Assessing the microstructure of motion correspondences with non-retinotopic feature attribution.

The motion correspondence problem, one of the classical examples of perceptual organization, addresses the question of how elements are grouped across space and time. Here, we investigate motion correspondences using a new feature attribution technique. We present, for example, a grating of four lines followed by a spatially shifted grating of three lines. Observers perceive a contracting grating. To study individual line-to-line correspondences, (1) we add, as a "perceptual marker," a small Vernier offset to one line of the first grating and (2) determine to which line of the second grating this offset is attributed. This procedure allows us inferring motion correspondences because this kind of feature attribution follows perceptual grouping in dynamic displays (H. Oğmen, T. U. Otto, & M. H. Herzog, 2006). Our results show that feature attribution between outer lines of the grating is more consistent than between inner lines. We interpret our results according to the principle of the "primacy of bounding contours," which states that bounding contours of an object provide a framework for element correspondences that is more important than the internal structure of that object.