Paper Reading #18: Biofeedback Game Design: Using Direct and Indirect Physiological Control to Enhance Game Interaction

Reference Information
Biofeedback Game Design: Using Direct and Indirect Physiological Control to Enhance Game Interaction
Lennart E. Nacke, Michael Kalyn, Calvin Lough, Regan L. Mandryk
Presented at CHI 2011, May 7-12, 2011, Vancouver, British Columbia, Canada

Author Bios

• Lennart E. Nacke is an Assistant Professor of HCI and Game Science at the University of Ontario Institute of Technology. As a postdoctoral researcher, he worked in the Interaction Lab of the University of Saskatchewan and studied affective computing.

• Michael Kalyn is an undergraduate student in the Interaction Lab of the University of Saskatchewan's Department of Computer Science. His focuses are in affective feedback and interfacing sensors.

• Calvin Lough is affiliated with the Interaction Lab of the University of Saskatchewan's Department of Computer Science. His research is in affective computing.

• Regan L. Mandryk is an Assistant Professor in the Interaction Lab of the University of Saskatchewan's Department of Computer Science. Her research focuses on affective computing and ubiquitous and mobile gaming.

Summary
Hypothesis
How do users respond to physiological sensors that work with game controllers? Which types of physiological sensors work for certain game tasks?

Methods
The authors developed a side-scrolling shooter that uses a traditional control as the normal form of input. Physiological sensors augment the controller through indirectly or directly controlled input. There were thus three versions of a game that participants played. Two game conditions used  direct sensors and four used indirect. The direct measures were respiration and EMG on the leg, and the indirect included GSR and EKG. Both physiological games had the eye gaze power-up, though the control lacked it. All participants played the three games, presented in random order, after playing a training level. The players completed questionnaires that asked about their experience after each game and again after completing all the levels. The players were not very experienced with side-scrolling shooters and mostly used Nintendo's Wii and DS as their sole form of novel input.

Results
Players found physiological controls to be more fun than just playing with the controller, with 90% preferring some sort of physiological control. The pleased users liked the increased level of involvement and variations. The participants agreed that the physiological control was novel, involving a little learning at first, but then feeling quite natural. Users preferred eye gaze the most, but only 1/20 of the votes were for indirect sensing. Overall, direct input was preferred to indirect in each category tested. The GSR and EKG sensors were difficult to use, EMG responses were split fairly evenly, and the respiration sensor was liked due to its ease of use. The temperature sensor was easy at first, but users found it tedious over time. Users preferred multiple forms of input. Direct controls were more real-time and suited for controlling the player icon, but indirect controls were slower to respond and thus were better to control the environment. Direct controls were also thought to increase the player's sense of accomplishment. Natural mappings were preferred. The players were comfortable with wearing sensors if they contribute to gameplay.

Contents
The authors developed a classification of direct and indirect sensor input to work with traditional game control. Current physiological game design paradigms revolve around indirectly controlled signals, like heart rate. Eye gaze and muscle flexion are directly controlled. Computer games allow for a low-risk way of testing physiological HCI. This sort of interaction is called affective gaming and relies on the player's emotional state. Replacing traditional controls with biofeedback has not worked well in the past. Adapting affective games use biofeedback to alter the technical parameters or user preferences based on controller movement or button pressure, for example. Indirect controls allow players to learn to control their brainwaves, though a previous study showed that people liked explicit biofeedback in first-person shooters. Various physiological measures include eye gaze, electromyography (EMG), galvanic skin response (GSR), electrocardiography (EKG), respiration sensors, and temperature sensors. The premise of biofeedback training is to turn indirect physiological measures into increasingly directly controlled ones. Indirect sensors are available to consumers, but direct ones are not available at the moment.

The authors' game used controller mappings common in Xbox 360 shooter games with physiological input controlled separately. The game features bosses and checkpoints, which can only be activated when a player kills all the enemies. The size of enemy targets' shadows increased based on physiological control and provided a larger hit box. The backup flamethrower's range is variable. Speed and jump height also varied, though these factors were tied together. The rate of snowfall during the final boss fight also changed. An eye gaze power-up was included, but only lasted for 20 seconds to reduce eye strain and maintain game balance. The sensors were integrated through a custom C# library.

Discussion
The authors tested user preference for biofeedback controls as part of a game and which types of controls are ideal for certain tasks. Their user test was small and focused on a single genre, but they created enough of a basic framework that a large body of future work will be able to rely upon.

I was initially concerned that the sensors that were applied to users would be cumbersome. However, the players were okay with most sensors so long as they contributed to gameplay and were not excessively taxing. That brought up an important limitation: the types of sensors used must not tire the user.

I hope that future work is performed with regard to additional genres. The next foreseeable step is in first-person shooters, which are closely related to their side-scrolling brethren. I would be very interested in seeing how well "God games" like Civilization could be played with biofeedback, since that seems like the least likely effective genre imaginable for the technology.