title: Response from maddess, srinivasan and Davey.
authors.affiliation: Centre for Visual Science, Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Maddess
authors.forename: M V
authors.initials: MV
authors.lastname: Srinivasan
authors.forename: M P
authors.initials: MP
authors.lastname: Davey