[gwern]

http://www.terrierman.com/russianfoxfarmstudy.pdf

"At seven or eight months, when the foxes reach sexual maturity, they are scored for tameness and assigned to one of three classes. The least domesticated foxes, those that flee from experimenters or bite when stroked or handled, are assigned to Class III. (Even Class III foxes are tamer than the calmest farm-bred foxes. Among other things, they allow themselves to be hand fed.) Foxes in Class II let themselves be petted and handled but show no emotionally friendly response to experimenters. Foxes in Class I are friendly toward experimenters, wagging their tails and whining. In the sixth generation bred for tameness we had to add an even higher-scoring category. Members of Class IE, the “domesticated elite,” are eager to establish human contact, whimpering to attract attention and sniffing and licking experimenters like dogs."

Pretty hard and fast criteria. Hard to let a slightly bushier tail affect your evaluation of whether a fox just snapped at you.

[tlb]

https://en.wikipedia.org/wiki/The_Mismeasure_of_Man describes research that also had hard and fast criteria, yet thumbs somehow ended up on scales anyway. The criteria you quote are a little fuzzy around the edges. "Eager to establish human contact" might well be correlated with fox cuteness.

[gwern]

_The Mismeasure of Man_ is biased garbage written by someone with an axe to grind who attacked strawmen and may well have made up some of his findings of 'bias' and more importantly, has completely failed to predict subsequent decades of psychological, psychiatric, and genetics results: IQ is stronger and more vindicated than ever and a major driver of molecular genetics & neuroimaging research. Try again.