Brain Size in Cubic Centimeters versus Standardized Test Scores

References:

The credible worldwide TIMSS and TIMSS-R studies demonstrated a wide range of academic skills amongst nations, with 8th grade students in Korea scoring 85 points higher than American 8th graders, 121 points higher than Israeli 8th graders, and 312 points higher than South African 8th graders.  Such a wide variation in scores, coupled with the consistent 15-60 point gap between boys and girls at the 12th grade level, suggests that there is a physiological explanation.  One of the candidates is brain size, though there is so much disinformation regarding the differences in brain sizes between races and  sexes that there  doesn't seem to be a final authority for such figures.  The most credible source for average brain sizes by race and sex is provided by J. Phillipe Rushton of the University of Western Ontario in Canada, who  shows that the average brain size for Asian men is 1,472 cubic centimeters (cc's), which is 21% greater than that for African women at 1,217 cubic cc's.

Should we expect that a 21% variation in brain size could account, at least partially, for a 121% variation in TIMSS scores?   Once brain size is correlated, by race and sex, with the Graduate Record Exam, International Assessment of Education Progress, TIMSS (Third International Math and Science Study), and TIMSS-R scores, we find the following values for r-squared:

Numbers in Red are estimates.

A partial explanation for the lower correlation for TIMSS-R Math and IAEP Math is that the countries used as examples are not 100% of any race.  Taiwan, France, and Mozambique were used for the IAEP correlation;  and Singapore, the Netherlands, and South Africa were used for the TIMSS-R Math correlation.   While these countries are as close to one race as any other countries, the 3 percent of blacks in the Netherlands, France, and Switzerland, the 15 percent of Whites in Mozambique and South Africa, and a few percent of non-Taiwanese in Taiwan would be expected to skew the results even further than the graphs indicate.   It can be seen from the graphs that correlation of TIMSS and IAEP would be closer to the correlation for GRE if such data were available by race rather than country.

*There are no 12th grade TIMSS scores available for any Asian nation because no Asian nation participated in that portion of the study.  So the 12th grade TIMSS score correlations are based on *estimates* of where Japan would be expected to have scored from reviewing the projected data.  Using these estimates for Japan and the actual scores for Switzerland and South Africa produced a correlation which is between that for GRE Quantitative and GRE Verbal.  It should be noted that their actual score might have been, and most likely would have been, higher than this estimate

Compared to African women, Asian men:

Within each race, the standard deviations for both sexes will be larger than for a single sex.  Where the standard deviation for Europeans is 35, or 2.6%, it is *possible* that the sd for one sex would be 18, or 1.3%.   The larger standard deviations for Asians and Africans may be due to a bigger difference between men and women than for Europeans.

Copyright @ 2007 by Fathers' Manifesto & Christian Party