A brain anomaly can make the saying "I know how you feel" literally true in hyper-empathetic people who actually sense that they are being touched when they witness others being touched.

The condition, known as mirror-touch synesthesia, is related to the activity of mirror neurons, cells recently discovered to fire not only when some animals perform some behavior, such as climbing a tree, but also when they watch another animal do the behavior. For "synesthetes," it's as if their mirror neurons are on overdrive.

"We often flinch when we see someone knock their arm, and this may be a weaker version of what these synesthetes experience," University College London cognitive neuroscientist Jamie Ward said.

Now scientists find these synesthetes possess an unusually strong ability to empathize with others. Further research into this condition might shed light on the roots of empathy, which could help better understand autism, schizophrenia, psychopathy and other disorders linked with empathy.

Blended experiences

Synesthesia is a condition where sensations that normally are experienced separately get blended together. The most common form is color-grapheme synesthesia, where a person experiences colors upon hearing or reading words. Others can taste words.

In mirror-touch synesthesia, when another person gets touched, the synaesthete feels a touch on their body. University College London cognitive neuroscientist Sarah-Jayne Blakemore discovered a mirror-touch synesthete in 2003 by a stroke of good luck.

"I was giving a talk and mentioned synesthesia, and that anecdotally there were reports that some people felt touches they only observed, and there was a woman in the audience who asked, 'Doesn't everyone experience that? Isn't that completely normal?'" Blakemore recalled.

Until that point, that 39-year-old woman did not realize her mirror-touch synesthesia was unusual. "It was something she's always had," Blakemore told LiveScience. In fact, a cousin of hers also has it, suggesting it runs in families.

When the woman faced someone and saw that person get touched on the left cheek, she felt it on her right cheek. On the other hand, if she stood next to somebody and that person got touched on the right side, she felt a touch on her right side.

The pain of horror films

Now Ward and doctoral student Michael Banissy reveal 10 more mirror-touch synesthetes they discovered among University College London students, as well as among people who possess other types of synesthesia. (The woman that Blakemore has 11 relatives with color-grapheme synesthesia, and that woman had color-grapheme synesthesia herself when she was younger.)

The researchers had the mirror-touch synesthetes take a questionnaire designed to measure empathy. For instance, they were asked to agree or disagree with statements such as "I can tune into how someone feels rapidly and intuitively."

The mirror-touch synesthetes scored significantly higher than people without synesthesia, findings detailed in the July issue of the journal Nature Neuroscience.

One mirror-touch synaesthete, Alice, said "I have never been able to understand how people can enjoy looking at bloodthirsty films, or laugh at the painful misfortunes of others when I can not only not look but also feel it." Another, Jane, said she felt her synesthesia is "a positive thing because I believe it makes me more considerate about the feelings of others."

Overactive mirrors

Banissy told LiveScience that "when we observe another person being touched, we all activate areas of our brain similar to those activated when we are physically touched." In mirror-touch synesthetes, this mirror system is overactive. The resulting high level of empathy they demonstrate supports the notion that people learn to empathize by putting themselves in someone else's shoes.

"It is extraordinary to think that some people experience touch on their own body when they merely watch someone else being stroked or punched. However, this may be an exaggeration of a brain mechanism that we all possess to some degree," Ward said.

UCLA neuroscientist Marco Iacoboni explained a better understanding of the mirror system could help shed light and treat autism, "which is well-known for not understanding the emotional states of others." Blakemore added such research could also help research into psychopaths, "where empathy goes wrong and people don't feel empathy in the normal way."

On a fundamental level, University of Parma cognitive neuroscientist Vittorio Gallese suggested this system "might be relevant for the ability to entertain an abstract notion of touch, such as upon watching objects touch each other."