This site contains different examples of the tunnel paradigm for the categorization modus
, the egocentric
and the allocentric
you encounter any problems while viewing the mpg-files online,
please download the files to a temporary folder and use Windows Media
Player to view the examples. Please note that the examples
might be displayed slower than the original files from the experimental
platform. This might be due to slow internet connection and/or the
process of making a movie from continuous visual flow information. We
are working on it and try to improve the temporal resolution of
visual flow patterns in the movies.
This MPG-file is a demonstration of the categorization
of the tunnel task. The categorization is used to identify different
strategies, i.e. the preference to use an egocentric or an
frame of reference in spatial navigation a priori. Subjects are
categorized with respect to their preferred use of one frame of
reference allowing to use the preferred strategy as factor for the
statistical analyses of performance and electrocortical data.
Below you find the instructions for the categorization task. If you are
interested in finding out what your preferred strategy is, please read
the following instructions carefully and try to remember which arrows
you selected (the solutions is given at the bottom of this page).
Otherwise, you can view the movies to gain a better understanding of
how the tunnel paradigm works.
you for participating in our study. We hope that you will enjoy it. The
experiment is concerned with how humans orient in space. If you are
interested in the background of the experiment, please feel free to ask
the investigator after the experiment.
Before and after each
trial, a fixation cross will appear which you should focus on. The task
on each trial comprises a virtual journey through simulated tunnels
with straight and curved segments. At the end of the journey, your task
is to point back to the tunnel entrance, that is, the starting point of
your journey. To solve this task, it is crucial that you keep up
orientation during the journey.
A single trial will look like
this: each tunnel starts with a straight segment and ends with a
straight segment. After each curve, a straight segment follows. During
this simulation, you are “moving” forward into the depth of the
simulated space through straight and curved segments. Imagine that the
first segment points into the depth of the simulated space. At the end
of the tunnel, you stand still while viewing outside of the last
segment (the last segment will stay on screen for a little while).
Then, after a short time, two arrows will appear, pointing toward the
starting point of the tunnel, the tunnel entrance. Your task is to
decide which one of the two arrows represents the correct direction
toward the tunnel entrance.
If it is the right arrow, please
press the right mouse button; if it is the left arrow, please press the
left button. Take your time for the decision to avoid premature
answers. If you lost orientation during the passage, choose the arrow
that you feel most likely represents the correct answer. If you have
any questions concerning the task or the experiment, please contact
your investigator now.
Thank you very much.
Tunnel egocentric and allocentric modus
The MPG-files include demonstrations of tunnel trials in the allocentric modus
the egocentric modus
of experimental trial is used in the main experiments where
subjects actively have to adjust the homing vector so that it points
back to the starting point of the tunnel passage. This way several
performance measures (e.g. side errors, absolute and signed errors) can
be recorded and subsequently analyzed.
In the present examples the navigator uses either an allocentric
or an egocentric
frame of reference
adjust the homing vector after the tunnel passage. The Figure
explains the terms for a tunnel with a turn to the right.
a passage through a tunnel with a turn to the right, with nonparallel
start and end segments. The most left column displays the navigator’s
view into (A) the first straight segment, (B) a segment with a turn to
the right, and (C) a straight segment after the turn. The second left
column displays a nonturner (dark grey head representing the perceived
heading and the small light grey head representing the cognitive
heading) using an allocentric frame of reference, with the navigator's
heading during (A) the first straight segment, during (B) the turn, and
during (C) the straight segment after the turn. Note that the perceived
and the cognitive heading diverge during the turn. On the right, a
turner (light grey head representing the perceived cognitive heading
which is assumed to be identical to the cognitive heading) is displayed
who uses an egocentric frame of reference. During (A) the first
segment, the turner's heading is the same as that of a nonturner.
During the turn (B), the axis of orientation changes. At the end of the
tunnel, the turner's cognitive heading is different from that of a
nonturner. Note that turners build up an additional allocentric frame
of reference if they are forced to react based on an allocentric frame
of reference. There is no depiction of an additional allocentric
reference frame for turners to emphasize the preferred use of an
egocentric frame of reference by this strategy group. To the right-side
of the figure, examples of homing vectors are displayed with the
correct angular adjustment for a tunnel with one turn of 60° to the
right ending up at 45° eccentricity, with panel D depicting the correct
homing vector for nonturners, and panel E that for turners. The most
right column displays (F) the coordinate system underlying the
allocentric cognitive heading (grey dotted arrows) and the coordinate
system of the monitor (black solid arrows) and (G) the coordinate
system underlying the egocentric cognitive heading (grey dotted arrows)
and the coordinate system of the monitor (black solid arrows). When the
coordinate system underlying the egocentric cognitive heading is
rotated back into the initial coordinate system of the monitor the
starting point of the tunnel passage is rotated accordingly, resulting
in a homing vector pointing to the right of the subject.