# Effect of Target Size, Location, and Input Method on Interaction in Immersive Virtual Reality
## 6 Conclusions  
In this study, we analyzed the effect of target position and task performance when a continuous target selection task was performed with a VR device. The experimental area was set larger than the maximum viewing angle represented by the VR HMD. The target size was divided into two levels. The target selection method consisted of the manual-selection method and the gaze-selection method. The results show that the effect of the target size on the task completion time was different according to the two selection methods. Additionally, the error rate was significantly higher at manual selection than at gaze selection, but it was analyzed that there was no effect by target size. The task completion time was different according to the target location, but it did not affect the error rate. Additionally, the degree of motion sickness was measured by the VRSQ to investigate the level of motion sickness during the target pointing task. It is considered that the extension of the viewing angle and the extended use time influenced motion sickness. Additional experiments are needed to clarify which factors are more influential because there were great differences when comparing the VRSQ scores of this study and [PERSON] et al. [51]. As the research on virtual reality mainly focused on technology for commercialization, there were relatively few basic usability studies. Virtual reality also interacts with the user through the screen, but it is a platform that has distinguished characteristics than other devices with displays. Therefore, the results of this study are meaningful in that separate basic research is needed to reflect the unique characteristics of virtual reality. For example, virtual reality is visually expressed in three dimensions, but manipulation can be carried out in two dimensions, moving the head tracking-based cursor. These characteristics were once again confirmed by the fact that the data obtained from this study were better suited to the lower-dimensional Fitts' law than the three-dimensional expansion formula. However, because the target width and height are the same, there is a limitation in that the result cannot be compared with the 2D Fitts' law model reflecting the target area. We expect that the effects of size and shape of the target on the movement of the pointing task in the VR environment can be clarified by comparing the results obtained by experimenting with varying target distances or setting different widths and heights instead of squares or circles. Additionally, it is expected that the results of experiments can be compared by placing the targets at various distances and heights in order to reflect the characteristics of virtual reality further in future studies. Thus, it is possible to develop a new time prediction model by adding a variable that reflects the VR environment by searching for the relationship. Another limitation of this paper was that the recruited subjects were relatively young, so it was not possible to compare the results with the elderly. For example, there are researchresults showing that there is a statistically significant difference in the level of VR sickness by age group [61; 62; 63]. Considering that older people also use virtual reality technology for reasons such as treatment or education, it is necessary to analyze the results obtained from various age groups in the future. Conceptualization, software, data collection, analysis, and writing-original draft preparation M.C. ; writing review and editing, supervision, and funding acquisition J.P.; writing review and editing, H.K.K. All authors have read and agreed to the published version of the manuscript. This work was supported by Incheon National University Research Grant in 2021 (Grant No. : 20210226). The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board of Incheon National University (IRB No. 7007971-201801-003-02). Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.