Costly Signaling

The peacock’s tail is a disaster for survival: heavy, conspicuous to predators, metabolically expensive. But that’s the point. Only a genuinely fit peacock can afford to handicap himself so extravagantly. The tail is a signal precisely because it’s costly — a cheap signal would be worthless because anyone could fake it.

Amotz Zahavi called this the handicap principle. Signals are credible when faking them is prohibitively expensive. The gazelle that stots (bounces slowly) in front of a lion is saying: “I’m so fast I can waste energy showing off.” The signal works because only truly fast gazelles can afford to send it.

Human signaling follows the same logic. The expensive wedding proves commitment because uncommitted people won’t waste the money. The luxury degree proves ability because unqualified people can’t survive the program. The tattoo proves group loyalty because defectors would regret the permanent mark. Cost creates credibility.

This explains apparent waste. Conspicuous consumption isn’t just vanity — it’s proof of resources. Religious rituals that demand sacrifice aren’t just tradition — they’re proof of commitment. Long courtships that delay gratification aren’t just caution — they’re proof of patience. What looks irrational becomes rational when you see it as signaling.

The insight has dark sides. Signaling arms races waste resources: everyone buys credentials, no one gains advantage, but no one can quit. Costly signals can be gamed by those willing to incur costs they can’t afford. Some costly signals prove the wrong things — endurance, not competence; conformity, not character.

The practical lesson: when evaluating signals, ask what they actually prove. A costly signal credibly demonstrates the capacity to bear that cost. Whether that capacity is what you care about is a separate question.