Relating to our attempt to better understand the what and how of sports fandom, I wanted to flag this commenter Deborah:

Mirror neurons! I finally remembered the thing about watching other people do stuff, neuroscientifically. If you're interested in the very raw level of what happens when a crowd watches people do adrenaline pumping stuff, the thrill of victory and the agony of defeat, this is worth delving into. 

Start of wikipedia article: A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another.[1][2][3] Thus, the neuron "mirrors" the behaviour of the other, as though the observer were itself acting. Such neurons have been directly observed in primate and other species including birds. In humans, brain activity consistent with that of mirror neurons has been found in the premotor cortex, the supplementary motor area, the primary somatosensory cortex and the inferior parietal cortex.