Blushing as Real-Time Social Displacement Signal: Facial Vasodilation, Honest Signaling Theory, and the Melanin-Legibility Interface

We apply the Displacement Framework to blushing, formalizing it as an involuntary index signal of social displacement cost D(xi_social). Blushing tracks perceived displacement from S0_social — not culpability — explaining why innocent people blush when accused and shameless individuals do not blush when guilty. The honest-signaling function depends on a melanin-legibility interface: the blush signal is physiologically identical across populations but externally visible only in low-melanin skin.

The full high-transparency cluster (fair skin, light eyes, MC1R/red hair) represents the maximum legibility configuration, where social displacement cost is broadcast in real time. Five formal propositions are derived.