ANNOTATED BIBLIOGRAPHY

This list attempts to provide a broad survey of the literature in the area of believable agents, ranging from the animation issues to models of emotion and cognition. It is by no means a complete list, and many if not most of these authors have more work available on the subject. However, we felt that it is representative of much current work and a good starting point for reading.

Comments and suggestions are most welcome at pdoyle@cs.stanford.edu.

Annotated Bibliography

  1. L. Abbott. Active Acting: Exercises and Improvisations Leading to Performance. Star Publishing Company: Belmont, CA, 1987. See also: Johnstone, 1992; Nachmanovitch, 1991.

  2. E. Andre, Ed. Notes of the IJCAI-97 Symposium on Animated Interface Agents: Making Them Intelligent, Nagoya, Japan, Aug. 1997. Representative survey of current work on animated agents, covering issues in effective presentation, affective modeling, social impact, and character design. See also: Lester et al., 1997; Elliott et al., 1997.

  3. N. Badler, "Real-Time Virtual Humans," in Proc. 1997 Pacific Graphics Conf., Seoul, Korea, 1997. Survey of issues in creating real-time animated human figures, with focus on design of Jack architecture and discussion of systems that employ it. Used by: Rickel and Johnson, 1997. See also: Smith et al., 1997.

  4. G. Ball, D. Kurlander, J. Miller, D. Pugh, T. Skelly, A. Stankosky, D. Thiel, M. Van Dantzich, and T. Wax, "Lifelike Computer Characters: the Persona Project at Microsoft Research," in Software Agents, J. Bradshaw, Ed. AAAI Press: Menlo Park, CA, 1997. Overview of Microsoft work on building animated, conversational assistants. Focus on Peedy, a parrot that processes spoken requests for music. Emphasis on technical issues (e.g., voice recognition, animation, etc.). See: Lester et al., 1997b; Rist et al., 1997.

  5. J. Bates, A. B. Loyall, and W. S. Reilly, "Integrating Reactivity, Goals, and Emotion in a Broad Agent," in Proc. 14th Ann. Conf. of the Cognitive Science Society, Bloomington, IN, July 1992. Describes the Oz architecture, especially the interface between its emotion model and action-selection system. Brief, but useful introduction to issues in the use of emotion to drive behavior. Elaborated in: Bates et al., 1992b.

  6. J. Bates, A. B. Loyall, and W. S. Reilly, "An Architecture for Action, Emotion, and Social Behavior," Tech. Report CMU-CS-92-142, School of Computer Science, Carnegie Mellon University, Pittsburgh, July 1992. Describes the Oz architecture, including its reactive action planner (Hap) and emotion model (Em). Analyzes a sample interaction between a user and Lyotard, an agent with simple emotional intelligence. Good introduction to technical problems of building emotional intelligence. Extends: Bates et al., 1992a.

  7. J. Bates, "The Nature of Characters in Interactive Worlds and The Oz Project," Tech. Report CMU-CS-92-200, School of Computer Science, Carnegie Mellon University, Pittsburgh, Oct. 1992. Summarizes the Oz project's motivation and goals. Discusses possible types of interaction between users and believable agents. Primarily of historical interest.

  8. J. Bates, "The role of emotion in believable agents," in Comm. of the ACM, vol. 37(7), pp. 122-125, July 1994. Summarizes techniques Disney animators used to convey emotion in animated characters. Illustrates derivative heuristics for interactive agents with the "Edge of Intention" system. Widely cited introduction to artistic antecedents and resources for technical audience. See: Thomas and Johnson, 1981.

  9. B. Blumberg, "Action-Selection in Hamsterdam: Lessons from Ethology," in Proc. Third Int. Conf. on Simulation of Adaptive Behavior, Brighton, England, 1994. Presents computational model of agent behavior based on biological factors, e.g. hunger, fear. Interesting alternative to psychological and artistic metaphors.

  10. B. Blumberg, "Old Tricks, New Dogs: Ethology and Interactive Creatures." Ph.D. Thesis, Media Lab., Massachusetts Inst. Technol., Cambridge, MA, 1996. Presents an ethnologically-inspired architecture for synthetic characters. "Silas T. Dog" incorporates virtual vision, learning, and simple goals/motivations in animated agent. First chapter provides excellent motivation for building believable characters in general. Extends: Blumberg, 1994.

