1. The Validity of
Astrology

3. Most scientists belong here
Do not believe in astrology

4. Overview: What is astrology? “Fairest test” Problems
Countering potential criticisms
New criticisms and changes
New study (then)
Results of the new study
Final point
Conclusion

5. What is Astrology?
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.”

6. “Fairest test” of Astrology:
To test the reliability of predictions made by qualified astrologers based on global interpretations of complete horoscopes

7. Problems:
Predict single dimensions of personal information
(not the full pattern of the person’s life experience/ personal characteristics)
small sample size
No blinding
Not planned closely with astrologers
(vulnerable to criticism that test is not a fair representation)

8. Countering Potential Criticisms:
Previously, not planned closely with astrologers
Astrologers and scientists design a test of the hypothesis together

9. Study consisted of 2 parts: Part 1 Part 2
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
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

11. New Criticisms and Changes:
CPI may not include information astrologers need to match to horoscope successfully
Astrologers list personal information they need to match accurately
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
Astrologers asked for information on significant events in test subject’s lives
Changes made to present study:
Changes made to present study:

12. New Study (then): X 23 6 Astrologers Practiced astrology before
Control: Graduate in clinical psychology
Native born Americans; aged 30 / 31
Blinded
Record choices on an answer form

13. Astrologers then match the personal information to corresponding birth information of the 23 people

14. Results: 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

15. Results:
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

16. So far, results are…

17. 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”
HOWEVER…

18. Failure to demonstrate interjudge reliability / convergence
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

19. What Does This Mean?
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

20. Final Point:
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?

21. Conclusion:
Astrology?

23. Reference: 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