[1] Katholieke Univ Leuven, Fac Psychol & Educ Sci, Res Grp Expt Psychol, Lab Perceptual Dynam, B-3000 Louvain, Belgium
[2] Katholieke Univ Leuven, Dept Comp Sci, B-3001 Heverlee, Belgium
[3] Queen Mary Univ London, Sch Engn & Mat Sci, London E1 4NS, England
[4] Eindhoven Univ Technol, Dept Mech Engn, Dynam & Control Grp, NL-5600 MB Eindhoven, Netherlands