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The Validity of
Astrology
Attend to
astrological
predictions some
times
Believe in
astrology
Do not believe in astrology
Most scientists
belong here
Do not believe in astrology
• What is astrology?
• “Fairest test”
- Problems
• Countering potential criticisms
• New criticisms and changes
• New study (then)
• Results of the new study
• Final point
• Conclusion
It’s claim: “The psychological attributes and personal destinies
of individual human beings are related to the positions of
heavenly bodies at the moment of each person’s birth.”
To test the reliability of predictions made by qualified
astrologers based on global interpretations of
complete horoscopes
small sample
size
Predict single
dimensions of
personal information
(not the full pattern of the person’s life
experience/ personal characteristics)
No blinding
Not planned closely
with astrologers
(vulnerable to criticism that test is not a
fair representation)
• Previously, not planned closely with astrologers
• Astrologers and scientists design a test of the hypothesis
together
• Study consisted of 2 parts:
Part 1
Non- astrologer subjects have equal difficulty in
choosing a horoscopic interpretation (out of 3) that
best describe themselves and in choosing from 3
profiles from the California Personality Inventory
(CPI) that best describe themselves
-
No clear conclusion on reliability of personality
descriptions obtained from astrology
Part 2
Astrologer subjects were not able to choose 1 out of
3 CPI profiles o match test subjects whom they have
the horoscope
-
Strong case against natal astrology
1. CPI may not include information astrologers need
to match to horoscope successfully
Changes made to
present study:
Astrologers list personal information they need to
match accurately
2. Previous studies of astrology limited to see if
astrologers can predict personality traits
• Astrology often used to predict whether an event
occur or when it’ll occur
Changes made to
present study:
Astrologers asked for information on significant events
in test subject’s lives
Practiced astrology before
Control:
Graduate in
clinical
psychology
1. Native born Americans;
aged 30 / 31
2. Blinded
3. Record choices on an
answer form
6 Astrologers
Astrologers then match the personal information to
corresponding birth information of the 23 people
• Correct first choice attempts ranged from 0 to 3 astrologers
• Control managed to get 3 correct matches
• Generally, astrologers were certain in their predictions
- Mean confidence rating = 73.5%
• Between astrologers, Pearson correlation between number of correct
predictions and mean self-rated certainty was not significant
- r = 0.03
• For those who had at least 1 correct match, confidence ratings
for both correct and incorrect predictions were not significantly
different
• When second choices are considered, astrologers still did not
do better than chance
- But control achieved more matches than any astrologer
If astrology have a coherent system of analysis and prediction, its
practitioners should be able to apply the method in a dependable and
convergent manner
- If predictions are wrong, they should at least “show a pattern of internal
consistency or interastrologeragreement”
• Pairwise comparisons between astrologer’s forecast for the 23 people
obtained a mean of only 1.4 agreements
• Across 15 pairwise comparisons among 6 astrologers, no. of
agreements range from 0 to 3
Failure to demonstrate interjudge reliability / convergence
• Each astrologer use his own system to predict
• On average, each horoscope can be confidently prescribed to at least 6
different people
• BUT horoscope is VERYY complex, provide very differing “predictions”
about a person
- Hence, astrologers need to emphasise some aspects of the chart and
downplay others
• What could be the reason for the results obtained: Numerous possible
combinations that result from placing different weightings to different
aspects of the chart
Experimental task was much simpler compared to counselling
practice of astrologers
- In practice, each astrologer must use birth information to
“select” the right interpretation that matches the individual
from so many possibilities, not only 23 like in the experiment
If they cannot perform a simple task accurately, how
can they accurately perform a more complex one?
Mcgrew, J.H. and Mcfall, R.M. (1990).
A scientific inquiry into the validity of astrology. Journal
of
Scientific Exploration, vol 4, No 1, pp. 75-83.