Abstract
When a transparent liquid flows, the background image behind the flow dynamically deforms due to light refraction. The dynamic deformations of a background image (dynamic image deformations) are one of the visual features used by the visual system to infer the existence of a transparent liquid flow. Although previous studies have discussed the role of the narrow band components of the spatiotemporal deformation frequency, it was still unclear whether motion signals, one of the constituents of dynamic image deformations, were the determinant of the perception of a transparent liquid. Manipulating the flow speed of image deformation, which is a critical parameter for changing motion signals in dynamic image deformations, we asked observers to judge whether a transparent liquid was included in the clips or not. We found that the proportions of reporting that they saw a transparent liquid increased with the flow speed of image deformations. Analyzing motion signals of the stimulus clips, we found that the faster the flow of image deformations the fewer linear motion signals were contained. The results indicate that the perception of a transparent liquid arises when the dynamic image deformations contain fewer linear motion signals.
Highlights
The visual system takes various approaches to infer the presence of materials or stuff (Adelson, 2001; Adelson & Bergen, 1991)
We conducted multiple comparison tests (Ryan, 1959) and found that the proportion of reporting a transparent liquid occurred more often at the higher flow speeds than at the lower flow speeds (Table 1). The proportion of those reporting a transparent liquid was higher as the flow speed increased
The results indicate that a paucity of linear motion signals in dynamic image deformations is a key factor in determining whether dynamic image deformations are perceived as a transparent liquid or not
Summary
The visual system takes various approaches to infer the presence of materials or stuff (Adelson, 2001; Adelson & Bergen, 1991). A different study (Kawabe & Kogovsek, 2017) sought to identify what feature was critical for differentiating hot air from water, both of which are transparent materials, and found that the magnitude of dynamic image deformations was a vital image cue for human observers to differentiate them These previous studies have used stimulus clips wherein the entire spatial region of the clip was filled with the dynamic image deformations of a background scene. Values in the deformation vector maps are occasionally very different across adjacent parts, a particular area in the background image occasionally undergoes pixel shifts in different directions across frames In this scenario, linear motion signals were generated to a lesser degree. We discuss the proposition that the perception of a transparent liquid is based on small coverage of linear motion signals in dynamic image deformations
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