WEIRD Samples
WEIRD stands for Western, Educated, Industrialized, Rich and Democratic, and the acronym names the gap between the population psychology actually studies, mostly undergraduates at universities in a handful of wealthy countries, and the species its findings get written up as being about. The descriptive claim, that the samples are overwhelmingly WEIRD and that this limits generalisation, is about as well established as anything in this library, because it is a fact about publication records. The stronger historical explanation attached to it is a live argument. The acronym is Joseph Henrich, Steven Heine and Ara Norenzayan's, from 2010.
What it is
The critique is not that the research is bad. It is that "people do X" is a claim about humans while the sample supporting it is a claim about a sliver of them. The uncomfortable version of the argument goes further: that this sliver is not merely unrepresentative but genuinely unusual, so the discipline has been building its account of human nature on its strangest available case.
Adrian Furnham devotes a chapter of The New Psychology to it and credits Henrich's 2020 book with the strong thesis, that WEIRD people are psychologically distinctive, being more individualistic, analytical, impartially rule-following and cooperative toward strangers than most human populations, and that the pattern has a historical cause in Western Christianity's marriage and family programme breaking up extended kin groups.
Two things he does around that thesis are worth keeping. He flags the historical account as open to challenge rather than presenting it as settled, which is the right calibration. And he raises an objection of his own, that WEIRD lumps together Western cultures which differ from each other substantially, so the acronym flattens on one axis while sharpening on another. He also supplies the historical note that about forty years ago the label WASP performed the same critical function in the same argument.