E. André and T. Rist, Presenting through performing, Proceedings of the 5th international conference on Intelligent user interfaces , IUI '00, pp.1-8, 2000.
DOI : 10.1145/325737.325745

E. André and T. Rist, From adaptive hypertext to personalized web companions, Communications of the ACM, vol.45, issue.5, pp.43-46, 2002.
DOI : 10.1145/506218.506243

G. Ball and J. Breese, Emotion and personality in a conversational agent, Embodied Conversational Agents, pp.189-219, 2000.

A. L. Baylor, E. Shen, and X. Huang, Which Pedagogical Agent do Learners Choose? The Effects of Gender and Ethnicity, Proceedings of ELearn (World Conference on ELearning in Corporate, Government, Healthcare, & Higher Education). Phoenix, 2003.

T. Bickmore, Social Dialogue is Serious Business, CHI 2002 Workshop on Socially Adept Technologies Conference Proceedings, 2002.

T. Bickmore and R. Picard, Subtle Expressivity by Relational Agents, Proceedings of the CHI 2003 Workshop on Subtle Expressivity for Characters and Robots, 2003.

T. Bickmore, Relational agents, Proceedings of the SIGCHI conference on Human factors in computing systems , CHI '01, 2003.
DOI : 10.1145/365024.365304

S. Branham, Creating physical personalities for agents with faces: modelling trait impressions of the face, Proceedings of the UM2001 Workshop on Attitudes, Personality and Emotions in User- Adapted Interactions, 2001.

J. Cassell and K. Thórisson, The power of a nod and a glance: Envelope vs. emotional feedback in animated conversational agents, Applied Artificial Intelligence, vol.13, issue.4-5, pp.519-538, 1999.
DOI : 10.1080/088395199117360

T. W. Chan, Learning Companion Systems, Social Learning Systems and the Global Social Learning Club, International Journal of Artificial intelligence in Education, vol.7, issue.2, pp.125-159, 1996.

C. Chou, T. Chan, and C. Lin, Redefining the learning companion: the past, present, and future of educational agents, 16th International Conference on Computer Animation and Social Agents; (CASA 2003, pp.255-269, 1934.
DOI : 10.1016/S0360-1315(02)00130-6

S. Craig, B. Gholson, and D. Driscoll, Animated pedagogical agents in multimedia educational environments: Effects of agent properties, picture features and redundancy., Journal of Educational Psychology, vol.94, issue.2, pp.428-434, 2002.
DOI : 10.1037/0022-0663.94.2.428

D. Dehn and S. Van-mulken, The impact of animated interface agents: a review of empirical research, International Journal of Human-Computer Studies, vol.52, issue.1, pp.1-22, 2000.
DOI : 10.1006/ijhc.1999.0325

P. Dillenbourg, Collaborative Learning: Cognitive and Computational Approaches, 1999.

C. Dowling, The socially interactive pedagogical agent within online learning communities, International Conference on Computers in Education, 2002. Proceedings., pp.20-34, 2002.
DOI : 10.1109/CIE.2002.1185855

C. Dowling, The Role of the Human Teacher in Learning Environments of the Future, 2003.

C. Elliott, J. Rickel, and J. Lester, Lifelike Pedagogical Agents and Affective Computing: An Exploratory Synthesis, Artificial Intelligence Today, pp.195-211, 1999.
DOI : 10.1007/3-540-48317-9_8

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=

T. Gard, Building character Gama Network: Gamasutra.com. http//www.gamasutra.com/features, 2000.

B. Goodman, A. Soller, F. Linton, and R. Gaimari, Teaching tactics and dialog in AutoTutor, International Journal of Artificial Intelligence in Education, vol.12, pp.257-279, 1998.

A. Graesser, K. Vanlehn, C. Rose, P. Jordan, and D. Harter, Intelligent tutoring systems with conversational dialogue, pp.39-51, 2001.

A. Gulz, Spatially Oriented and Person Oriented Thinking -Implications for User Interface Design. Education and Information Technologies, pp.67-80, 2002.

A. Gulz and M. Haake, Revised version submitted Design of Animated Pedagogical agents -A Look at their Look and Visual Form, International Journal of Human-Computer Studies, 2004.

