The term mirror neurons refers to the controversial proposition that the same neuron fires both when a person engages in some activity and when that person witnesses others engaging in the same activity, either by seeing or hearing them do it. While it was initially believed that the brain’s frontal and parietal regions contained mirror neurons, evidence suggests that other brain regions are involved as well. Researchers believe that mirror neurons are essential for humans to be able to understand the actions of others, as well as to be able to imitate and learn new skills. Mirror neurons develop in the first months of life and are largely responsible for helping babies learn actions by mimicking those around them. Mirror neurons are also suspected to be involved in the development of human emotion, like empathy. Experiments using imaging machines, like the MRI, show that particular areas in the brain become activated when one experiences a particular emotion and the same areas are activated when one witnesses another person experiencing the same emotion.