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.