This study uses cortisol measurements to obscure the fact that one group was asked to do a stressful public speaking task first: > Human participants (males an

This study uses cortisol measurements to obscure the fact that one group was asked to do a stressful public speaking task first: > Human participants (males and females) completed a charitable donation task before and after they underwent either a psychosocial stressor or a control manipulation, while their brain activity was measured using functional magnetic resonance imaging (fMRI). Most of these "cortisol does X" studies are deeply flawed because they try to pretend like cortisol is some independent variable, when really it's an artifact of having asked the people to do something stressful. In this case, the study is best interpreted as "Certain people are less altruistic immediately after being forced to do a stressful public speaking task".