Costly religious displays signal hard-to-fake commitment to group beliefs, like romantic love signals fidelity.

Evidence

Why would religious devotees do such things that sabotage one’s fitness? Evolutionary scientists have long puzzled over such extravagant practices and rituals, found in some religious groups, that demand sacrifices of time, effort, resources, and in some cases of life and limb. These displays—such as rites of terror, scarification, and various restrictions on behavior (sex, material belongings, giving away valuable animals), diet (long fasts and costly food taboos), and lifestyle (strict marriage rules, dress codes)—are endemic, though not unique, to prosocial religions. They are often costly, are emotionally loaded, and appear irrational to outsiders. However, just as the irrationality of falling in love tells us that there is a genuine commitment to a romantic relationship, religious fervor may have its logic too: it communicates a hard-to-fake commitment to the beliefs of the religious group. — Norenzayan, Ara, Big gods - how religion transformed…, 331

Categorization

• XREF: The core mechanism in the reader’s project: costly public display (Cavadee) is the honest-signal complement to the fumi-e’s manufactured apostasy display. The fumi-e inverts this — forcing a cheap, coerced signal rather than a costly voluntary one.
• QUESTION: If costly displays signal genuine commitment to the group, what does forced cheap apostasy (fumi-e) signal — and does it work as a solidarity-disruptor precisely because it floods the honest-signal channel with noise?
• corroborated: 2 independent passages support this claim — Norenzayan, Ara, Big gods - how religion transformed…, 331