Affective Conversational Agents: the Role of Personality and Emotion in Spoken Interactions

203 Chapter 9 Affective Conversational Agents: The Role of Personality and Emotion in Spoken Interactions Zoraida Callejas University of Granada, Spain Ramón López-Cózar University of Granada, Spain Nieves Ábalos University of Granada, Spain David Griol Carlos III University of Madrid, Spain ABSTRACT In this chapter, we revisit the main theories of human emotion and personality and their implications for the development of affective conversational agents. We focus on the role that emotion plays for adapting the agents’ behaviour and how this emotional responsivity can be conveniently modified by rendering a consistent artificial personality. The multiple applications of affective CAs are addressed by describing recent experiences in domains such as pedagogy, computer games, and computer-mediated therapy. 1 INTRODUCTION to the credibility and motivation of agent based interfaces and its positive effect on the users’ Conversational agents (CAs) represent a higher attitude towards the system (Lester et al., 1997). level of intelligence with respect to traditional However, as Picard (2003) highlights, the more spoken interfaces as, especially in the case of complex the system, the more complex the user’s embodied conversational agents (ECAs), they demands and when CAs are highly realistic but fail foster the so-called “persona effect”, which refers to sufficiently simulate humans, they may have a negative effect on the users, a phenomenon called DOI: 10.4018/978-1-60960-617-6.ch009 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Affective Conversational Agents “uncanny valley” (Beale & Creed, 2009). Thus, significant insight into the emotion science. A it is important to endow CAs with emotional and relevant example is Darwin’s evolutional expla- socially rich behaviours to make more natural nation for emotional behaviour (Darwin, 1872), and compelling interactions possible and meet with which he gave evidence of the continuity of the users’ expectations. emotional expressions from lower animals to hu- Emotions provide an additional channel mans, and described emotions as being functional of communication alongside the spoken and to increase the chances of survival. According to graphical exchanges from which very valuable Plutchik (2003, chapter 2), one of the implications information can be obtained in order to adapt of these findings is that research in emotion was the CAs’ behaviour (Ball, 2003). In contrast with expanded from the study of subjective feelings the Descartian concept of rational intelligence, to the study of behaviour within a biological and psychologists have introduced the term emotional evolutionary context. intelligence to describe the necessary emotional Based on the evolutionary perspective, Rolls processing to tailor our conducts and cognitions to (2007, chapter 2) states that genes can specify our environment. To endow CAs with emotional the behaviour of animals by establishing goals awareness makes it possible to recognize the instead of responses. According to Rolls, these user’s emotions and adapt the agent functionalities goals elicit emotions through reward and punisher to better accomplish his/her requirements. Stern evaluation or appraisal of stimuli. Due to a process (2003) also provides empirical evidence that if a of natural selection, animals have built receptors user encounters a virtual character that seems to for certain stimuli in the environment and linked be truly emotional, there is also a potential to form them to responses. Rolls suggests several levels emotional relationships with each other. of complexity of such mechanism, in the most Additionally, the similarity-attraction principle complicated, the behaviour of humans is guided states that users have a better attitude toward agents by syntactic operations on semantically grounded which exhibit a personality similar to their own. symbols. Thus, personality plays a very important role on Other authors have adopted a physiological how users assess CAs and their willingness to perspective by studying how subjective feelings interact with them. In the same way as humans are temporally related to bodily changes such as understand other humans’ behaviour and react heart rate, muscle tension or breathing rate. Some accordingly to it in terms of the observation of authors, leaded by the seminal work by James everyday behaviour (Lepri et al., 2009), the per- (1884), argue that humans feel emotions because sonality of a CA can be considered as a relatively they experience bodily changes. According to his stable pattern that affects its emotion expression theory, it is impossible to feel an emotion without and behaviour and differentiates it from other CAs experiencing any physiological change. James’ (Xiao et al., 2005). work was fundamental for the development of studies on autonomic physiological changes in relation to emotion. In Section 4 we will describe 2 BACKGROUND: HUMAN several methods for emotion recognition based on EMOTION AND PERSONALITY such physiological autonomous changes. However, James’ theory was refuted by Can- Many authors in research fields such as psychol- non (1929), who probed that this cause-effect ogy, biology and neurology have proposed differ- relationship was not possible and pointed out a ent definitions of the term emotion from a diversity more plausible sequence of events: the perception of perspectives, each of which has contributed of a situation gives rise to an emotion, which is 204 Affective Conversational Agents then followed by bodily changes. Cannon was corroborate that older individuals regulate their interested not only in the behavioural and physi- emotions more frequently, especially in the case ological correlates of emotion, but also on the of negative affect. Personality also affects emo- neural correlates which indicate how emotions tion perception and expression. Although there is are represented within the brain. no universal definition of personality, it can be Heath, Cox and Lustick (1974) pointed out described as a complex organization of mental that all major parts of the brain participate in and biological systems that uniquely character- emotional states. As described in (Fox 2008, ize an individual’s behaviour, temperament and chapter 1) recent research indicates that different emotion attributes. brain circuits control different aspects of emotion Fox et al. (2008) argue that personality pre- and many brain areas involved in emotion also dicts emotional expression both in general and participate in a range of other functions. Emotion in particular scenarios, concretely they studied is highly related to cognition; in Section 3 we will public and private interaction. Larsen and Ketelaar study the implications of such relationships for (1991) have detected that extraversion is associ- modelling affect in CAs. ated with an increased responsivity to controlled For a long time, introspection has been the main inductions of positive (but not negative affect), way of emotional research so that psychologists whereas neuroticism would be associated with an have based their work on self reports of emotions. increased responsivity to controlled inductions However, as discussed in (Fox 2008, chapter 2), of negative (but not positive) affect. In Section such subjective reports are generally not reliable. 5, several applications of CAs using personality As Freud claimed, emotions are complex inner models to modify their emotional behaviour are states subject to repression and modification for described. conscious as well as unconscious reasons. Thus, it Additionally, personality does not only influ- is necessary to have information about the causes ence emotion perception and reaction, but also of emotion, as they can be elicited by the pres- modulates neural mechanisms of learning (Hooker ence of non conscious stimuli which cannot be et al., 2008), which for example has a deep im- described with self reports. As will be addressed pact on intelligence and academic performance in Section 3, the representation of emotion in (Rindermann & Neubauer, 2001). CAs is usually based on models of the emotions’ causes and appraisals. Several attempts have been made to identify the 3 REPRESENTATION OF EMOTION nature of eliciting situations. For example, Rose- AND PERSONALITY IN CAS man, Spindle and Jose (1990) proposed five types of appraisals of events which determine which 3.1 Basic Emotions and particular emotional responses are appropriate. Personality Traits Kentridge and Appleton (1990) suggested that the suitability of emotional responses and expression As explained in (Plutchik 2003, chapter 4), one is assessed by humans to reduce the possibility of the difficulties of reporting and understand- of an undesirable event or increasing the chances ing emotion is that we assume that the listener of a desirable event, which demands sufficient understands the terms we use when describing cognitive capacities to predict future events. affect because of similar experiences and through Additionally, emotional expression is influ- empathy. However, it might not be so, precisely enced by individual characteristics such as age. because of the inaccuracy of self reports, for For example, Scheibe and Carstensen (2010) example due to stimuli out of conscious aware- 205 Affective Conversational Agents ness. Additionally, there are words that describe Regarding personality, it describes what it is similar states, which are

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