Scientific Reports 3, Article number: 1099 (2013); Published: 22 January 2013; Updated: 18 February 2013

The authors have noticed that the original version of this Article contained a typographical error in the spelling of the author Hoifung Poon which was incorrectly given as Hoifung Poong. Furthermore, the author Jeff Baxter was incorrectly listed as Scott Baxter. These changes have now been corrected in both the PDF and HTML versions of the Article.