From the source at http://www.pnas.org/content/early/2010/08/06/1001509107.full.pdf+html http://www.pnas.org/content/early/2010/08/06/1001509107.full... "We re

From the source at http://www.pnas.org/content/early/2010/08/06/1001509107.full.pdf+html http://www.pnas.org/content/early/2010/08/06/1001509107.full... "We recruited 505 participants through Craigslist in seven US metropolitan areas: New York, Philadelphia, Washington DC, Houston, Dallas, Denver, and Los Angeles."