Why does it hurt when you see others getting hurt?

Have you ever had such an experience? In life, when you see someone else's finger being cut by a sharp knife, your own finger will also feel a dull pain; when reading a novel, even if you know the content is fictional, you will still be heartbroken by the tragic fate of the protagonist; when chatting with friends, even if you just hear the description, you will still be frightened by your friend's dangerous encounter. You obviously have not experienced these scenes at all, but why do you always have a feeling of "the pain is in your body, the pain is in my heart"? These are collectively called "pain empathy" in psychology.

Under normal circumstances, the brain constantly integrates various senses about the body - vision, hearing, balance (vestibular sense), and sensations from joints and muscles, and finally forms a perception that "the body belongs to oneself". This perception of oneself is called body self-perception.

However, when the brain integrates various senses, conflicts sometimes occur. At this time, vision often dominates. When we see others get hurt or form pictures in our brains through others' descriptions, this kind of visual preconception may cause the brain to fall into "self-perception illusion". The illusion mainly occurs due to the asynchrony of visual and tactile stimulation. The brain thinks that vision and touch will occur at the same time, so it automatically completes the "signal completion" and matches the visual signal with tactile sensation.

In addition to the perceptual illusion caused by visual dominance, what kind of neural mechanism does the occurrence of "pain empathy" rely on?

First of all, we need to understand what "empathy" means.

"Empathy" refers to an individual's sensitivity to the psychological state of others, including a series of psychological processes such as being infected by the state of others, evaluating the causes of the state, and understanding the thoughts of others. It includes both relatively simple and primary emotional imitation and more complex and advanced perspective-taking. "Pain empathy" is a typical manifestation of "empathy", which refers to an individual's perception, judgment and emotional response to the pain experienced by others. That is, when others suffer pain, we have the ability to "feel" their pain and sadness.

So what is the reason for this "ability"? Scholars have conducted in-depth research on this and found that "mirror neurons" may be the basis for us to imitate other people's actions and understand other people's emotions. For example, a study published in the Annals of the New York Academy of Sciences in 2022 by scientists from the Institute of Psychology of the Chinese Academy of Sciences explained this problem.

As we all know, the functional cells of the brain are neurons. A brain functional area often gathers a large number of neurons to collaboratively process the same information and complete the corresponding functions. Mirror neurons were first discovered by scholars at the University of Parma in Italy at the end of the 20th century: Scientists have discovered that there is a special type of neuron in the monkey brain that can recognize the potential meaning of the observed object's actions and behaviors through internal imitation like looking in a mirror, and make corresponding emotional responses. The human brain also has such mirror neurons. In other words, when we see others make a certain action or hear a certain melody, we can't help but react. This is because there are mirror neurons responsible for movement in the functional area of ​​the brain responsible for controlling muscle movements. The mirror mechanism in the brain will quickly understand the received signals and make an imitative response. When we observe the pain suffered by others, it will also form a brain area activation that is very similar to the neural response pattern caused by our personal experience of pain, which makes us have similar emotional experiences.

Does this empathy for others’ pain just cause us more trouble? The answer is definitely no.

Pain often indicates danger and is of great significance to an individual's survival. Therefore, even the empathy felt due to the pain of others will make the observer sensitive and alert. This operation of the brain not only helps us activate the self-protection mechanism and escape from potential danger in time, but also allows us to experience and understand the pain and negative emotions suffered by the other person, prompting us to think from the other person's perspective and engage in pro-social and altruistic behavior.

However, it is not difficult to find that this kind of "pain empathy" often varies according to the degree of closeness between the other party and ourselves. We can empathize with the pain of relatives, friends, and positive characters in movies and TV dramas, but for strangers, enemies, or negative characters in movies, our pain level will be greatly reduced, or even indifferent. This phenomenon shows that our brain can automatically judge who is more worthy of sympathy, that is, our pain empathy is biased, mainly because pain empathy is affected by many factors such as personal experience, interpersonal relationships, and psychological state.

First, it has a preference for intimacy.

In 2020, an article was published in the journal Royal Society. The authors found through a series of experiments that parents and other people react more strongly to the cry of a familiar child than to the cry of an unfamiliar baby, as evidenced by increased activation of the orbitofrontal cortex, midbrain, striatum, cingulate gyrus, amygdala, and insula. The activation of these brain areas suggests that the activation of human brain mechanisms related to empathy, regulation, reward, and motivation is the basis for further caring behaviors towards familiar children. Close relationships affect the cognitive processing of pain empathy. People have stronger pain empathy for their loved ones than for strangers.

Second, it has a same-race preference.

In 2015, the research results of Chinese researchers were published in Cognitive Neuroscience. The researchers used magnetic resonance imaging technology to explore the pain empathy of Asians and Europeans for people of the same race and people of different races. The results showed that compared with people of different races, the test subjects had stronger pain empathy for people of the same race, as shown by significant activation of the anterior cingulate gyrus and insular cortex. This is mainly based on group identity.

Again, it has a moral preference.

In life, people tend to show more pain empathy to vulnerable groups because the physical or psychological vulnerability of vulnerable groups will arouse more empathy. In addition, people can distinguish the morality of other people's behavior and have a higher level of pain empathy for those whose behavior conforms to moral standards. This also explains why we feel happy when watching movies and TV shows about the pain of the villains.

In addition to race, intimacy, and moral performance, other social categorization standards, such as gender, cooperative relationships, religious beliefs, etc., will also have different degrees of influence on the "preference" of pain empathy. Through researchers' in-depth exploration of pain empathy mechanisms, influencing factors, and regulatory methods, it will help us to conduct more effective and precise interventions for groups with abnormal empathy, such as autistic children and schizophrenia patients, and provide corresponding protection for vulnerable groups.

Moreover, pain empathy can activate an individual’s early warning system for similar scenarios, allowing us to perceive danger in advance and escape in time. At the same time, it is also a powerful adhesive in interpersonal communication. By understanding and indirectly experiencing the pain of others and promoting prosocial behavior, it constitutes the foundation of social morality and is also beneficial to maintaining good interpersonal relationships and social stability.

This article is a work supported by Science Popularization China Starry Sky Project

Team/Author Name: Tiangeng

Review: Tao Ning

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.