Most of recent studies in this area have adopted this strategy (Su et al., 2016a;Lipton et al., 2016;Zhao and Eskenazi, 2016;Williams et al., 2017;Dhingra et al., 2017;Liu and Lane, 2017;Peng et al., 2017b;Budzianowski et al., 2017;Peng et al., 2017a).
user simulators usually lack the conversational complexity of human interlocutors, and the trained agent is inevitably affected by biases in the design of the simulator.