Sunday, August 13, 2006

"Barroids" for the brain?   posted by Darth Quixote @ 8/13/2006 12:29:00 AM
StumbleUpon Toolbar Digg Reddit Ma.gnolia Newsvine

I have just reread the epic book chapter "Physical Correlates of Human Intelligence" by Arthur Jensen and S.N. Sinha. This is still a gold mine of theoretical insight and empirical findings, documenting among other matters (1) cross-assortative mating as the likely cause of the correlation between IQ and height, (2) the correlation between IQ and head size with body size partialed out, (3) the differences in brain weight upon autopsy between blacks and whites, and (4) much, much more.

Included in the "much, much more" is a passage concerning serum uric acid that somehow failed to capture my attention the first time that I read this chapter and that I now think is worth summarizing here. As you will see, I think that beneficial applications can come out of exactly these kinds of findings from biologically oriented behavioral sciences. I hit up Google Scholar and Pubmed for "serum uric acid" and got nothing recent pertaining to its behavioral correlates, so I assume that the review by Jensen and Sinhan (1994) is still adequate. (Perhaps sharper-eyed readers can help us out here.)

A belief in an association betweeng gout and eminence supposedly goes to back to antiquity. The British psychologist Havelock Ellis (1904) was the first to provide formal evidence of this association when he found a much higher incidence of gout in a sample of intellectually eminent Britishers than in the population at large.

Gout results form inflammation as a result of uric acid crystals forming in a joint. Uric acid is excreted in urine and carred in low concentrations in the blood as serum uric acid (SRA). At higher concentrations SUA forms the crystals deposited in the joints that lead to gout. In all mammals except Homo sapiens and the other great apes, uric acid is not the end product of its pathway; in the other mammals the enyzme uricase oxidizes uric acid to allantoin, which is excreted as the end product of this metabolic chain. Presumably, the great apes fixed a loss of function that prevents uricase from doing its work and leaves uric acid as the end product of purine metabolism. The molecular structure of uric acid is highly similar to that of caffeine, which as we all know is a central nervous system stimulant. Parent-offspring regressions indicate a narrow-sense heritability of SUA level between 0.30 and 0.40.

The hypothesis that SUA is an endogenous stimulant somehow related to the mental capacities of great apes stimulated hundreds of studies. What follows is a summary of this research.

  • SUA levels and retarded/nonretarded show a significant point-biserial correlation. Also, groups with above-average IQ (Ph.D. students, med students, business executives) show higher levels of SUA. The overall correlation between SUA and IQ is rather small, however, averaging about 0.085 over several studies with a combined N in the thousands.
  • It appears that the SUA exerts its chief causal influences on achievement per se rather than sheer ability, as if SUA acted as a drive-inducing cortical stimulant. In a study of 149 male high school students, SUA level was most notably correlated with the residual of the regression of GPA on IQ. SUA level was also correlated with number of extracurricular activities. In another study SUA showed a significant point-biserial correlation with "school dropout/persistance in school" as well as correlations with "need for achievement."
  • When 144 university professors were rated on overall level of achievement, the ratings were correlated 0.50 with SUA level. Among nontenured faculty, number of publications was correlated 0.37 with SUA level.
  • Several studies have found that SUA level is correlated with upward social mobility, although apparently one large study is contra.
  • One large study (N = 1500) found higher SUA levels in professionals and executives than in farmers and unskilled workers.
Given the great promise of these findings, I'm somewhat puzzled that there has not been more recent follow-up of this area. Why not manipulate SUA levels experimentally to determine which way the causal arrow point in these correlations? Which, of course, leads naturally to this: if SUA does indeed have some causal effect on achievement drive and motivation, why not develop a form that humans can self-administer?

Feeling low on inspiration for papers and the tenure clock is running? Inject some SUA into your ass and boom! 73 papers belted out in one year. Feel like the dumbest person at the conference and you have to give your talk after the next break? Instead of going over your Powerpoint slides again, just slip into the bathroom, get out the syringe ... and come out ready to blow everyone away!