Role of form information in motion pooling and segmentation

Abstract

Traditional theories of visual perception have focused on either form or motion processing, implying a functional separation. However, increasing evidence indicates that these features interact at early stages of visual processing. The current study examined a well-known form-motion interaction, where a shape translates along a circular path behind opaque apertures, giving the impression of either independently translating lines (segmentation) or a globally coherent, translating shape. The purpose was to systemically examine how low-level motion information and form information interact to determine which percept is reported. To this end, we used a stimulus with boundaries comprising multiple, spatially-separated Gabor patches with three to eight sides. Results showed that shapes with four or fewer sides appeared to move in a segmented manner, whereas those with more sides were integrated as a solid shape. The separation between directions, rather than the total number of sides, causes this switch between integrated or segmented percepts. We conclude that the change between integration and segmentation depends on whether local motion directions can be independently resolved. We also reconcile previous results on the influence of shape closure on motion integration: Shapes that form open contours cause segmentation, but with no corresponding enhanced sensitivity for shapes forming closed contours. Overall, our results suggest that the resolution of the local motion signal determines whether motion segmentation or integration is perceived with only a small overall influence of form.

Towards a unified perspective of object shape and motion processing in human dorsal cortex

“…A moving background may change the apparent size, shape and position of briefly flashed objects (Anstis & Cavanagh, 2017). Movement speed can affect perceptual grouping and global shape (Anstis, 2005), and, in a now well-studied occluded-aperture stimulus, stimulus configuration can affect whether four bars appear to be a single object moving coherently in one direction or as four separate objects moving independently (Lorenceau & Alais, 2001; Lorenceau & Shiffrar, 1992; McDermott & Adelson, 2004; Shiffrar & Lorenceau, 1996; Tang, Dickinson, Visser, Edwards, & Badcock, 2015). Rotational motion in particular has been found to distort the perceived shape and size of objects (Anstis, Sturzel, & Spillmann, 1999; Caplovitz & Tse, 2006; McDermott & Adelson, 2004; Meyer & Dougherty, 1990; Shiffrar & Pavel, 1991; Stanley, 1968; Weiss & Adelson, 2000).…”

Temporal synchrony is an effective cue for grouping and segmentation in the absence of form cues

“…The authors modulated the contrast of each component and showed that by manipulating whether modulation occurred asynchronously or synchronously across the components, perception could be biased towards either the local or global solution, respectively. However, their stimulus contained form information, i.e., an unambiguous diamond shape, which has been shown to augment temporal synchrony-based grouping (Leonards, Singer, & Fahle, 1996;Tang, Dickinson, Visser, Edwards, & Badcock, 2015;Usher & Donnelly, 1998) in excess of the probability summation of the two properties (Lee & Blake, 2001). Similarly, Blake (1999, 2001) and Morgan and Castet (2002) demonstrated the capacity of temporal synchrony to drive segmentation using static stimuli.…”

Visual awareness during the attentional blink is determined by representational similarity

“…The increased in accuracy of similar targets reported in Experiment 1, along with the attractive biasing of target orientations are reminiscent of serial dependency effects 28,29 and opposite to tilt-aftereffects where adaptation to an orientation causes repulsion for similar orientations and decreased accuracy 71,72 . The repulsive tilt aftereffect is well predicted by simple information channel models 72,73 , which are consistent with the neurophysiological evidence that visual neurons exhibit orientation-selective adaptation with the most similar orientations causing the greatest adaptation 74,75 . Using the same simple model architecture, but having the adapter increase the sensitivity of the affected channels allows for attractive aftereffects which are consistent with serial dependency 72 .…”