Before revision:  In our model, non-equilibrium signals are sent by young senders as experiments to learn about receivers' behavior , and different types of senders have different incentives for these various experiments.
After revision:  In our model, young senders are uncertain about the prevailing distribution of play, so they rationally send out-of-equilibrium signals as experiments to learn about receivers' behavior , and different types of senders have different incentives for these various experiments.