The Display of Affect through Physical Behavior
CS 543
Overview
Motivation
Psychological View of Nonverbal Behavior
• Encoding Vs. Decoding
• Expression of Emotion through Nonverbal
Behavior
Realizing Emotional Expression
• Animation Techniques
• The Expressive Gaze Model
Conclusion
Motivation
What is interesting about the display of
emotion?
The development of Virtual characters
• Believable
• Capable of open-ended interaction
• Engaging
• For this, a character must be able to signal
its internal state through its external
behavior
“It is the simple idea that "lifelike" doesn't mean "has movement"; "lifelike" means "has a brain." The underlying notion of Pixar and Disney animation is that action is driven by cognitive processes in the character, that there is intelligence and personality and emotion.
Remember that it is crucial that the audience understand the intelligence and personality and emotion. The continual challenge to the animator is in depicting in an unmistakable yet compelling way that the brain is driving the action.”
-Tom Porter
Visual Effects Supervisor
Pixar Studios
Motivation – Continued
Using nonverbal display of emotion to
recognize affective state
• Improve Human-Computer Interaction
• Reliable
• Requires user modeling/theory of mind
Overview
Motivation
Psychological View of Nonverbal Behavior
• Encoding Vs. Decoding
• Expression of Emotion through Nonverbal
Behavior
Realizing Emotional Expression
• Animation Techniques
• The Expressive Gaze Model
Conclusion
Nonverbal Behavior
Encoding
• The display of information through
external behavior
Decoding
• The comprehension of information
through observation of external behavior
Encoding
Types of encoding
• [Ekman & Friesen, 1969] define three
types of coding
• Arbitrary
• No relation between coding and meaning
• Iconic
• Coding is representation of meaning
• Intrinsic
• Coding is meaning
Encoding Research
1. Induce an emotional state into a subject
2. Evaluate the emotional induction.
3. Evaluate the subject‟s behavior within a
specific context
4. Compare the resulting behavior to a
subject that has not gone through the
emotional induction
Encoding – Complications
Encoding may not be deliberate
Encoding may be used to mask information
Men and women encode & decode differently
Different cultures have different coding rules
Encoding may be idiosyncratic
Evaluating Emotion in humans is problematic
• How do we know what lies beneath the
display we‟ve just seen?
Decoding Research
1. Produce stimuli of portrayed nonverbal
behaviors
2. Have subjects rate the emotional content
of the stimuli
Realistic vs. Believable
Decoding research is easier than Encoding research
Generating Believable expressive behavior is easier than generating Realistic expressive behavior
• “Realistic” -> behavior as a human would have performed it
• “Believable” -> behavior understandable by an observer
Overview
Motivation
Psychological View of Nonverbal Behavior
• Encoding Vs. Decoding
• Expression of Emotion through
Nonverbal Behavior
Realizing Emotional Expression
• Animation Techniques
• The Expressive Gaze Model
Conclusion
Nonverbal Communication
Technically, communication without words
• Extremely broad field [Knapp & Hall, 1997]
• Includes:
• Environment
• Appearance
• Dress, grooming
• Height, weight
• Race & gender
• None of these really express emotion
• However, they may affect appraisal ratings
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Expression of Emotion in Man and Animals [Darwin, 1872].
Posture - Demonstration
Posture - Demonstration
Posture - Demonstration
Torso Posture
Torso Posture is affected less by emphasis
and other speech-related behaviors [Bull
& Connelly, 1985]
Positive and Negative emotions are both
easily distinguished both from static body
postures [Coulson, 2004], [Schouwstra &
Hoogstraten, 1995], and from dynamic
trunk movement [de Meijer, 1989].
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Head Position
Head Position
Movement of the head is tightly connected
to speech [Hadar et al., 1985],
[McClave, 1999].
Static posture of the head is still useful for
the display of emotions
• Head which is tilted upwards is viewed
as more dominant, and displaying a
more positive than one tilted downwards
[Kappas et al., 1994], [Mignault &
Chaudhuri, 2003].
