19-12-2012, 06:11 PM
HUMAN RECOGNITION OF BASIC EMOTIONS FROM POSED AND ANIMATED DYNAMIC FACIAL EXPRESSIONS
[attachment=44482]
Abstract
Facial expressions are crucial for social communication, especially because they make
it possible to express and perceive unspoken emotional and mental states. For example,
neurodevelopmental disorders with social communication deficits, such as Asperger
Syndrome (AS), often involve difficulties in interpreting emotional states from the facial
expressions of others.
Rather little is known of the role of dynamics in recognizing emotions from faces.
Better recognition of dynamic rather than static facial expressions of six basic emotions
has been reported with animated faces; however, this result hasn’t been confirmed
reliably with real human faces. This thesis evaluates the role of dynamics in recognizing
basic expressions from animated and human faces. With human faces, the further
interaction between dynamics and the effect of removing fine details by low-pass filtering
(blurring) is studied in adult individuals with and without AS. The results confirmed that
dynamics facilitates the recognition of emotional facial expressions. This effect, however,
was apparent only with the facial animation stimuli lacking detailed static facial features
and other emotional cues and with blurred human faces. Some dynamic emotional
animations were recognized drastically better than static ones. With basic expressions
posed by human actors, the advantage of dynamic vs. static displays increased as a
function of the blur level. Participants with and without AS performed similarly in
recognizing basic emotions from original non-filtered and from dynamic vs. static facial
expressions, suggesting that AS involves intact recognition of simple emotional states
and movement from faces. Participants with AS were affected more by the removal of
fine details than participants without AS. This result supports a “weak central coherence”
account suggesting that AS and other autistic spectrum disorders are characterized by
general perceptual difficulties in processing global vs. local level features.
INTRODUCTION
Faces are crucial for social communication. Faces carry information about the identity,
sex and age of their owners. Facial movements have several roles in conversation. Visible
articulatory movements are known to enhance and influence the perception of speech.
Facial actions punctuate and emphasize speech (e.g. brow movements), convey signals of
their own that typically depend on culture (head nodding and shaking and eye winking),
and regulate turns during speech (changes in head position and eye gaze) [1, 2].
Importantly, facial expressions also allow an access into the internal emotional and
mental states of others.
According to a classical emotion theory, there are six or seven basic emotions, shared
by all people regardless of their origin [3]. Such a conclusion has been supported by
studies showing that people across the world from Westerners to members of isolated
tribes are able to recognize these emotions readily from stereotypical facial displays (e.g.
[4]). These and later studies on the recognition of emotions from human faces have until
recently been conducted almost exclusively with photographs of facial expressions with
only a few studies using moving faces as research stimuli. Consequently, there exists
relatively little information on the role of motion in recognizing emotions from faces. The
lack of emotion studies with moving facial expressions is partly explained by the lack of
available stimuli. A picture collection of basic expressions by Ekman and Friesen [5] was
collected already in the 1970’s and has since been used widely in emotion research.
Video sequence collections comparable to this collection have been non-existent until
recently and their availability remains scarce.
Theory of basic emotions
Basic postulations
The historical roots of basic emotion theory originate from Charles Darwin, who as a
part of his evolutionary theory suggested that the emotional expressions of man were
descendants from other animals [9] (cf. [4: pp. 169-75]). Darwin not only made
observations on the behavior of animals but also set to study the question of whether
some emotions were universal to all men. Although the idea of universal basic emotions
had been mentioned already many centuries before Darwin in the writings of
philosophers such as Descartes, Hobbes and Spinoza [10] and influential facial
expression studies had been conducted by other 19th century scientists such as Guillaume
Duchenne [11], Darwin appears to have conducted the first scientific evaluation studies
on the recognition of emotions from faces. Darwin studied which emotions were
recognized consistently from photographs of representative emotional facial expressions
in England [9] (cf. [4: pp. 169-75, 12]) and made the first attempts to evaluate the
universality of emotions by interviewing his fellow countrymen living abroad on the
expression of emotions in other cultures [4: pp. 169-75]. The method of asking subjects
to judge emotions from certain facial expressions has remained a part of contemporary
research methodology.
Conceptual and methodological problems
The basic emotion theory proposed by Ekman has been criticized because of various
conceptual and methodological problems (see especially [13, 17]).
