Lead author Jean Decety and Stephanie Cacioppo, both of the University of Chicago, said the findings help explain how the brain is hard-wired to recognize when another person is being intentionally harmed.
"Our data strongly support the notion that determining intentionality is the first step in moral computations," Decety said in a statement.
The researchers analyzed adults who watched videos of people who suffered accidental harm such as being hit with a golf club and intentional harm such as being struck with a baseball bat. As the study subjects watched the videos, brain activity was collected with equipment that accurately maps responses in different regions of the brain. The technique is known as high-density, event-related potentials technology.
The study, scheduled to be published in the December issue of the Journal of Neurophysiology, found the intentional harm sequence produced a response in the brain almost instantly -- within 60 milliseconds, the right posterior superior temporal sulcus, located in the back of the brain, was first activated, with different activity depending on whether the harm was intentional or accidental.
This was followed in quick succession by the amygdala, often linked with emotion, and the ventromedial prefrontal cortex -- which took180 milliseconds -- the portion of the brain that plays a critical role in moral decision-making, but there was no response in the amygdala and ventromedial prefrontal cortex when the harm was accidental, the study said.