This video clip is from a PBS documentary on mirror neurons. It describes how their existence was discovered in monkeys when the brain of a monkey responded exactly how it would if the monkey were picking up a peanut when the monkey observed as researchers picked up the peanut. The findings were generalized to humans who were also found to possess neurons that seem to mirror the actions of others when we are observing them as if we are actually carrying out the action.
In one part of the clip, the narrator walks down a street filled with pedestrian traffic carrying a large stack of unwieldy packages. Many of the people on the street stare at him, some even looking pained as they watch him struggle with the load. The narrator explains the response of the pedestrians as stemming from their mirror neurons which are causing them to feel the sensation of carrying a large stack of boxes as they observe him. Since they have been in situations where they have carried large loads, they are able to feel what it must be like for him.
Applying the scientific thinking principle of Occam's Razor to this scene, it is possible to come up with a simpler explanation for the pedestrians' reactions. It seems more likely that they were staring not because they were empathizing with the pain of carrying boxes, but rather because a man carrying a huge stack of boxes down a busy sidewalk is an unusual sight. Without even asking the pedestrians what they were feeling as they watched the narrator, it is impossible to conclude that they were actually experiencing his pain.