1. Believability and expectations BACKGROUND Believability is a form of judgment associated to specific emotional and behavioral reactions. It is especially in the framework of fictional virtual entities that the need for a characterization of the notion of believability arises. When we consider a certain experience as believable we do not necessarily consider the experience as being true, in the sense of being an experience with real, existing objects. Neither we consider that experience as being susceptible of becoming true of the real world, either in the future, as show by the fact that fictional characters can be considered as believable. ‘Un-believable’ has a different meaning than ‘un-true’ because the judgment of un-believability implies impossibility and not only falsity: something which is judged as un-believable is something that can’t be as it appears (to perception or reasoning). Hence, the judgment of believability is a judgment of possibility or impossibility, at least within a certain context (such as the one represented in the virtual or fictional world). A believable experience is not necessarily the experience of something real or existent. A believable experience does not necessarily resemble to an experience with real or existent entities, at least not in the sense that believable entities simulate the physical aspect and behavior of real entities. The conditions that trigger believability are hence not necessarily coincident with reality or realism; furthermore, phenomena such as the so-called Uncanny Valley effect suggest that realism as simulation could present disruptive effects upon believability. Also, when an experience is judged as believable, the subject does not necessarily experience an illusion of reality but he is simply into the condition of acting and reacting as if the virtual or fictional world was true. The situation resembles much more to a game of make-believe rather than to an illusion of reality. In fact, the reactions in fictional and virtual interactions are never exactly the same as those expressed in the interaction with real worlds. One significant condition for triggering believability seems to be represented by the respect of the users’ or audience’s expectations. In fact, when expectations are unfulfilled by a certain experience, and they are not revised or modified, the subject can experience a violation of coherence or conflict. Coherence is a regulatory principle for the cognitive system and violations of coherence are perceived as impossible conditions. It can be hence hypothesized that the experience that mismatches with expectations is un-believable because if it were true a conflict or violation of coherence would arise, an impossible situation which is unacceptable for the cognitive system. OBJECTIVES Identify the conditions that make an experience with virtual or fictional entities believable even in absence of simulation of the phenomenological aspect and behavior of real entities. Fictional and virtual worlds constitute a vast domain: narrative, films, dramatic arts in general ad VR in its different declinations. A good characterization of the notion of believability should apply to all these situations, and to believability in the real world too. In order to respond to the requirement of generality, the characterization of the notion of believability should be minimalist: provide the minimal necessary conditions for believability and eventually provide the rules for producing believability in different situations. In this way, general characteristics of instruments for testing believability can be indicated that are valid for all kinds of situations. METHODS Characterize the notion of expectation Describe different forms of expectations in respect to Their behavioral and emotional reactions With special attention for the reaction of surprise Their relationship with automatic/conscious mental states and processes Their relationship to different types of knowledge Describe the effect of expectations upon believability through the description of the Effects of violation of expectations upon adaptive behavior Effects of the violation of expectations upon epistemic judgments Describe the ways in which expectations can be acquired, generated, activated and de-activated Indicate the conditions for testing believability in terms of expectations and the factors for enhancing believability by the suitable activation/de-activation of expectations. DISCUSSION Expectation can be characterized in relation to the reaction of Surprise. When an event produces that has never been experienced before two reactions can be observed in people: they are surprised by the event or they just accept the event and integrate the informational contents it represents. If someone is surprised, it means he was holding some expectation concerning that event that do not match with the event as it has produced. Expectations are hence necessary in order to justify the reaction of surprise and surprise can be characterized as being the reaction to the frustration of an expectation (Davidson, 2004). Expectations can be expressed in the form of anticipations, at least après- coup - after that a certain state of affairs has provoked a reaction of surprise and hence alerted the subject to the fact that he must have entertained a certain expectation or at least one or more expectations from which the unfulfilled expectations can be derived (1). (1) Davidson, D. (2004). Problems of rationality. Oxford: Clarendon Press. Dennett, D. C. (2001). Surprise, surprise," commentary on O'Regan and Noe. Behavioural and Brain Sciences, 24(5), 982. DISCUSSION Expectations are in relationship to different forms of knowledge. Expectations based on beliefs have a symbolic nature and are acquired through the acquisition of symbolic knowledge but are not necessarily linguistically expressed or consciously manipulated. They can be based upon scientific or commonsense knowledge of different domains. These beliefs range from very general beliefs concerning the way the world is constituted to specific beliefs concerning the laws that organize our world and the specific entities with which it is filled in. It is proposed here that other forms of expectation exist that do not necessarily have a belief for content or a symbolic nature: expectations based on a form of enactive knowledge, related to the acquisition of motor skills and sensori-motor habits (2) and expectations based on perceptual anticipations, laws of perception, sensori-motor matching activities and inter-sensory connections (3). Non-symbolic expectations can be acquired through selection, habits, statistical learning based on co-activation, training. Non-symbolic expectations can be evinced from the existence of illusions related to the perception of movement or to the role of movement in perception; these illusions give rise to more or less immediate reactions of surprise (4). Non-symbolic expectations that operate at an automatic, sensori-motor level can be considered as forms of representation (sensori-motor representations) or they can be considered as the effect of the existence of forms of connections between perceptual systems or motor and perceptual systems, with no need to make recourse to the notion of representation. (2) Bruner, J. (1966). Toward a theory of instruction. Cambridge, MA: Belknap Press of Harvard University Press. Bruner, J. (1968). Processes of cognitive