Fifteen males (22.3±4.6 years) and fifteen females (20.5±3.5 years) from National Chiao-Tung University, Taiwan, participated in the experiment after providing informed consent. The participants were college students, were not personally related to the authors, had normal or corrected-to-normal vision, and did not exhibit any neurological or psychological pathology. Twelve males and six females reported that they played video games frequently on a questionnaire asking for their demographic information (that is, “Do you play computer games frequently?”). Participants received monetary compensation of NT$200 (approximately US$6.50) for their time.
3.1.2. Apparatus and materials
The virtual maze environment was implemented with a custom software system that displayed 3D environments and allowed users to navigate using a first-person view. The field-of-view (FOV) of the VE was approximately 37 degrees. The participants used four arrow keys on a QWERTY keyboard to move forward, backward, left, and right inside the maze. The layout of the maze included a 5 × 5 grid of interweaving roads and cubic blocks surrounded by walls (Figure 8a).
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Figure 8. (a) A bird’s eye view of the simple maze structure adopted in the current study; (b) first-person view of the global-landmark condition; (c) first-person view of the local-landmark condition.
To examine whether global (Figure 8b) and local (Figure 8c) landmarks lead to differential performance, we constructed two types of mazes. In the environment with global landmarks, eleven enormous structures (for example, a tower, lighthouse, water tower, windmill, and other buildings, Figure 9), which participants could see from everywhere inside the maze, were placed outside the surrounding walls. In the environment with local landmarks, eleven different cartoon pictures (an axe, banana, bell, bird, bow, radish, deer, fish, desk lamp, scissors, and umbrella, Figure 10) were placed on the sides of the cubic blocks inside the maze. Each local landmark appeared on only one side of a given cube.
Participants could see a particular local landmark only from a few restricted orientations at certain locations inside the maze. However, if a participant modified his/her view by rotating at any position, he/she would see at least one landmark. Either local or global landmarks were displayed in each trial.
Four targets (an airplane, bicycle, grape, and penguin under the global landmark condition; and a candle, duck, flag, and kettle under the local landmark condition) were placed at different locations under each type of landmark condition. Each target was displayed on one side of a block that formed the internal structure of the maze, or on one segment of the surrounding walls. An icon of the target picture (0.1 width × 0.15 length of the screen) was
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shown at the bottom of the display before its location was found. Locations and the appearance of the targets differed between the global and local landmark conditions.
Figure 9. Global landmarks and targets.
Figure 10. Local landmarks and targets
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3.1.3. Procedure
All participants were tested in both global and local landmark mazes: half of the participants were first tested with global landmarks, whereas the other half were first tested with local landmarks. Before the formal experiment started, the participants were briefed about the procedure and stimulus configuration, and they practiced using the arrow keys for controlling movement in the VE for approximately five minutes. The formal experiment involved eight trials under each landmark condition. Each trial started with a learning period in which participants could search for the targets until all were found or until a 6-minute period had elapsed. The learning period in each trial allowed participants to become familiar with the positions and spatial relationships among targets and landmarks. The testing period immediately followed the learning period, and the search time for each target location was limited to 20 seconds. Only one target was shown until it was found or until the 20-second time limit had elapsed. After finding a target, the participant's current view in the virtual environment was immediately transformed to another random location, and a new target picture appeared. During the testing period, each target appeared three times, giving a total of twelve target-searching periods. The testing period lasted until all targets were found or until the time limit (four minutes) was reached. The order of the targets in the learning and testing periods was randomized in each trial.
3.1.4. Dependent measures
Six dependent variables were involved in the wayfinding task:
1. The ratio of the actual travel distance divided by the optimal travel distance (corrected path, P);
2. The travel time between the beginning and the end of target searching (T);
3. The proportion of time when the participant was moving away from the target location (TRaway);
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4. The proportion of time when the participant was not traversing (TRno-translation);
5. Accumulated angle of rotation when the participant was traversing (ROTtranslation);
6. Accumulated angle of rotation when the participant was not moving (ROTno-translation).
Although the corrected path and the overall travel time are regularly considered in wayfinding studies, the other dependent measures are rarely examined, and this study further investigates these measures to facilitate our understanding of wayfinding. Both TRaway and TRno-translation were ratios of their defining durations to the total travel duration. The duration of TRaway was calculated when the Euclidean distance between the current location and the target location at a given frame was increasing, as compared with the preceding frame. The duration of TRno-translation was calculated when the participant was not traversing (but could still be rotating at the same location) in the environment.
By definition, TRaway and TRno-translation should develop in opposite directions. In the scenario of a small TRaway and a large TRno-translation during wayfinding, the participant may often stay in the same location to compare visual scenes carefully with mental representations of the environment in order to plan the optimal path. By contrast, in the scenario of a large TRaway and a small TRno-translation, the participant may either get lost frequently or adopt an exploratory strategy of continuing to move in hopes of finding a recognizable landmark. The latter scenario naturally results in a larger P than does the former.
ROTtranslation and ROTno-translation were derived by tallying the absolute values of the difference in heading orientation between successive frames when the participant was moving or not moving, respectively. A large ROTtranslation may result from frequent instances of unnecessary detours, and a large ROTno-translation
may imply difficulty in determining the direction of the next move.
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In the framework for levels of measurement metrics in wayfinding by Ruddle and Lessells [53], P and T were termed “performance measures”, whereas TRaway, TRno-translation, ROTtranslation, and ROTno-translation were termed
“physical behavior measures”. Here, we refer to the former group as “overall measures” because they are indicative of the overall wayfinding performance, but they do not represent the minute (or “fine-grained”) details of how participants find their way. We refer to the latter group of measures as
“fine-grained measures” because each of these measures captures a structural aspect of wayfinding behavior, such as moving away from targets (TRaway), stopping (TRno-translation), changing direction while moving (ROTtranslation), and changing orientation while stopped (ROTno-translation).
3.1.5. Data analyses
For each trial, twelve values, each representing one type of variable, were collected, and each participant completed eight trials in the global and local landmark conditions, respectively. The data from the first four trials and the data from the second four trials were averaged separately. All dependent variables from the thirty participants were subjected to a three-way mixed-design ANOVA, with gender as a between-subject factor and landmark type (global versus local) and trial blocks (the first and the second block) as within-subject factors. The significance level for all statistical comparisons was set at p-value <
0.05. Post hoc analysis was conducted with Tukey’s HSD test.
3.2. Experiment 2: retrieving EEG