The cultural fascination with the idea of an “intelligence quotient” or IQ seems to be experiencing a resurgence. Relentless testing is a feature of schooling and school admissions, and tests are used for a variety of occupational screenings. The practice reflects an intuition we all have: some bulbs are brighter than others. Surely there is nothing wrong with knowing, measuring, and acting on that information, however difficult it might be to assess.
Where matters become elusive is in codifying those skills, reducing them all to a single quantitative number, aggregating them based on other demographic traits, assessing the variability of the results, comparing the results across large population groups, determining the variety of causal factors – genetic, environmental, sheer personal determination – that make up what we call intelligence, and cobbling together a plan for what to do with the results.