Interactive visualization of honest signaling, separating equilibrium, and Spence job market model
Costly Signaling Theory (CST) explains how honest signals evolve and remain stable when individuals have conflicting interests. The key insight: signals must be sufficiently costly so that only high-quality individuals can afford them, making signals reliable quality indicators.
The Handicap Principle (Zahavi, 1975) proposes that traits which reduce survival can nevertheless evolve because they reliably indicate genetic quality. Grafen (1991) formalized this mathematically, showing that costly signals can be evolutionarily stable.
Spence (1973) applied this idea to economics: education serves as a signal of worker productivity, even when education itself does not enhance productivity. The separating equilibrium occurs when high-ability workers invest in education because it is less costly for them.
Real-World Examples: Peacock tails (biology), Gazelle stotting (anti-predator), University degrees (job market), Luxury brands (Veblen goods), Religious rituals (costly commitment), Charity/donation (competitive altruism).