In parallel with our studies on human eye movements, we have investigated image processing algorithms that predict where human eyes fixate. These loci of fixations, traditionally named Regions-of-Interest, ROIs, are strategically important both for computer applications and for cognitive studies of human visual processing. A very important aspect of our methodology, beyond the specific image processing algorithms used, is how to select from a large initial set of candidates, usually local maxima in the processed image, a final set of few ROIs. In this paper we analyze this latter aspect, proposing and comparing different clustering procedures and study how different procedures may affect the fidelity of comparisons with human selected ROIs.
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