Stacy Marsella

A domain-independent framework for modeling emotion

In this article, we show how psychological theories of emotion shed light on the interaction between emotion and cognition, and thus can inform the design of human-like autonomous agents that must convey these core aspects of human behavior. We lay out a general computational framework of appraisal and coping as a central organizing principle for such systems. We then discuss a detailed domain-independent model based on this framework, illustrating how it has been applied to the problem of generating behavior for a significant social training application. The model is useful not only for deriving emotional state, but also for informing a number of the behaviors that must be modeled by virtual humans such as facial expressions, dialogue management, planning, reacting, and social understanding. Thus, the work is of potential interest to models of strategic decision-making, action selection, facial animation, and social intelligence.

EMA: A process model of appraisal dynamics

A computational model of emotion must explain both the rapid dynamics of some emotional reactions as well as the slower responses that follow deliberation. This is often addressed by positing multiple levels of appraisal processes such as fast pattern directed vs. slower deliberative appraisals. In our view, this confuses appraisal with inference. Rather, we argue for a single and automatic appraisal process that operates over a persons interpretation of their relationship to the environment. Dynamics arise from perceptual and inferential processes operating on this interpretation (including deliberative and reactive processes). This article discusses current developments in a computational model of emotion processes and illustrates how a single-level model of appraisal obviates a multi-level approach within the context of modeling a naturalistic emotional situation.

Toward the holodeck: integrating graphics, sound, character and story

We describe an initial prototype of a holodeck- like environment that we have created for the Mission Rehearsal Exercise Project. The goal of the project is to create an experience learning system where the participants are immersed in an environment where they can encounter the sights, sounds, and circumstances of real-world scenarios. Virtual humans act as characters and coaches in an interactive story with pedagogical goals.

Interactive pedagogical drama

This paper describes an agent-based approach to realizing interactive pedagogical drama. Characters choose their actions autonomously, while director and cinematographer agents manage the action and its presentation in order to maintain story structure, achieve pedagogical goals, and present the dynamic story to as to achieve the best dramatic effect. Artistic standards must be maintained while permitting substantial variability in story scenario. To achieve these objectives, scripted dialog is deconstructed into elements that are portrayed by agents with emotion models. Learners influence how the drama unfolds by controlling the intentions of one or more characters, who then behave in accordance with those intentions. Interactions between characters create opportunities to move the story in pedagogically useful directions, which the automated director exploits. This approach is realized in the multimedia title Carmen’s Bright IDEAS, an interactive health intervention designed to improve the problem solving skills of mothers of pediatric cancer patients.

Toward a new generation of virtual humans for interactive experiences

Virtual humans - autonomous agents that support face-to-face interaction in a variety of roles - can enrich interactive virtual worlds. Toward that end, the Mission Rehearsal Exercise project involves an ambitious integration of core technologies centered on a common representation of task knowledge.

Toward virtual humans

This article describes the virtual humans developed as part of the Mission Rehearsal Exercise project, a virtual reality-based training system. This project is an ambitious exercise in integration, both in the sense of integrating technology with entertainment industry content, but also in that we have joined a number of component technologies that have not been integrated before. This integration has not only raised new research issues, but it has also suggested some new approaches to difficult problems. We describe the key capabilities of the virtual humans, including task representation and reasoning, natural language dialogue, and emotion reasoning, and show how these capabilities are integrated to provide more human-level intelligence than would otherwise be possible.

Tears and fears: modeling emotions and emotional behaviors in synthetic agents

Emotions play a critical role in creating engaging and believable characters to populate virtual worlds. Our goal is to create general computational models to support characters that act in virtual environments, make decisions, but whose behavior also suggests an underlying emotional current. In service of this goal, we integrate two complementary approaches to emotional modeling into a single unified system. Gratchs Émile system focuses on the problem of emotional appraisal: how emotions arise from an evaluation of how environmental events relate to an agents plans and goals. Marsella et al. s IPD system focuses more on the impact of emotions on behavior, including the impact on the physical expressions of emotional state through suitable choice of gestures and body language. This integrated model is layered atop Steve, a pedagogical agent architecture, and exercised within the context of the Mission Rehearsal Exercise, a prototype system designed to teach decision- making skills in highly evocative situations.

Towards a common framework for multimodal generation: the behavior markup language

This paper describes an international effort to unify a multimodal behavior generation framework for Embodied Conversational Agents (ECAs). We propose a three stage model we call SAIBA where the stages represent intent planning, behavior planning and behavior realization. A Function Markup Language (FML), describing intent without referring to physical behavior, mediates between the first two stages and a Behavior Markup Language (BML) describing desired physical realization, mediates between the last two stages. In this paper we will focus on BML. The hope is that this abstraction and modularization will help ECA researchers pool their resources to build more sophisticated virtual humans.

Virtual rapport

Effective face-to-face conversations are highly interactive. Participants respond to each other, engaging in nonconscious behavioral mimicry and backchanneling feedback. Such behaviors produce a subjective sense of rapport and are correlated with effective communication, greater liking and trust, and greater influence between participants. Creating rapport requires a tight sense-act loop that has been traditionally lacking in embodied conversational agents. Here we describe a system, based on psycholinguistic theory, designed to create a sense of rapport between a human speaker and virtual human listener. We provide empirical evidence that it increases speaker fluency and engagement.

Evaluating a Computational Model of Emotion

Spurred by a range of potential applications, there has been a growing body of research in computational models of human emotion. To advance the development of these models, it is critical that we evaluate them against the phenomena they purport to model. In this paper, we present one method to evaluate an emotion model that compares the behavior of the model against human behavior using a standard clinical instrument for assessing human emotion and coping. We use this method to evaluate the Emotion and Adaptation (EMA) model of emotion Gratch and Marsella. The evaluation highlights strengths of the approach and identifies where the model needs further development.