Actual lively interaction between humans is based on active communication using language, non-verbal gestures and emotions. Artificial companions are already capable of using language as a mean of communication with humans. Emotions are not well exhibited by artificial agents. Affective communication and empathy is highly recommended for realistic and long interactions. LIREC and many other researchers focus on implementing affective and emotional agents using certain frameworks and systems to model emotions and their relations to behaviors and actions.

Empathy is a feeling evoked as a result of a person attending and understanding the emotional expression of another person. It is one of the methods used by humans to maintain a relationship Bickmore & Picard (2003). Social agents that are humans-relations inspired could also use empathy as part of their communication and interaction methods. Virtual and social agents have already been acting empathetic with other agents and humans. As an example, the use of empathetic characters offers great advantages in children educational software applications. These interactive characters can autonomously act according to their own state and emotions resulting in unlimited possibilities of behaving and predictability of their actions would be minimized while the believability increases. Reaching such autonomous and empathetic characters requires the implementation of an emotional framework as Thomas and Johnston put it:” it has been the portrayal of emotions that has given the Disney characters the illusion of life” (Thomas, F., Johnston, O.: Disney Animation: The Illusion of Life. Abbeville Press, New York 1981).

Relating emotions with human behavior and actions is the essence of the appraisal theory. This idea goes back to the old time of Aristotle. It basically describes the appraisal process that is a cognitive process in which an individual generates emotions according to the events in the environment impacting its well being resulting in a subjective judgment on how bad or good an event is (Lazarus 1991). It is agreed upon that there are two types of appraisal. The first appraisal refers to whether the event is relevant to the agent or not. The secondary appraisal refers to coping options if the event was irrelevant to the agent. In order to deal with a threat to the agent’s goal, the agent can either try to plan for an action that will avoid the threat, or one can simply accept that the goal will fail and lower its importance in order to avoid negative feelings about it. Personality affects the coping strategy of the agent just as it does in the case of humans where we all differ in our coping strategies against similar events.

EMA (Gratch, 20004; Gratch 2003; Marsella, 2006) is a computational model that follows the cognitive-motivational-emotive psychological theory (Lazarus, 1991). In this model the appraisal process assesses certain variable to judge the situation and elicit the related emotion. It depends on the perspective of who is the subject experiencing the event and what is the desirability of this event. Who is responsible for causing the event, the temporal status changeability and controllability of the event along with its likelihood all contribute to eliciting the related emotion and its intensity.

After appraising a situation or an event, the agent has to respond to the appraisal by taking or planning for certain actions or changing the agent’s beliefs and hopes. The EMA model includes many strategies to use for coping. The agent can act or plan for an act by itself or by using help and support. In case it can’t induce the appropriate action to do, it can try to reappraise negative events trying to find something positive about them. if there isn’t any positive interpretation for the event then the agent has three choices: either to accept the undesirable and unchangeable threat or to deny the negative appraisal trying to minimize it or to mentally disengage by reducing the desirability of the unachievable goal resulting in reducing the emotional intensity of the event. One last option the agent can still do is to hope and wait for a change in the environment without taking any part in it.

Many theories model emotions and related reasoning. One main and well-known model is the OCC theory (Ortony et al., 1988). Many researchers think of this theory as the ultimate solution to build emotions for synthetic character. It is widely used because the authors developed a computational model for emotions (Bartneck 2002) making it easy to implement in computer science because of its straightforward appraisal theory. Certain aspects of this theory make it reliable and adequate for describing artificial agents emotions. Since the appraisal precedes emotions, it complies with the computational process that precedes eliciting the agent’s emotion to a certain situation. Differences in appraisal account for individual differences that will not restrict the computationally generated emotions to follow one pattern; rather there will be differences in emotional expressions of different agents. At the end of the processing time, appraisal will elicit an emotion that will be expressed by facial expressions or body movements or any other form possible for the agent. OCC defines a group of emotions in 22 categories organized in a specific hierarchy. This model has five main phases to process an event starting with classifying the emotional categories for an event, object or action. The intensities of categories are quantified and used to define the emotional values that will be mapped and expressed by the agent.

Emotions are important to reach a believable and effective interaction with agents. Over long time, the emotional reactions have to comply with the personality of the agent or else the agent would be perceived as randomly reacting. Modeling personality is important aspect to have in long-term companions. The difference between emotions, moods, and personalities is the time periods; emotions last for minutes while moods last for days and weeks but personality lasts for years or lifetime. OCC defines a personality by setting thresholds for emotions so that if the intensity is not higher than the emotion’s threshold it won’t evoke this emotion. This way the same event would be differently reacted to according to the personalities or the set of thresholds of emotions related to this event.