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".