About the Authors
The authors have declared that no competing interests exist.
CKK, JAM, HR, JM, PK, and JDK conceived and designed the experiments. KA, JAM, and HR analyzed the data. KA, CKK, JAM, HR, JM, PK, and JDK wrote the paper. JM worked closely with Better World Advertising in the planning and development of the campaign in 1999.