respective hardware technologies and era of graphical
technology. Each of the games used were chosen
according to their graphical maturity and gradually
increased in graphic complexity. Also, the games
presented cover a range of genres such as arcade, 2D
platform, 3D platform, racing simulation and first
person shooter to ensure adequate coverage of
gameplay mechanics and dynamics [18][19].
Section 2 provides details on the methodology
for the study. Section 3 is the data analysis section.
Section 4 presents the results of the study. Section 5
provides a discussion and section 6 concludes the
paper.
2. METHODOLOGY
2.1. Paradigm
The presentation environment used in the study
was developed using the Unity 3D [20] game
development engine. Five on screen virtual buttons,
placed in a horizontal arrangement at the top of the
computer screen form the m YEP game controller
used in the study. In order to avoid visual distractions
in the immediate area surrounding each m YEP
button, the buttons were placed centrally within a
plain white background acquiring approximately
13% of the total screen space. Each mVEP button
subtends a visual field of 1.24° length x 0.76° height
with the red coloured vertical moving line being 0.66°
in height.
Each mVEP button has a number (1 to 5) placed
directly on top which differentiates them from each
other. The subject identifies which button to
concentrate on when the number of the current target
button changes from black to red. The users'
instructions were to focus their attention on the
moving line of the currently active button (Fig. 1
shows the basic (no graphics) level with the '2' button
as currently active while '2' is also the users current
target (number highlighted red). A button activation
constitutes one horizontal movement of the vertical
red line from the left hand side to the right hand side
of the vacant rectangle (lasting 140 milliseconds).
The timing protocol for this study followed
closely to that of [17]. Each game level consisted of
300 trials. Each level lasted 540 seconds, during
which each m YEP button will have been activated 60
times.
'
During each trial, each of the five m YEP
buttons are active a total of five times. Each button is
highlighted in tum starting from 1 through to 5 in a
linear fashion. In order to avoid user habituation,
each of the buttons are activated in random order.
The Stimulus Onset Asynchrony (SOA) between
each button activation is 200ms. The motion of the
vertical line moving from right to left in each button