###### Abstract
Several techniques are used to evaluate the functionality conveyed by products, such as semantic differential [26], where participants provide subjective judgments on pairs of opposite adjectives (e.g., classic/modern) using a numerical scale. However, Eye-Tracking (ET) technology offers a more objective way to assess how a product communicates functionality by recording a user's gaze position and movement to indicate where their attention is focused [27]. Gaze patterns are quantified through various objective parameters, such as fixations, saccadic movements, and scan paths [28]. ET has been used in evaluating product affordances and usability. [PERSON] et al. [18] explored the affordance of easily opening food packaging by analysing the cognitive load required under conditions of cognitive distraction. They measured gaze diversion and task completion times, demonstrating a relationship between task difficulty and cognitive load. [PERSON] and [PERSON] [29] recorded subjects' gaze while they observed products with innovative designs and used a questionnaire to determine whether participants had perceived the main affordance of each product. They defined the expected interaction area with the product as the area of interest (AoI), such as the bows of a pair of scissors, and analysed the number of fixations, the time to the first fixation, and whether it occurred within the AoI. However, they were unable to demonstrate that participants primarily focused on the expected interaction areas. Instead, their results suggested that affordances could often be perceived by attending only to certain elements of the product and that excessive visual exploration might indicate a lack of clarity in the design. This finding suggests that users do not need to observe the entire product or all its components to perceive its affordance; rather, attention to a few key elements can be enough. [PERSON] al. [30] explored functional affordances of design elements using ET, while [PERSON] and [PERSON]'s [31] focused on usability affordances of tools, finding that fixation duration indicated greater attention on manipulation areas compared to other parts of the tools. Similarly, [PERSON] et al. [32] investigated the relationship between ET metrics and user experience in product evaluation using smartphone pictures as stimuli. They found that products with a higher perceived user experience elicited a shorter time to first fixation, indicating quicker attentional capture. These studies support the use of ET to explore how users perceive and evaluate product usability. However, they also reveal methodological challenges and highlight that attentional patterns do not always directly reflect affordance perception. Despite these insights, research on affordance analysis through ET remains limited, particularly in ADs for manipulation tasks. The primary objective of this study is to explore the effectiveness of ET technology as a tool for assessing the usability affordances of a specific category of ADs: those designed for jar opening. This study examines the role of rubber in the grip area as a signifier for various aspects of usability by comparing on-screen assessments of ADs with and without rubber. Heatmaps are used to identify other design elements acting as signifiers. Additionally, correlations between ET metrics and on-screen assessments are used to identify metrics that effectively gauge the usability of jar-opening ADs. Finally, on-screen assessments are compared with evaluations conducted after physically using the real devices to reinforce ET's potential in analysing usability affordances. By addressing these objectives, this work seeks to contribute to product usability assessment by confirming the potential of ET technology and providing quantifiable metrics. Moreover, it highlights the suitability of ET for early-stage design evaluation, offering objective insights to guide design decisions.