Evaluation of an Adaptive Game that Uses EEG Measures Validated during the Design Process as Inputs to a Biocybernetic Loop

Abstract

Biocybernetic adaptation is a form of physiological computing whereby real-time data streaming from the brain and body is used by a negative control loop to adapt the user interface. This article describes the development of an adaptive game system that is designed to maximize player engagement by utilizing changes in real-time electroencephalography (EEG) to adjust the level of game demand. The research consists of four main stages: (1) the development of a conceptual framework upon which to model the interaction between person and system; (2) the validation of the psychophysiological inference underpinning the loop; (3) the construction of a working prototype; and (4) an evaluation of the adaptive game. Two studies are reported. The first demonstrates the sensitivity of EEG power in the (frontal) theta and (parietal) alpha bands to changing levels of game demand. These variables were then reformulated within the working biocybernetic control loop designed to maximize player engagement. The second study evaluated the performance of an adaptive game of Tetris with respect to system behavior and user experience. Important issues for the design and evaluation of closed-loop interfaces are discussed.

Keywords: EEG; adaptive interface; effort; engagement; gaming; physiological computing; psychophysiology.

Figure 1

Motivational Intensity Model (MIM) adapted by the addition of four categories of user state.

Figure 2

Game-board during incentive + feedback condition: coins are displayed pictorially in a 7 × 10 matrix on the left of the screen and turn from dark blue to gold to indicate coin achievement. A separate row of coins above indicates the number of coins awaiting award at the next 10 s time-point (one coin in this example). The coin score (bottom) and remaining game time are presented in numerals on the left of the screen.

Figure 3

Grand average topographic distribution of spectral power at the frequency of peak power for low, high and excessive demand (N = 20: incentive and no-incentive conditions are collapsed). Peak frequency = 6 Hz (the frequency at which a clear peak in EEG power was evident within the 4–7 Hz range); this was identified by visual inspection of the grand average frequency-power spectral plot. Images were constructed using spherical spline interpolation.

Figure 4

Grand average spectral electroencephalography (EEG) power at 11.5 Hz (N = 20) for low, high and excessive cognitive demand on the Tetris game with and without a game based incentive (spherical spline interpolated; image displays rear of scalp).

Figure 5

Two dimensional representation of the user state using EEG measures (cortical activation is inversely proportional to alpha band power).

Figure 6

Components of the biocybernetic loop.