  11. P. Curtis, "Mudding Social Phenomena in Text-Based Virtual Realities," in Proc. 1992 Conf. on Directions and Applications of Advanced Computing, Berkeley, CA, May 1992. Describes the origin and user activities of LambdaMOO, the most famous of the text-based virtual worlds. Focuses on social phenomena, e.g. community building, interpersonal relations, conflict resolution. Widely cited classic reference.

  12. P. Doyle and B. Hayes-Roth, "Guided exploration of virtual worlds," in Network and Netplay: Virtual Groups on the Internet, F. Sudweeks, Ed. MIT Press: Cambridge, MA, 1997. Introduces concept of "annotated environments" that encode structured domain descriptions in virtual worlds for use by intelligent agents. Emphasis on increasing agent believability through enhancing domain intelligence. Sample dialogs in educational children's environment. Extended by : Doyle and Hayes-Roth, 1998. See also: Norman, 1993.

  13. P. Doyle and B. Hayes-Roth, "Annotating Virtual Worlds," in Proc. 1998 Virtual Worlds and Simulation Conf., San Diego, CA, Jan. 1998, pp. 195-200. Details of possible annotations of virtual spaces to support believable agent intelligence. Draws parallels with HCI concepts of affordance and natural design. Several examples drawn from educational text world. Extends: Doyle and Hayes-Roth 1997a. See also: Norman 1993.

  14. C. Dyer, "Interpersonal goals and satisfaction with interactions." Ph.D. Thesis, Dept. of Communications, Stanford Univ., Stanford, CA, 1993. Provides evidence that people seek out more interaction with people whose personalities complement (rather than resemble) their own. Complementary means opposite on dominance/submissiveness axis and similar on affiliation index.

  15. L. Egri, The Art of Dramatic Writing. Simon & Schuster: New York, 1949. Discussion of effective techniques for writing drama, particularly applicable to scripts and playwriting.

  16. C. Elliott, "The Affective Reasoner: A Process Model of Emotions in a Multi-Agent System." Ph.D. Thesis, The Institute for the Learning Sciences, Northwestern Univ., 1992. Thesis presents comprehensive computational model of emotion and reasoning system based on work of Ortony, Clore, and Collins. Agents reason about one another through emotional models, including expectation, conflicting emotion, and relationships. Widely cited system. Extended by: Elliott, 1993; Elliott, 1997a, 1997b. See also: Elliott, 1995; Elliott, 1997c.

  17. C. Elliott, "Using the affective reasoner to support social simulations," in Proc. 13th Int. Joint Conf. on Artif. Intell., Chambery, France, Aug. 1993. Summarizes Affective Reasoner architecture. Discusses issues involved in creating distinct emotional personalities in that system. Demonstrates both flexibility and limitations of system and underlying theory. Best high-level technical view of Affective Reasoner. Extends: Elliott, 1992.

  18. C. Elliott, "Research problems in the use of a shallow Artificial Intelligence model of personality and emotion," in Proc. 12th Natl. Conf. on Artif. Intell., Seattle, WA, Aug. 1995, pp. 9-15. Presents open research issues in building computational models of emotion. Examples of affective user modeling and using emotions to model relationships. Argument for emotional intelligence to create believable characters. Extensive references to literature.

  19. C. Elliott, J. Lester, and J. Rickel, "Integrating Affective Computing into Animated Tutoring Agents," in Notes of the IJCAI '97 Workshop on Animated Interface Agents: Making Them Intelligent, Nagoya, Japan, Aug. 1997, pp. 113-121. Describes approaches to integrating Affective Reasoner into existing agent systems. Examples of enhancing didactic value of characters through use of emotion. Creatively ties together three large projects. In: Andre, 1997. See also: Lester et al., 1996; Rickel and Johnson, 1997.

  20. C. Elliott, "I Picked Up Catapia and Other Stories: A Multimodal Approach to Expressivity for 'Emotionally Intelligent' Agents," in Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 451-457. Study using emotional expressivity to disambiguate spoken speech. Emotionally intelligent agents outperform human actors in clearly conveying intended emotions. Interesting motivation for incorporating emotion into agents beyond characters. Expands on: Elliott, 1992.

  21. C. Elliott, "Hunting for the Holy Grail with ‘emotionally intelligent’ virtual actors," to appear in ACM Intelligence. Presents broad, shallow emotional model for building entertainment agents. Examples of affective impact in storytelling. Describes "virtual actor" experiments with Affective Reasoner. Broadest survey of Elliott's work. Extends: Elliott, 1997a.

