6 ideas
Each culture selects a few dominant purposes and bends its institutions, rituals, and emotional norms toward them, the way an individual's temperament organizes their behavior. Traits borrowed from elsewhere get reworked to fit this dominant configuration, so the whole culture is more than a sum of its separate customs.
Human possibilities form a vast arc of potential interests and behaviors, and every culture builds itself from a small segment of it while ignoring or suppressing the rest. Any given society's 'human nature' is therefore a selection, not the full range of what people can be.
Cultures can be sorted by whether they value moderation, restraint, and ritual order (Apollonian) or seek value through excess, frenzy, and breaking ordinary limits (Dionysian). The restrained, collective, ceremony-centered Zuni show the first; Plains groups that chase visions through fasting, torture, and ecstasy show the second.
Among the Dobu, sorcery, treachery, and fear of poisoning structure marriage, gardening, and trade, and a person's success is assumed to come at someone else's secret loss. Traits that would read as paranoia elsewhere are the normal, rewarded posture there, which shows how culture defines what counts as sane.
Kwakiutl chiefs competed for prestige by giving away or destroying huge amounts of property to shame rivals, and the behavior extended to grandiose self-glorification and responses to insult. Wealth mattered less as material comfort than as a weapon in a contest for rank.
Whether a person counts as deviant depends on whether their temperament fits the traits their culture happens to reward, so someone labeled abnormal in one society would be honored in another. This undercuts treating any single culture's standards as the benchmark of mental health or morality and grounds the case for cultural relativism and tolerance.