Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents
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Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents A thesis submitted for the degree of Doctor of Philosophy (Ph.D) at Newcastle University by John Shearer BEng(Hons)(York) School of Computing Science Claremont Tower Newcastle University NE1 7RU United Kingdom October 2008 Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Abstract Abstract i Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Realism for embodied conversational agents (ECAs) requires both visual and behavioural fidelity. One significant area of ECA behaviour, that has to date received little attention, is non-verbal behaviour. Non-verbal behaviour occurs continually in all human-human interactions, and has been shown to be highly important in those interactions. Previous research has demonstrated that people treat media (and therefore ECAs) as real people, and so non-verbal behaviour is also important in the development of ECAs. ECAs that use non-verbal behaviour when interacting with humans or other ECAs will be more realistic, more engaging, and have higher social influence. This thesis gives an in-depth view of non-verbal behaviour in humans followed by an exploration of the potential social influence of ECAs using a novel Wizard of Oz style approach of synthetic ECAs. It is shown that ECAs have the potential to have no less social influence (as measured using a direct measure of behaviour change) than real people and also that it is important that ECAs have visual feedback on their interactants for this social influence to maximised. Throughout this thesis there is a focus on empirical evaluation of ECAs, both as a validation tool and also to provide directions for future research and development. Present ECAs frequently incorporate some form of non-verbal behaviour, but this is quite limited and more importantly not connected strongly to the behaviour of a human interactant. This interactional aspect of non-verbal behaviour is important in human- human interactions and results from the study of the persuasive potential of ECAs support this fact mapping onto human-ECA interactions. The challenges in creating non- verbally interactive ECAs are introduced and by drawing corollaries with robotics control systems development behaviour-based architectures are presented as a solution towards these challenges, and implemented in a prototypical ECA. Evaluation of this ECA using the methodology used previously in this thesis demonstrates that an ECA with non-verbal behaviour that responds to its interactant is rated more positively than an ECA that does not, indicating that directly measurable social influences will be possible with further development. Abstract ii Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Acknowledgements Acknowledgements iii Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents I would like to acknowledge the following people who have been involved with my PhD. I am grateful to you all. Pressies and actual spoken thanks on its way. I also wish to express my deepest sadness that my good friend Rumesh is no longer here to have come to this point together, but had a wonderfully energetic and positive impact on me and so many others. Patrick Olivier for reading, re-reading, and then saying "whatever". seriously thanks so much. Dan Jackson code god #1 Chris Malkin the rock of Devonshire fun James Shearer for about a million hours proof-reading and being great Annabel Bixby from day 1 Jennifer Shearer for politely remembering not to mention the certain 3 letters Phil Heslop bringing it right back Wayne Smith just cause I want to Louise Pease cause she know the right answer to: pub? Cas Ladha so that's what 15,000 volts feels like Fiona Shearer got out of proofreading the easy way Peg Shearer for another million hours proof-reading and being lovely Tania Brodie-Clarke for letting me win Bob Hurling for being a vital part of the Unilever crew Ali McGowan handstands rule ok Robyn Taylor definitely on the list of best visitors Dave Mawer officially holds the prize of longest housemate ever Paul Dunphy for that peaceful easy feeling Jurgen Wagner for being the legend of the Jurg Stephen Lindsay didn't want to miss a thing Jon Hook VJ, smeeJ Marco De Boni Unilever made it happen Jayne Wallace gromit? Qaz Chaudry dude, where's my car? Pauline Addis what are all these bees about? Krish Korvi for doctoring so well Christine Niedermeier you thought I'd forget! Everyone else in space 2 who read through stuff or just was generally good fun Everyone who took part in my studies – couldn't have done it without you all Acknowledgements iv Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Publications Publications v Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Shearer, J., Olivier, P., Heslop, P., & Boni, M. D. (2006). Requirements of non-verbal communication in believable synthetic agents. Paper presented at the AISB’06: Adaptation in Artificial and Biological Systems conference, Bristol, UK. Heslop, P., Shearer, J., & Olivier, P. (2006). Synthetic character fidelity through non- verbal behaviour in computer games. Paper presented at the iDiG International Digital Games Conference conference, Portalegre Shearer, J., Olivier, P., & Boni, M. D. (2007). On the simulation of interactive non- verbal behaviour in virtual humans. Paper presented at the AISB 07 conference, Newcastle Shearer, J., Olivier, P., Boni, M. D., & Hurling, R. (2007). Exploring persuasive potential of embodied conversational agents utilizing synthetic embodied conversational agents. Paper presented at the Persuasive 2007 conference, Stanford, CA Shearer, J., Heslop, P., Olivier, P., & De Boni, M. (2008). Non-verbal behaviour for believable synthetic agents. AISB Journal(to appear). Publications vi Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Contents Contents vii Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents Abstract............................................................................................................................... i Acknowledgements...........................................................................................................iii Publications ....................................................................................................................... v Contents........................................................................................................................... vii Figures and Tables............................................................................................................ xi 1. Introduction ................................................................................................................. 1 2. Non-verbal behaviour in people .................................................................................. 6 2.1 Purposes of non-verbal behaviour...................................................................... 9 2.2 Verbal versus non-verbal behaviour ................................................................ 12 2.3 Classifications of non-verbal behaviour .......................................................... 15 2.4 Spatial-task context.......................................................................................... 30 2.5 Managing interaction ....................................................................................... 34 3. Embodied Conversational Agents (ECAs) ................................................................ 36 3.1 Anatomy of an ECA......................................................................................... 39 3.2 Evaluating ECAs.............................................................................................. 41 3.3 Existing ECA evaluation methods ................................................................... 43 4. Persuasive potential of ECAs: introducing synthetic ECAs...................................... 46 4.1 Empirical evaluation of persuasive potential................................................... 49 4.2 Social influence in ECAs ................................................................................. 51 4.3 Synthetic ECAs................................................................................................ 52 4.4 Implementation of a synthetic ECA................................................................. 53 4.5 Verification of validity of synthetic ECA........................................................ 58 5. Persuasive effect of synthetic ECAs.......................................................................... 69 5.1 Direct measure of behaviour change................................................................ 71 Contents viii Persuasive Interactive Non-Verbal Behaviour in Embodied Conversational Agents 5.2 Experimental designs ....................................................................................... 71 5.3 Subjects ............................................................................................................ 72 5.4 Wizard behaviour............................................................................................. 73 5.5 Procedure ......................................................................................................... 73 5.6 Measures .......................................................................................................... 74 5.7