  22. S. Fiske and S. Taylor, Social Cognition. McGraw-Hill: New York, 1991. Chapter 7 discusses people’s desire to use schemas in dealing with one another in order to predict/understand behavior.

  23. L. Foner, "What's An Agent, Anyway? A Sociological Case Study," Agents Memo 93-01, M.I.T. Media Lab., Massachusetts Inst. Technol., Cambridge, MA, May 1993. Categorizes agency in terms of social abilities and groundedness in context. Lengthy transcripts of an agent, Julia, interacting with users in a text-based virtual world. Emphasis on believability. A classic paper on agency and believability.

  24. D. Goleman, Emotional Intelligence. Bantam Books: New York, 1997. Defines and compares rational vs. emotional behavior. Explores skills of "emotional intelligence," and argues it is key to human success, rather than simply rational thinking.

  25. B. Hayes-Roth, L. Brownston, R. Huard, B. Lent, and E. Sincoff, "Directed improvisation," Tech. Report KSL-94-61, Knowledge Systems Lab., Stanford Univ., Stanford, CA, Sept. 1994. Implementation and operations of directed improvisation system. Description of agent designs in CAIT. Best introduction to early Virtual Theater work.

  26. B. Hayes-Roth, "Directed Improvisation: A New Paradigm for Computer Games," in Proc. 9th Computer Game Developers' Conf., Santa Clara, Apr. 1995, pp. 36-43. Application of Virtual Theater "improv puppets" to computer games. Overview of CAIT system describes potential uses of semi-autonomous characters as avatars or other characters in games. See also: Hayes-Roth and van Gent, 1996.

  27. B. Hayes-Roth, "Agents on Stage: Advancing the State of the Art in AI," in Proc. 1995 Int. Joint Conf. on Artif. Intell., Montreal, Canada, Aug. 1995, pp. 967-971. Argument that AI should take a comprehensive approach to building intelligent agents, and that interactive characters is a promising area as it demands integration of all major components. Position paper rather than technical.

  28. B. Hayes-Roth, R. v. Gent, and D. Huber, "Acting in character," in Creating Personalities for Synthetic Actors, R. Trappl and P. Petta, Eds. Springer-Verlag: Berlin, 1997. Casts improvisational drama in computational terms. Detailed examination of master-servant status scenarios according to personality and status variations of autonomous characters. Good bridge between improvisation literature and computation.

  29. B. Hayes-Roth and R. van Gent, "Improvisational Puppets, Actors, and Avatars," in Proc. Computer Game Developers' Conf., Santa Clara, 1996, pp. 199-208. Applications of improvisational computer puppets and actors to computer gaming. Discussion of "improv avatars" as intelligent combination of computer- and user-control of avatars in multi-player environments. Speculations about future avatar design. See also: Hayes-Roth 1995a.

  30. B. Hayes-Roth and R. van Gent, "Story-Making with Improvisational Puppets," in Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 1-7. Short survey of Virtual Theater work on "improv puppets." Brief summary of developmental psychology experiments using puppets, relation to other Virtual Theater work. See also: Hayes-Roth et al., 1994.

  31. B. Hayes-Roth, L. Brownston, and R. van Gent, "Multiagent collaboration in directed improvisation," in Proc. 1st Int. Conf. on Multi-Agent Systems, San Francisco, 1995; Reprinted in Readings in Agents, M. Huhns and M. Singh, Eds. Morgan-Kaufmann: San Francisco, 1997. Presents directed improvisation; users influence but do not control autonomous, emotional agents. Description of agents in CAIT system. Collaborative storytelling under dynamic user constraints. Reprinted.

  32. B. Hayes-Roth, "Mask and Cyber Mask," in Proc. Computer Game Developers’ Conf., Santa Clara, CA, 1997. Reviews traditional concepts of Mask as a source of manifestation of both persona and animus. Discusses techniques for creating Cyber Mask, incorporating these elements, to facilitate people’s role-play in online dramatic environments.

  33. B. Hayes-Roth, G. Ball, C. Lisetti, R. Picard, A, Stern. "Affect and Emotion in the User Interface," in Proc. Conf. on Intell. User Interfaces, San Francisco, Jan. 1998, pp. 91-96. Panel position papers discuss the role of affect in both perception and expression of behavior.

  34. A. Horton. Writing the character-centered screenplay. University of California Press: Berkeley, CA, 1994. Process and recommendations for developing strong characters, then building a narrative around them. Draws examples from contemporary film.

