Moody5: Personality-biased agents to enhance interactive storytelling in video games

In story-driven video games, such as Role-Playing Games (RPGs), a static and repetitive interaction with Non- Player Characters (NPCs) can negatively impact fun and immersion. On the contrary, an NPC able to show emotions and endowed with a personality that matches its behavior can keep the user engaged for a longer time, thus increasing the game’s replayability. Unfortunately, this aspect is still an open issue. We propose a preliminary solution: Moody5 has been designed to help game designers create “personality-biased” agents able to interact in sensible ways in the framework of interactive storytelling. In particular, it supports the creation of agents that exploit the Goal-Oriented Action Planning technique to reach their goals but whose chain of actions is affected by their personality and emotions. To obtain this result, we have borrowed some ideas from the Big Five theory [1] and the Emotion Facial Action Coding System (EMFACS) by Ekman & Friesen [2]. Therefore, we obtain NPCs that are a proxy good enough to approximate human behavior in games. We validated the proposed solution in a narrative test scenario inspired by the Harry Potter universe. Our preliminary survey demonstrated that Moody5 could improve the gameplay experience and replay value while providing a helpful Unity plugin for game developers.