe in astrology. In this way a vicious circle of reinforcement is established whereby astrologers and their clients become more and more convinced astrology works. Examples from palmistry and phrenology are cited to show how hidden persuaders are not unique to astrology.

Unaided human reasoning is subject to artifacts due to systematic errors (we call them hidden persuaders) that can explain why an astrology based on experience should seem to work even if it were totally invalid. For example hidden persuaders explain why tens of thousands of Western tropical astrologers can say that in their experience Scorpios really are intense, while hundreds of thousands of Eastern sidereal astrologers can look at the same piece of sky, which they call Libra, and agree that in their experience it is not intense but relaxed. The same applies to all the others factors that astrologers disagree about, which is most of them. In technical terms hidden persuaders can be described as "statistical artifacts and inferential biases."

As shown in the companion article Artifacts on this website, artifacts in data tend to be small and resistant to detection, and some became famous in their day as the best claimed evidence for astrology. In contrast, artifacts in reasoning tend to be large and have literally become the foundation on which the practice of astrology rests.

Caution. You will be led seriously astray if you learn about astrology without first learning about hidden persuaders. Unless you can be sure that hidden persuaders have been ruled out, don't believe what you read in astrology books. In particular the claim that astrologers proudly and repeatedly make, that astrology is unassailable because it is based on experience, is (as we shall see) simply mistaken -- what they see as its strength is actually its weakness.

How not to test a reading
If the above statement sounds preposterous, consider the following quote from psychologist Ray Hyman, How not to test mediums, Skeptical Inquirer 27(1), 20-30, January-February 2003. Hyman has devoted more than half a century to the study of psychic and other readings, especially to why such readings can seem so compelling.

"As a way to earn extra income, I began reading palms when I was in my teens. At first, I was skeptical. I thought that people believed in palmistry and other divination procedures because they could easily fit very general statements to their particular situation. To establish credibility with my clients, I read books on palmistry and gave readings according to the accepted interpretations for the lines, shape of the fingers, mounds, and other indicators. I was astonished by the reactions of my clients.

"My clients consistently praised me for my accuracy even when I told them very specific things about problems with their health and other personal matters. I even would get phone calls from clients telling me that a prediction that I had made for them had come true. Within months of my entry into palm reading, I became a staunch believer in its validity. My conviction was so strong that I convinced my skeptical high school English teacher by giving him readings and arguing with him. I later also convinced the head of the psychology department where I was an undergraduate." (page 22)

Doing what every astrologer shouod do but never does
Thus far it could be any astrologer talking about astrology. They read charts and they become staunch believers in astrology's validity. As in Hyman's case, their experience seems totally compelling. But this is not the way to test a reading. Hyman then did something every astrologer should do but never does:

"When I was a sophomore, majoring in journalism, a well-known mentalist and trusted friend persuaded me to try an experiment in which I would deliberately read a client's hand opposite to what the signs in her hand indicated. I was shocked to discover that this client insisted that this was the most accurate reading she had ever experienced. As a result, I carried out more experiments with the same outcome. It dawned on me that something important was going on. Whatever it was, it had nothing to do with the lines in the hand. I changed my major from journalism to psychology so that I could learn why not only other people, but also I, could be so badly led astray." (page 22)

Hidden persuaders
The answer to Hyman's puzzle is hidden persuaders, factors that can make a vague reading seem so uncannily accurate that it becomes almost impossible not to believe in the system's validity. There are many hidden persuaders, of which thirty-four are listed below. All are an active component of experience and all are in routine use in astrology consulting rooms. For convenience we have grouped them under seven descriptive strategies:

1. Select initial hurdles
Preach to the converted (client predisposition)
Ignore everything on this website (ignorance is bliss)
The best things in life are not free (charging a fee)

2. Stifle chances of being wrong
Appeal to birth chart complexity (nonfalsifiability)
Avoid conflict, see what you believe (cognitive dissonance)
Believe what you cannot prove (unavailable data)
Remember the hits, forget the misses (selective memory)
Ask only confirming questions (stack deck)
Ignore disconfirming evidence (confirmation bias)
Deny that astrology can be tested (testability veto)

3. Use cues
Let context give the game away (vital statistics)
Let body language be your guide (cold reading)

4. Make astrology look good
The importance of first impressions (halo effect)
If it looks right then it is right (face validity)
Style is more important than content (Dr Fox effect)
Underestimate chance effects (chance baseline shift)
More is better (Aunt Fanny effect)

5. Make clients feel good
Use a kind heart to entice belief (tea and sympathy)
The power of positive thinking (Pollyanna principle)
It does us good if we think it does (placebo effect)
Having control makes us feel better (misattribution)
Just naming the unknown is enough (Rumpelstiltskin effect)
Closeness is its own reward (rapport)

