Interesting article here about a study that indicates that the type of music played in restaraunts affects the spending of the diners:
http://www.cnn.com/2003/TECH/science/10/07/offbeat.music.ap/index.html

Interesting. My first thought was that the conclusion seems to be what common sense would tell us. But the study is, IMO, quite limited, refering to just one culture (british). Also, it seems to me that it would be easy to introduce a bias in the results choosing a certain class of restaurant (only one was tested). Finally there were only three possibilities: no music/classical music/pop music. The abstract of the full published paper (reference included) can be found here: http://www.le.ac.uk/psychology/acn5/amber.html

-- José.