KEY SCIENTIFIC STUDIES ON EMPATHY AND OUR BRAINS SHED LIGHT ON THIS UNIVERSAL FEELING AND ITS EFFECTS ON BEHAVIOR
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KEY SCIENTIFIC STUDIES ON EMPATHY AND OUR BRAINS SHED LIGHT ON THIS UNIVERSAL FEELING AND ITS EFFECTS ON BEHAVIOR
WASHINGTON, DC, November 13, 2005 — New research is offering fascinating insights into what happens to our brains when we empathize with the feelings of others. Such research supports the concept of “maternal love” and suggests neurological reasons for monogamy. It also promises to lead to a greater understanding of depression and neurological disorders characterized by a deficit of empathy, such as autism and schizophrenia.
“At this time when conflicts among groups of people across the world are increasingly threatening individual safety, it is more important than ever that we understand what drives human social interactions,” says Elizabeth Phelps, PhD, a professor of psychology and neural science at New York University. “The ability to empathize with others promotes greater bonding and less hostility. This collection of studies starts to explain how the brain enables empathy and the individual factors that may moderate this response.”
As every parent knows, human babies communicate their needs mainly through crying and involuntary facial expressions. For babies to survive, they need adults to empathize with their discomfort or pain and respond with food or other appropriate care.
Scientists have used brain imaging technologies to study the affective response of mothers toward their own children—so-called “maternal love.” They have found that areas of the brain linked to affective responses and, in particular, to positive emotions become activated in a mother’s brain when she sees pictures of her child. Little is known, however, about how the brains of mothers—and of other adults—respond when viewing pictures of suffering children who are not their own.
Researchers at the University of Milan-Bicocca recently compared brain activation in women and men as they viewed black-and-white images of babies unknown to them. The study recruited 40 individuals: 10 female parents, 10 male parents, 10 female non-parents, and 10 male non-parents. Using a technique called event related potentials (ERPs) to investigate face processing, the researchers measured how quickly the study’s subjects distinguished between distressed or happy expressions on the images of the unfamiliar babies.
All the groups responded to the images of distressed babies, but both female and male parents had a stronger reaction. “The female parents showed the greatest and earliest response,” says Alice Proverbio, PhD, one of the authors of the study. The groups exhibited no differences in their responses to happy or comfortable infants.
“These findings suggest a strong interaction between genetic predisposition—being female—and the experience of parenthood in eliciting empathic responses toward children, including children who are not our own,” says Proverbio. She and her colleagues next intend to see if they can replicate these findings with images of older children.
Can empathy alter our own perception of pain? A study recently conducted at McGill University in Montreal suggests that it can. Researchers recruited 12 mothers of young adult children, aged 18 to 30. During the experiment, the mothers immersed their right hand in circulating hot water while watching 2-minute videos of their child and of another young adult experiencing similar pain. After each video, the mothers rated the intensity of their own pain and the unpleasantness of the video. They also estimated the pain experienced by their child and by the other young adult. Each mother also completed a questionnaire that measures the degree to which a person is able to empathize with others.
The mothers’ ratings of their own pain correlated with how much pain they thought their offspring was experiencing, but not with the pain experienced by the young adult who was unknown to them, the researchers reported. The higher the mother’s estimation of their child’s pain, the higher they rated the unpleasantness of the video—and the higher they rated their own pain. Mothers with higher scores on the empathy questionnaire tended to have higher unpleasantness ratings for the videos involving their son or daughter.
The study suggests that empathizing with someone’s pain may alter the observer’s own perception of pain, possibly by engaging emotional pathways in the brain that in turn alter pain transmission.
The McGill researchers next hope to determine whether the phenomenon they observed in this study is specific to mothers and their children or if it can be extended to other pairs of people who share an empathic bond—including strangers.
“For reasons often obscure to us, we sometimes experience a deep affective response while witnessing the pain of a particular stranger, while another stranger’s distress can leave us relatively indifferent,” says Catherine Bushnell, PhD, one of the authors of the study. If it could be shown, she adds, that our own pain perception is affected when we witness the pain of strangers with whom we feel an empathic bond but not when we observe the pain of those with whom we do not feel such a bond, it would further confirm that empathy can alter pain perception.
Another new study reveals that when male prairie voles become isolated from their female partners, they show depressive-like behavior. These findings suggest that negative as well as positive factors may motivate lifelong pair bonding in mammals that form monogamous relationships. Prairie voles form lifelong bonds with a single mate, placing them among the 5 percent of mammals that demonstrate monogamous mating habits.
