When we look at an enemy, hate takes a similar path in our minds to the path taken by love, at least according to a small study published today in the Public Library of Science.
Researchers in Britain used brain imaging to map what happens when people look at photos of individuals they hate, or individuals they neither cared for or hated.
Seventeen people in the study brought in photos of their ex-girlfriends, co-workers, acquaintances and despised public figures. When a photo of their enemy appeared, researchers using functional MRI found a distinctive pattern in the brain.
The researchers, professors Semir Zeki and John Romaya of the Wellcome Laboratory of Neurobiology at the University College of London, called the pattern a "hate circuit."
Researchers also found that some activation of the "hate circuit" in the insular part of the brain was remarkably similar to a previous "love circuit" they found.
"They were almost identical to the ones activated in the love study," said Zeki. "I was mildly surprised, although love can transmute into hate."
Yet, despite the interesting findings, other scientists question how well brain imaging can explain complex emotions.
"There are a number of very good studies now that look at things that seem kind of ineffable," said Scott Huettel, an associate professor of psychology and neuroscience at Duke University in Durham, N.C.
Huettel, who was not involved in the research, said scientists are making surprising gains into understanding subtle emotions, such as attachment, altruism and disgust by doing brain imaging with functional MRI.
But Huettel said the multifaceted working of the brain makes studying these emotions an enormous amount of work.
"It's hard for us to make it precise," he said.
According to Huettel, looking at a functional MRI scan is like looking at areas of little computations in the brain. Each area that lights up should be doing something, but what isn't always clear.
"Some regions may do computations related to a topic, like faces or words," Huettel said. "Others may do computations related to functions," such as starting, stopping, relating, etc.
When more than one area lights up, as happened with the "hate circuit," trying to parse what each area is doing is like trying to solve an equation with multiple unknowns, he said.
"Each person hated only one other person, so there are probably a lot of other things that are wrapped into the expressions of hatred here," Huettel said. These could be thoughts of other people related to their enemy, or a reaction to an image.
"We have to look at other studies to separate what they're doing," he said.
However, Huettel said he thinks the initial study of the "hate circuit" could be a great start for more research.
"Does this go broader than just looking at the photo of someone you hate?" he asked.
Dr. Cameron Carter, professor of psychiatry and director of the imaging resource center University of California at Davis, agrees.
"I think that it's interesting and it's a very preliminary study," Carter said. "They saw different activities in different areas and then they speculate as to what that activity may have meant."
In those speculations, Zeki noted that an image of an enemy lit up areas of the cerebral cortex part of the brain, which is associated with judgment and reasoning, while an image of a loved one didn't activate those areas.
"I was surprised by the level of deactivation in the case of love, than in the case of hate," said Zeki. "But if you see a person and if you love them, and you trust them, you don't have to watch every step."
By Zeki's estimation, his experiment implies that hate is much more calculating, while love is much more trusting.
"It's interesting," Carter said. "But the study seems to be more of an exploratory kind."
The U.K. study may be one of a kind, too. Zeki could not find many studies on pure love and hate.
"This is the first study to look at brain activity that underlies the emotional response of hatred to the picture of a face," said Kevin S. LaBar, associate professor at the Center for Cognitive Neuroscience at Duke University.
"It would be really interesting to know if the brain activity reported here in response to an individual face generalizes to hatred of groups, which can motivate prejudice," he said.
"People have done lots of studies that have involved using lots of different facial emotions: faces from in-groups, faces from out-groups, faces of smiling people, faces of different races," Carter said. "But people were inferring a certain emotion from those faces."
With this study, Carter noted, the scientists flat out asked the people how they felt about these faces and then ran the scans. In this case, the assumption wasn't an emotion, but what was happening in the functional MRI scan.
Zeki wants to use this new approach to do more studies.
"We've got many other follow-up studies to do, and even this is a follow-up study to the love study," Zeki said. "For example, romantic love is usually directed at one person at any given time, but with hate it can be directed at a group or an individual member of the group."
To Zeki, that makes hatred more complicated than love.