1. University of Bristol, Department of Experimental Psychology, 8 Woodland Road, Bristol, BS8 ITN, UK.
2. Georgetown University, Health Policy Institute, Georgetown Public Policy Institute, 2233 Wisconsin Ave, NW, Suite 525, Washington DC 20007, USA
3. University of Pennsylvania, Department of Psychiatry, Center for Neurobiology and Behavior, Room 111 Clinical Research Building, 415 Curie Bvd, PA 19104, USA
4. University of Pennsylvania, Transdisciplinary Tobacco Use Research Center, Abramson Cancer Center, 3535 Market St, Suite 4100, PA 19104, USA