From the first works of Buswell, Yarbus, and Noton and Stark, the scan path for viewing complex images has been considered as a possible key to objective estimation of cognitive processes and their dynamics. However, evidences both pro and con were revealed in the modern research. In this article, the results supporting the Yarbus-Stark concept are presented. In psychophysical tests, two types of images (three paintings from Yarbus` works and four textures) were used with two instructions, namely, "free viewing" and "search for modified image regions." The focus of the analysis of experimental results and modeling has been given to local elements of the scan path. It was shown that each parameter used (square of viewing area, S; distance between center of mass of viewing area and image center, R; parameter Xi, based on duration of the current fixation and angle between preceding and following saccades), reflects the specificity of both visual task and image properties. Additionally, the return gaze fixations which have a set of specific properties and mainly address to the areas of interest on image were revealed. Evidently these facts can be formalized in an advanced mathematical model as additional instrument to study the mechanisms of complex image viewing.

Allocation of informative regions in images depends on a visual task. We propose two criteria for allocation of informative regions in images considering visual recognition of objects in images using a space-variant foveal filter. The first criterion relates to descriptor completeness. This criterion is formalized as a measure of similarity of an original image to an image reconstructed from foveal filter responses. The second criterion relates to descriptor distinctiveness. This criterion relates to the problem of retrieving discriminative and repeatable features in images of objects. It is formalized as a variation of descriptor elements of different objects within the same class. We reveal that regions of interest produced by these criteria are distributed in the areas of high variety of brightness gradients orientations.

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