Some science behind persuasion

Fundraising communications professionals aren't the only ones who want to influence people; so do business marketers, salespeople, politicians...the list goes on.  Thanks to the diversity of folks who want to sway others, there is a good amount of research devoted to the science of persuasion.  There is an article in Business Week about scientifically-proven principles for influencing others, which includes:

• Liking: People like those...who like them.
  Or, be friends with your donors.  This is why fundraising letters should sound like a letter from a pal—a pal who really appreciates everything you've done for him, of course.
  
  
• Reciprocity: People repay in kind.
  The Business Week article actually uses nonprofit fundraising in this example, the good old "free personalized address labels included" tactic.  I would be interested to see some more recent research about this technique, as I wonder if it is starting to turn donors off due to the market being saturated with it.  People may tire of getting items they didn't ask for, but the idea of reciprocity (you helped me, now I feel compelled to help you) in humans is timeless.
  
  
• Social Proof: People follow the lead of similar others.
  Katya Andresen's blog has a great article about what happened when researchers put a clear donation box in the entrance to a gallery.  You should read the article if you haven't, but in (very) short: people gave more when there was money in the box than when the box was empty.  Takeaway: people want to fit in, and most people don't want to be first.  So, if you have a sign-up sheet, sign a few people in at the top so that no one has to be first.  If you want to use a thermometer showing how far along you are in your goal, don't share that thermometer until you have received some money already.  If you are going to have a live auction, make sure you have someone in the audience who is willing to be the first to bid.
  
  
• Authority: People defer to experts who provide shortcuts to decisions requiring specialized information.
  Good fundraising materials tug at the heartstrings, but donors have to trust that you know what you're talking about.  The best way for this to happen is for your organization to become a trusted authority on your subject(s)—think of the reputations of the ACLU or the World Wildlife Fund.  You can also quote other respected sources discussing your organization or the problem it aims to solve.