Incredible but true, this is today's comment on a Kevin Drum post.
I have a problem with the argument that cortisol levels show that low social status is correlated with high stress, with the argument not the conclusion. How did levels of cortisol become the best measure of stress ? In the first place, there has to be some independent measurement of stress which lead to the conclusion that stress causes high cortisol levels. So we know cortisol levels are correlated with stress.
But then cortisol levels are treated as an objective measure of stress. How did that happen ? Correlated with is not the same as the same as. An indicator does not become the one right indicator just due to the passage of time.
I happen to know of one very early experiment related to how it was decided (correctly I'm sure) that cortisol levels have a lot to do with something rather like stress. Some people were being trained to be paratroopers. Levels of various molecules (including nerve growth factor (NGF) a signal upstream from cortisol) were measured resting, after their first jump and after they were told they would jump for the first time the following day but before the jump.
Clearly being told that you are going to jump out of a plane whether you want to or not is stressful. But note what else is going on -- the people were being ordered around. A decision was made over which they had no control.
It happens to be a fact that every article on how low status people suffer more stress which I hav ever encountered mentions cortisol levels. I ask does cortisol measure stress or the experience of having to bite one's tongue because one is in the present of a more powerful mammal (submission saying_uncle or something) ? Or both ? How would we know ?
I note that the source of high quantities of NGF (which triggers release of cortisol) was the salivary glands of adult male mice. Not female not juvenile (not there). Exactly the mice who struggle for dominance and exactly in the fluid which enters a rival mouse following a bite. OK so if I were to bite (I don't really I don't bite) I would want to inflict pain, stress, fear and makemsayuncleness.
Letting a concrete objective indicator take the place of the abstract subjective phenomenon we wish we could measure is tempting but it doesn't constitute proof of anything.