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Facial Expression
Facial expression is one of the stronger channels for emotional expression
Paul Ekman
• Performed many of early experiments on facial expression
• Found that facial expression was highly cross cultural
• Developed the Facial Action Coding System (FACS)
Happiness
Anger
Sadness
Fear
Disgust
Facial Expression
Other researchers have shown that
• Children who are Deaf/Blind from birth
share many of the same facial
expressions
• As do very young infants
• As well as monkeys
• [Knapp & Hall, 1997]
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Hand Gestures
Much of the research on hand gesture focuses
on the association of gestures with the
cognition and communication [McNeill, 1992].
However, there is still evidence that not only the
motion qualities of hand gestures, but the
selection of gestures and hand positions can
be affected by emotional state.
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Gaze Behavior
What do we mean by gaze behaviors?
• Eye shape and eyebrow position are part of facial expression
• Speed of eye movement is highly stereotypical
• Length of gaze & mutual gaze
• Gaze attraction vs. aversion
• Relation of eye movement to head and body movement
Non-Emotional Gaze
Gaze is closely linked to speech-related
behaviors
• Patterns of gaze for individuals speaking
are often different from patterns of gaze
for listeners [Kleinke, 1986].
Attention and Saliency also control eye
movement [Argyle & Cook, 1973].
Gaze and Dominance
Gaze is very important in signaling
dominance [Exline, 1971]
• However this relationship is not fully
understood
• Seen in the way monkeys perform
dominance displays when looked at by
experimenters
• Highly dominant individuals look less
while listening, and more while speaking
than do individuals of low dominance
[Knapp, 1997].
Gaze and Arousal
Gaze is also closely related to physiological
arousal [Argyle & Cook, 1973]
• Receiving gaze and engaging in mutual
gaze increases arousal
• Gaze is used as a regulation for
physiological arousal
• Increased blinks, and increased pupil
dilation are also strong signals of arousal
Gaze and Preference
Gaze also has a drastic effect on liking
• Individuals who gaze very little at people
they interact with are rated lower on
scales of preference, credibility,
attractiveness, and are less likely to be
hired [Burgoon et al., 1985], [Argyle &
Cook, 1973].
Individuals are also more likely to look at
people that they like [Argyle & Cook,
1973]
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Prosodic Information
Nonverbal information contained in the voice.
Often examined through a signal processing
paradigm [Bulut, Lee, Narayanan, ‟07].
Expression of Emotion
What nonverbal behaviors display emotion?
• Torso Posture
• Head Position
• Facial Expression
• Hand Gestures
• Gaze Behavior
• Prosody
• Movement
Movement & Locomotion
Emotion can be recognized through how
people walk
But further, emotion can be recognized
through the movement of simple
geometric shapes [Rime et al., 1985]
Movement
Locomotion
Synchrony
The interactions of all of these behaviors is
as important as any single behavior
• If not, emotional signals lack coherency
• The ability of users to recognize emotion
decreases
• Believability and engagement decrease
Conclusion – Nonverbal
While there are many different ways emotion can be signaled through nonverbal behavior
• Often difficult to clearly differentiate between individual emotional categories
• Much nonverbal behavior research done using dimensional models of emotion that are derived from factor analyses of nonverbal behavior results
Overview
Motivation
Psychological View of Nonverbal Behavior
• Encoding Vs. Decoding
• Expression of Emotion through Nonverbal
Behavior
Realizing Emotional Expression
• Animation Techniques
• The Expressive Gaze Model
Conclusion
Virtual Characters
Keyframe Animation
• Classic technique from 2D cell animation
• Skilled animator develops key frames
• Interpolation between them creates movement
• Slow, iterative process
Produces most realistic behavior
Takes very long time to develop
Animations are not reusable
Keyframe Animation
Skilled animators drew
key frames