Attribution vs. expression of emotions
Reasoning behind the emotion judgment studies used to evaluate basic emotion theory
is that certain emotions are basic because they are recognized universally from certain
facial expressions. However, universal attribution of certain emotion labels to certain
facial expressions doesn’t necessarily imply the universal expression of the referred
emotions by those facial expressions (cf. [13, 27]). In order to prove the latter, it would
be necessary to show that certain facial expressions accompany certain emotional events
universally. On the contrary, it appears that similar events may lead to different emotions
and emotional expressions in different cultures [4: pp. 174-87]. How could such variation
be compatible with the existence of basic emotions? According to a neuro-cultural theory
of emotions suggested by Ekman [4: pp. 175-9, 22: pp. 212-35], certain basic emotions
are universal but their eliciting situations and display rules controlling their expression
differ between cultures. Display rules have been claimed to work by intensifying,
deintensifying, neutralizing or masking the emotional facial expressions [22: pp. 212-35].
Before studying the cross-cultural expression of emotion in a certain situation, one would
need to show that the situation elicits a similar emotion in the studied cultures and that no
display rules affecting the results would be evident.
The relation between basic emotions and facial expressions
The emotion judgment studies also assume that certain facial expressions are
characteristic of certain basic emotions. This assumption raises further questions on the
relation between facial expressions and emotions. Silvan Tomkins has suggested the face
as “[…] of the greatest importance in producing the feel of affect” [28: p. 212]. Tomkins
had a strong influence on Ekman’s thinking, who has for example expressed doubts on
the very concept of facial expression of emotion: “[…] in my view expression is a central
feature of emotion, not simply an outer manifestation of an internal phenomena” [25: p.
384].
Can facial expressions occur without emotions? Some facial expressions certainly do
occur without any emotion because only a minority of all facial expressions are related to
emotions (cf. [29: p. 337]). A less trivial question is whether emotional facial expressions
can occur without emotion. Ekman suggests that some facial muscles related to genuinely
felt emotions are extremely difficult to activate voluntarily [25: pp. 389-91], for example
the activation of orbicularis oculi (a circular muscle surrounding the eye) may
discriminate genuine from non-genuine smiles. Furthermore, some tentative evidence
exists on the fact that consciously posing emotion-related facial expressions can produce
slight emotional experiences [30] (as cited in [25: p. 50]). Of course, facial expressions
alone should not be expected to induce strong emotions because emotions (and facial
expressions) are usually triggered in real or imagined situations.
[attachment=44482]
Abstract
Facial expressions are crucial for social communication, especially because they make
it possible to express and perceive unspoken emotional and mental states. For example,
neurodevelopmental disorders with social communication deficits, such as Asperger
Syndrome (AS), often involve difficulties in interpreting emotional states from the facial
expressions of others.
Rather little is known of the role of dynamics in recognizing emotions from faces.
Better recognition of dynamic rather than static facial expressions of six basic emotions
has been reported with animated faces; however, this result hasn’t been confirmed
reliably with real human faces. This thesis evaluates the role of dynamics in recognizing
basic expressions from animated and human faces. With human faces, the further
interaction between dynamics and the effect of removing fine details by low-pass filtering
(blurring) is studied in adult individuals with and without AS. The results confirmed that
dynamics facilitates the recognition of emotional facial expressions. This effect, however,
was apparent only with the facial animation stimuli lacking detailed static facial features
and other emotional cues and with blurred human faces. Some dynamic emotional
animations were recognized drastically better than static ones. With basic expressions
posed by human actors, the advantage of dynamic vs. static displays increased as a
function of the blur level. Participants with and without AS performed similarly in
recognizing basic emotions from original non-filtered and from dynamic vs. static facial
expressions, suggesting that AS involves intact recognition of simple emotional states
and movement from faces. Participants with AS were affected more by the removal of
fine details than participants without AS. This result supports a “weak central coherence”
account suggesting that AS and other autistic spectrum disorders are characterized by
general perceptual difficulties in processing global vs. local level features.
INTRODUCTION
Faces are crucial for social communication. Faces carry information about the identity,
sex and age of their owners. Facial movements have several roles in conversation. Visible
articulatory movements are known to enhance and influence the perception of speech.
Facial actions punctuate and emphasize speech (e.g. brow movements), convey signals of
their own that typically depend on culture (head nodding and shaking and eye winking),
and regulate turns during speech (changes in head position and eye gaze) [1, 2].
Importantly, facial expressions also allow an access into the internal emotional and
mental states of others.
