# FaceReader Insights into the Emotional Response of Douro Wines
## 3 Results and Discussion
### Statistical Grouping Analysis  
A principal component analysis (PCA) was carried out to categorize and understand patterns within the emotional responses. This allows the grouping of wines based on the emotions they elicit. By visualizing how different wines cluster together according to the emotional responses they evoke, it is possible to identify similarities or relationships among the various variables. Figure 4 presents an explanatory graphic derived from PCA, illustrating how white, red, and Port wines from Douro are aligned based on the specific emotions they evoke. Figure 4 presents three clear groups based on wine types: white, red, and Port wine, consistent with the results in Figure 2. To identify the structure of relationships among the observed data, a principal component analysis (PCA) was performed. The first principal component explains 75.15% of the total variance, and the second explains 24.85%. Together, these two components capture the emotional responses elicited by the different wine types. White wines evoke stronger and more diverse emotional reactions, as they are freshening and acidic wines linked to the aromatic compounds produced during grapevine metabolism, including terpen, norisoprenoids, benzene derivatives, and C6 alcohols [42]. [PERSON] and [PERSON] [43] suggest that emotional responses are often shaped by physiological factors (hunger, satiation, and physiological reward mechanisms), psychological factors (age, expectations based on previous experiences, memory and habit formation, emotional coping mechanisms, restrained eating tendencies or personality traits such as manic-depressive tendencies), and sociological factors (economic status, social nature of the eating situation, or eating culture). Emotional state influences how pleasant food is, and the effect  
Figure 3: Arousal elicited by the wine per gender. (**a**) WW1; (**b**) WW2; (**c**) RW1; (**d**) RW2; (**e**) PW1; and (**f**) PW2. varies between new and familiar foods [30]. For instance, sweetness is commonly linked to positive emotions, whereas bitterness can provoke negative feelings [44,45]. Furthermore, flavors such as salty and sour can trigger many emotions, including surprise, sadness, and fear. Port wines, while not as strongly associated with emotional diversity as white wines, show a notable connection to happiness, surprise, and fear. These wines, known for their sweetness and richness, evoke a heightened response to the emotion of surprise, which could be attributed to their complex flavor profiles and the contrast between sweetness and other flavor dimensions, such as bitterness or alcohol warmth. Port wines may elicit more reflective or bittersweet emotions, possibly due to the more profound, more contemplative experience they provide. The sociocultural context in which Port wines are typically consumed, often in relaxed or celebratory settings, could also influence the emotional responses associated with them. Studies on multisensory food and drink experiences have shown that wine's sensory complexity can evoke surprise when unexpected flavor contrasts, such as between sweetness and bitterness, are encountered [46,47]. On the other hand, red wines occupy a separate cluster in the PCA plot, suggesting an absence of emotional triggers. Away from variables related to emotions like happiness, anger, or sadness, red wines appear to evoke more neutral or subdued emotional reactions. This could be due to the tannic or astringent properties commonly found in red wines, which may lead to a more restrained emotional response. Tannins, which contribute to the mouth-drying sensation, are a significant component in red wine and can lead to a perception of astringency. This drying and puckering sensation is primarily a result of tannin binding with salivary proteins, leading to the aggregation of protein-tannin complexes that heighten this sensation.