An fMRI study also showed that mirror neurons respond to the action of grasping a cup differently depending on context (to drink a cup of coffee vs. to clean a table on which a cup was placed). One criticism of mirror neurons is that since they show that same muscle groups is used for someone watching an action as someone completing an action, they only predict actions, not beliefs or desires. While someone acts a certain way, they may not believe that what they are doing is the right thing. Shared neural representation for a motor behavior and its observation has been extended into the domains of feelings and emotions. Not only movements but also facial expressions activate the same brain regions that are activated by direct experiences. In an fMRI study, same brain regions on action representation found to be activated when people both imitated and observed emotional facial expressions such as happy, sad, angry, surprise, disgust, and afraid. Observing video clips that displayed facial expression of feeling disgust activated the neural networks typical of direct experience of disgust. Similar results have been found in the case of touch. Watching movies that someone touched legs or faces activated the somatosensory cortex for direct feeling of the touch. A similar mirror system exists in perceiving pain. When people see other people feel pain, people feel pain not only affectively, but also sensorially. These results suggest that understanding other's feelings and emotions is driven not by cognitive deduction of what the stimuli means but by automatic activation of somatosensory neurons. A recent study on pupil size directly demonstrated emotion perception was automatic process modulated by mirror systems. When people saw sad faces, pupil sizes influenced viewers in perceiving and judging emotional states without explicit awareness of differences of pupil size. When pupil size was 180% of original size, people perceived a sad face as less negative and less intense than when pupil was smaller than or equal to original pupil size. This mechanism was correlated with brain regions that implicated in emotion process, the amygdala. Furthermore, viewers mimic the size of their own pupils to those of sad faces they watched. Considering that pupil size is beyond voluntary control, the change of pupil size upon emotion judgment is a good indication that understanding emotions is automatic process. However, the study could not find other emotional faces such as happiness and anger influence pupil size as sadness did. Understanding other's actions and emotions is believed to facilitate efficient human communication. Based on findings from neuroimaging studies, de Vignemont and Singer proposed empathy as a crucial factor in human communication arguing its epistemological role; "Empathy might enable us to make faster and more accurate predictions of other people's needs and actions and discover salient aspects of our environment."