"Liking, or disliking, the person you’re watching can actually have an effect on how the brain processes movement. 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 researchers at the University of Southern California (USC), appearing in PLOS ONE, shows that liking someone can affect 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,” says Lisa Aziz-Zadeh, assistant professor with the Brain and Creativity Institute. “These results indicate that an abstract sense of group membership, and not only differences in physical appearance, can affect basic sensory-motor processing."