What Mirror Neurons Do and Do Not Explain About Empathy.

Mirror neurons are brain cells that fire both when an animal performs an action and when it watches another do the same action.^[1] Do they explain human empathy? Not on their own. A pooled analysis of about fifty studies in healthy people found mixed associations between the mirror neuron system and emotional and cognitive empathy.^[15] Few of its studies tested motor empathy, the automatic copying of others' movements and expressions, which the popular story treated as the foundation. Those few found no significant link.^[15]

What was actually found? In macaque monkeys, researchers recorded single cells that fire both ways.^[1] In humans, the evidence is mostly indirect, from brain scans. Only one study has recorded such cells directly in humans, in people with epilepsy who had electrodes in the brain for medical reasons.^[12]

So what does empathy depend on? It draws on three brain networks, or circuits.^[6][9] The mirror neuron system gives a fast, automatic motor simulation, a rough model of what someone is doing.^[5] The affective resonance system, called here the feeling-sharing network, centres on the anterior insula and the anterior cingulate cortex (ACC). It gives the "as-if" bodily sense most people mean when they say they "feel" someone's pain.^[6][7] The mentalizing system, called here the perspective-taking network, centres on the temporoparietal junction (TPJ) and the medial prefrontal cortex (mPFC). It handles perspective-taking: working out what someone believes, intends or needs.^[8][9]

The first recordings were made in macaque monkeys. A research team saw that some cells in area F5 of the monkey's premotor cortex, a movement-planning area, fired when the monkey grasped a peanut. They fired again when it only watched an experimenter grasp one.^[1] The cells did not respond to the peanut alone or to aimless hand movements. They responded to the match between seeing an action and doing it. The team had found what became one of the most hyped ideas in neuroscience.^[1][2]

Within a decade, the story had outgrown the data. Mirror neurons were said to explain empathy, language, culture and even the roots of civilisation.^[3][4] An article for business leaders claimed that mirror neurons let leaders emotionally resonate with their teams.^[26] Publication output in mirror neuron research peaked in the early 2010s.^[27] One critical review called the idea a "brand": a promise of one neat explanation for the hardest thing the brain does, which is understanding other people.^[14]

The neat explanation did not hold up, as the pooled analysis showed.^[15] Mirror neurons are real, and they do something important.

Each network answers a different question. The mirror system asks: what is this person doing? The feeling-sharing network asks: what are they feeling? The perspective-taking network asks: what are they thinking? Judging what someone feels may draw on more than one network at once, as one brain-scan study suggests.^[10]

This matters because much popular advice has taught the wrong model: that empathy is one capacity you have or lack, kept in one place in the brain. That model hides what goes wrong when someone struggles to read people. Confusing your own feelings with someone else's, for example, is a problem of self-other distinction.^[19]

The research after the hype is more useful because it is more specific. Trials in health-care education show that training can raise measured empathy.^[23] Other work suggests that the type of training matters.^[20] This article reads those findings as a reason to match the training to the network that is weak. That matching is a synthesis of the cited studies; no study has tested it as a whole.

The first network, and the one that drew all the attention, is the mirror neuron system. In macaques, mirror neurons have been recorded in premotor area F5 and in the inferior parietal lobule, a parietal area further back.^[14] They fire when the monkey performs a goal-directed action, such as grasping food, and when it watches someone else do the same. In the first recordings, a minority of the F5 cells fired both ways.^[1] The cells were choosy: they responded to someone acting on an object, rather than to the object or the actor alone.^[1]

In humans, the evidence is mostly indirect. Functional MRI (fMRI) brain scans find areas that respond both when people act and when they watch.^[2][5] These areas are the inferior frontal gyrus and the inferior parietal lobule, which researchers compare with the monkey's premotor and parietal areas.^[2][5] But fMRI tracks blood flow, not single cells. The only direct recording of single human cells comes from one study.^[12] Its subjects were people with epilepsy who had electrodes in the brain for medical reasons, a method called intracranial recording.^[12] In twenty-one patients, the study recorded single cells and small groups of cells, and found matching responses when patients made an action and when they watched one.^[12] Cells in the supplementary motor area (SMA), a movement-planning area, responded to both more often than chance would explain.^[12][13]

That detail matters. Mirror-like responses were found in the SMA and in medial temporal areas around the hippocampus. The study did not record from the outer premotor and parietal areas studied in monkeys, so it could not test whether similar cells occur there.^[12]

The second network is the one most people mean by empathy. The feeling-sharing network centres on the anterior insula on both sides of the brain and on the front and middle of the cingulate cortex.^[6][7] It responds both when you feel pain and when you see someone else in pain.^[6][7] This overlap is one of the most often replicated findings in social neuroscience.^[7] A pooled analysis of brain-imaging studies found that the insula and ACC form the core network for empathy for pain.^[7]

This network deals in feelings rather than actions. When you watch a friend get an injection, the insula produces a vicarious bodily response, an "as-if" feeling that gives you a sense of their pain without the injury.^[6][8] A major review found that this affective sharing changes with context: who the other person is, whether they belong to your group, and whether you judge that they deserve empathy.^[6]

Brain scans show this. In studies, ingroup members in pain trigger a stronger insula response than outgroup members in pain.^[6][11] At the brain level, empathy is not an automatic reflex. It is a regulated process that the brain turns up or down, depending on how it judges the social situation.

The third network works at a higher level. The perspective-taking network centres on the temporoparietal junction and the medial prefrontal cortex. It handles theory of mind: working out what another person believes, intends or knows.^[8][9] This network's work, called mentalizing, involves considering another person's thoughts and feelings.^[9]

One brain-scan study tested empathic accuracy, how well people judge what others feel. People judged more accurately when both the simulation areas and the perspective-taking areas were more active.^[10]

This is where the three-network model becomes useful. It suggests that problems in reading people may differ by network, and that each network may respond to different training.

One small behavioural study separated two kinds of empathy.^[29] Adults with Asperger syndrome had lower cognitive empathy than controls, but did not differ from them in emotional empathy.^[29]

Brain-imaging research has also studied psychopathy. A systematic review and pooled analysis of this work focused on people with high psychopathic traits.^[16] In those scans, taken during emotional-face processing, people with high traits showed changes in both mirror-system and emotion-related areas.^[16]