6. Make the chart fit
Find meaning where none exists (faces in clouds)
Read specifics into generalities (Barnum effect)
See only what you want to see (illusory correlation)
Accentuate the positive (social desirability)
Be seduced by resemblance (magical thinking)
Afterwards we knew it all along (hindsight bias)
Sound arguments yes, sound data no (stereotypes)

7. Make the client fit
Find something, anything, to match the chart (repertoire)
Let client role-play their chart (self-fulfilling prophecy)
Force client to fit their chart (Procrustean effect)
Winter does not last forever (regression to mean)

None require that astrology be true
Each hidden persuader reflects the systematic error in human reasoning shown in parentheses, for which we have used the accepted name if there is one, or a provisional name if not. In the early days it was usual for critics to explain why clients were satisfied with astrology readings only in terms of the Barnum effect, the reading of specifics into generalities such as "you have problems with money", where sense appears to come from the reading when in fact it comes from our ability to make sense out of vagueness. Today, as shown above, many more hidden persuaders are known. They vary in effectiveness, and in a given situation some may be irrelevant, but all lead to client satisfaction and none require that astrology be true.

But if clients are going to be satisfied, astrologers can hardly fail to believe in astrology. In this way a vicious circle of reinforcement is established whereby astrologers and their clients become more and more convinced that astrology works. Note that there are no hidden persuaders to convince us that astrology does not work other than the informed critical mind, which of course is not an error as such but rather a defence against errors. An astrologer typically makes no effort to become informed about research or to acquire critical thinking skills, preferring instead to spend years learning to read charts, during which time they have ample chance to respond to the above reinforcement. And of course to build up a huge vested interest in continuing their ill-founded beliefs. If this still seems preposterous, consider the salutary case of phrenology:

The salutary case of phrenology
The same hidden persuaders explain how phrenology (head reading), once more popular and far more influential than astrology is today, could be accepted as totally valid even though it is now known to be totally invalid. As noted in 1985 by Dean and Mather (Astrological Journal 28(1), 23-30, Winter 1985):

"Astrologers are like phrenologists: their systems cover the same ground, they apply them to the same kinds of people, they turn the same blind eye to the same lack of experimental evidence, and they are convinced for precisely the same reasons that everything works. But the phrenologists were wrong. So why shouldn't critics conclude for precisely the same reasons that astrologers are wrong?" (page 25)

That was 20 years ago, but no reply from astrologers has been forthcoming other than to dismiss phrenology as irrelevant. But perhaps no reply is required. After all, it could be argued that the existence of mutually incompatible systems throughout astrology (for example tropical and sidereal zodiacs), all of which are nevertheless seen as completely valid by their users, has already put this question to the test and given us convincing answers.

Indeed, hidden persuaders are at their most glaringly obvious when a chart that fits is later found to be wrong, a not uncommon experience. For example one British astrologer in Phillipson's Year Zerp notes how it has "happened to a lot of astrologers. Some of the best readings have been with wrong charts" (p.118). Even worse, Dean (1992) found that readings which were the opposite of what the chart indicated were as acceptable to clients as authentic readings, just as Hyman had found for palmistry, and just as hidden persuaders might predict. But if wrong charts work as well as authentic charts then what price astrology?

Astrology outside the consulting room
Thanks to hidden persuaders, the bottom line could hardly be simpler -- astrology in the consulting room does not need to be true. So in principle any chart might do. But what about astrology outside the consulting room, for example in astrology books and journals where charts are compared with their owners to convince readers that astrology works. Here there are no clients to interact with the astrologer, so most of the above 34 hidden persuaders would seem to no longer apply. But one of them remains rampant, namely the one labelled above as "ask only confirming questions".

This hidden persuader could also be called "consider only confirming cases" or "heads I win and tails is irrelevant". It appears again and again in every astrology book and journal, making nonsense of the associated claims. Astrologers see that a chart fits the person or event, thus making a confirming case, and conclude that astrology works. What could be more straightforward? In fact it does not follow at all. The problem is that astrological symbolism is so flexible that almost any chart will fit almost any person or event (thus making a confirming heads-I-win case), giving the wrong impression that astrology works. To see how it works, look at how one big-name astrologer tested the claim of another using the consider-only-confirming-cases persuader. First the claim:

Elwell's claim
British astrologer Dennis Elwell claims that certain events and planetary conditions tend to occur together because at a higher level they belong together. He calls the effect multicongruence, and claims it can be seen by comparing the chart with newspapers for the same day. If the chart contains X-type indications then the newspapers will report X-type happenings. It is as simple as that.

Heath's test of Elwell's claim
British astrologer Robin Heath tested this claim in his article "Time-slice testing Elwell's multicongruence" in Astrological Journal Nov-Dec 2000 pages 12-15. For his test Heath chose the chart for 7-15 August 2000 because two rather nasty aspects were then exact within five degrees, namely Sun opposition Uranus (disruption, discovery, leadership, high-tech industries, aviation) and Mars opposition Neptune (weakness, scandal, war, machinery, sea, media). He then searched through four British dailies for matching stories over the same period.

