1 Department of Psychology, Columbia University, 406 Schermerhorn Hall, 1190 Amsterdam Avenue, New York, NY 10027, Mail Code 5501, USA Tel.: +1 212 854 1860; fax: +1 212 854 9648. Department of Psychology and Neuroscience, University of Colorado, Muenzinger D244, 345 UCB, Boulder, Colorado, 80309-0345, USA Tel.: +1 303 492 7487; fax: +1 303 492 2967.