Multimodal vs. Unimodal Physiological Control in Videogames for Enhanced   Realism and Depth
  (arXiv abridged abstract) In the last two decades, videogames have evolved in a nearly explosive way from the pixelated graphics to today's near-realistic 3D environments. The interaction devices traditionally used in videogames have not evolved with the same intensity, but recent HCI studies have explored biofeedback interaction - the explicit manipulation of a person's physiological data as input to a system - as an alternative to them. Traditional biofeedback prototypes apply 1 sensor to each game mechanic (unimodality).   In this dissertation, we introduce the combination of 2 physiological sensors simultaneously per game mechanic (multimodality) and present a First-Person Shooter game comprised of 8 game mechanics with three interaction flavours (no biofeedback/vanilla, unimodal and multimodal). An empirical study with 32 regular players was employed to explore and study differences between the three interaction types and where they can be best employed.   Players compared the three games in terms of Fun, Ease of Use, Originality, Playability and Favourite Condition. For the sake of completeness, other evaluation methods were used as well: IMI Questionnaire, keywords association and open-ended commentaries. The vanilla version was considered easier to use, but both biofeedback versions were considered the most fun. Both versions were praised differently: the unimodal version for its simplicity of use, and the multimodal for its realism, activation safety of game mechanics and depth added to the game. Our conclusion is that multimodal biofeedback can have a relevant impact in terms of added depth, depending on the way it is used inside the game. On a boundary case, it can be used to increase the feeling of empowerment on the player when using certain abilities, or to intentionally make in-game actions more difficult by demanding more physical effort from the player. 
Gon\c{c}alo Amaral da Silva
cs.HC