Abstract
A spinning, moving object, such as a football with a surface texture, combines motion signals from rotation and translation. The interaction between these two kinds of signal was studied psychophysically with moving, circular clouds of dots, which also could move within the cloud. If the cloud moved near-vertically downwards but the dots within it moved obliquely, the apparent path of the cloud was attracted to that of the dots, as previously demonstrated with moving Gabor patches (Tse & Hseih Vision Research, 46, 3881-3885, 2006; Lisi & Cavanagh Current Biology, 25, 2535-40, 2015). This attractive effect was enhanced in parafoveal viewing and by not presenting a frame around the dots. A larger effect in the opposite direction (repulsion) was found for the perceived direction of the dots when they moved near-vertically and the cloud containing them moved obliquely. These results are discussed in relation to Gestalt principles of perceived relative motion and, more recently, Bayes-inspired accounts of the interaction between local and global motion.
Highlights
Several well-known demonstrations by the Gestalt school showed that it is difficult for observers to sense the trajectory of a moving object in retinal coordinates when it is accompanied by other objects, such as moving frame (Dunkner, 1938). Johansson (1975) showed that the perceived trajectory of a moving dot could be profoundly altered by that of flanking dots
In one version of the stimulus, a single Gabor patch moves in one direction while its carrier drifts in the orthogonal direction
The repulsion of the trajectory of dots moving within an envelope, away from the envelope trajectory, is consistent with many previous findings on relative motion (Johannson, 1975, Dunkner, 1938, Cutting & Profitt, 1982; Dakin & Mareschal, 2000)
Summary
Several well-known demonstrations by the Gestalt school showed that it is difficult for observers to sense the trajectory of a moving object in retinal coordinates when it is accompanied by other objects, such as moving frame (Dunkner, 1938). Johansson (1975) showed that the perceived trajectory of a moving dot could be profoundly altered by that of flanking dots. In Experiment 1, observers were asked which dot cloud contained dots that moved more vertically (i.e., less obliquely), with respect to the screen. They may have an additional offset from zero (μ) caused by the perceptual context, such as might be provided by effect of the envelope angle in Experiment 1.
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