  Reinforcement learning has been widely successful in producing agents capable
of playing games at a human level. However, this requires complex reward
engineering, and the agent's resulting policy is often unpredictable. Going
beyond reinforcement learning is necessary to model a wide range of human
playstyles, which can be difficult to represent with a reward function. This
paper presents a novel imitation learning approach to generate multiple persona
policies for playtesting. Multimodal Generative Adversarial Imitation Learning
(MultiGAIL) uses an auxiliary input parameter to learn distinct personas using
a single-agent model. MultiGAIL is based on generative adversarial imitation
learning and uses multiple discriminators as reward models, inferring the
environment reward by comparing the agent and distinct expert policies. The
reward from each discriminator is weighted according to the auxiliary input.
Our experimental analysis demonstrates the effectiveness of our technique in
two environments with continuous and discrete action spaces.
