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From Wikipedia, the free encyclopedia
The simulation theory is not primarily a theory of empathy, but rather a theory
of how we understand others -- that we do so by way of a kind of empathetic
response. The theory holds that humans anticipate and make sense of the
behavior of others by activating mental processes that, if carried into action,
would produce similar behavior. This includes intentional behavior as well as
the expression of emotions.
Origin
The simulation theory is actually based in philosophy of mind, especially the
work of Alvin Goldman and Robert Gordon. Then, the discovery of mirror neurons
in macaque monkeys has provided a physiological mechanism for the common coding
between perception and action (see Wolfgang Prinz) [1] and the hypothesis of a
similar mirror neuron system in the human brain.[2][3] Since the discovery of
the mirror neuron system, many studies have been carried out to examine the
role of this system in action understanding, emotion and other social
functions.
Development
Mirror neurons are activated both when actions are executed and the actions are
observed. This unique function of mirror neurons may explain how people
recognize and understand the states of others; mirroring observed action in the
brain as if they conducted the observed action [4].
Two sets of evidence suggest that mirror neurons in the monkey have a role in
action understanding. First, the activation of mirror neurons requires
biological effectors such as hand or mouth. Mirror neurons do not respond to
the action with tools like pliers. [5] Mirror neurons respond to neither the
sight of an object alone nor an action without an object (intransitive action).
Umilta and colleagues [6] demonstrated that a subset of mirror neurons fired
when final critical part of the action was not visible to the observer. The
experimenter showed his hand moving toward a cube and grasping it, and later
showed the same action without showing later part grasping the cube (placing
the cube behind the occluder). Mirror neurons fired on both visible and
invisible conditions. On the other hand, mirror neurons did not discharge when
the observer knew that there was not a cube behind the occluder.
Second, responses of mirror neurons to same actions are different depending on
context of the action. A single cell recording experiment with monkeys
demonstrated the different level of activation of mouth mirror neurons when
monkey observed mouth movement depending on context (ingestive actions such as
sucking juice vs. communicative actions such as lip-smacking or tongue
protrusions). [7] An fMRI study also showed that mirror neurons respond to the
action of grasping a cup differently depending on context (to drink a cup of
coffee vs. to clean a table on which a cup was placed). [8]
Emotion understanding
Shared neural representation for a motor behavior and its observation has been
extended into the domains of feelings and emotions. Not only movements but also
facial expressions activate the same brain regions that are activated by direct
experiences. In an fMRI study, same brain regions on action representation
found to be activated when people both imitated and observed emotional facial
expressions such as happy, sad, angry, surprise, disgust, and afraid. [9].
Observing video clips that displayed facial expression of feeling disgust
activated the neural networks typical of direct experience of disgust. [10].
Similar results have been found in the case of touch. Watching movies that
someone touched legs or faces activated the somatosensory cortex for direct
feeling of the touch. [11] A similar mirror system exists in perceiving pain.
When people see other people feel pain, people feel pain not only affectively,
[12] but also sensorially. [13]
These results suggest that understanding other's feelings and emotions is
driven not by cognitive deduction of what the stimuli means but by automatic
activation of somatosensory neurons. A recent study on pupil size directly
demonstrated emotion perception was automatic process modulated by mirror
systems. [14] When people saw sad faces, pupil sizes influenced viewers in
perceiving and judging emotional states without explicit awareness of
differences of pupil size. When pupil size was 180% of original size, people
perceived a sad face as less negative and less intense than when pupil was
smaller than or equal to original pupil size. This mechanism was correlated
with brain regions that implicated in emotion process, the amygdala.
Furthermore, viewers mimic the size of their own pupils to those of sad faces
they watched. Considering that pupil size is beyond voluntary control, the
change of pupil size upon emotion judgment is a good indication that
understanding emotions is automatic process. However, the study could not find
other emotional faces such as happiness and anger influence pupil size as
sadness did.
Epistemological role of empathy
Understanding other s actions and emotions is believed to facilitate efficient
human communication. Based on findings from neuroimaging studies, de Vignemont
and Singer [15] proposed empathy as a crucial factor in human communication
arguing its epistemological role; Empathy might enable us to make faster and
more accurate predictions of other people s needs and actions and discover
salient aspects of our environment. Mental mirroring of actions and emotions
may enable humans to understand other s actions and their related environment
quickly, and thus help humans communicate efficiently [16].
In an fMRI study, a mirror system has been proposed as common neural substrates
to mediate the experiences of basic emotions [17]. Participants watched video
clips of happy, sad, angry and disgust facial expressions, and measured their
Empathy Quotient (EQ). Specific brain regions relevant to the four emotions
were found to be correlated with the EQ while the mirror system (i.e., the left
dorsal inferior frontal gyrus/premotor cortex) was correlated to the EQ across
all emotions. The authors interpreted this result as an evidence that action
perception mediates face perception to emotion perception.
Empathy for pain
A paper published in Science (Singer et al., 2005)[18] challenges the idea that
pain sensations and mirror neurons play a role in empathy for pain.
Specifically, the authors found that activity in the anterior insula and the
anterior cingulate cortex was present both when one's self and another person
were presented with a painful stimulus, two regions known to be responsible for
the affective experience of pain, but the rest of the pain matrix, responsible
for sensation, was not active. Furthermore, participants merely saw the hand of
another person with the electrode on it, making it unlikely that 'mirroring'
could have caused the empathic response. However, a number of other studies,
using magnetoencephalography and functional MRI have since demonstrated that
empathy for pain does involve the somatosensory cortex, which supports the
simulation theory.[19][20][21][22]
Support for anterior insula and anterior cingulate cortex being the neural
substrates of empathy include Wicker et al., 2003 who report that their "core
finding is that the anterior insula is activated both during observation of
disgusted facial expressions and during the emotion of disgust evoked by
unpleasant odorants"[23] (p. 655).
Furthermore, one study demonstrated that "for actions, emotions, and sensations
both animate and inanimate touch activates our inner representation of touch."
They note, however that "it is important at this point to clarify the fact that
we do not believe that the activation we observe evolved in order to empathize
with other objects or human beings"[24] (p. 343).