Book Cover

John Allen Paulos


Innumeracy-Chapter 2:Probability and Coincidence

It is no great wonder if ,in the long process of time,while fortune takes her course hither and thither,numerous coincidences should spontaneously occur.


"You're a Capricorn ,too.That's so exciting."

4. Li'l Ol' Me and the Stars

Astrology is a particularly widespread pseudoscience.The shelves of bookstores are stuffed with books on the subject,and almost every newspaper publishes a daily horoscope.A 1986 Gallup poll reports that 52 percent of American teenagers believe in it,and a distressing number of people in all walks of life seem to accept at least some of it's ancient claims.I say "distressing" because if people believe astrologers and astrology,it's frightening to consider whom or what else they'll believe.It's especially so when,like President Reagan,they have immense power to act on these beliefs.

Astrology maintains that the gravitational attraction of the planets at the time of one's birth somehow has an effect on one's personality.This seems very difficult to swallow,for two reasons: (a) no physical or neurophysiological mechanism through which this gravitational (or other sort of ) attraction is supposed to act is ever even hinted at,much less explained;and (b) the gravitational pull of the delivering obstetrician far outweighs that of the planet or planets involved. Remember that the gravitational force an object exerts on a body - say, a newborn baby - is proportional to the object's mass but inversely proportional to to the square of the distance of the object from the body - in this case the baby.Does this mean that fat obstetricians deliver babies that have one set of personality characteristics,and skinny ones deliver babies that have quite different characteristics?

These deficiencies of astrological theory are less visible to the innumerate,who are not likely to concern themselves with mechanisms,and who are seldom interested in comparing magnitudes.Even without a comprehensible theoretical foundation,however,astrology would deserve respect if it worked,if there were some empirical support for the accuracy of its claims.But, alas,there is no correlation between the date of one's birth and scores on any standard personality test.

Experiments have been performed (recently,by Shawn Carlson at the University of California) in which astrologers have been given three anonymous personality profiles,one of which was the client's.The client supplied all the relevant astrological data about his life (via questionnaire,not face-to-face) and the astrologer was required to pick the personality profile of the client.There were 116 clients altogether,and they were presented to the top (as judged by their peers) European and American astrologers.The result:the astrologers picked the correct personality profile for the clients about one out of three times,or no better than chance.

John McGervey,a physicist at Case Western Reserve University,looked up the birth dates of more than 16,000 scientists listed in American Men of Science and 6,000 politicians listed in Who's Who in American Politics and found the distribution of their signs was random,the signs uniformly distributed throughout the year.Bernard Silverman at Michigan Sate University obtained the records of 3,000 married couples in Michigan and found no correlation between their signs and astrologers' predictions about compatible pairs of signs.

Why ,then,do so many people believe in astrology? One obvious reason is that people read into the generally vague astrological pronouncements almost anything they want to,and thus invest them with a truth which is not inherent in the pronouncements themselves.They are also more likely to remember true "predictions," overvalue coincidences,and ignore everything else.Other reasons are its age ( of course,ritual murder and sacrifice are as old),its simplicity in principle and comforting complexity in practice,and its flattering insistence on the connection between the starry vastness of the heavens and whether or not we'll fall in love this month.

One last reason,I would guess,is that during individual sessions astrologers pick up clues about the clients' personalities from their facial expressions, mannerisms, body language,etc.Consider the famous case of Clever Hans,the horse who seemed to be able to count.His trainer would roll a die and ask him what number appeared on the die's face.Hans would slowly paw the ground the appropriate number of times and then stop,much to the amazement of onlookers.What was not so noticeable,however,was that the trainer stood stone-still until the horse pawed the correct number of times,and then,consciously or not,stirred slightly,which caused Hans to stop.The horse was not the source of the answer but merely a reflection of the trainer's knowledge of the answer.People often unwittingly play the role of the trainer to astrologers who,like Hans,reflect their clients' needs.

The best antidote to astrology in particular and to pseudoscience in general is,as Carl Sagan has written,real science, whose wonders are as amazing but have the added virtue of probably being real.After all ,it's not the outlandishness of its conclusions that makes something a pseudoscience:lucky guesses,serendipity,bizarre hypotheses,and even an initial gullibility all play a role in science as well.Where pseudosciences fail is in not subjecting their conclusions to a test,in not linking them in a coherent way to other statements which have withstood scrutiny.It's hard for me to imagine Shirley Maclaine,for example,rejecting the reality of some seemingly paranormal event such as trance channelling merely because there isn't enough evidence for it,or because there is a better alternative explanation.


File Info: Created ~ 9/12/2001 Updated 3/1/2017 Page Address: