Representation and selection of relative position

Part 1 concerns representation: We demonstrate pop-out for a target that can be distinguished from the distractors only by the relative position of its components and thereby show that simple shape information is represented preattentively. We discuss our findings in terms of theories of search and texture segregation. Part 2 concerns selection: We demonstrate strong learning in a varied-mapping paradigm and show that preattentive shape information can be used for selection. Finally, we suggest an account fo the learning, namely the group scale hypothesis, and present a final experiment to test it. Our results confirm and extend the emphasis placed by Duncan and Humphreys' (1989) attentional engagement theory on grouping processes in visual search.