According to Noam Chomsky, analysis of the psychological implications of wage slavery goes back to the Enlightenment era. In his 1791 book "On the Limits of State Action", classical liberal thinker Wilhelm von Humboldt explained how "whatever does not spring from a man's free choice, or is only the result of instruction and guidance, does not enter into his very nature; he does not perform it with truly human energies, but merely with mechanical exactness" and so when the labourer works under external control, "we may admire what he does, but we despise what he is." Both the Milgram and Stanford experiments have been found useful in the psychological study of wage-based workplace relations. Additionally, as per anthropologist David Graeber, the earliest wage labour contracts we know about were in fact contracts for the rental of chattel slaves (usually the owner would receive a share of the money, and the slave, another, with which to maintain their living expenses.) Such arrangements, according to Graeber, were quite common in New World slavery as well, whether in the United States or Brazil. C. L. R. James argued in "The Black Jacobins" that most of the techniques of human organisation employed on factory workers during the industrial revolution were first developed on slave plantations.