## 3 Materials and Methods
### Visual Attention--Eye Tracking  
The study presented consumers with nine hypothetical products to choose from according to the protocol [8]. Two purchase situations were used for fresh and cooked beef, as well as a combination of information on visual cues including color, marbling, breed, tenderness, flavor, and aroma, in order to evaluate whether visual attention interferes with the probability of consumer choice.  
Two different visual stimuli were created to represent hypothetical products to consumers, a vacuum-packed striploin representing fresh beef and a dish with striploin steak representing cooked beef. The attributes were inserted directly into the images with the same spacing, font size, and image, mitigating the risks of interference in the readability of the information. Each product was compared by occupying the right and left positions to avoid favoring visual field position, and a total of 18 visual stimuli were presented in each purchasing situation. After visualizing the stimulus, the consumer had to indicate which product was their choice (\"product on the right\", \"product on the left\", or \"none of the products\").  
All visual stimuli were presented to participants on Microsoft(r) PowerPoint(r) with standard slide (4:3) maximized and used eye-tracking equipment (Tobii T120, Edge Eye, Stockholm, Sweden) with an integrated monitor, on a 17\" screen with a resolution of 1280 \(\times\) 935 pixels and full-screen adjustment. Before starting the presentation of the images to consumers, the equipment was calibrated for each participant, considering equipment distance and height, to ensure better capture of the field of vision. Calibration was performed according to the manufacturer's recommendations.  
The images were displayed in sequence and the transition time was 10 s. Amongst the transitions, there was a black background image, with the aim of \"cleaning the image\" and preparing the consumer for comparison with the following products. Before being presented to consumers, the areas of interest for capturing visual attention in the images were marked around the quality cues studied, with the geometric shape of identical areas for all attributes, according to Figure 1.  
Eye tracking metrics used were the tree [18]:  
* Time to First Fixation: This refers to the elapsed time until the user's gaze first fixates on a specific area of interest. A shorter time indicates that the visual characteristics of the area are more effective in capturing attention. This metric is particularly valuable when analyzing attention to a specific target [1].
* Fixation Duration: This metric captures the total time and average location of a sequence of fixations within a designated area of interest. It may include multiple fixations and short saccades between them. The fixation sequence is considered complete when the gaze moves outside the area of interest [1].
* Number of Fixations (Visits) on an Area of Interest: A higher number of fixations suggests that the area holds greater significance for the viewer. This measure is closely related to fixation duration and helps assess the total number of fixations in tasks of varying lengths. The number of times an element is fixated on reflects its perceived importance [69; 70].  
A total of 414 observations were collected from the 23 participating consumers (23 participants \(\times\) 18 questions = 414 observations) for each situation. These data were initially used as variables of a Logit regression model, making it possible to find their effects on the choice of the visualized product.  
Figure 1: Areas of interest demarcated: (**a**) cooked beef; (**b**) fresh beef.