Assessing naturalness and emotional intensity: a perceptual study of animated facial motion

Animated characters appear in applications for entertainment, education, and therapy. When these characters display appropriate emotions for their context, they can be particularly effective. Characters can display emotions by accurately mimicking the facial expressions and vocal cues that people display or by damping or exaggerating the emotionality of the expressions. In this work, we explored which of these strategies would be most effective for animated characters. We investigated the effects of altering the auditory and facial levels of expressiveness on emotion recognition accuracy and ratings of perceived emotional intensity and naturalness. We ran an experiment with emotion (angry, happy, sad), auditory emotion level (low, high), and facial motion magnitude (damped, unaltered, exaggerated) as within-subjects factors. Participants evaluated animations of a character whose facial motion matched that of an actress we tracked using an active appearance model. This method of tracking and animation can capture subtle facial motions in real-time, a necessity for many interactive animated characters. We manipulated auditory emotion level by asking the actress to speak sentences at varying levels, and we manipulated facial motion magnitude by exaggerating and damping the actress's spatial motion. We found that the magnitude of auditory expressiveness was positively related to emotion recognition accuracy and ratings of emotional intensity. The magnitude of facial motion was positively related to ratings of emotional intensity but negatively related to ratings of naturalness.

[1]  J. N. Bassili.  Facial motion in the perception of faces and of emotional expression. , 1978, Journal of experimental psychology. Human perception and performance.

[2]  J. N. Bassili.  Emotion recognition: the role of facial movement and the relative importance of upper and lower areas of the face. , 1979, Journal of personality and social psychology.

[3]  J. Russell.  A circumplex model of affect. , 1980 .

[4]  F. Thomas,et al.  Disney Animation: The Illusion of Life , 1981 .

[5]  D. Watson,et al.  Toward a consensual structure of mood. , 1985, Psychological bulletin.

[6]  K. Scherer,et al.  Cues and channels in emotion recognition. , 1986 .

[7]  M. Bradley,et al.  Remembering pictures: pleasure and arousal in memory. , 1992, Journal of experimental psychology. Learning, memory, and cognition.

[8]  D. Massaro,et al.  Perceiving affect from the voice and the face , 1996, Psychonomic bulletin & review.

[9]  D. Perrett,et al.  Computer-enhanced emotion in facial expressions , 1997, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[10]  U. Hess,et al.  The Intensity of Emotional Facial Expressions and Decoding Accuracy , 1997 .

[11]  Timothy F. Cootes,et al.  Active Appearance Models , 1998, ECCV.

[12]  John Lasseter,et al.  Principles of traditional animation applied to 3D computer animation , 1987, SIGGRAPH.

[13]  D. Perrett,et al.  Caricaturing facial expressions , 2000, Cognition.

[14]  J. Vroomen,et al.  The perception of emotions by ear and by eye , 2000 .

[15]  C. Nass,et al.  Machines and Mindlessness , 2000 .

[16]  Timothy F. Cootes,et al.  View-based active appearance models , 2000, Proceedings Fourth IEEE International Conference on Automatic Face and Gesture Recognition (Cat. No. PR00580).

[17]  F. Pollick,et al.  Recognising Facial Expression from Spatially and Temporally Modified Movements , 2003, Perception.

[18]  Simon Baker,et al.  Active Appearance Models Revisited , 2004, International Journal of Computer Vision.

[19]  J. Cohn,et al.  Deciphering the Enigmatic Face , 2005, Psychological science.

[20]  Christoph Bartneck,et al.  Subtle emotional expressions of synthetic characters , 2005, Int. J. Hum. Comput. Stud..

[21]  N. Troje,et al.  Range- and domain-specific exaggeration of facial speech. , 2005, Journal of vision.

[22]  Denis G. Pelli,et al.  ECVP '07 Abstracts , 2007, Perception.

[23]  Russell Beale,et al.  Affective interaction: How emotional agents affect users , 2009, Int. J. Hum. Comput. Stud..

[24]  Jeffrey R. Spies,et al.  Effects of damping head movement and facial expression in dyadic conversation using real–time facial expression tracking and synthesized avatars , 2009, Philosophical Transactions of the Royal Society B: Biological Sciences.

[25]  Jeffrey R. Spies,et al.  Mapping and Manipulating Facial Expression , 2009, Language and speech.

[26]  C. Wallraven,et al.  Dynamic information for the recognition of conversational expressions. , 2009, Journal of vision.

[27]  Gray Hodgkinson.  The seduction of realism , 2009, SIGGRAPH ASIA '09.

[28]  Mark Grimshaw,et al.  Facial expression of emotion and perception of the Uncanny Valley in virtual characters , 2011, Comput. Hum. Behav..

[29]  Jessica K. Hodgins,et al.  Perceptual effects of damped and exaggerated facial motion in animated characters , 2013, 2013 10th IEEE International Conference and Workshops on Automatic Face and Gesture Recognition (FG).