  35. R. D. Huard and B. Hayes-Roth, "Children's collaborative playcrafting," Tech. Report KSL-96-17, Knowledge Systems Lab., Stanford Univ. Stanford, CA, May 1996. An examination of children's social interactions on a computerized story activity. Analyzed the user's interaction style and how it affected the learning process. Good discussion on future directions for research in children's collaborative computer work. See also: Huard, 1996b; Hayes-Roth and van Gent, 1997.

  36. R. D. Huard and B. Hayes-Roth, "Children's play with improvisational puppets," Tech. Report KSL-96-27, Knowledge Systems Lab., Stanford Univ., Stanford, CA, Nov. 1996. Examines the importance of play and storycrafting experiences in children's learning and development. Provides criteria for creating intrinsically motivating learning environments for young children using interactive storytelling and autonomous puppets. See also: Hayes-Roth and van Gent, 1997.

  37. R. Huard, and B. Hayes-Roth. "Character mastery with improvisational puppets," in Notes of the IJCAI ’97 Workshop on Animated Interface Agents, Nagoya, Japan, Aug. 1997, pp. 85-90. Experimental study of children’s play with three kinds of toys: commercial art software, traditional puppets, and improvisational puppets that have animate minds and animated bodies. Results show that children enjoy all three kinds of toys, but only play with improvisational improves their master of characters and their performance on associated measures of social understanding, story comprehension, and storycrafting.

  38. K. Isbister. "Personality in Interactive Computer Characters: The Importance of Consistency," unpublished manuscript. Reports evidence that people prefer consistent personality traits to inconsistent personality traits, even when the consistent value is not preferred. Consistency refers to similarity of passive/dominant mode in verbal and physical behaviors. See also: Isbister and Hayes-Roth, 1998.

  39. K. Isbister, and B. Hayes-Roth. Social Interaction with Characters. Submitted to J. of Applied AI, Special Issue on Animated Interface Agents, 1998. Analysis of transcripts from web site visitors interacting with an animate character, Erin the Bartender. Results indicate that a character’s role-appropriate behavior can induce role-appropriate behavior in users.

  40. W. James, Psychology. Holt: New York, 1900. Classic, comprehensive view of the science of psychology. Introduces concepts and terminology in general use today. Still widely cited.

  41. L. Johnson and B. Hayes-Roth, Eds. Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997. Broad survey of current work on autonomous agents, but several sessions focus specifically on believable agents and actors. Good general view of current work.

  42. K. Johnstone, IMPRO: Improvisation and the Theater. Routledge: New York, 1992. Describes issues and methods in improvisational theater. Presents clear theory for modeling certain improvisational interactions. Excellent background reading for issues in character interaction.

  43. C. Jones, Chuck Amuck: The Life and Times of an Animated Cartoonist. Avon Books: New York, 1990. Biography of author of Road Runner cartoons et al. Survey and anecdotes of character design, early problems and evolved solutions in creating believable animated characters. Widely cited artistic reference. See also: McCloud, 1993; Thomas and Johnson, 1981.

  44. E. Jones, Interpersonal Perception. W. H. Freeman & Co.: New York, 1990. Discusses the psychological effects of social interaction, with particular emphasis on how humans influence and are influenced by perceptions of others; significance of context in social perception; "expectancy effects" in interactions. See also: Dyer, 1993; Fiske and Taylor, 1991; James, 1900.

  45. M. T. Kelso, P. Weyhrauch, and J. Bates, "Dramatic Presence," PRESENCE: The Journal of Teleoperators and Virtual Environments, vol. 1(1), pp. 133-138, 1992. Preliminary paper on the Oz project. Introduces concept of "interactive drama," theory of plot construction, principles of interactive story design. Describes real-world tests measuring engagement in acted stories with limited sophistication, including transcripts and commentary. Best paper motivati ng principles of the Oz project.

  46. H. Kitano, Ed. Notes of the 1996 AAAI Workshop on Entertainment and AI/A-Life, Portland, OR, Aug. 1996. Range of papers on entertainment issues not limited to agents; include theater, pedagogy, logical formalisms for believability, environments to support characters, social aspects of AI. Some unusual points of view. See also: Andre, 1997.

  47. J. Lasseter, "Principles of traditional animation applied to 3D animation," in Proc. SIGGRAPH '87, Anaheim, FL, July 1987, pp. 35-44. Summary of Disney animation principles and explanation of how they apply to computationally generated 3D believable characters. Examples and images drawn from "Luxo Jr." short film et al. Excellent bridge between traditional and computational character animation. See also: Pixar, 1986; Thomas and Johnston, 1981.