•Later drew in “in-
betweens”
Developed principles
such as “Squash &
Strech”, “Anticipation”,
and “Follow Through”
Keyframe Animation
Extremely slow process
• Highly iterative
• Highly intuitive
• Very difficult to clearly explain
• Requires great deal of training, and a
certain amount of talent
• Results are excellent
Analyzing 2D Animation
[Lance et al., 2004], and [Chafai et al.,
2006] were attempts to analyze keyframe
animation for information on nonverbal
behavior for gaze and gesture,
respectively
• Moderately successful
• Extremely labor intensive
KeyFrame Animation
Motion Capture
Motion Capture Animation
• Cameras record movement of sensors placed on an
actor
• Software reconstructs movement and
approximation of character‟s anatomy
• Allows for quicker generation of movement
• Requires expensive hardware and analysis tools
• Captured sequences difficult to reuse
• Can be difficult to retarget captured motion to 3D
model being animated
Motion Capture
Procedural Animation
Generation of movement without human oversight
• Virtual Agents
• Video Game Characters
• Can use libraries of keyframe or motion capture animation
• Or movement can be generated through mathematical methods
• Allow for dynamic or interactive environments
• Often lack the quality of previous two methods
Motion Capture Library
Procedural Animation
Overview
Motivation
Psychological View of Nonverbal Behavior
• Encoding Vs. Decoding
• Expression of Emotion through Nonverbal
Behavior
Realizing Emotional Expression
• Animation Techniques
• The Expressive Gaze Model
Conclusion
Gaze Model:
Expressive Gaze Model (EGM)
• Combination of Motion Capture and Procedural animation techniques
• Motion Capture for Head & Torso• [Lance & Marsella, IVA „07]
• Procedural for Eye Movement• [Lance & Marsella, AAMAS „08]
• Produces integrated Eye, Head, and Torso movement for emotionally expressive gaze
The Expressive Gaze Model
-
+
Emotional Movement
Non-Emotional Movement
Procedural Eye Movement
Animated Gaze Shift
+
New Non-Emotional
Movement
Gaze
Warping
Transformation
EGM:
Eye vs. Body Movement
• Use separate methods for modeling the head/torso movement and the eyes.
• Eye movement by itself stereotypical and not expressive
• Eye and head/torso movement function on different time scales with different constraints
• Chosen to model eye and head/torso movement differently, while constraining the relationship between them
GWT:
Neutral Gaze Shift
GWT:
Applied GWT
EGM:
Eye Model Overview
• Procedural model of eye movement
• Basic Eye behaviors
• Integration with head movement
• Based on constraints described in Visual Neuroscience Literature
• Leigh & Zee, 2006; Stark et al., 1980; Zee, 1976; Guitton & Volle, 1987; Gresty, 1974; Uemura et al., 1980
• Relationship between saccades, VOR, and head movement
Eye Model Example
Gaze Model
• Generate gaze to arbitrary location while displaying
desired gaze behaviors
• Provides property of composability of behavior
• Exploited this property to explore relationship
between behavior and emotion
• Using the P-A-D dimensional model of emotion,
found a strong relationship between behaviors and
individual emotional dimensions
• Revealed complexity of multidimensional PAD
space
Conclusion
Many sources of information for the expression of
emotion through human behavior
• Lots of them are qualitative
• Or not experimentally verified
• Or describe more subtle relationships than
direct emotional state -> behavior
• Picture is still very incomplete
Still lots of good information for a starting point!
References
Argyle, M., Cook, M. Gaze and Mutual Gaze. Cambridge University Press. 1976.
Bull, P., Connelly, G. Body Movement and Emphasis in Speech. Journal of Nonverbal Behavior, 9(3). Fall 1985.
Bulut, M., Lee, S., Narayanan, S.: Analysis of emotional speech prosody in terms of part of speech tags. Interspeech, Antwerp, Belgium, August 2007.
Burgoon, J., Manusov, V., Mineo, P., Hale, J. Effects of Gaze on Hiring, Credibility, Attraction and Relational Message Interpretation. Journal of Nonverbal Behavior. 9(3). Fall 1985.
Chafai, N., Pelachaud, C., Pele, D., Breton, G. Gesture Expressivity Modulations in an ECA Application. Proceedings of the Intelligent Virtual Agents IVA 2006 Conference. 2006.
