Individual pattern representations are context independent, but their collective representation is context dependent Thomas Lachmann University of Leipzig, Leipzig, Germany, and Brain Science Institute, RIKEN, Wako-shi, Japan Cees van Leeuwen Brain Science Institute, RIKEN, Wako-shi, Japan and University of Sunderland, Sunderland, UK We studied context dependency of the representations underlying perceptual “goodness”. Three experiments used a same–different task with classical Garner 5-dot patterns presented with an interstimulus interval (ISI) of 500 ms. Same patterns were allowed to be rotated or reflected ver- sions of each other. Pattern goodness was varied according to rotation and reflection equivalence, using Garner’s equivalence set size (ESS) measure. The ESS of both first and second patterns affected reaction time and accuracy. A model based on assumptions that Garner’s equivalence sets constitute the generic representation of these patterns and that items within these sets are accessed serially was fitted to the data. Excellent fits were obtained, which were robust against frequency-induced bias at the level of the individual pattern, but sensitive to such bias at the level of the equivalence set. It was concluded that individual pattern representations are context inde- pendent, whereas their collective representations are context dependent. Simplicity and likeli- hood principles, therefore, seem to apply to different levels of a representation hierarchy. Visual perception presents our environment as structured and extended in space and time. For practical purposes, we may agree that this is the case because certain relational pro- perties in our environment, such as proximity and symmetry, specify it to be that way. Experimental psychology has made important progress in identifying laws in which such THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 2005, 57A (X), XXX–XXX © 2005 The Experimental Psychology Society http://www.tandf.co.uk/journals/pp/02724987.html DOI:10.1080/02724980443000584 Correspondence should be addressed to Thomas Lachmann, University of Leipzig, Department of Psychology, Seeburgstrasse 14/20, D-04103 Leipzig, Germany. Email: lachmann@rz.uni-leipzig.de This work was supported by Grant La 1281/2-1 from the Deutsche Forschungsgemeinschaft (DFG) to Thomas Lachmann. Thanks are due to Robert Proctor, Lester Krueger, Beverly Roskos-Ewoldson, Peter van der Helm, and John Flowers for their critical and very helpful remarks on earlier drafts. pQ JA151-03RR.qxd