1. Sloan - Swartz Center for Theoretical Neurobiology, MC 139-74, California Institute of Technology, Pasadena, CA 91125, USA; and Department of Cognitive Science, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA
2. Division of Biology, Computation and Neural Systems, MC 139-74, California Institute of Technology, Pasadena, CA 91125, USA; and JST ERATO Shimojo Implicit Brain Function Project