Conversation on the McGrew-McFall "Validity of Astrology" Test

Feb 12, 2011 at 1:32 PM
 Dear .....,

An astrology skeptic has brought an article to my concern. This article, "A Scientific Inquiry Into the Validity of Astrology," published in JSE in 1990, acknowledges some of the initial criticism of the Carlson study and presents a supposedly better test design. http://www.scientificexploration.org/journal/jse_04_1_mcgrew.pdf 

In this study, six astrologers used a 61-item questionnaire developed specifically for the test by a larger team of astrologers. From this test and the 1996 Rob Nanninga test, both of which failed for the astrologers, it seems that astrologers are not so good at developing questionnaires.

The six astrologers were asked to match 23 charts with 23 volunteer test cases. For each chart, the astrologers were allowed to match a first, second, and so on choice of test case, although not all astrologers exercised this option. They were also asked to give a 0-100% confidence rating to their choices.

This gives the impression that the choices were ranked and rated, though I'm not sure this is the best way to do it. In my mind, accurately matching 23 charts to 23 cases seems like a nearly impossible task, even though the authors consider the mathematical probability.

One claim in particular stands out for me (p. 81):

"One final point should be mentioned. The experimental task probably was considerably easier and, presumably, easier to perform accurately, than the task that astrologers attempt in their counseling practices. That is, without a priori information, because each individual is unique, in practice an astrologer must use the birth information to "select' the one correct interpretation that uniquely matches that individual from nearly countless possibilities, not just from 23 possibilities. Thus, our task can be seen as a simplification of the task that astrologers routinely undertake as a part of their daily professional practice. The conclusion one can draw from this inference is unequivocal. If our task provides a simplification of standard astrological practice, and if the astrologers cannot perform a simplified task accurately, then it is not likely that they will be able to perform a more complicated task accurately."

I am skeptical of the "unequivocal" truth of this statement. Am I incorrect to think that it is a simpler task for an astrologer to interpret one chart to match one person than it is to interpret 23 charts and match them to all the possible choices among 23 cases? While it is true that there are "only" 23 cases, there are also 23 charts!

Regards,

~Ken

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Feb 12, 2011 at 3:52 PM
Dear Ken,

"That is, without a priori information, because each individual is unique, in practice an astrologer must use the birth information to "select' the one correct interpretation that uniquely matches that individual from nearly countless possibilities, not just from 23 possibilities. Thus, our task can be seen as a simplification of the task that astrologers routinely undertake as a part of their daily professional practice. The conclusion one can draw from this inference is..."

I fully agree with you. The astrologers experimental task was not a simplification of their ordinary business. On the contrary, it was much more difficult. 

Even Carlson’s task was simpler for astrologers than that of McGrew-McFall. The reason the two authors provide for their judgment is not at all convincing.

~....