Paradoxical perception of object identity in visual motion

Abstract

In the course of perceptual organization, incomplete optical stimulation can evoke the experience of complete objects with distinct perceptual identities. According to a well-known principle of perceptual organization, stimulus parts separated by shorter spatial distances are more likely to appear as parts of the same perceptual identity. Whereas this principle of proximity has been confirmed in many studies of perceptual grouping in static displays, we show that it does not generalize to perception of object identity in dynamic displays, where the parts are separated by spatial and temporal distances. We use ambiguous displays which contain multiple moving parts and which can be perceived two ways: as two large objects that gradually change their size or as multiple smaller objects that rotate independent of one another. Grouping over long and short distances corresponds to the perception of the respectively large and small objects. We find that grouping over long distances is often preferred to grouping over short distances, against predictions of the proximity principle. Even though these effects are observed at high luminance contrast, we show that they are consistent with results obtained at the threshold of luminance contrast, in agreement with predictions of a theory of efficient motion measurement. This is evidence that the perception of object identity can be explained by a principle of neural economy rather than by the empirical principle of proximity.

Distinct Rules for Binding in Position-Based and Velocity-Based Motion Systems

“…Previous studies were able to detect significant effects with very small sample sizes (<10) for our two experimental manipulations (Perceptual grouping: Anstis and Kim, 2011;Zharikova et al, 2017;stroboscopic motion: Allard and Arleo, 2021). Accordingly, we aimed to collect a minimum of 20 participants within the time frame imposed by our research proposal.…”

“…Manipulating the distances within-and between dot pairs, as well as cueing different percepts through contrast groupings are known to moderate the probability of each percept (Anstis & Kim, 2011;Zharikova et al, 2017), indicating an influence of grouping principles DISTINCT RULES FOR BINDING IN MOTION PERCEPTION 7 such as proximity and similarity. Nevertheless, the probabilities of perceiving the two alternative percepts do not perfectly follow Gestalt principles as the global motion still dominates at proximity configurations that should favor the local motion more (Zharikova et al, 2017). If the static cues are important for the position-based motion system but not for the velocity-based system, impairing the velocity-based motion system should make static cues more influential in determining how the individual moving dots will be grouped.…”