He found a dozen major stories that matched -- Concorde crash explained, disruptive solar flares, sex scandal, persecution by vigilantes, NASA to visit Mars, car repairs unsafe, submarine sinks, army overstretched, police kill armed man, sailor rescued, satellites launched, and bomb kills eight in Moscow. Lesser stories also matched -- fatal aircraft crash, army officers shot, police chief killed, fatal glider crash, hints of government betrayal, protesters upset grouse shooting, spies caught, fatal coach crash, massive forest fires, wasps attack family, and photographer sues vodka maker for misusing best photo.

Heath finds the matches to be totally convincing. He concludes that Elwell's multicongruence is a fact, and that it "invites us to explore an awesome property of nature little known and even less understood." He notes that his study is not scientific, but this "reflects more badly on the limited axioms of the scientific method than on my limited grasp of astrological truths."

Now for the problems
Ironically Heath is shooting himself in the foot. Disruption, scandal and death are what sell newspapers. Throughout the world they occur many times every day, so a national daily will seldom be without them. So Heath could hardly fail to find matches, like people in a rainstorm can hardly fail to get wet. This is the consider-only-confirming-cases persuader at work, or heads I win and tails is irrelevant. The real issue is whether 7-15 August 2000 matches Sun-Uranus-Mars-Neptune better than other periods, but Heath does not tell us. (Here "other periods" is the control that Dennis Elwell flatly rejects as unnecessary, see Jaws on this website under Outrage.)

Adding to the confusion
Two more artifacts add to the confusion. First, Heath is testing factors in isolation, which according to astrologers is not acceptable because only the whole chart can be meaningful. For example if Mars were making close harmonious aspects to other planets, as it does in this case, the difficulty of Mars-Neptune might no longer exist. Here you can see how astrologers want it both ways -- breaking the rules is acceptable if it produces positive results, but not if it produces negative results.

Second, astrological symbolism can be made to fit almost anything. For example Heath says car repairs (Mars, metal) were unsafe (Mars-Neptune, weakness). But if we consider the rest of the chart we could just as easily say car repairs (Moon, change) were unsafe (Moon-Pluto, too much change), or car repairs (Venus, care) were unsafe (Venus-Saturn, inhibition), or car repairs (Mercury, instruction manuals) were unsafe (Mercury-Jupiter, vague), or even car repairs (Mars, metal) were not unsafe but safe (Mars-Neptune, idealistic ends), just as we can easily reverse the others by putting Pluto = powerful, Saturn = directed, and Jupiter = comprehensive. Indeed, who says the repair has to involve metal? It could just as easily involve only fabric, glass, ceramic, plastic, or rubber.

Ironically articles drawing attention to this hidden persuader appeared in Correlation in 1997-1999 and would have been seen by Heath, who was then editor of the Astrological Journal and later a consulting editor of Correlation. This illustrates how astrologers are not interested in avoiding artifacts even when prompted, preferring instead to see their faulty reasoning as revealing "an awesome property of nature" or "the limited axioms of the scientific method". More examples of this potent hidden persuader at work will be found elsewhere on this website, see Index.

Hidden persuaders are artifacts arising from our normal reasoning processes that generate the illusion that astrology works when in fact nothing special is happening. Hidden persuaders are raging out of control everywhere in astrology, misleading astrologers and their clients just as they previously misled phrenologists and their clients. They are an active component of experience, which is why appeals to experience are meaningless unless hidden persuaders can be ruled out (which in astrology has never been the case). Astrologers interested in avoiding hidden persuaders in astrology will find much useful information in Gambrill (1990).

Further reading

Dean G (1992). Does astrology need to be true? In K Frazier (ed). The Hundredth Monkey and other paradigms of the paranormal. Prometheus Books, Amherst NY, pages 279-319 with 126 references. Update of a two-part article first published in Skeptical Inquirer 1986-1987. The answer to the title question is no.

Dean G, Kelly IW, Mather A, and 5 others (1999). Astrology and Human Judgement. Correlation 17(2), 24-71. A comprehensive survey with 160 references.

Dean G, Kelly IW, & Mather A (2002). Undeceiving ourselves. In Shermer M (ed), The Skeptic Encyclopedia of Pseudoscience, Volume 1. ABC-CLIO, Santa Barbara CA, pp.272-277 with 9 annotated references.

Gambrill E (1990). Critical Thinking in Clinical Practice: Improving the Accuracy of Judgements and Decisions about Clients. Jossey-Bass, San Francisco. 432 pages, 660 references. How to reduce reasoning errors in psychology, medicine and the helping professions. Well organised, packed with information, many examples, a few references to astrology (but only to illustrate reasoning errors), each chapter has a summary. Equally applicable to astrology. Should be read by every astrologer.

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