Aug 222006

Possibly the most annoying truth in the world is that good qualities cluster. People who are good at something tend to be good at many things.

The psychometric version of clustering is g, or general intelligence. The existence of g is not seriously disputed in the field, and g-deniers like Howard Gardner, with his theory of “multiple intelligences,” or the late paleontologist-cum-Marxist Stephen Jay Gould, are regarded as cranks or axe-grinders. The Wechsler scale, the most complex (and expensive) of all intelligence tests, measures thirteen apparently widely disparate skills, including vocabulary, picture completion, matrix reasoning, and the ability to repeat back a string of digits. Bad news! Each skill, without exception, correlates positively with all the others. Seventy-eight possible correlations, and every one positive. The correlations range from 0.3 (weakish) to 0.8 (very strong), where 0 indicates no relationship and 1 an exact match. If you suck at math, the parsimonious explanation isn’t that your true talents lie in writing or painting. The parsimonious explanation is that you suck.1

Intelligence isn’t everything, you say. Quite so. Nevertheless intelligence correlates quite highly with other happy outcomes, like money and status (0.5 or so), long, healthy lives, and staying out of jail. Not to mention height. About the only negative quality definitely associated with high IQ is myopia.

The news gets worse, much worse. Smart people tend to be good-looking. Since intelligence also correlates significantly with income and status, this should surprise no one. Rich, high-status men marry better-looking women and sire better-looking offspring. QED. Models aren’t stupid after all.2

Jocks aren’t stupid either. Reaction time, essential in many sports, correlates moderately with IQ. The data is spotty for most sports, but pro football players have a significantly higher average IQ than the population at large.3 Again, no surprise; learning an NFL playbook is probably pretty demanding.

Clustering offends the human sense of fairness. The world is frequently imagined as if God gives out qualities one at a time — brains for you, beauty for her, and for him, let’s see, how about a sense of humor? — seeing to it that things somehow even out in the end. Jocks and models must be dumb; they already expended their early-round draft picks on something else. Geniuses are crazy; it’s their handicap. Ugly girls have nice personalities. And most of all, you can be anything you want to be, in Lake Wobegon, where all the children are above average.

1By “you” I mean an abstract individual, a statistical creation, not you, dear reader. No statistics could possibly apply to you. You are special, and Jesus loves you.

2Again, these remarks should not be construed as a reflection on any particular model, like, say, Claudia Schiffer (Schiffer-Brains, as she is known in the industry).

3Assuming the same racial composition.

Update: Matt McIntosh comments. Elsewhere, I mean. The Mechanical Eye comments. I will reply if I can find the time in my busy schedule of feeding Christians to lions, building palaces, and oppressing the peasantry. Ilkka Kokkarinen comments. Degrees of Freedom comments. Noneuklid comments.