Coulson, M. Attributing Emotion to Static Body Postures: Recognition Accuracy, Confusions, and Viewpoint Dependence. Journal of Nonverbal Behavior. 28(2). Summer 2004.
Chi, D., Costa, M., Zhao, L., Badler, N. The EMOTE Model for Effort and Shape. Proceedings of the 27th Annual Conference on Computer Graphics and Interactive Techniques. ACM Press/Addison-Wesley Publishing, New York, NY. 2000.
Darwin, C., The Expression of Emotions in Man and Animals. 1872.
Ekman P., Friesen, W.V., The Repertoire of Nonverbal Behavior: Categories, Origins, Usage, and Coding. Semiotica. 1, 49-98. 1969.
Exline, R. Visual Interaction: The Glances of Power and Preference. In Weitz, S. (ed), Nonverbal Communication: Readings with Commentary. Oxford University Press, 1974.
Hadar, U., Steiner, T. J., Rose, F. C. Head Movement During Listening Turns in Conversation. Journal of Nonverbal Behavior, 9(4). Winter 1985.
Kappas, A., Hess, U., Barr, C., Kleck, R. Angle of Regard: The Effect of Vertical Viewing Angle on the Perception of Facial Expressions. Journal of Nonverbal Behavior. 18(4). Winter 1994.
Kleinke, C. Gaze and Eye Contact: A Research Review. Psychological Bulletin. v. 100, n. 1. 1986.
References (Cont.)
Knapp, M., Hall, J. Nonverbal Communication in Human Interaction. Fourth Edition. Harcourt Brace Publishers. 1997.
Lance, B., Marsella, S., Koizumi, D. Towards Expressive Gaze Manner in Embodied Virtual Agents. AAMAS Workshop on Empathic Agents. 2004.
Lance, B., and S. C. Marsella. 2007. Emotionally Expressive Head and Body Movement During Gaze Shifts. Lecture Notes in Computer Science 4722: 72.
Lance, B. J., and S. C. Marsella. 2008. A Model of Gaze for the Purpose of Emotional Expression in Virtual Embodied Agents. International Foundation for Autonomous Agents and Multiagent Systems Richland, SC , 199-206.
Lasseter, J. Principles of Traditional Animation Applied to 3D Computer Animation. Computer Graphics. v. 21, n 4. July 1987.
Marsella, S., Carnicke, S. M., Gratch, J., Okhmatovskaia, A., Rizzo, A. An Exploration of Delsarte‟s Structural Acting System. Proceedings of the Intelligent Virtual Agents IVA 2006 Conference. 2006.
McClave, E. Linguistic Functions of Head Movements in the Context of Speech. Journal of Pragmatics. v. 32, 2000.
de Meijer, M. The Contribution of General Features of Body Movement to the Attribution of Emotions. Journal of Nonverbal Behavior. 13(4). Winter 1989.
Mignault, A., Chaudhuri, A. The Many Faces of a Neutral Face: Head Tilt and Perception of Dominance and Emotion. Journal of Nonverbal Behavior. 27(2). Summer 2003.
Pollick, F., Paterson, H., Bruderlin, A., Sanford, A. Perceiving Affect from Arm Movement. Cognition. i 82, B51-B61. 2001.
Porter, T. “Creating lifelike characters in Toy Story,” ACM SIGART Bulletin 8 (1997): 10-14.
Rime, B., Boulanger, B., Laubin, P., Richir, M., Stroobantst, K. The Perception of Interpersonal Emotions Originated by Patterns of Movement. Motivation and Emotion. v. 9, n. 3. 1985.
Schouwstra, S., Hoogstraten, J. Head Position and Spinal Position as Determinants of Perceived Emotional State. Perceptual and Motor Skills. v. 81, 1995.
Thomas, F., Johnston, O. The Illusion of Life: Disney Animation. Walt Disney Productions. 1981.
Zhao, L., Badler, N. Acquiring and Validating Motion Qualities from Live Limb Gestures. Graphical Models. v. 67 i. 1. January, 2005.