1. Department of Psychiatry, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, UK
2. Center for Bioethics, Harvard Medical School, Boston, MA 02115, USA
3. Oxford Uehiro Centre for Practical Ethics, Suite 8, Littlegate House, St Ebbes Street, Oxford OX1 1PT, UK
4. Behavioral and Clinical Neuroscience Institute, Herchel Smith Building for Brain and Mind Sciences, Forvie Site, Robinson Way, Cambridge CB2 0SZ, UK