Klaus Gramann

Download Instruction

This site contains different examples of the tunnel paradigm for the categorization modus, the egocentric and the allocentric experimental modus. If 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 the visual flow patterns in the movies.

Tunnel Categorization

This MPG-file is a demonstration of the categorization modus of the tunnel task. The categorization is used to identify different strategies, i.e. the preference to use an egocentric or an allocentric 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.


Thank 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 and the egocentric modus. This kind 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 to adjust the homing vector after the tunnel passage. The Figure explains the terms for a tunnel with a turn to the right. Depiction of 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.

Department Psychology, Ludwig-Maximilians-University Munich
Swartz Center for Computational Neuroscience, UCSD