Just like in a recent TV commercial, seeing someone perform a good dead often leads to another charitable act.  That's according to research done by psychological scientists at the University of Cambridge and UCLA.  Researchers gathered volunteers and had them watch TV clips.  Some were uplifting showing good deeds being done, some were humorous others were just neutral clips.  They discovered focus group participants who watched the uplifting clip were more likely to volunteer for another research study than the others.  Your keyword is "NICE"

In the end it was determined seeing someone help another person makes us feel good.  Many study participants reported feeling a warm, fuzzy feeling in the chest.  The positive emotion often leads to the viewer performing a positive act themself.  Full study details are reported in the journal "Psychological Science."