Irrationality in animal communication Stefano Ghirlanda 1,2 Magnus Enquist 1,3 Carl-Adam Wachtmeister 1,3 Anthony Arak 4 1 Group for Interdisciplinary Cultural Studies, University of Stockholm 2 Department of Psychology, University of Bologna 3 Zoology Institution, University of Stockholm 4 Archway Engineering, Elland, UK PED, Harvard, 2006-09-22