A. Gulz, M. Bergling, and C. Balkenius, Unbelievable Agents, 2004.

P. Hietala and T. Niemirepo, The Competence of Learning Companion Agents, International Journal of Artificial Intelligence in Education, vol.9, pp.178-192, 1998.
URL : https://hal.archives-ouvertes.fr/hal-00197370

K. Höök, P. Persson, and M. Sjölinder, Evaluating users' experience of a character-enhanced information space, AI communications: the European Journal on Artificial Intelligence, vol.13, issue.3, pp.195-212, 2000.

W. Johnson, J. Rickel, and J. Lester, Animated pedagogical agents: Face-to-face interaction in interactive learning environments, International Journal of Artificial Intelligence in Education, vol.11, pp.47-78, 2000.

W. Johnson, E. Shaw, A. Marshall, and C. Labore, Evaluation of user Interaction: The Case of Agent Adele, IUI, pp.93-100, 2003.

W. Johnson, Interaction tactics for socially intelligent pedagogical agents, Proceedings of the 8th international conference on Intelligent user interfaces, IUI '03, pp.251-253, 2003.
DOI : 10.1145/604045.604090

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=

S. Kalick, Physical attractiveness as a status cue, Journal of Experimental Social Psychology, vol.24, issue.6, pp.469-489, 1988.
DOI : 10.1016/0022-1031(88)90047-9

A. Kapoor, . S. Mota, and R. W. Picard, Towards a Learning Companion that Recognizes Affect Proceedings of Emotional and Intelligent II: The Tangled Knot of Social Cognition, pp.67-72, 2001.

S. Kiesler and L. Sproull, Social" Human-Computer Interaction, Human Values and the Design of Computer Technology, pp.207-219, 1997.

J. Keller, Motivational design of instruction Instructional Design, Theories and Models: An Overview of their Current Status, pp.383-434, 1983.

K. Knoll and S. L. Jarvenpaa, Learning to work in global virtual teams, Proceedings of the twentyeighth Hawaii International Conference of Systems Sciences, pp.92-101, 1995.

T. Koda and P. Maes, Agents with faces: the effect of personification, Proceedings 5th IEEE International Workshop on Robot and Human Communication. RO-MAN'96 TSUKUBA, pp.189-194, 1996.
DOI : 10.1109/ROMAN.1996.568812

B. Kort, R. R. Picard, and R. , An affective model of interplay between emotions and learning: reengineering educational pedagogy-building a learning companion, Proceedings IEEE International Conference on Advanced Learning Technologies, pp.43-46, 2001.
DOI : 10.1109/ICALT.2001.943850

T. Koschman, CSCL: Theory and Practice of an Emerging Paradigm, 1996.

K. Kreijns and P. Kirschner, The sociability of computer-supported collaborative learning environments, Journal of Education Technology & Society, vol.5, issue.1, pp.8-22, 2001.

B. Laurel, Interface Agents: Metaphors with Character, Human Values and the design of Computer Technology, pp.207-219, 1997.

K. Lee, Integration of various emotion eliciting factors for life-like agents, Proceedings of the seventh ACM international conference on Multimedia (Part 2) , MULTIMEDIA '99, pp.155-158, 1999.
DOI : 10.1145/319878.319920

J. Lester, B. Stone, S. Converse, S. Kahler, and S. Barlow, Animated pedagogical agents and problem-solving effectiveness: a large-scale empirical evaluation, Proceedings of the 8th World Conference on Artificial Intelligence in Education, pp.23-30, 1997.

J. Lester, S. Converse, S. Kahler, S. Barlow, B. Stone et al., The persona effect, Proceedings of the SIGCHI conference on Human factors in computing systems , CHI '97, pp.359-366, 1997.
DOI : 10.1145/258549.258797

J. Lester, S. Towns, C. Callaway, J. Voerman, and P. Fitzgerald, Deictic and emotive communication in animated pedagogical agents, Embodied Conversational Agents, pp.123-154, 2000.

J. Lester, C. Callaway, J. Grégoire, G. Stelling, S. Towns et al., Animated pedagogical agents in knowledge-based learning environments, pp.269-298, 2001.

T. Malone, Toward a Theory of Intrinsically Motivating Instruction*, Cognitive Science, vol.149, issue.4, pp.333-369, 1981.
DOI : 10.1207/s15516709cog0504_2

D. Massaro, M. Cohen, J. Beskow, and R. Cole, Developing and Evaluating conversational Agents, Embodied Conversational Agents, pp.287-318, 2000.
DOI : 10.1016/B978-012322735-5/50008-7

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=

E. Mathes, The Effects of Physical Attractiveness and Anxiety on Heterosexual Attraction over a Series of Five Encounters, Journal of Marriage and the Family, vol.37, issue.4, pp.769-773, 1975.
DOI : 10.2307/350828

L. Mcarthur, Judging a book by its cover: a cognitive analysis of the relationship between physical appearance and stereotyping, pp.149-209, 1982.

