This book is the final product of a conference organized at the Free Univer­ sity, Amsterdam, by some members of the Dutch Human Performance Group and sponsored by the Dutch Psychonomic Society. We first of all thank the Society for financially supporting this publication, and the Free University for providing technical support. P.J.G. Keuss, A.A.J. Mannaerts, and W. Hulstijn, members of the organizing commitee, and J.A. Michon and W. Molenaar collaborated with the editors in defining the fields dealt with at the conference and in the book and in getting together the team of authors. All the chapters in this volume have been reviewed by a team of external referees, who generously spent their time to improve the readability, coher­ ence, and scientific standard of the work as a whole: H. Bogers, Institute for Experimental Psychology, University of Groningen, The Netherlands; P. Innocent, Leicester Polytechnic, UK; G.A.M. Kempen, Institute for Cogni­ tion Research and Information Technology, Nijmegen, The Netherlands; J. Moraal, Institute for Perception RVO/TNO, Soesterberg, The Netherlands; I.M. van Oorschot, Department of Economics, Free University, Amsterdam, The Netherlands; G.R.E. Ouweneel, Institute for Experimental Psychology, Haren, The Netherlands; J.G.W. Raaymakers, Institute for Perception RVO/TNO, Soesterberg, The Netherlands; G. Rohr, IBM Science Center, Heidelberg, FRG; M.J. Tauber, Department of Computer Science, University of Paderborn, FRG; Y. Waern, Department of Psychology, University of Stockholm, Sweden; G. d'Ydewalle, Department of Psychology, University of Leuven, Belgium.