Lying with Statistics



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Ten-Percent Myth

Copyright by Julija Sapic, at Fotolia "We use only ten percent of our brains." It's a myth, but nevertheless it might be true for those who continuously  keep the rumour alive.

From an evolutionary point of view, it is not very probable that such large brains as the human one would have been developed without the need for it. The brain needs a lot of our energy, i.e. a brain cell needs about twice as much energy as other cells in our body. So it is clear, that a 90 percent smaller brain could be more economically nourished. Evolution hasn't provided us with a spare heart, lungs, and so on, why should there be such a unnecessary huge brain?

There is something "mystical" about the number ten itself. Ten seems to imply some kind of completeness. People are crazy about the top ten in music, literature, films etc. Having a top nine would look as if the list is incomplete, as if we couldn't find the data. It's like a human being with just 9 fingers. A top eleven on the other hand would seem to be superfluous, a kind of monstrosity.

The by far best known top ten list in history is the Ten Commandments of the Bible. The ten plagues in Egypt as described in the Book of Exodus are another famous example from ancient times. Copyright by Fotolia

If there is insufficient data and if people think that the percentage might be small, they make the number "complete" by "making" it ten: If people use phrases like "Nobody does it", "Everybody knows that ...", "There is nobody in the whole world ....", "10 percent of all ..." you can bet that his or her saying is in most cases not based on facts. If something can't be "turned" into "nobody" and it is a lot less than "half" than the favourite guess will be 10 %.

Or what about our fascination with decades? Even those who should know better treat decades, as if they are brackets in the time line, as if the course of events is split by decades into units which are uniform and separated, e.g. the psychedelic sixties with free-love, anti-war movements, the nineties, end of the cold war and the beginning of globalization etc.

Other examples of the ten-percent mania:
  • Ten percent of the male population is homosexual:
    The scientific background for this statement is a book published in 1948 by the sex researcher Alfred Kinsey (Kinsey, Pomeroy and Martin): "Sexual Behaviour in the Human Male". They examined the sexual preferences and experiences of 5,300 American men. His results shocked the Americans: 37 percent of the participants admitted at least one homosexual experience since their adolescence1 and one out of every 10 males considered himself a homosexual, i.e. claimed to have been gay for at least three years.
    Kinsey never started this "rumour", he spoke about 10 percent of those he surveyed and not 10 percent of the male population of the United States. In their book "Kinsey, Sex and Fraud"2, Reisman and Eichel point out that Kinsey's data base was not representative of the American male population, i.e. his participants included about 25% prison inmates and known sex offenders. (But we have to be careful, this shows that the survey was not representative and NOT, that gays are more likely than other people to be criminals.) Newer surveys in the United States, West Germany, and Canada estimate the percentage of gays between 0.3 percent to 6.2. Numbers which are for some conservatives more comforting.
    By the way, 10 percent of the Americans were more inclined in the last election to vote for a candidate who supported gay marriage, on the other hand 49 percent of voters who were less likely to vote for such a candidate.
  • According to The National Institute on Alcohol Abuse and Alcoholism (NIAAA) Chronic alcohol consumption increases a woman's risk of developing breast cancer by about 10 percent3
  • Ten percent of the women have never experienced an orgasm. The New York Times made it a bit more "precise": "Five to 10 percent never had orgasms.4 Yet many of the women became pregnant." Seems precise, but what about Kinseys "exact" figures: "39 to 47 percent of women reported that they always, or almost always, had orgasm during intercourse."5
  • Roughly 10 percent of Mexico's population of about 107 million is now living in the United States, estimates show.
  • "a 10 percent increase in the price of alcohol reduces consumption of beer "
  • "Only about 10 percent of all drinkers account for 50 percent of the total alcohol consumption in the United States per year"6

When did the inclination for "ten percent" begin?
The special attraction to the number ten is definitely due to the fact that our number system, the decimal system, is based on ten digits and on the fact that we have 10 fingers. The cruel action of decimating in ancient Rome is another example of the strange attraction to the number ten. Decimate originally referred to the killing of every tenth person, a punishment used in the Roman army for mutinous legions.

What is the myth keeping alive?

People like bare and simple facts and no complicated explanation. The "fake" ten percent suggests the kind of security and precision people are longing for. Fraction and decimal numbers look for many people like inaccuracy.

1 Kinsey, Pomeroy and Martin, Sexual Behavior in the Human Male (Philadelphia: Saunders Press, 1948), p. 625.
2 Judith A. Reisman, Edward W. Eichel, J. Gordon Muir, J. H. Court Kinsey, Sex and Fraud: The Indoctrination of a People (Lafayette: Huntington, 1990) (Lochinvar-Huntington House pub., 1990)
3Friedenreich, C.M.; Howe, G.R.; Miller, A.B.; and Jain, M.G. A cohort study of alcohol consumption and risk of breast cancer. American Journal of Edidemiology 137(5):512-520, 1993.
4New York Times, May 17, 2005, A Critic Takes On the Logic of Female Orgasm, Dinitia Smith 5Kinsey, Alfred C. et al. (1953/1998). Sexual Behavior in the Human Female.
6Abhinandana Anantharaju, M.D., and David H. Van Thiel, M.D., "Liver Transplantation for Alcoholic Liver Disease", National Institute on Alcohol Abuse and Alcoholism, September 2004
7 Kinsey, Pomeroy and Martin, p. 638.
8Beyerstein, B. L. (1995) Distinguishing science from pseudoscience. Victoria, B.C., The Centre for Curriculum and Professional Development
9Beyerstein, B.L. (1999) Whence cometh the myth that we only use ten percent of our brains? In, S. Della Sala (Ed.), Mind Myths: Exploring Everyday Mysteries of the Mind and Brain (pp. 1-24). Chichester, UK: John Wiley and Sons., Ltd.
10Paulos, John Allen, A Mathematician Reads the Newspaper, 1995, New York Kinsey, Pomeroy and Martin, p. 638.

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