# Trust Model of Privacy-Concerned, Emotionally Aware Agents in a Cooperative Logistics Problem
## 2 State of the Art  
### Computational Representation of Emotions  
There is no consensus in the academic literature as to how emotions can be categorized or how emotions arise and are applied [2]. The simplest classifications distinguish either six (anger, disgust, fear, joy, sadness and surprise [3]) or eight (trust, fear, surprise, sadness, disgust, anger, anticipation and joy [4]) basic/primary/inmate emotions. Howeverwhen emotions are limited to facial expressions, the authors of [5] reduced them to four instances: anger, sadness, fear, joy and surprise. A more fine-grained representation [6] includes secondary emotions that result from the evaluation of expectations, such as relief or hope. The adoption of these emotions in an affective state (called mood) involve at least one dimension: the pleasure it generates (called valence), which can be either a positive (good/pleasant) or negative value (bad/unpleasant). The most complete categorization is the so-called OCC (based on name of its authors) cognitive theory [7], which distinguishes emotions according to the source: events, agents or objects. A human/agent is in a particular mood when they feel an emotion with sufficient intensity, which decreases over time. Therefore, many formalizations [8; 9] include at least a second dimension, noted as arousal, which represents the (positive) level of intensity/excitement regarding the given emotion. But the most widely used model, known as the PAD (pleasure, arousal and dominance) model [10], includes a third dimension: dominance. The PAD model represents the level of control felt by the human/agent in facing the current situation. A positive value indicates that the human/agent is dominant (in control of the emotion), and a negative value indicates that the human/agent is submissive to it. In the PAD model, an emotion is represented by a point in three-dimensional space. A mood is adopted when a given emotion exceeds a given threshold and decreases over time (a forgetting curve) depending on the personality of the human/agent. Unlike mood, personality is not temporal and does not depend on the occurrence of a particular event/context. The most extended theory [11] of personalities considers five factors: openness, conscientiousness, extroversion, neuroticism and agreeableness, whereas a another popular personality theory [12] considers just three factors: extroversion, neuroticism and psychoticism. Extroversion is linked to increased display, sensitivity and duration of positive emotions, whereas neuroticism has a similar effect but with respect to negative emotions [13]. Additionally, neuroticism is associated with a reduced ability to focus attention to complete tasks [14] jointly with an aversion to novelty and uncertainty [15]. Psychoticism traits are associated with rejection of cultural norms and non-compliance with social expectations [16].  
Emotions arise in an uncontrolled way (particularly submissive emotions), producing sudden embodied effects that may be observed physically [6; 17]. Several previously described anthropomorphic systems employ fully embodied agents to show emotions, for instance, in physical interactions [18; 19] and in conversations [20; 21]. Overall, the most frequently used method of showing emotions is through facial expressions [22; 23]. Although less used as a way to show and perceive emotions, the gait of humans and embodied agents has also been studied [24; 25]. Additionally, automated detection of human emotions has raised considerable privacy and legal concerns [26; 27] that are not addressed in this contribution.