R. Moreno, R. Mayer, H. Spires, and J. Lester, The Case for Social Agency in Computer-Based Teaching: Do Students Learn More Deeply When They Interact With Animated Pedagogical Agents?, Cognition and Instruction, vol.23, issue.2, pp.177-213, 2001.
DOI : 10.1037//0022-0663.82.4.616

M. Moundridou and M. Virvou, Evaluating the persona effect of an interface agent in a tutoring system, Journal of Computer Assisted Learning, vol.3, issue.3, pp.253-261, 2002.
DOI : 10.1046/j.0266-4909.2001.00237.x

C. Nass, J. Steuer, and E. Tauber, Computers are social actors, Proceedings of the CHI 1994 Conference on Human Factors in Computing Systems (CHI'94), pp.72-78, 1994.
DOI : 10.1145/191666.191703

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=

S. Oivatt and B. Adams, Designing and evaluating conversational interfaces with animated characters, Embodied Conversational Agents, pp.319-345, 2000.

O. Neill-brown and P. , Setting the stage for a culturally adaptive agent, Socially Intelligent Agents, Papers from the 1997 AAAI Fall Symposium, pp.93-97, 1997.

A. Paiva and I. Machado, Vincent, an Autonomous Pedagogical Agent for On-the-Job Training, Proceedings of the Fourth International Conference on Intelligent Tutoring Systems, pp.584-593, 1998.
DOI : 10.1007/3-540-68716-5_64

B. Reeves and C. Nass, The Media Equation: How People Treat Computers, Televisions and New Media Like Real People and Places, 1996.

J. Rickel and L. Johnson, Task-oriented collaboration with embodied agents in virtual worlds, Embodied Conversational Agents, pp.95-122, 2000.

R. Rickenberg and B. Reeves, The effects of animated characters on anxiety, task performance, and evaluations of user interfaces, Proceedings of the SIGCHI conference on Human factors in computing systems , CHI '00, pp.49-56, 2000.
DOI : 10.1145/332040.332406

K. Ryokai, C. Vaucelle, and J. Cassell, Virtual peers as partners in storytelling and literacy learning, Journal of Computer Assisted Learning, vol.66, issue.1, pp.195-208, 2003.
DOI : 10.1046/j.0266-4909.2003.00020.x

E. Shaw, W. Johnson, and R. Ganeshan, Pedagogical agents on the Web, Proceedings of the third annual conference on Autonomous Agents , AGENTS '99, pp.283-290, 1999.
DOI : 10.1145/301136.301210

L. Sproull, M. Subramani, S. Kiesler, J. Walker, and K. Waters, When the Interface Is a Face, Human Values and the Design of Computer Technology, pp.163-190, 1997.
DOI : 10.1007/BF00288060

A. Takeuchi and T. Naito, Situated facial displays, Proceedings of the SIGCHI conference on Human factors in computing systems, CHI '95, 1995.
DOI : 10.1145/223904.223965

Y. Takeuchi, Y. Katagiri, and . T. Takahashi, Learning Enhancement in Web Contents through Inter- Agent Interaction, Proceedings of INTERACT '01, pp.480-487, 2001.

J. Tholander, F. Rutz, P. Johannesson, K. Karlgren, and R. Ramberg, A Pedagogical Assistant for Learning Object-Oriented Design: Nagging Students into Self-Reflection, Proceedings of PEG99, pp.382-388, 1999.

J. Tholander, K. Karlgren, F. Rutz, P. Johannesson, and R. Ramberg, Design and Evaluation of an Apprenticeship Setting for Learning object-Oriented Modelling, th International Conference on Computers in Education, 1999.

S. Turkle, . Simon, . Schuster, S. Van-mulken, E. André et al., The Second Self: Computers and the Human Spirit The persona effect: how substantial is it, People and Computers XIII: Proceedings of HCI'98, pp.53-66, 1984.

L. S. Vygotsky, Mind in society: The development of higher psychological processes, 1978.

J. Walker, L. Sproull, and R. Subramani, Using a human face in an interface, Proceedings of the CHI 1994 Conference on Human Factors in Computing Systems (CHI'94), pp.85-91, 1994.