With a flip of a switch, Tania Singer triggered an electrical shock to her female subject’s right hand. With a flip of another switch, the subject’s husband received a similar shock. The woman, seated next to an MRI scanner, could see nothing of her husband except for his hand, but she watched a screen indicating whether she or her partner was receiving a painless electrical shock or one about as painful as a bee sting. The MRIs showed that when witnessing her loved one in pain, certain parts of the woman’s brain would become active, echoing a similar brain response when she herself was in pain. This example of empathy showed that, in a limited sense, the phrase “I feel your pain,” can be true.

Empathy – the act of knowing how others feel, feeling what others feel and caring what others feel – has long been the domain of philosophers and social scientists. This study, published in Science in early 2004, marks the most recent example of a move in empathy research from the field of social science to neurology. Empathy is the English translation of the German word Einfuhlung, which literally means “feeling into.” The idea was first presented in 1873 by German theorist Robert Vischer as a term used in aesthetics – the theory that dynamics in a work of art could be used to suggest muscular and emotional attitudes in a viewer, making them experience the related emotions. It wasn’t until 1903 that empathy entered the field of psychology thanks to philosopher Theodore Lipps. He put forth the theory that perceiving an emotion in another person can activate the same emotion in the viewer.

Over a century later, Tania Singer, a research fellow at the University College of London, has the MRI scans that prove him right.

To study empathy, Singer needed to differentiate between a patient feeling an emotion and a patient witnessing it in someone else, to determine if the same neural circuits were involved. Scientists are finding that it’s possible to be empathetic without fully taking on the feelings involved. Though the brain does echo what would occur if the feeling or stimulus was applied to the self, it is not a true mirror image when it is applied to others.

Singer and her colleagues examined how much of another person’s pain their subjects would feel – that is, how empathetic they were to the pain. They chose 16 couples because they assumed that couples would be more likely to be empathetic towards each other, said Singer. The women were seated next to MRI scanners that were able to measure the brain activity by looking at the blood flow to certain regions of the brain. As certain regions of the brain are activated, blood flow increases and they light up on the scanner. By comparing the MRI images of a woman when she was being shocked to when her husband was being shocked, the scientists were able to see what areas of the brain were triggered by the physical sensation of pain versus the knowledge that a loved one was feeling that pain.

Singer and her colleagues found that the women responded to their partner’s pain by echoing some of the same brain activity that would occur when they themselves were in pain, but not all of it. They only felt some of their partner’s pain. The women’s brains failed to register the partner’s pain as a physical sensation of pain, but rather evoked the emotional suffering of what that pain would feel like.

What actually occurs when the brain feels empathy is a complex behavior that relies on several systems, says Marco Iacoboni, a neuroscientist at the University of California, Los Angeles. One of the key participants is an almond-shaped region of the forebrain known as the amygdala, which showed increased blood flow. This makes sense, since the amygdala is part of the limbic system or “emotional brain.” The region has strong connections to people’s emotions, especially fear and nervous reactions, and scientists suspect it mediates both inborn and acquired emotional responses as well. Now scientists are finding the frontal lobe is also activated during the studies, making it a key component of empathy.

“Although empathy is experienced as a feeling, it has a cognitive as well as affective component,” according to William Damon, a developmental psychologist at Stanford University. The frontal lobe is part of the cerebrum, the more cognitive part of the brain. It receives information from the senses and the emotions and integrates that data into a plan of action for the individual, as well as choosing whether or not to follow through with the plan. So empathy employs not only the feeling part of the brain, but thinking parts as well.

As a fundamental building block of our social interactions, empathy plays a vital role in how we interact with each other. “Empathy puts the brakes on violence. Empathy allows communication. Empathy allows one to understand another’s behavior. Empathy allows altruism,” says Simon Baron-Cohen, a research fellow at the University of Cambridge. “Do you need any more reasons to justify the importance of empathy?”

The ability to put oneself in another’s position hinges on the theory of mind – the ability to attribute mental states like our own to others, taking into account what others are thinking. This usually develops around age four, allowing people to understand that other people are like themselves, with their own internal mental lives, and makes it possible to not only learn from each other, but through each other’s experience. “There is good evidence that we can figure out how others are feeling, what they intend and how they are likely to act by putting ourselves in their shoes, so to speak,” said Ralph Adolphs, a neurologist at the University of Iowa.

Putting ourselves in another’s shoes involves a certain amount of imitation, whether it’s an outer expression of the emotion like facial expressions and posture or an inner expression through the activation of similar regions of the brain. In a study on imitation, Iacoboni found that overt imitation of gestures or facial expressions increased the inner level of imitation; increased the amount of brain activity that was echoed. Eleven subjects were underwent MRI scanning while they either imitated or simply observed various facial expressions from happiness and surprise to anger, sadness, disgust and fear. When the subjects simply observed the faces, activity occurred in the emotional centers of the brain, like the amygdala. When the subjects actually imitated the faces, the brain became far more active. Part of the activity was in regions that deal with physical motion, which wouldn’t be triggered by observation alone, but even the areas like the amygdala that only deal with emotion showed more blood flow, meaning more activity. “The more one tends to imitate others,” said Iacobini, “the more one is empathetic.”

The imaging data corroborates previous work that used the older psychological questionnaires. Through the surveys, scientists found that people with something called the chameleon effect – a tendency to imitate mannerisms, expressions, accents and postures of other people automatically and subconsciously – would test higher on the empathy scales. The more in tune their physical body was to the people around them, the more in tune they were to the mental aspects of those surrounding them. “If you really want to understand what the mental state of the person is, you still have to invoke some of the mental aspects that are associated with that state,” said Iacoboni.

The use of brain imaging in empathy has led researchers to consider empathy as more than just a philosophical moral value, but as something that is actually hard-wired into the brain. Scientists not only see how empathy is expressed neurologically, but are able to find out the explanations for the information they’ve learned from psychological empathy testing. For instance, it’s long been believed, based on survey evaluations, that women are more empathetic than men. According to Baron-Cohen, women average about ten points higher than men on EQ scores, the emotional equivalent of an IQ test. That’s why Singer’s pain study focused on women. “They are known for being more empathetic but there is no brain scan evidence of it,” she said.

But there may soon be. Singer’s latest work is will switch the roles between the men and women studied to see if men show a similar empathic response. Baron-Cohen is wrapping up a study that uses MRIs to show the difference in empathetic response between men and women. They hope that through brain imaging, they will answer the question of whether there is an actual biological difference in both how and to what extent men and women feel empathy.