Nothing in here indicates a causal cortisol->~altruism connection was discovered, nor did they attempt at hinting towards causality (e.g. via instrumental varia

Nothing in here indicates a causal cortisol->~altruism connection was discovered, nor did they attempt at hinting towards causality (e.g. via instrumental variable estimation). The described findings appear entirely consistent with stressful situations both increasing cortisol levels and decreasing altruism through an unrelated mechanism. So I'm not sure I see the point of mentioning, let alone highlighting, a specific hormone rather than the causal variable they did study and discover, which is the stress itself.