  48. B. Laurel, "Interface Agents: Metaphors with Character," in The Art of Human-Computer Interaction Design, B. Laurel, Ed. Addison-Wesley: Reading, MA, 1990. Presents key characteristics of interface agents. Examines arguments pro and con; emphasis on anthropomorphism, dramatic character of agents. Considers motivations for building such agents. See also: Laurel, 1993.

  49. B. Laurel, Computers as Theatre. Addison-Wesley: Reading, MA, 1993. Explores metaphor of computer as theatrical device. Computational context for engagement, drama, story. Widely cited support for interactive agents in computing.

  50. J. Lester, M. O'Leary, and B. Stone, "Animated Pedagogical Agents for Intelligent Edutainment," in Notes of the AAAI Workshop on Entertainment and AI/ALife, Portland, OR, Aug. 1996, pp. 44-49. Describes method for sequencing believable behaviors amidst pedagogical activities. Categorizes kinds of behaviors by sensory impact; provides algorithm for sequencing. Illuminating approach to integrating believability with substantive acts. Extended by: Stone and Lester, 1996; Lester and Stone, 1997a.

  51. J. Lester and B. Stone, "Increasing Believability in Animated Pedagogical Agents," in Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 16-21. Details of action-selection in "Design-A-Plant" system via competition-based approach. Defines criteria for techniques to enhance believability in actions of pedagogical agents. Novel approach emphasizing sensory impact of actions. Extends: Lester et al., 1996.

  52. J. Lester, S. Converse, S. Kahler, T. Barlow, B. Stone, and R. Bhogal, "The Persona Effect: Affective Impact of Animated Pedagogical Agents," in Proc. CHI '97 Conf., Atlanta, GA, Mar. 1997. Large-scale user testing of believable pedagogical character in "Design-A-Plant" system. Details of study concluding personality and character enhance user engagement and retention of learned material. See also: Lester et al., 1996; Lester and Stone, 1997a.

  53. J. Lester, J. Voerman, S. Towns, and C. Callaway, "Cosmo: A Life-Like Animated Pedagogical Agent with Deictic Believability," in Notes of the IJCAI '97 Workshop on Animated Interface Agents: Making Them Intelligent, Nagoya, Japan, 1997, pp. 61-70. Presents framework for building believable pedagogical agents. Emphasis on "deictic believability," ability to refer to objects and entities in context of discourse. Examples of planning deixis in Internet tutoring system "Cosmo."

  54. A. B. Loyall and J. Bates, "Hap: A Reactive, Adaptive Architecture for Agents," Tech. Report CMU-CS-91-147, School of Computer Science, Carnegie Mellon University, Pittsburgh, June 1991. High-level technical description of Hap architecture underlying Oz agents. Plan memory, theory of activity. Comparison to other agent architectures. Best technical summary of Oz agent system.

  55. Lucasfilm Ltd. Computer Graphics Division, The Adventures of Andre and Wally B., (film), 1984. Early computer-animated short film. Attempt to apply traditional animation principles in computer graphics. Largely of historical interest. See also: Lasseter, 1987; Pixar, 1986.

  56. P. Maes, T. Darrell, B. Blumberg, and A. Pentland, "The ALIVE System: Full-body Interaction with Autonomous Agents," in Proc. Computer Animation '95 Conf., Geneva, Switzerland, Apr. 1995. Presents ALIVE system for wireless full-body interaction between humans and animated virtual agents. Approach to interface through video sensing and wall-sized display without intrusive hardware. Interesting alternative approach to building immersive environments.

  57. P. Maes, "Artificial Life Meets Entertainment: Interacting with Lifelike Autonomous Agents," in Comm. of the ACM, vol. 38(11), pp. 108-114, Nov. 1995. Summarizes research in lifelike agent systems as distinct from believable agent systems. Overview of ALIVE project and tools for physical interactivity with virtual agents. Widely cited, general if brief survey. Details in: Maes et al., 1995a.

  58. H. Maldonado, A. Picard, P. Doyle, and B. Hayes-Roth, "Tigrito: A Multi-Mode Interactive Improvisational Agent," in Proc. 1998 Int. Conf. on Intelligent User Interfaces, San Francisco, CA, Jan. 1998, pp. 29-32. Describes implementation of Tigrito, an affective computer pet. System supports several modes of interaction with characters (avatar, disembodied, "movie" mode). Focus is effectiveness of different modes at producing a sense of engagement.

