We study the monotonicity of sender's equilibrium strategy with respect to her type in signalling games. We use counterexamples to show that when the sender's payoff is non-separable, the Spence-Mirrlees condition cannot rule out equilibria in which the sender uses non-monotone strategies. These...

We study the monotonicity of sender's equilibrium strategy with respect to her type in signalling games. We use counterexamples to show that when the sender's payoff is non-separable, the Spence-Mirrlees condition cannot rule out equilibria in which the sender uses non-monotone strategies. These...