A
facial expression is one or more motions or positions of the muscles beneath
the skin of the face. According to one set of controversial theories, these
movements convey the emotional state of an individual to observers. Facial
expressions are a form of nonverbal communication. They are a primary means of
conveying social information between humans, but they also occur in most other
mammals and some other animal species. (For a discussion of the controversies
on these claims, see Fridlund[1] and Russell & Fernandez Dols.[2]). The
pioneer F-M Facial Action Coding System 2.0 (F-M FACS 2.0) [3] was created in
2017 by Dr. Freitas-Magalhães, and presents about 2,000 segments in 4K, using
3D technology and automatic and real-time recognition.
Humans
can adopt a facial expression voluntarily or involuntarily, and the neural
mechanisms responsible for controlling the expression differ in each case.
Voluntary facial expressions are often socially conditioned and follow a
cortical route in the brain. Conversely, involuntary facial expressions are
believed to be innate and follow a subcortical route in the brain.
Facial
recognition is often an emotional experience for the brain and the amygdala is
highly involved in the recognition process.
The
eyes are often viewed as important features of facial expressions. Aspects such
as blinking rate can be used to indicate whether or not a person is nervous or
whether or not he or she is lying. Also, eye contact is considered an important
aspect of interpersonal communication. However, there are cultural differences
regarding the social propriety of maintaining eye contact or not.
Beyond
the accessory nature of facial expressions in spoken communication between
people, they play a significant role in communication with sign language. Many
phrases in sign language include facial expressions in the display.
There
is controversy surrounding the question of whether or not facial expressions
are worldwide and universal displays among humans. Supporters of the
Universality Hypothesis claim that many facial expressions are innate and have
roots in evolutionary ancestors. Opponents of this view question the accuracy
of the studies used to test this claim and instead believe that facial
expressions are conditioned and that people view and understand facial
expressions in large part from the social situations around them.
Emotions
have been studied for a long time and results show that they play an important
role in human cognitive functions. In fact, emotions play an extremely
important role during the communication between people. And the human face is
the most communicative part of the body for expressing emotions; it is
recognized that a link exists between facial activity and emotional states. In
order to make computer applications more believable and friendly, giving them
the ability to recognize and/or express emotions are research fields which have
been much focused on. Being able to perform these tasks, firstly, we need to
have knowledge about the relationship between emotion and facial activity.
Up
to now, there have been proposed researches on this relationship. However,
almost all these researches focused on analyzing the relationship without
taking into account time factors. They analyzed the relationship but did not
examined it in the time domain. In this paper, we propose a work on analyzing
the relationship between emotions and facial activity in the time domain. Our
goal is finding the temporal patterns of facial activity of six basic emotions
(happy, sad, angry, fear, surprise, disgust). To perform this task, we analyzed
a spontaneous video database in order to consider how facial activities which
are related to the six basic emotions happen temporally. From there, we bring
out the general temporal patterns for facial expressions of each of the six
emotions.
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