For the study, which was conducted by researchers from Emory University in Atlanta, Georgia, and from the Institute for Zoology at the University of Regensburg in Regensburg, Germany, male prairie voles were paired either with a female or with a male sibling for five days, after which half the males from each group were isolated for three days. The male subjects were tested for passive coping strategies as well as anhedonic behavior. Passive coping and anhedonia (inability to experience pleasure) are symptoms of a depressive-like state.
“The isolated males that had bonded with the females were significantly more passive and showed a blunted ability to experience pleasure than those separated from siblings,” says Oliver Bosch, PhD, one of the authors of the study. “Hence, being separated from a female mate induces a depressive-like state among male prairie voles.”
The researchers also measured the genetic expression of a protein known as corticotropin-releasing factor (CRF) in several areas of the voles’ brains. CRF helps coordinate the brain’s response to stress. The study found that males isolated from their female partner had significantly higher amounts of CRF gene expression in a region of the brain called the bed nucleus of the stria terminalis (BNST) than did males that remained with their partner. The BNST is known to control anxiety and depression behavior.
In a second experiment, the researchers tested for blood levels of a stress hormone known as corticosterone in paired and isolated males. Increased levels of the human form of this stress hormone are known to occur in people who are depressed. Interestingly, male prairie voles separated from their female partner had higher levels of corticosterone than those remaining with their partner.
“Our findings suggest that there are brain mechanisms in place to maintain social bonds. When such bonds are disrupted these brain mechanisms may be activated and lead to an aversive state similar to depression,” says Hemanth Nair, PhD, the other author of the study. Such mechanisms may have evolved in mammals that require social bonds for survival. Nair and Bosch suggest that similar mechanisms could be present in humans where social bonds play a critical role in health and well being.
Studies have shown that different brain structures respond to different basic emotions. The amygdala (a subcortical structure), for example, is involved in processing fear and the insula (located in the cerebral cortex) in processing disgust. Studies also have shown that some individuals are more empathetic than others when responding to the facial expressions of others. Recently, researchers at the University of Cambridge in the United Kingdom looked at how the brains of people at different points on the empathizing spectrum respond to different basic emotions. They wanted to determine if a single brain structure of a fixed set of structures subserved an individual’s ability to empathize. Such a structure/network would respond equally to all emotions, depending on how empathetic a person was.
For the study, 25 student volunteers (13 females, 12 males) with a variety of Empathizing Quotient (EQ) scores were matched for age, IQ, and educational background. While in a 3T magnetic resonance imaging (MRI) scanner, the subjects were shown a series of short videos depicting one of five facial expressions: happy, sad, angry, disgusted, or neutral. The videos, which were developed at the Cambridge lab, are more realistic that the static photographs of facial emotional expressions generally used for such studies. The subjects were instructed to look at the faces and press a button at each new stimulus. Images of the whole brain (in 21 slices) were taken every 1.1 seconds.
After analyzing the data, the researchers identified specific regions involved in processing different expressions of emotion. These findings were in close agreement with those of previous studies. The researchers then ran a correlational analysis between the individual EQ scores and the brain activations observed for different emotions.
“We found that the EQ scores predicted different response profiles for different emotions,” says Bhismadev Chakrabarti, lead author of this new study. Specific findings included the following:
- For happy faces, a higher EQ score predicted a higher response in the striatum, a set of structures involved in reward processing. This suggests, says Chakrabarti, that the more empathetic we are, the stronger the response in our brain’s reward-related structures.
- For sad faces, a higher EQ score predicted a lower response in the striatum. This suggests that the more empathetic we are, the less our reward-related structures respond when we see a sad face.
- For angry faces, a higher EQ score predicted a higher response in the superior temporal gyrus, an area well known for its role in understanding intentions. A higher EQ score also predicted a higher response in the precuneus and inferior parietal lobe, regions of the brain that have been consistently implicated in “self-other” distinction tasks. This suggests that more empathetic individuals activate more other-related areas of the brain compared to self-related ones when they perceive angry faces.
- For disgust faces, a higher EQ predicted a lower response in the insula and the basal ganglia, regions implicated in disgust processing. This suggests that more empathic individuals are less disgusted by facial expressions of disgust. A higher EQ also predicted a lower response in the anterior cingulate cortex and the medial prefrontal cortex, areas implicated in understanding other’s intentions. This suggests that higher EQ individuals recruit less other-related areas in processing expression of disgust.
“Our study confirms that different emotions are processed by distinct structures in the brain,” says Chakrabarti, “and that there is no unitary neural correlate of empathizing across the different emotions. Depending on how empathetic we are, we recruit different areas to varying extents when we see others’ emotion expressions.” These findings promise to help scientists better understand the nature of how emotion recognition becomes impaired in certain neurological disorders, including autism and schizophrenia.