@ariadne tiny nit to pick: psychometric tests are perfectly good at measuring specific things about a person's brain function in a repeatable way. Having that kind of assessment if you have difficulties with work or school can change your life for the better.

The completely careless ways educators, policy makers, the general public, and business people use the single numeric summaries of those tests is completely deranged and I agree with you completely there.

IQ as a single number is bonkers.