Wikipedia has a good definition of what a mirror neuron is:
- A mirror neuron is a neuron which fires both when an animal performs an action and when the animal observes the same action performed by another (especially conspecific) animal. Thus, the neuron "mirrors" the behavior of another animal, as though the observer were himself performing the action.
Mirror neurons allow us to learn how to do something by just watching other people. What's fascinating is that primates developed this ability (to imitate each other) before they developed the ability to be consciously aware of themselves (for more info, see "The Emerging Mind", a talk by Vilayanur Ramachandran).
Imitation probably developed before consciousness because imitation is a handy survival trait; when another primate has learned a valuable survival skill, your genes can spread further if you learn it too. So, to learn it as fast as possible, our genes gave us the ability to directly copy the actions of another individual. If you copy it properly, you now posess that same skill. (Interestingly, other species have mirror neurons too; birds have mirror neurons that fire when they hear other birds singing, and if they don't hear birds singing early in life, they never learn how to sing properly.)
So, how do celebrities fit in? Well, when I was explaining this concept to someone recently, it suddenly struck me why people love celebrities.
First, there are individuals with celebrity status even in lower primate societies. I read about a study in which they used little monkeys who like juice a lot. The experiments revolved around offering the monkeys two choices:
- a cup of juice
- a cup of less juice, but they also get to look at a picture of a high-ranking monkey (or a female monkey's butt)
9 times out of 10, the monkeys chose the second option. What's also interesting is that when option #2 was "more juice, but they have to look at a picture of a lower-ranking monkey", they chose less juice.
I think the reason why the monkeys want to look at high-ranking monkeys is because high-ranking individuals are successful; they're sought after by the opposite sex, they get lots of fringe benefits like free food and control over other monkeys. These individuals are successful because they have whatever skills it takes to make it to the top of the heap in a monkey society. So, the theory goes that if you watch these guys, you could learn their tricks -- how they dominate and placate other monkeys, how they get the womens, etc.
Conversely, low-ranking monkeys posess skills that others should definitely not develop. That's why a monkey would rather have less juice than look at a picture of a low-ranking monkey. (There's another interesting related article called Angry/Negative People can be Bad for Your Brain.)
At this point it should be obvious why humans love celebrities. 