  59. M. Mauldin, "ChatterBots, TinyMUDs, and the Turing test: Entering the Loebner prize competition," in Proc. 12th Natl. Conf. on Artif. Intell., Seattle, WA, July 1994, pp. 16-21. Description of ChatterBot "Julia," a MUD agent capable of limited conversation. Details conversational model and response design. Analysis of interaction in a limited Turing test, with comparisons to ELIZA and PARRY. Provides useful insights into heuristics for conversational believability. See also: Curtis, 1992; Weizenbaum, 1966.

  60. S. McCloud, Understanding Comics: The Invisible Art. HarperPerrenial: New York, 1993. Introduction to comic strip design. Discusses details of presentation, image emphasis, separation of text and graphics, focus, and flow. Excellent alternative view of interface, story, and believability. See also: Thomas and Johnson, 1981; Jones, 1990.

  61. Y. Moon, "Can computer personalities be human personalities?" in Int. Journal of Human-Computer Studies, vol. 43, pp. 223-239, 1995. Summarizes evidence that people prefer individuals with personality attributes similar to their own. Includes review of studies of a range of relationships, e.g. marital satisfaction, roommate relationships, interest in strangers.

  62. J. Murray, Hamlet on the Holodeck: The Future of Narrative in Cyberspace. The Free Press: New York, 1997. Examination of interactive narrative as a medium. Computational limitations, interface design issues, and problems of creating satisfying interactive experiences. Ties together narrative theory and computer-designed experiment. Conceptual rather than technical.

  63. S. Nachmanovitch. Free Play: Improvisation in Life and Art. Jeremy P. Tarcher, Inc.: Los Angeles, 1991. Explores the origins of the creative process, arguing that improvisation is the key to creative expression. Broadly motivating, non-technical.

  64. C. Nass, J. Steuer, and E. Tauber, "Computers are Social Actors," in Proc. CHI '94 Conf., Boston, MA, Apr. 1994. Introduces thesis that interaction with computers is fundamentally social. Brief analysis of experiments in which users work with and then evaluate computer tutoring systems. Often cited psychological justification for character-based interfaces. Expanded by: Nass et al., 1995.

  65. C. Nass, Y. Moon, B. J. Fogg, B. Reees, and C. Dryer, "Can computer personalities be human personalities?" in Int. Journal of Human-Computer Studies, vol. 43, pp. 223-239, 1995. Study supporting thesis that people prefer to interact with others of similar personality. Results indicate personality can be conveyed by simple, superficial cues. Some summary of psychological literature. Expands on: Nass et al., 1994.

  66. A. Newell. Unified Theories of Cognition. Harvard University Press: Cambridge, MA, 1990. Newell puts forth the proposition that the field of AI should focus on building integrated intelligent agents. He illustrates the goal and process with a detailed report of his own group’s work on the Soar architecture.

  67. D. Norman, Things That Make Us Smart. Addison-Wesley: Reading, MA, 1993. Emphasizes design of systems to match human strengths, rather than adapting humans to computers. Many concepts apply to design of spaces for intelligent characters. Widely cited HCI reference. See also: Doyle and Hayes-Roth, 1998.

  68. T. Oren, G. Salomon, K. Krietman, and A. Don, "Guides: Characterizing the Interface," in The Art of Human-Computer Interface Design, B. Laurel, Ed. Addison-Wesley: Reading, MA, 1990. Describes personality-based interface to encyclopedic survey of American history. Issues of designing personalities, incorporating multiple guides with distinct interests, user response to distinct characters, experiments in several presentation modes. Detailed examination of how believable agents might be used in pedagogy. In: Laurel, 1990.

  69. K. Perlin, "Real time responsive animation with personality," IEEE Transactions on Visualization and Computer Graphics, vol. 1, 1995. Technical details of character animation system. System is concerned with physics and dynamics of representing animated characters, rather than internal motivation. Extended in: Perlin, 1996.

  70. K. Perlin and A. Goldberg, "Improv: A System for Scripting Interactive Actors in Virtual Worlds," Computer Graphics, vol. 29, 1996. Presents an authoring system for movement and action of graphical characters. Behavior engine uses simple scripting language to control cues, character behaviors; animation engine translates programmed canonical motions into natural noisy movement. Focus on physical action without high-level intelligent control. Used in: Hayes-Roth et al., 1996. Related work: Badler 1997.

  71. R. Picard, Affective Computing. MIT Press: Boston, MA, 1997. Argues the need for emotion in computing applications. Describes design requirements of emotional computers, technical and social issues of affective computing, instances of fielded applications.

