# Changes in Pupil Size According to the Color of Cosmetic Packaging: Using Eye-Tracking Techniques
## 1 Introduction  
Neuromarketing, a methodology applied to marketing using cognitive neuroscience, is increasingly being used. Eye tracking is a method of analyzing the physical characteristics of the eye, such as eye movement, pupil size, and blinking. Compared to other neuromarketing analysis techniques, eye tracking has the advantages of being simple and cost-effective. Eye-tracking research has recently gained interest due to technological advances in this field. Smaller and more efficient devices have been created, and more comprehensivesoftware has been developed. An eye tracker may record gaze position and identify the size of the pupil to provide information on what humans pay more attention to. Research using eye tracking has been conducted in various fields, such as marketing and advertising [1; 2], human-computer interaction [3], business [4], aviation [5], language [6], education [7], and medical imaging [8; 9]. Color is an essential element influencing emotions and behaviors in a particular environment. Thus, in terms of marketing, deciding whether to use packaging colors to focus consumers' interests and attention more effectively is important. This study presents a study on how eye trackers can be used to identify pupil sizes and colors of consumer interest. Electrooculography (EOG) is a method of measuring the electric potential of the eyeball, and its most common use is to identify diseases [10]. EOG is also used to track eye movement. The eye makes saccade movements when looking at an image [11; 12]. The pupil enlarges or decreases depending on the light conditions, but it also varies depending on a person's emotional interest and cognitive load [13]. This study differentiates itself from existing research in several ways. First, unlike studies focusing on food packaging [14] or high-end goods like perfume [15], this research targets cosmetic packaging, where color strongly influences emotional and psychological responses. Second, while prior studies analyzed packaging design's impact on visual attention and emotions, this study quantitatively examines how color affects cognitive and emotional reactions by analyzing changes in pupil size. Third, using eye-tracking technology to measure microscopic changes in pupil size provides physiological evidence of how color induces cognitive load and emotional interest. Lastly, this study explores the specific impact of cosmetic packaging on consumer preference and purchase potential, offering actionable insights for marketing and design strategies. These contributions make this research a unique addition to consumer behavior and marketing studies. Research on pupil size and color has been conducted in various fields using eye-tracking techniques. [PERSON] et al. (2018) examined eye tracking as a measure of cognitive load utilizing pupil diameter and microsaccades with fixed gaze. It was reported that the change between the test of pupil diameter and fine sandpaper size properly distinguished cognitive load according to the difficulty of work [16]. Using eye-tracking techniques, [PERSON] et al. (2022) quantitatively studied the relationship between color and visual comfort in subway spaces. They found that orange, yellow, and green were preferred [17]. [PERSON] and [PERSON] (2022) studied whether color affects visual attention in the living environment of the elderly. The results showed that the elderly paid more attention to color combinations, including red and black. Older people saw red-black combinations faster than white combinations in the same location and stayed focused longer on red-black combinations [18]. [PERSON] and [PERSON] (2020) investigated color efficacy in perceived luxury and preference to remain using eye-tracking methodology. They studied the collective emotional, cognitive, and behavioral effects generated by the combination of colors applied to space.