Whether you like someone can affect how your brain processes their actions, according to new research from the Brain and Creativity Institute at the USC Dornsife College of Letters, Arts and Sciences.

Most of the time, watching someone else move causes a “mirroring” effect — that is, the parts of our brains responsible for motor skills are activated by watching someone else in action.

But a study by USC researchers appearing in PLOS ONE shows that whether you like the person you’re watching can actually have an effect on brain activity related to motor actions and lead to “differential processing” — for example, thinking the person you dislike is moving more slowly than they actually are.

“We address the basic question of whether social factors influence our perception of simple actions,” said Lisa Aziz-Zadeh, assistant professor with the Brain and Creativity Institute and the Division of Occupational Science. “These results indicate that an abstract sense of group membership, and not only differences in physical appearance, can affect basic sensory-motor processing.”