1 Center for Neural Science and Department of Psychology, New York University, 4 Washington Place, Room 809, NY 10003, New York, USA Tel.: +1 212 998 2104. Electronic address: nathaniel.daw@nyu.edu.
2 Department of Cognitive and Linguistic Science and Psychology, Brown Institute for Brain Science, Brown University, 190 Thayer St. Providence, RI 02912-1978, USA Tel.: +1 401 863 6872; fax: +1 401 863 2255. Electronic address: michael_frank@brown.edu.