Scientific Skepticism: Testing Claims

Back to Skepticism

Using the tools of logic and science to test extraordinary claims

Table of Contents

  1. Some Extraordinary Claims
  2. Dowsing (Water Witching)
  3. Seeing Auras
  4. Extra Sensory Perception
  5. Astrology
    1. How it Works
    2. A Natal Chart
    3. A Test of Astrology
    4. Astral Twin Argument Against Astrology
Some Extraordinary Claims
  • Dowsing (Water Witching)
    • Dowsers can find underground water using a dowsing rod.
  • Auras
    • Human auras are energy fields emanating from a person’s body, visible only to those with special powers. 
  • ESP: Extra Sensory Perception
    • Telepathy: Some people can communicate mind-to-mind or “read” other people’s minds.
    • Clairvoyance: Some people can “see” things without visually perceiving them in the normal way.
    • Precognition: Some people have psychic knowledge of an event before it happens.
  • Astrology: A causal link exists between (a) the positions of the heavenly bodies when a person is born and (b) their personality and events in their life.
Dowsing (Water Witching)
  • In 1979 James Randi tested four dowsers as part of his One Million Dollar Paranormal Challenge.
  • He outlined a plot of ground 10×10 meters
  • Plastic pipes, an inch in diameter, ran 1.5 feet underground through the area, carrying flowing water.
  • Having agreed to the conditions of the test, the dowsers placed pegs in the ground above where they thought water was flowing.
  • No dowser past the test.
Seeing Auras
  • Randi’s Aura Test
    • Presented with twenty people on stage, a psychic said she saw auras emanating a foot or two above everyone’s head. After the subjects left the stage, a curtain was lifted, revealing twenty full-height screens. Behind some of the screens were subjects. The psychic’s task was to identify those screens. She said she saw auras above every screen. The screens were removed. Only six subjects were onstage. 
Extra Sensory Perception
  • ESP
    • Telepathy: Ability to communicate mind-to-mind or “read” others’ minds.
    • Clairvoyance: Psychic ability to “see” things without visually perceiving them in the normal way.
    • Precognition: Psychic knowledge of an event before it happens
  • Zener Cards
    • A deck of 25 cards, consisting of five of each of the following
    • Randomly guessing averages 20% correct.  Doing significantly higher consistently would be evidence of ESP.
How it Works
A Natal Chart
  • Astronomical Facts
    • Sun in Aquarius
    • Sun in 4th House
    • Moon in Taurus
    • Libra is Rising 
    • Aries is Descendant
    • Most planets are above the horizon
    • Mercury and Venus are in Capricorn
    • Mars, Uranus, and Saturn are in Gemini
A Test of Astrology
  • A Double-blind Test of Astrology, Shawn Carlson, Nature 1985
    • The tests used 28 well-regarded astrologers and hundreds of subjects.
    • First Test: Subject selection of natal chart interpretations
      • Astrologers were given the date, time and place of a subject’s birth, which they used to construct a natal chart and describe the subject’s personality traits.  The subject was given that interpretation plus natal chart interpretations of two other, randomly-selected subjects in the test The subject had to determine which of the three natal chart interpretations was his.
      • The subjects did no better than chance
    • Second Test: Natal Chart/CPI Matching
      • Subjects took the California Personality Inventory (CPI), a standard assessment of personality traits.  Each astrology was given the CPI result and natal chart of a subject along with the CPI results of two other, randomly-selected subjects.  The astrologer had to match the natal chart with the correct CPI result.
      • The astrologers did no better than chance.
Astral Twin Argument Against Astrology
  • The Argument:
    • Astral twins, people born near each other around the same time, have the same natal chart.
    • Were astrology true, people with the same chart would have the same personality traits.
    • Thus, were astrology true, astral twins would have the same personality traits.
    • But many astral twins have different personality traits.
    • Therefore, astrology is false
  • In 2010 Geoffrey Dean and Ivan Kelly conducted a study of thousands of  “time twins,” people born within five minutes of each other.  They found the twins’ personalities no more alike than those of non-twins.
  • Historical Note: In Book 7 of the Confessions, written 400 CE, Saint Augustine rejects astrology because a noble and a slave born at the same time will be very different.