Simulation theory of empathy

People share emotions with other people. People feel happy when they see others laugh. On the other hand, people feel sad, when they see others cry. This ability to share emotions and sensations is called empathy. The simulation theory of empathy is a theory that explains why and how humans can share emotions and sensations with other people. Theoretical rationale of the simulation theory of empathy is that observing others’ experiences automatically activates shared neural networks of viewers so that people could experience same emotions and sensations of the observed. For example, people feel disgust when they see others smell bad odor , people feel pain when they see others being pierced by a needle or get electrical shock , people sense touching when they see others being brushed , or people feel sad when they see others’ sad facial expression The simulations theory of empathy posits that the perceived emotion and sensations are distinguished from the observers by attributing them to be belonged to the observed

Origin

The neural mechanism that enables humans to share emotions and sensations is called a mirror system enabled by neurons that have mirror property. Mirror neurons has been found in the macaque monkey’s brain in a series of single neural cell recording experiments (di Pellegrino, Fadiga, Fogassi, Gallese, & Rizzolatti, 1992). It was in the midst of experiments to record the activities of motor neurons in the University of Parma in early 1990s. The Italian scientists, Rizzolatti and colleagues, had been monitoring the neural activities in the premotor area; neurons buzzed when the monkey moved its arms such as grasping a peanut. One day, the researchers observed unexpected neural activities (Blakeslee, 2006 Jan 10). While the researchers recorded activities motor neurons of a monkey, a graduate student entered the lab with an ice cream cone in his hand. When the monkey stared at him who moved the ice cream cone to his lips, the neurons in the premotor area of the monkey buzzed. The monkeys had been sitting still and doing nothing. They tried to find feasible explanation for the mysterious neural activities in the premotor area, and they caught the right moment of the neural activities (Nash, 2007 Jan 29). When a researcher picked up some seeds to place them on a tray for monkeys, the same neurons buzzed again in the same pattern. The researchers concluded that the neurons buzzed both when the monkey executed actions and watched the actions. At first, they called the neurons “monkey-see-monkey do” neurons, and they later coined them mirror neurons because the monkeys were mentally mirroring the actions they observed. By a series of experiments, the Italian researcher proved the existence of mirror neurons in the inferior frontal lobe (Gallese, Fadiga, Fogassi, & Rizzolatti, 1996; Rizzolatti, Fadiga, Gallese, & Fogassi, 1996; Rizzolatti, Fadiga, Matelli et al., 1996), and later in the interior parietal lobe, too(Fogassi et al., 2005). Mirror neurons were also identified in the human brain by fMRI study (Iacoboni et al., 1999).

The Development of the Theory: Action Understanding

Mirror neurons are activated both when actions are executed and the actions are observed. This unique function of mirror neurons explains how people recognize and understand the states of others; mirroring observed action in the brain as if they conducted the observed action. Watching and mentally mirroring the actions enables humans to understand other’s actions quickly (Gallese, Keysers, & Rizzolatti, 2004). Social cognitive role of mirror neurons can be explained with the two perspectives. First, the activation of mirror neurons requires biological effecters such as hand or mouth. Mirror neurons do not respond to the action with tools like pliers (Gallese et al., 1996; Rizzolatti, Fadiga, Gallese et al., 1996). Mirror neurons respond to neither the sight of an object alone nor an action without an object (intransitive action). Umilta and colleagues (2001) 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) (Ferrari, Gallese, Rizzolatti, & Fogassi, 2003). 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) (Iacoboni et al., 2005).

The Development of the Theory: 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 (Carr, Iacoboni, Dubeau, Mazziotta, & Lenzi, 2003). Observing video clips that displayed facial expression of feeling disgust activated the neural networks typical of direct experience of disgust (Wicker et al., 2003). 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 (Keysers et al., 2004; Singer et al., 2004). A similar mirror system exists in perceiving pain. When people see other people feel pain, people feel pain not only affectively (Botvinick et al., 2005; Singer et al., 2004) but also sensorially (Avenanti et al., 2005; Avenanti et al., 2006). Understanding other's feelings and emotions is mainly 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 (Harrison et al., 2006). 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.

The Development of the Theory: Epistemological Role of Empathy

Understanding other’s actions and emotions is not only to serve as motivation for prosocial behavior but also to facilitate efficient human communication (de Vignemont & Singer, 2006). Based on recent findings from neuroimaging studies, de Vignemont and Singer (2006) propose 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” (p.440). Mentally mirroring the actions and emotions enables humans to understand other’s actions and their related environment quickly, which help humans communicate efficiently (Gallese et al., 2004). In a recent fMRI study, a mirror system has been proposed as common and discrete neural substrates to mediate the experiences of basic emotions (Chakrabarti, Bullmore, & Baron-Cohen, 2007). 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 evidence that action perception mediates face perception to emotion perception.

