American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

Imagine that, 150 years ago or whenever, some clever soul had decided to make a written test to measure niceness, and called the test score Niceness Quotient. And the first version sucked, but some other folks iterated on it and over time the test was improved until it correlated pretty well to the sorts of things you would think that niceness would correlate to. 150 years of progress later, we'd have a whole field of Niceometry and researchers trying to isolate sub-areas like charity, friendliness, etc, and trying to suss out an underlying factor of general amiability, and the whole thing would be so well embedded in to the culture that almost no one remembers that "nice" is just a regular word with no objective or scientific definition, and that we measure it with a written test not because that's a good way to measure niceness but because we can't find a better way.

This is a terrible analogy, IQ tests measure something real and objective called the g factor : https://en.wikipedia.org/wiki/G_factor_(psychometrics)

Also, intelligence tests are but a tiny part of psychology, I would hardly call it a "whole field".

> IQ tests measure something real and objective called the g factor

Sure, and NQ tests do too, because look how well graciousness correlates with cheerfulness! That can't be an accident, can it?

Less snarkily, a better analogy would be athletic ability. Suppose you take a bunch of people and measure how fast they can run, how well they can shoot free throws, and how far they can throw a football. Will the results be correlated? Of course, some people are more athletic than others. Does that mean there's a quantity called 'athleticism' that we can objectively measure with a number? No; and not because all people are equally athletic, but because you're trying to take a squishy subjective English language word and pretend it's a scalar value.

> I would hardly call it a "whole field".

The problem isn't the size of the field, it's that academics work within their field, they don't refute it. There's a very uncomfortable result about IQ tests that a generation of psychologists have tried to explain away, and I maintain that the reason they haven't succeeded is because they are institutionally incapable of saying, "Hey, maybe this is pseudoscience."

The g factor is predictive of performance in jobs and income though. Even in your own example, yes we could make a test that involves running and throwing, and yes it would be predictive of performance in various sports. One of the tests for aerobic capacity is called VO2max. It is a number with units mL/g/min. Like IQ, this is not the only factor but it does have predictive power.