# Research on Effective Advertising Types in Virtual Environment
## 2 Related Work
### Visual Attention and Eye-Tracking  
Visual attention occurs selectively to efficiently process visual information to cognitively resolve visual stimuli [11]. Moreover, as the first step toward encouraging consumers to pay attention to advertisements, it is essential to review the production, placement, and application of marketing. If an advertisement does not attract consumers' visual attention, it cannot be perceived or interpreted [12]. Advertisement effects vary depending on users' focus [13,14]. Therefore, it is necessary to analyze which advertisement elements consumers pay attention to and how long they share at them.  
Previously, visual attention was mostly measured using post-questionnaires. The recall of advertisements, consumer attitudes toward brands, and purchase intentions have been investigated [15, 16, 17]. These measurements have been used for a long time and are considered reliable. However, this was not carried out simultaneously with the advertisement exposure, and subjective interpretation intervention was inevitable until the survey. Therefore, questions have been raised as to whether measurement results accurately reflect advertising effects. To compensate for this, quantitative measurement technology, such as eye-tracking technology, which responds immediately when a user sees an advertisement, is required.  
Eye-tracking is a technique that collects and analyzes information on how humans accept and respond to visual stimuli by observing eye movements [18]. Responses to visual stimuli are collected in real-time, which has the advantage of providing objective data with no time lag between stimuli and responses [19]. Furthermore, with the development of eye-tracking technology, modern eye-tracking equipment can record large amounts of eye movements under natural exposure conditions with high precision and low cost, making it easy to measure visual attention [3,14].  
Recently, eye-tracking has been used to analyze user reactions in virtual environments. Applying eye-tracking to VR environments can help analyze user gaze responses in real environments [20]. For example, Kellogg, a food manufacturer and marketing company, used VR and eye-tracking to analyze consumer reactions to a new product before launching it. By implementing a virtual store, data on the application of billboards for products placed on the shelves, route of application, and time of application were collected to present data for effective product marketing [21].  
Many studies have used fixation to analyze gaze responses using eye-tracking technologies. This is because to perceive visual objects and process information, it is necessary to provide a certain amount of time to view objects. Therefore, related research defines fixation as a state of fixing eyes to visual stimuli for a certain period [4,22]. In general, fixation is judged when the gaze is performed for more than 0.1-0.5 s and is appropriately adjusted for research [23,24,25]. The metrics for fixation were expanded to include fixation duration, number of fixations, first fixation, and entry time.  
An analysis of previous research on eye-tracking revealed that the number of fixations and fixation time were most frequently used to measure visual attention. Therefore, we adopted the number of gazes and gaze times as indicators to measure the user's visual attention in the VR environment. The number of fixations indicated the extent to which the area of interest was gazed at, and the fixation time was defined as the total amount of time spent gazing at the area of interest. Furthermore, we propose an eye-tracking VR ad monitoring system to measure the visual attention to ads presented in a VR environment.