A psychophysical evaluation of the a contrario detection theory

The a contrario theory is a mathematical formalization of the so-called non-accidentalness principle of perception, which states that an observed configuration is relevant only when it is unlikely to appear just by chance. It has been successfully applied to several image processing and computer vision problems. In this paper, human vision is compared to an a contrario based algorithm in a simple perceptual task. For this aim, a psychophysical experiment was set up, in which subjects and the algorithm were asked to detect alignments of Gabor patches. We found that the proposed algorithm predicted accurately the subjects´ responses, therefore providing an interpretation to perceptual thresholds.