Halo effect

Biological Parallel

Peacocks with elaborate trains signal not just mating fitness but also parasite resistance, foraging ability, and genetic quality—a single costly signal honestly advertising multiple underlying traits. Peahens don't separately assess each quality; the train's magnificence creates a halo of inferred superiority across dimensions. The halo effect evolved because in nature, costly signals reliably correlate with overall fitness: organisms capable of extreme displays in one domain typically excel across multiple domains due to shared underlying vitality.