According to a classical emotion theory, there are six or seven basic emotions, shared
by all people regardless of their origin [3]. Such a conclusion has been supported by
studies showing that people across the world from Westerners to members of isolated
tribes are able to recognize these emotions readily from stereotypical facial displays (e.g.
[4]). These and later studies on the recognition of emotions from human faces have until
recently been conducted almost exclusively with photographs of facial expressions with
only a few studies using moving faces as research stimuli. Consequently, there exists
relatively little information on the role of motion in recognizing emotions from faces. The
lack of emotion studies with moving facial expressions is partly explained by the lack of
available stimuli. A picture collection of basic expressions by Ekman and Friesen [5] was
collected already in the 1970’s and has since been used widely in emotion research.
Video sequence collections comparable to this collection have been non-existent until
recently and their availability remains scarce.
Theory of basic emotions
Basic postulations
The historical roots of basic emotion theory originate from Charles Darwin, who as a
part of his evolutionary theory suggested that the emotional expressions of man were
descendants from other animals [9] (cf. [4: pp. 169-75]). Darwin not only made
observations on the behavior of animals but also set to study the question of whether
some emotions were universal to all men. Although the idea of universal basic emotions
had been mentioned already many centuries before Darwin in the writings of
philosophers such as Descartes, Hobbes and Spinoza [10] and influential facial
expression studies had been conducted by other 19th century scientists such as Guillaume
Duchenne [11], Darwin appears to have conducted the first scientific evaluation studies
on the recognition of emotions from faces. Darwin studied which emotions were
recognized consistently from photographs of representative emotional facial expressions
in England [9] (cf. [4: pp. 169-75, 12]) and made the first attempts to evaluate the
universality of emotions by interviewing his fellow countrymen living abroad on the
expression of emotions in other cultures [4: pp. 169-75]. The method of asking subjects
to judge emotions from certain facial expressions has remained a part of contemporary
research methodology.
Conceptual and methodological problems
The basic emotion theory proposed by Ekman has been criticized because of various
conceptual and methodological problems (see especially [13, 17]).
Attribution vs. expression of emotions
Reasoning behind the emotion judgment studies used to evaluate basic emotion theory
is that certain emotions are basic because they are recognized universally from certain
facial expressions. However, universal attribution of certain emotion labels to certain
facial expressions doesn’t necessarily imply the universal expression of the referred
emotions by those facial expressions (cf. [13, 27]). In order to prove the latter, it would
be necessary to show that certain facial expressions accompany certain emotional events
universally. On the contrary, it appears that similar events may lead to different emotions
and emotional expressions in different cultures [4: pp. 174-87]. How could such variation
be compatible with the existence of basic emotions? According to a neuro-cultural theory
of emotions suggested by Ekman [4: pp. 175-9, 22: pp. 212-35], certain basic emotions
are universal but their eliciting situations and display rules controlling their expression
differ between cultures. Display rules have been claimed to work by intensifying,
deintensifying, neutralizing or masking the emotional facial expressions [22: pp. 212-35].
Before studying the cross-cultural expression of emotion in a certain situation, one would
need to show that the situation elicits a similar emotion in the studied cultures and that no
display rules affecting the results would be evident.
The relation between basic emotions and facial expressions
The emotion judgment studies also assume that certain facial expressions are
characteristic of certain basic emotions. This assumption raises further questions on the
relation between facial expressions and emotions. Silvan Tomkins has suggested the face
as “[…] of the greatest importance in producing the feel of affect” [28: p. 212]. Tomkins
had a strong influence on Ekman’s thinking, who has for example expressed doubts on
the very concept of facial expression of emotion: “[…] in my view expression is a central
feature of emotion, not simply an outer manifestation of an internal phenomena” [25: p.
384].
Can facial expressions occur without emotions? Some facial expressions certainly do
occur without any emotion because only a minority of all facial expressions are related to
emotions (cf. [29: p. 337]). A less trivial question is whether emotional facial expressions
can occur without emotion. Ekman suggests that some facial muscles related to genuinely
felt emotions are extremely difficult to activate voluntarily [25: pp. 389-91], for example
the activation of orbicularis oculi (a circular muscle surrounding the eye) may
discriminate genuine from non-genuine smiles. Furthermore, some tentative evidence
exists on the fact that consciously posing emotion-related facial expressions can produce
slight emotional experiences [30] (as cited in [25: p. 50]). Of course, facial expressions
alone should not be expected to induce strong emotions because emotions (and facial
expressions) are usually triggered in real or imagined situations.