  72. Pixar, Luxo Jr., (film), 1986. Classic short film about adventures of two animated lamps. Excellent example of animation principles in practice; extremely believable characters despite lack of facial features or speech. See also: Lasseter, 1987; Walt Disney Productions, 1995.

  73. B. Reeves and C. Nass, The Media Equation: How People Treat Computers, Televisions, and New Media Like Real People and Places. Cambridge University Press: New York, 1996. Full treatment of thesis that people treat computers as social entities. Extensive material drawn from psychological experiments, analysis. Extends: Nass et al., 1994; Nass et al., 1995.

  74. W. S. Reilly, "The Art of Creating Emotional and Robust Interactive Characters," in Working Notes of the AAAI Spring Symposium on Interactive Story Systems, Stanford, CA, 1995. Briefly presents the major issues in character design. Displaying emotions, robustness, scale of interactivity. Short but informative.

  75. W. S. N. Reilly, "Believable Social and Emotional Agents." Ph.D. Thesis, School of Computer Science, Carnegie Mellon University, 1996. Describes details of Em emotional model, illustrated with user testing over several scenarios with multiple autonomous emotional agents. Summary of character design methods and heuristics used. See also: Bates et al., 1992b; Bates 1993.

  76. W. S. Reilly, "A Methodology for Building Believable Social Agents," in Proc. First Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 114-121. Presents simple approach for modeling believable characters. Provides transcripts and analysis of user interactions to evaluate robustness and believability of agents in testbed environment. More useful for conceptual approach than practical results. Extended by: Reilly, 1996.

  77. B. Rhodes and P. Maes, "The Stage as a Character: Automatic Creation of Acts of God for Dramatic Effect," in Working Notes of the AAAI Spring Symposium on Interactive Story Systems, Stanford, CA, 1995. Proposes a dramatic "stage manager" to direct interactive storytelling with fully autonomous characters. Examples with Three Little Pigs tale. High-level coordination is an interesting contrast to the directed improvisation model. See also: Rhodes, 1996; Hayes-Roth et al., 1994.

  78. B. Rhodes, "PHISH-Nets: Planning Heuristically in Situated Hybrid Networks." Master's Thesis, Media Lab., Massachusetts Inst. Technol., 1996. Presents architecture for action-selection under multiple interacting goals. Architecture is used to implement the "Big Bad Wolf" in several variations of the Three Little Pigs tale. Describes technical details, models of character and goals, and experimental outcomes. Significant attempt to build an architecture for believable characters. See also: Rhodes and Maes, 1995.

  79. J. Rickel and W. L. Johnson, "Integrating Pedagogical Capabilities in a Virtual Environment Agent," in Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 30-38. Describes Steve, an animated, autonomous agent that demonstrates procedural skills in a graphical environment. Agent may appear in several forms depending on design needs. Uses the Jack character architecture. See also: Badler 1997; Elliott et al., 1997; Perlin, 1996.

  80. T. Rist, E. Andre, and J. Muller, "Adding animated presentation agents to the interface," in Proc. Int. Conf. on Intelligent User Interfaces, Orlando, FL, Jan. 1997, pp. 21-28. Describes PPP Persona, a system for building animated characters to present multimedia information. High-level overview; emphasis on architecture rather than character behaviors. See also: Rickel and Lewis, 1997.

  81. D. Rousseau and B. Hayes-Roth, "Personality in synthetic agents," Tech. Report KSL-96-21, Knowledge Systems Lab., Stanford Univ., Stanford, CA, July 1997. Describes model for building psychologies of intelligent actors, based upon psychology, AI, and drama theory. Provides survey of supporting research, outline of model, and examples of user interaction in "Cybercafe" scenario. Extended by: Rousseau, 1997c.

  82. D. Rousseau and B. Hayes-Roth, "Improvisational synthetic actors with flexible personalities," Tech. Report KSL-97-08, Knowledge Systems Lab., Stanford Univ., Stanford, CA, Sept. 1997. Presents social-psychological model for character interaction. Represents several characters using this approach, and evaluates user interactions in the "Cybercafe" scenario. Comprehensive description of a well-founded approach to character mentality. Expands: Rousseau, 1997b.

  83. D. Rousseau and B. Hayes-Roth, "La personalité dans les acteurs synthétiques," to appear in Analyse de Systemes, 1998. Threads literature in psychology, AI, and theater in discussion of computational improvisation. Description of personality model and implementation in Cybercafe system. In French. See also: Rousseau 1997a, Rousseau 1997c.

