Interactions between spatial and spatiotemporal information in spatiotemporal boundary formation

Abstract

The surface and boundaries of an object generally move in unison, so the motion of a surface could provide information about the motion of its boundaries. Here we report the results of three experiments on spatiotemporal boundary formation that indicate that information about the motion of a surface does influence the formation of its boundaries. In Experiment 1,shape identification at low texture densities was poorer for moving forms in which stationary texture was visible inside than for forms in which the stationary texture was visible only outside. In Experiment 2, the disruption found in Experiment I was removed by adding a second external boundary. We hypothesized that the disruption was caused by boundary assignment that perceptually grouped the moving boundary with the static texture. Experiment 3 revealed that accurate information about the motion of the surface facilitated boundary formation only when the motion was seen as coming from the surface of the moving form. Potential mechanisms for surface motion effects in dynamic boundary formation are discussed.

The Perceptual Influence of Spatiotemporal Noise on the Reconstruction of Shape from Dynamic Occlusion

“…It may also, however, be described as a single element field with a rapidly changing (i.e., Brownian) velocity, and thus the impairment could be accounted for by substituting the Brownian global velocity vector into the LES recovery stage. This latter explanation also accounts for the results in their other experimental conditions, and is consistent with Cunningham et al's [12] work on velocity vector substitution, and thus is the most parsimonious explanation.…”

“…Well-defined shapes are seen in the bidirectional displays, despite the absence of any form of shape information except dynamic occlusion [5]. Bidirectional displays were not used in the current experiment for theoretical reasons (i.e., there are some concerns about surface formation, the direction of surface binding, and the role of velocity vector substitution in bidirectional displays, see Cunningham et al [12] for more on this topic). The number of dots was systematically varied: The background had 100, 200, or 400 elements.…”

“…So far, all of the model's predictions reflect human performance: Collinearity of the transformations prevents SBF [5], identical orientations of the LES's hinders proper velocity recovery [13], and velocity vector substitution can improve the quality of the recovered shape [12]. What about the prediction that SBF should be strongly affected by dynamic noise (i.e., the presence of transformations that are not caused by dynamic occlusion)?…”

“…On the other hand, the presence of spurious appearances and disappearances (i.e., flickering elements) near the edges of the object should impair SBF. As a control condition, we examined the effect of a flickering texture that is far away from the moving figure. Since the global motion of a distant texture field does not affect SBF [12], the flickering elements should only affect SBF in the control condition if the spatial integration window for SBF is rather large (i.e., if SBF is more of a "global"than a "local"process).…”

“…Cunningham et al [12] explicitly tested whether humans can take advantage of the velocity vector substitution process predicted by the model. To do this, they added a set of additional texture elements that had the exact same velocity as the moving shapes.…”