## 5 The Use of Eye Tracking and FaceReader for Food Products
By evaluating emotions such as happiness, sadness, anger, surprise, fear, and disgust, FaceReader captures consumers' affective experiences during tasting sessions or product interactions [129]. FaceReader assesses emotional responses by analyzing facial expressions triggered by sensory stimuli, including olfactory experiences. Studies have demonstrated its capability to detect nuanced emotional reactions to different scents by measuring expressions linked to emotions such as happiness, surprise, or disgust [130]. When applied to olfactory research, the FaceReader can correlate specific scent exposures with emotional responses, providing insight into consumer preferences and product acceptance [131]. These data are valuable for understanding how taste, texture, or aroma influences consumer acceptance and emotional engagement [132]. Figure 1 illustrates an experimental design to evaluate the emotions elicited by different Douro wine samples. Further studies have highlighted the role of FaceReader in other areas, such as measuring emotional responses to food products through health claims. An experiment on extra-virgin olive oil showed that claims associated with high clarity increased perceived product healthiness and arousal, positively influencing consumer intentions [130]. Similarly, research on wine tasting underscored the effectiveness of FaceReader in detecting nuanced emotional responses associated with specific flavor profiles [133]. Several studies have identified key differences between traditional sensory evaluation and consumer research methods [120; 129; 133]. Traditional sensory analysis typically focuses on objective attributes such as taste intensity, texture, and chemical composition, relying on trained panels to assess product characteristics [120]. In contrast, consumer research incorporates emotional and psychological responses, providing a more holistic understanding of consumer preferences [134]. [PERSON] and [PERSON] [129] found that the sweetness and acidity of Douro wines elicited emotions like happiness and surprise, highlighting how sensory experiences shape consumer preferences and guide product optimization. By integrating FaceReader with traditional sensory evaluation methods, food companies can develop products tailored to elicit positive emotional responses, increasing consumer satisfaction and brand loyalty. In addition, FaceReader software can be applied as a neuromarketing tool to compare the olfactory preferences of customers in selected markets [131]. Eye tracking and FaceReader offer a complementary approach to sensory and consumer research. Eye tracking provides objective, visual data on consumer attention, while FaceReader captures the emotional engagement associated with product experiences. Combining these technologies enables a comprehensive understanding of how food products are perceived and how emotional responses correlate with visual attention. This integrated methodology is valuable for evaluating new product concepts, optimizing packaging design, and tailoring marketing campaigns to align with consumer preferences. Despite their advantages, these technologies also present several challenges (Table 1). For example, eye tracking requires specialized, high-cost equipment and controlled environments, which may limit its application in real-world settings. Similarly, FaceReader (facial recognition) has its limitations. The reliance on facial expressions as indicators of emotion  
Figure 1: The experimental scheme evaluated the emotions elicited by different types of Douro wine samples. The co-author, [PERSON], permitted the use of the original picture. can sometimes be influenced by external factors such as cultural differences, individual mood, or social context, potentially affecting the accuracy of emotional interpretations. Integrating eye tracking and FaceReader into food product research offers a new perspective on consumer behavior, attention, and emotional responses.