  84. N. M. Sgouros, P. Tsanakis, and G. Papakonstantinou, "A Framework for Plot Control in Interactive Story Systems," in Proc. 13th Natl. Conf. on Artif. Intell., Portland, OR, 1996. Briefly summarizes plot control architecture, describing canonical character roles and how interactions are represented. Interesting current work on building interactive stories.

  85. T. J. Smith, J. Shi, J. Granieri, and N. Badler, "JackMOO: An Integration of Jack and LambdaMOO," in Proc. Pacific Graphics 1997, Seoul, Korea, 1997. Describes integration of Jack as an avatar animation system and LambdaMOO as a control platform for creating virtual training scenarios. Technical details on client design and interface between Jack and LambdaMOO. Novel approach for combining proven technologies. See also: Badler, 1997; Rickel and Johnson, 1997.

  86. R. Sternberg and P. Ruzgis, Eds. Personality and Intelligence. Cambridge University Press: Cambridge, 1994.

  87. B. Stone and J. Lester, "Dynamically Sequencing an Animated Pedagogical Agent," in Proc. 13th Natl. Conf. on Artif. Intell., Portland, OR, Aug. 1996, pp. 424-431. Presents approach to designing "behavior spaces" to subdivide agent activities, and algorithms for sequencing an agent's actions within these spaces. Distinguishes pedagogical from believable, intrusive from subtle, and audio from video behaviors among others. Practical approach to integrating believable with other kinds of actions. Extends: Lester and Stone, 1996.

  88. D. Tannen, You Just Don’t Understand: Women and Men in Conversation. William Morrow & Co.: New York, 1990. Examination of different communication styles men and women use; where conflicts occur; approaches for improvement. Grounded in and with reference to linguistic and sociological research. See also: Tannen, 1997.

  89. D. Tannen, Talking From 9 to 5: Women and Men in the Workplace: Language, Sex, and Power. Avon Books: New York, 1997. Analysis of communication in the workplace, with focus on social and cultural impediments to communication. See also: Tannen, 1990.

  90. F. Thomas and O. Johnston, The Illusion of Life: Disney Animation. Hyperion Books: New York, 1981. Comprehensive guide to history of Disney animation. Illustrates principles for creating "illusion of life" in character presentation and animation, with emphasis on evolution of techniques. Widely cited guide to artistic principles amenable to computational modeling. See also: Jones, 1990; McCloud, 1993.

  91. R. Trappl and P. Petta, Eds. Creating Personalities for Synthetic Actors. Springer-Verlag: Berlin, 1996. Compilation of papers from major research groups on personality, physical embodiment, emotion and action-selection in autonomous characters. Some emphasis on physical rather than cognitive aspects of personality. A good survey of current work, particularly European.

  92. M. A. Walker, J. E. Cahn, and S. J. Whittaker, "Improvising Linguistic Style: Social and Affective Bases of Agent Personality," in Proc. 1st Int. Conf. on Autonomous Agents, Marina del Rey, CA, Feb. 1997, pp. 96-105. Presents details of system for improvising specific forms of character utterances based on mood, personality, and social status. Provides examples of variability in "Casablanca" dialog. Interesting approach to generating vocal behaviors based upon social models of interaction. See also: Elliott, 1997a.

  93. Walt Disney Productions, Snow White, (film), 1937. The world's first full-length animated film. Early example of then-new Disney animation principles used to make cartoon characters with depth and life. A classic. See also: Lasseter 1987.

  94. Walt Disney Productions, Toy Story, (film), 1995. First full-length computer animated cartoon. Disney principles applied to graphic design. Comparable to "Snow White" for redefining animated film. See also: Lasseter, 1987; Thomas and Johnston, 1981; Walt Disney Productions, 1937.

  95. J. Weizenbaum, "ELIZA – A Computer Program for the Study of Natural Language Communication Between Man and Machine," in Comm. of the ACM, vol. 9(1), pp. 36-45, 1966. Describes ELIZA, a text-based interactive Rogerian psychologist. Emphasis is on issues of parsing and text generation, not believability. Classic reference for early character design. See also: Foner, 1993; Mauldin, 1994.

  96. P. Zimbardo and M. Leippe, The Psychology of Attitude Change and Social Influence. McGraw-Hill: New York, 1991. Describes many techniques—intentional and unintentional—that people use to influence one another.

 

pdoyle@cs.stanford.edu April 22, 1998