The authors thank Fiorello Banci and Karl-Heinz Honsberg for constructing the stimulus and response device for the first three experiments, and Poldi-Eva Leo and Sabine Rau for conducting these experiments. Further, we thank Robert Goldstone and Richard Shiffrin for providing facilities to run the fourth experiment, Robert Proctor, Claire Michaels, Steven Yantis, and an anonymous reviewer for their helpful comments on a previous version of the article, and Robert Kennison for checking and improving the English. Correspondence should be addressed to Y. Lippa, Department of Psychology, University of California, Santa Barbara, CA 93106-9660 (e-mail: lippa@psych.ucsb.edu).An explanation of orthogonal S-R compatibility effects that vary with hand or response position:The This study presents an explanation of orthogonal stimulus-response compatibility (SRC) effects that vary with hand or response location: the end-state comfort hypothesis. It posits that responses are spatially transformed and cognitively mapped onto the stimulus dimension according to relative hand posture, thereby mediating the pattern of facilitation and interference in response selection. In the first three experiments, we investigated the eccentricity effect, finding that responses by the left hand in left hemispace are faster with up-left/down-right mapping while responses by the right hand in right hemispace are faster with up-right/down-left mapping (Michaels & Schilder, 1991, Experiment 1). The endstate comfort hypothesis correctly predicted that the eccentricity effect occurred irrespective of the relative position of the stimulus and response device in the sagittal plane (Experiments 1 and 2), and that it reversed when the stimulus-response set was reversed, regardless of the relative position of the stimulus and response device in the fronto-parallel plane (Experiments 2 and 3). Experiment 4 shows a new orthogonal SRC effect that was predicted by the end-state comfort hypothesis. Our results are inconsistent with other explanations, such as the virtual-lines hypothesis and the salient-features hypothesis.