growth: Infancy. Worcester, MA: Clark University Press. (3) Castelfranchi, C., & Lorini, E. (2003). Cognitive Anatomy and Functions of Expectations. Paper presented at the Proceedings of IJCAI’03 Workshop on Cognitive Modeling of Agents and Multi- Agent Interactions, Acapulco, Mexico. (4) Pasquinelli, E. (2006). An analysis of the notion of illusion and illusory phenomena. PhD Thesis. CONCLUSIONS The experience of the real world is mostly coherent. This might explain why believability represents an objective and a difficulty for the experience with fictional and virtual worlds, while the real world is trivially believable. Violations of coherence have in fact a disruptive effect on believability and the judgment of un-believability is related to the sense of wrongness or surprise that arises from the awareness that coherence has been violated. The respect of the different types of expectations entertained by the subject is a crucial condition for enhancing believability. For this reason indications for designing believable fictional or virtual worlds consist in: The identification of the methods for the activation and de- activation of expectations; The constitution of a data-base of commonsense beliefs; The suitable investigation of perceptual and motor processes that give rise to non-symbolic expectations. DISCUSSION The judgment of believability concerns some specific expectations that are activated in the course of the experience. Expectations can be the acquired through long-term, repeated experiences or be created during a specific experience. A class of expectations can be described that are not entertained by the subject but play an active role in the cognitive functioning, and specifically on surprise reactions: volatile expectations are generated from beliefs and entertained expectations by the context of the experience and eventually by the goals of the subject (6). Context of the experience (including the contents of the experience at all levels and the characteristics of the medium) and the presence of goals have an activating effect also on entertained (non-volatile) expectations (7). In fact, not all the expectations that are entertained have an effect upon the cognitive functioning and upon believability but only active, relevant expectations. Non relevant expectations can be de-activated by suitable mechanisms or simply non-activated by the context-goal situation. In the experience with fictional and virtual worlds, the activation and de-activation of expectations can be suitably manipulated in order to enhance believability and to overcome technological limitations. Expectations can be activated and de-activated at three levels: narrative, perceptual and motor-perceptual or interactive. Enactive and sensori-motor expectations are particularly relevant for the experience with enactive interfaces. (6) Casati, R., & Pasquinelli, E. (Forthcoming). How can you be surprised? The case for volatile expectations. In A. Noe (Ed.), Hetherophenomenology and Phenomenology, special issue of Phenomenology and the Cognitive Sciences. (7) Castelfranchi, C., & Lorini, E. (2003). Cognitive Anatomy and Functions of Expectations. Paper presented at the Proceedings of IJCAI’03 Workshop on Cognitive Modeling of Agents and Multi-Agent Interactions, Acapulco, Mexico. DISCUSSION The violation of expectations and of coherence breaks believability in the experience. We can consider the violation of expectations as a form of violation of coherence. Violations of coherence are esteemed to present a negative adaptive value, because they have the effect of blocking action and of imposing cognitive re-organization and for this reason many mechanisms are put in place for avoiding them (5). Coherence can hence be considered as to represent a regulatory principle for the cognitive and perceptual system. When coherence is violated the subject is alerted to the presence of something wrong, and a sense of impossibility arises. Even if in some cases the error cannot be precisely individuated, the alert to the presence of some error represents an epistemic value because the subject can put in action subsequent further exploration in order to individuate the error and take suitable decisions. The epistemic component of the awareness of coherence violation and of surprise is responsible for the disruption of believability. When an expectation conflicts with another expectation or with current experience and surprise arises, in fact, there are three possible consequences: The invalidating belief based on current experience is accepted as true, and the belief which is contained in the expectation is revised; The invalidating belief is not accepted, but the belief contained in the expectation is maintained. This case can give rise to a judgment of impossibility or un-believability of the invalidating belief. Finally, the subject cannot say which of the conflicting expectations is true or false, he only knows that something must be wrong, hence, that the whole experience is un-believable. Un-believability is hence not the only possible consequence of surprise and of the alert to error, but requires special conditions that preclude the revision of past expectations or the solution of a discrepancy. (5) Bruner, J., Postman, L. (1949). On the perception of incongruity: A paradigm. Journal of Personality, 18, 206-223. Stein, B. E., & Meredith, M. E. (1993). The merging of the senses. Cambridge, Mass.: MIT Press. Elena Pasquinelli Institut Jean Nicod - EHESS SUGGESTIONS It is suggested that suitable tests are put in place in order to evaluate the following hypotheses: Expectations derived from different forms of knowledge have a different strength (their violation provokes more or less un- believability) and stability (they can be more or less easily de- activated, for instance by suitable manipulations of the context). Repeated experiences with virtual worlds modifies the expectations that are hold during the experience of a virtual world, as it has been the case for more traditional media. The general methodology for testing the indicated conditions consists in the setting of an experience with virtual objects or virtual agents which is considered as believable by the participants to the experiment. Since believability is a form of judgment, a subjective assessment can be employed that measures believability in terms of possibility/wrongness, internal coherence/violation of internal coherence, respect of expectations/violation of expectations. In view of the fact that a believable experience enables the user to act and react as if the virtual objects and agents were real, objective assessments can be developed which include the measurement of emotional and psychophysical responses and the evaluation of the suitability of the actions of the subjects in respect to the characteristics of the represented object. Once a robustly believable experience is individuated, the conditions of believability are stretched in different directions (simplification, exaggeration) and in relationship to the different forms of expectations indicated in the discussion. The stretched conditions are re-tested following the subjective and behavioral methods employed for the first part of the experiment on the same subjects and on a new group of subjects following training with the virtual setting. Contact addresses: Elena.Pasquinelli@ehess.fr elena.pasquinelli.free.fr www.institutnicod.org