Artificial Intelligence in games has historically focused on providing a challenging opponent for a player and narrative development. Scope exists to increase the fidelity of synthetic characters throughout the game to create a more immersive game play experience. This requires both visual and behavioural fidelity, and while graphics are nearing photorealism, synthetic characters' behaviour is still unrealistic. Non-verbal behaviour of synthetic characters has to date received little attention and so the scope and participants of non-verbal behaviour requires identification. We review the range of spatial and task scenarios relevant in a game context, then identify categories of non-verbal behaviour and go on tot summarise their role in communication and propose their incorporation in the design of non-player characters. Finally we review how non-verbal behaviour of synthetic agents might increase immersion for a player and identify interaction techniques that might facilitate non-verbal communication with players and non-players characters alike
