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The event-related potentials (ERP) also seem to be modulated by the emotional
state of the user. Olofsson et al. provide a survey of this modulation in Olofsson
et al. (
2008
). For example, pleasant stimulus helps to induce larger P300 amplitude,
compared to an unpleasant one.
13.3.2 Task-Related State
The brain activity measurement could also provide information concerning the user
mental state related to an interaction task. In the following text, works that show
markers related to user
'
s perceived dif
culty of the task and differentiation of tasked
based on EEG activity are presented.
Lee and Tan (
2006
) found some differences in EEG patterns between different
kinds of video game interactions
3
(relaxation without playing, playing without
enemies, and playing with enemies). This work does not induce any modi
cation of
the game based on the acquired data. It reveals the feasibility of this kind of task
differentiation by providing an average classification accuracy of 92.4 %.
Girouard et al. (
2009
) have also explored the differentiation of task during
interaction with video game. They measure the blood oxygenation in cortical region
of a user playing a Pacman-like video game. Their BCI system was able to dis-
tinguish between dif
culty level and also active state versus passive state (user not
playing). We can note that the dif
culty level measured, as explained by Girouard,
re
ects the dif
culty sensed by the user, not the dif
culty of the game (the user can
work hard and performs poorly).
Reuderink and colleagues observed brain activity related to frustration during
video game interaction. They record EEG during a modi
ed version of Pacman
called
affective Pacman
(Reuderink et al.
2009
). In
affective Pacman,
the game
voluntary induced frustration by adding errors into movements (the key pressed did
not always induce the same character movement). This experiment and the pre-
liminary analysis reveal differences between normal and frustrated states. The
authors propose to continue to explore the effect of frustration on EEG activity.
They also propose to use the level of frustration as an interaction input to switch, for
example, between an easy mode (where the character is controlled by a keyboard)
and a dif
cult mode (where the user uses an explicit BCI to control the character).
13.3.3 Error-Related Potentials
Error-related potentials (ErrP) are a certain type of event-related potentials that can
be measured in the EEG activity when the user is aware of erroneous behavior. Four
kinds of ErrP have been identi
ed (Ferrez and Mill
n
2007
):
á
3
Halo, first person shooter game produced by Microsoft.
