Interesting question. This week it was reported that Gene Wilder passed away. Yet if you look at most photos he is smiling and as I look at them I cannot but help feel positive. Why?

    "The interesting part is that mirror 
     neurons fire in the same way when we 
     actually recreate that action ourselves." [0]

Is something to do with mirror neurons (not mentioned at all in the article), that govern our ability to mimic at the neuron level? These effects can be measured at cellular level without having to have a subject self report. There is ample evidence reported in Nature on both the mechanism and evidence supporting the idea that viewing of emotion cues in others, effects your own emotional response.

[0] Sourya Acharya,Samarth Shukla, "Mirror neurons: Enigma of the metaphysical modular brain"

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3510904/