Van Der Linde, IanCenter for Perceptual Systems, Department of Psychology, University of Texas at Austin, Austin, TX 78712, USA; Department of Computing, Anglia Ruskin University, Bishops Hall Lane, Chelmsford CM1 1SQ, UK. ianvdl@ece.utexas.edu Rajashekar, UmeshCenter for Perceptual Systems, Department of Psychology, University of Texas at Austin, Austin, TX 78712, USA; Department of Computing, Anglia Ruskin University, Bishops Hall Lane, Chelmsford CM1 1SQ, UK. ianvdl@ece.utexas.edu Bovik, AlanCenter for Perceptual Systems, Department of Psychology, University of Texas at Austin, Austin, TX 78712, USA Cormack, LawrenceCenter for Perceptual Systems, Department of Psychology, University of Texas at Austin, Austin, TX 78712, USA