Maybe a little bit in the vein of the handshaking socials being a back-and-forth interaction, why not make it so that when someone in a room uses the yawn social, anyone else in that room (or anyone watching/addressing them in a CROWDED room) has a small chance to automatically trigger a yawn social themselves and then, in turn, have a chance to propagate this again, perhaps with diminishing chance for those who already just yawned to yawn again.
It's mostly flavor and fun, but could also alert you to someone unexpectedly watching you, sometimes.
