Most of us have the similar experience: stage fright. Virtually all of us have found that its hard to recall key words at the right time, when we are doing presentation to our bosses or making a speech in front of our classmates. 　　Now scientists are giving us more explanation on why our brains go blank in situations like these. 　　Based on a new research conducted by Erno Hermans of New York University, on 80 healthy adults who are asked to watch extremely violent fight scenes, researchers found that disturbing images raised participants level of the stress hormone cortisol as well as their heart rates. 　　Scientists also saw an increase of activity in certain areas of the brain when the stress level is higher, including regions that deal with fear and other emotions and those with orienting attention. 　　To their discovery, parts of the prefrontal cortex involved in thought and reasoning began to shut down at the same time. 　　Researchers say that the finding means that when people are under stress, the brain automatically shifts its focus away from current activity, and instead, toward readiness for "fight or flight". That's why high stress has the capability to make our minds go blank, because that's just how the neural network functions.