Okay, let me try to explain why this interesting proposal wouldn't help much with the problem that you mention.

1) First of all, it is very possible for high-IQ persons to have irrational ideas. It happens all the time. Most high-IQ people don't notice when they are being irrational.

http://www.project-syndicate.org/commentary/stanovich1

The author of the article I have just linked has gathered numerous examples in a very readable and impeccably referenced book

http://www.amazon.com/What-Intelligence-Tests-Miss-Psycholog...

that I have had occasion to recommend here on HN before. Read the book at your earliest opportunity if you would like to understand all the barriers to human understanding and rationality besides IQ. You'll learn a lot from the book, particularly numerous cases of high-IQ persons (including members of high-IQ societies) believing things that are false and irrational.

See also

http://www.amazon.com/What-Intelligence-Beyond-Flynn-Effect/...

for additional forms of evidence showing that wisdom and correct beliefs are distinct from IQ scores.

2) Second, no one knows his IQ exactly, so no one can pull rank this way. All IQ tests have error of estimation, and no one brand of IQ test will yield the same score for the same individual on every occasion, nor will two different brands of IQ tests necessarily sort the same group of test-takers into the same rank order. Terman (the developer of the first widely used IQ test in the United States, the Stanford-Binet) noted that error of estimation in IQ scores increases as IQ scores are above the mean:

"The reader should not lose sight of the fact that a test with even a high reliability yields scores which have an appreciable probable error. The probable error in terms of mental age is of course larger with older than with young children because of the increasing spread of mental age as we go from younger to older groups. For this reason it has been customary to express the P.E. [probable error] of a Binet score in terms of I.Q., since the spread of Binet I.Q.'s is fairly constant from age to age. However, when our correlation arrays [between Form L and Form M] were plotted for separate age groups they were all discovered to be distinctly fan-shaped. Figure 3 is typical of the arrays at every age level.

"From Figure 3 [not shown here on HN, alas] it becomes clear that the probable error of an I.Q. score is not a constant amount, but a variable which increases as I.Q. increases. It has frequently been noted in the literature that gifted subjects show greater I.Q. fluctuation than do clinical cases with low I.Q.'s . . . . we now see that this trend is inherent in the I.Q. technique itself, and might have been predicted on logical grounds." (Terman & Merrill, 1937, p. 44)

3) Third, a slightly different point from point 2), anyone's IQ can change over the course of life. (Pinneau 1961; Truch 1993, page 78; Howe 1998; Deary 2000, table 1.3). "Correlation studies of test scores provide actuarial data, applicable to group predictions. . . . Studies of individuals, on the other hand, may reveal large upward or downward shifts in test scores." (Anastasi & Urbina 1997 p. 326).

4) The best way to put this method to the test, I suppose, is to ask you which of my opinions you would accept if I could show that I have a higher IQ than you have. How much of a difference would force you to credit my opinions with being true? If the difference in IQ score were slight, would you propose that we each be retested?

5) Anyway, the suggestion, although interesting, is illogical, because what someone's IQ score is has no sure relationship with the truth of a person's beliefs, the adequacy of the person's education on particular matters of fact, or the person's willingness to reconsider opinions based on new evidence.

REFERENCES

Anastasi, Anne & Urbina, Susana (1997). Psychological Testing. Upper Saddle River, NJ: Prentice Hall.

Deary, Ian J. (2000) Looking Down on Human Intelligence: From Psychometrics to the Brain. Oxford: Oxford University Press.

Howe, Michael J. A. (1998). Can IQ Change?. The Psychologist, February 1998 pages 69-72.

Pinneau, Samuel R. (1961). Changes in Intelligence Quotient Infancy to Maturity: New Insights from the Berkeley Growth Study with Implications for the Stanford-Binet Scales and Applications to Professional Practice. Boston: Houghton Mifflin.

Terman, Lewis & Merrill, Maude (1937). Measuring Intelligence: A Guide to the Administration of the New Revised Stanford-Binet Tests of Intelligence. Boston: Houghton Mifflin.

Truch, Steve (1993). The WISC-III(R) Companion: A Guide to Interpretation and Educational Intervention. Austin, TX: Pro-Ed.