The conclusions are pretty sound IMHO because they match so well other studies of this kind. E.g. when doing IQ tests on people who are poor part of the year an

The conclusions are pretty sound IMHO because they match so well other studies of this kind. E.g. when doing IQ tests on people who are poor part of the year and much better off the other half of the year, once can see a 14 point difference in score. That is quite profound. Basically the stress of poverty pulls people down in every possible way. It is not just in terms of producing plates, but also in your ability to perform mental tasks. There are also other studies that show that people who are paid below what they feel they are worth, will perform less well. Basically human productivity seems to work in thresholds. If you are above the threshold, then increases in salary does not improve your performance. Being paid a million or 2 million makes little difference. But if you are getting way below what you seem descent and normal for the type of work you are doing or you feel unfairly compensated relative to other workers, then performance has been shown to typically lag. Basically there is a price to pay when engaging in unfairness. It affects people. We can even find the same results within animals. An animal can be fine eating one kind of food, but when that animal learns that that a peer is getting significantly better food, it will often get very upset, angry and stressed.