References

Avenanti, A., Bueti, D., Galati, G., & Aglioti, S. M. (2005). Transcranial magnetic stimulation highlights the sensorimotor side of empathy for pain. Nature Neuroscience, 8(7), 955-960. Avenanti, A., Paluello, L. M., Bufalari, I., & Aglioti, S. M. (2006). Stimulus-driven modulation of motor-evoked potentials during observation of others' pain. Neuroimage, 32(1), 316-324. Botvinick, M., Jha, A. P., Bylsma, L. M., Fabian, S. A., Solomon, P. E., & Prkachin, K. M. (2005). Viewing facial expressions of pain engages cortical areas involved in the direct experience of pain. Neuroimage, 25(1), 312-319. Carr, L., Iacoboni, M., Dubeau, M. C., Mazziotta, J. C., & Lenzi, G. L. (2003). Neural mechanisms of empathy in humans: A relay from neural systems for imitation to limbic areas. Proceedings of the National Academy of Sciences of the United States of America, 100(9), 5497-5502. Chakrabarti, B., Bullmore, E., & Baron-Cohen, S. (2007). Empathizing with basic emotions: Common and discrete neural substrates Social Neuroscience, 1(3&4), 364-384. de Vignemont, F., & Singer, T. (2006). The empathic brain: How, when and why? Trends in Cognitive Sciences, 10(10), 435-441. di Pellegrino, G., Fadiga, L., Fogassi, L., Gallese, V., & Rizzolatti, G. (1992). Understanding motor events - A neurophysiological study. Experimental Brain Research, 91(1), 176-180. Ferrari, P. F., Gallese, V., Rizzolatti, G., & Fogassi, L. (2003). Mirror neurons responding to the observation of ingestive and communicative mouth actions in the monkey ventral premotor cortex. European Journal of Neuroscience, 17(8), 1703-1714. Fogassi, L., Ferrari, P. F., Gesierich, B., Rozzi, S., Chersi, F., & Rizzolatti, G. (2005). Parietal lobe: From action organization to intention understanding. Science, 308(5722), 662-667. Gallese, V. (2001). The 'shared manifold' hypothesis: From mirror neurons to empathy. Journal of Consciousness Studies, 8(5-7), 33-50. Gallese, V. (2003). The roots of empathy: The shared manifold hypothesis and the neural basis of intersubjectivity. Psychopathology, 36(4), 171-180. Gallese, V., Fadiga, L., Fogassi, L., & Rizzolatti, G. (1996). Action recognition in the premotor cortex. Brain, 119, 593-609. Gallese, V., Keysers, C., & Rizzolatti, G. (2004). A unifying view of the basis of social cognition. Trends in Cognitive Sciences, 8(9), 396-403. Harrison, N. A., Singer, T., Rotshtein, P., Dolan, R. J., & Critchley, H. D. (2006). Pupillary contagion: Central mechanisms engaged in sadness processing. SCAN, 1, 5-17. Iacoboni, M., Molnar-Szakacs, I., Gallese, V., Buccino, G., Mazziotta, J. C., & Rizzolatti, G. (2005). Grasping the intentions of others with one's own mirror neuron system. Plos Biology, 3(3), 529-535. Iacoboni, M., Woods, R. P., Brass, M., Bekkering, H., Mazziotta, J. C., & Rizzolatti, G. (1999). Cortical mechanisms of human imitation. Science, 286(5449), 2526-2528. Keysers, C., Wicker, B., Gazzola, V., Anton, J. L., Fogassi, L., & Gallese, V. (2004). A touching sight: SII/PV activation during the observation and experience of touch. Neuron, 42(2), 335-346. Nash, J. M. (2007 Jan 29). The gift of mimicry. Time, 169(5), 108-110, 113. Blakeslee, S., (2006 Jan 10). Cells that read minds. New York times, Section F, Column 2 Rizzolatti, G., Fadiga, L., Gallese, V., & Fogassi, L. (1996). Premotor cortex and the recognition of motor actions. Cognitive Brain Research, 3(2), 131-141. Rizzolatti, G., Fadiga, L., Matelli, M., Bettinardi, V., Paulesu, E., Perani, D., et al. (1996). Localization of grasp representations in humans by PET .1. Observation versus execution. Experimental Brain Research, 111(2), 246-252. Singer, T., Seymour, B., O'Doherty, J., Kaube, H., Dolan, R. J., & Frith, C. D. (2004). Empathy for pain involves the affective but not sensory components of pain. Science, 303(5661), 1157-1162. Umilta, M. A., Kohler, E., Gallese, V., Fogassi, L., Fadiga, L., Keysers, C., et al. (2001). I know what you are doing: A neurophysiological study. Neuron, 31(1), 155-165. Wicker, B., Keysers, C., Plailly, J., Royet, J. P., Gallese, V., & Rizzolatti, G. (2003). Both of us disgusted in my insula: The common neural basis of seeing and feeling disgust. Neuron, 40(3), 655-664.