A Collaborative Vernon Clark Experiment

Author: McGrew, John H., McFall, Richard M.
Abstract: Six astrologers matched 23 birth charts to comprehensive case files, including photographs, as specified by them. The charts were of native Americans (4 men, 19 women) aged 30-32 years. Birth times were verified by birth records and in most cases were recorded with a precision of five minutes or better. The mean accuracy (i.e.., agreement with the case files), expressed as Cohen’s kappa, was 0.02. The mean agreement between astrologers was 0.03. Accuracy was unrelated to confidence or to birth time precision. In a follow-up study, five groups of 5-6 astrologers each matched a subset of 5 charts, so that collectively all 23 charts were matched. The mean accuracy was -0.15, or worse than chance. Although the astrologers had collaborated to make the experiment as fair as possible, the negative findings had no effect on their belief in the validity of astrology.
Keywords: Astrologer agreement, Belief in astrology, Vernon Clark test, birth time precision
Publication: Correlation: Astrological Association Journal of Research Into Astrology
Issue: Volume 11 Issue 2
Dated: 1992
Pages: Pages 2 – 10

Posted in Free Research Abstract