This paper deals with the achievement of the best contour grouping of an image from the point of view of the probability that the grouping corresponds to either an object or an object surface from the scene. For the grouping of the contours, the principle of non-accidentality has been used. This principle rests on psychological mechanisms of perceptual organization such as: proximity, colinearity, cocurvilinearity, convexity and closure. Neither all mechanisms of perceptual organization have the same degree of importance, nor the primitives they process are equal. In consequence, we propose a novel approach for perceptual grouping that takes into account the sequential order in the application of the different mechanisms for grouping of primitives, so that, it will change in function of the relative importance of the perceptual mechanisms in each particular case.