Validity of the Gaussian assumption in the analysis of ROC data obtained from scintigraphic-like images

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Abstract
The Gaussian assumption (GA) has been found experimentally to provide an acceptable fit to ROC data elicited from visual experiments. When the GA is satisfied the two-parameter index D( Delta m,s) determines the ROC completely. It is however not known whether the GA is an intrinsic property of the eye-brain system, or whether it is a consequence of the type of visual stimuli selected for the experiments. Using scintigraphic-like images to test the validity of the GA, it is found that (i) series of visual stimuli with as few variables as possible produce ROC data compatible with the GA, but (ii) it is possible to find stimuli for which the GA provides a very poor account of experimental data. These results lead the authors to doubt that the GA is an intrinsic property of the human visual system.