University of Cambridge Cognitive Ability Test

I still do not understand why we are wasting scientific resources trying to stack rank humans on arbitrarily defined concepts like cognitive ability or intelligence.

After over a century of psychometric research in cognitive abilities and intelligence, what do we have to show for it? Whose life has actually improved for the better? Have the benefits from such research, if any, outweighed the amount of harm that has already been caused?

Psychometrics has clear value. Cognitive ability predicts academic/job performance (Schmidt & Hunter 1998, Psych Bull), and standardized tests reliably forecast college outcomes (Kuncel, Hezlett & Ones 2004, Science). Conscientiousness adds further predictive power (Poropat 2009, Psych Bull). The science is robust. The issue is the discomfort it causes, not lack of benefit or predictive power.

Intelligence testing is not widely used in employment hiring, despite many attempts. Why is that?