I don’t know if this reveals anything we don’t already know, but it’s an interesting study:
http://www.iop.org/EJ/article/1367-2630/10/3/033001/njp8_3_033001.html

New Scientist report: http://preview.tinyurl.com/2weqk9

Accompanying video: http://www.youtube.com/watch?v=Suugn-p5C1M