## 1 Introduction  
Spatial ability is an important skill to have in the modern day and age, as multiple jobs require a well-developed spatial ability [1]. If this skill is well-developed, it allows the person to understand the spatial relations between objects and space. It is possible to improve this skill by solving simple geometric problems. Tests were created with this goal in mind in the last century in paper-based formats. Multiple types of these tests exist, but the authors chose three of them for this research: The Mental Rotation Test (MRT) [2], where the user has to rotate objects in their mind; the Purdue Spatial Visualization Test (PSVT) [2, 3], where the user also has to rotate objects in their mind; and the Mental Cutting Test (MCT) [2, 4], where the user has to cut and also rotate objects in their mind. Since these tests mostly exist on paper, and virtual reality can improve the learning skills [5] and even the spatial skills [6, 7, 8] of students, a question arises: What happens when these tests are taken in VR? When doing the tests in VR, new factors must be considered such as Human-Computer Interaction (HCI) and the display parameters in the virtual environment. While the latter makes it possible to see the application with different graphical and display settings, the former differs from application to application. The behavior and interaction of humans towards the computer dependson the tasks, the available devices and even the design of the application [9]. With the use of HCI principles, applications for different purposes can be designed, such as learning applications [10; 11], mobile applications [12], helping with assistive technologies [13], entertainment applications [14], interfaces in VR [15], and even the virtual environments themselves [16]. The latter paper also states that there is no perfect HCI principle for VR, as this greatly depends on the type of the application. However, according to them, user-centric development proved to be useful in the past [17]. While the authors of this manuscript did not follow the user-centric development, their aim was to find an optimal preference that was the most user-centric for virtual environments. For this, the authors developed an application for the mentioned spatial ability tests and added options for the users with the ability to change the display parameters on each device. Since this developed application is in VR, it has an interaction that is greatly different from the paper-based methods used previously. As the tests are not on paper, they can be solved with a keyboard and a mouse on a desktop display and with the touchpad on the Samsung Gear VR. Though the application measures spatial ability skills, it also logs which display factors are used in the tests with each device. These factors are the virtual camera type, its field of view, its rotation, the contrast ratio between the foreground object and the background, and lastly whether shadows are turned on or off. These factors were examined to determine the most user-centric virtual environment and to see how these new factors in the virtual environment influence the users in achieving better results during the spatial ability tests. After gathering data from 240 students who used a desktop display and 61 who used the Gear VR, the authors analyzed them. In the first round, the authors evaluated one factor. Then, the examination continued by evaluating in pairs. However, those factors which did not have a significant influence on the results were deliberately left out from further examination. After completing the analysis in pairs, the authors continued by evaluating in triplets, and lastly, in four factors. The maximum examination number of four was due to only four factors having significant influences. With these analyses, the authors determined the effects of each display parameter and device separately. However, these factors depend on and even influence each other; therefore, the interactions between them were also investigated.