title: Mimicry and expressiveness of an ECA in human-agent interaction: familiarity breeds content!
abstract: BACKGROUND
  Two experiments investigated the effect of features of human behaviour on the quality of interaction with an Embodied Conversational Agent (ECA).
  
  
  METHODS
  In Experiment 1, visual prominence cues (head nod, eyebrow raise) of the ECA were manipulated to explore the hypothesis that likeability of an ECA increases as a function of interpersonal mimicry. In the context of an error detection task, the ECA either mimicked or did not mimic a head nod or brow raise that humans produced to give emphasis to a word when correcting the ECA's vocabulary. In Experiment 2, presence versus absence of facial expressions on comprehension accuracy of two computer-driven ECA monologues was investigated.
  
  
  RESULTS
  In Experiment 1, evidence for a positive relationship between ECA mimicry and lifelikeness was obtained. However, a mimicking agent did not elicit more human gestures. In Experiment 2, expressiveness was associated with greater comprehension and higher ratings of humour and engagement.
  
  
  CONCLUSIONS
  Influences from mimicry can be explained by visual and motor simulation, and bidirectional links between similarity and liking. Cue redundancy and minimizing cognitive load are potential explanations for expressiveness aiding comprehension.
authors.affiliation: MARCS Institute for Brain, Behaviour & Development, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia ; School of Social Sciences & Psychology, Western Sydney University, Penrith, Australia.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Stevens
authors.affiliation: MARCS Institute for Brain, Behaviour & Development, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia ; School of Social Sciences & Psychology, Western Sydney University, Penrith, Australia.
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Pinchbeck
authors.affiliation: Informatics and Engineering, Flinders University, Adelaide, Australia.
authors.forename: Trent
authors.initials: T
authors.lastname: Lewis
authors.affiliation: Informatics and Engineering, Flinders University, Adelaide, Australia.
authors.forename: Martin
authors.initials: M
authors.lastname: Luerssen
authors.affiliation: School of Business, Charles Darwin University, Darwin, Australia.
authors.forename: Darius
authors.initials: D
authors.lastname: Pfitzner
authors.affiliation: Informatics and Engineering, Flinders University, Adelaide, Australia.
authors.forename: David M W
authors.initials: DM
authors.lastname: Powers
authors.affiliation: MARCS Institute for Brain, Behaviour & Development, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia ; Psychology Department, Neurosciences Institute, Stanford University, Stanford, USA.
authors.forename: Arman
authors.initials: A
authors.lastname: Abrahamyan
authors.affiliation: MARCS Institute for Brain, Behaviour & Development, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Leung
authors.affiliation: MARCS Institute for Brain, Behaviour & Development, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751 Australia ; INSERM, U846, 18 avenue Doyen Lépine, 69500 Bron, France ; Université de Lyon, Université Lyon 1, 69003 Lyon, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Gibert
keywords: Avatar; Chameleon effect; Emotion; Evaluation; Expression; Intelligibility; Likeability; Mirroring; Talking head