Is Gloss a cue for Real-World Object Size?
Brown, James Michael
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Two separate lines of research in object recognition are studies of materials perception and studies of real-world object size perception. Recent object size investigations of texture indicate mid-level features may cue representations of object size in the absence of object identity. However, these findings are somewhat controversial, and beyond that what mid-level features cue object size is not clear. Mid-level features have always been the focus of materials perception studies of gloss and specular highlights, but to date no research has been conducted that attempts to link findings on the perception of materials to high-level object features like real-world object size. Three separate experiments were conducted to study the relationship between perceived surface glossiness and specular highlights, and perceived real-world object size. Previous research on the relationship between perceived object size and real-world object size were replicated. A significant two-way interaction between ratings of perceived glossiness, object size, and texture was found. Follow-up analyses indicated that perceptions of gloss were present across categorical differences in real-world object size in both the object image and texture image task groups. For the normal object images, small objects were perceived as being glossier than big objects. For the texture images, big objects were perceived as being glossier than small objects. Between the conditions, small normal and small texture object images were not significantly different in perceived glossiness. Between the conditions, glossiness ratings for big texture object images were significantly greater than those for the normal big object images.
General Audience Abstract
The goal of this project was to understand if category level perceptions of surface gloss (i.e. dull/matte surface reflectance versus shiny/glossy surface reflectance) could predict category level differences in the "actual" size of the objects in the real-world (i.e. small objects versus big objects). Previous research on the relationship between perceived object size and real-world object size were replicated. Moreover, in an experiment in which human subjects were tasked with rating the glossiness of images depicting small and large manmade of objects, category level distinctions in the average perceived glossiness of objects also extended to category level distinctions in perceived real-world object size; on average, small objects were perceived as being glossier than big objects. Similar effects were also found for synthetic textures created from the ordinary real-world object images; on average, big objects were rated as being glossier than small objects. Although categorical distinctions in perceived glossiness extended to real-world object size across image conditions, because there were no significant differences in the average perceived glossiness of small objects across the normal image and texture image conditions, the change in perceived glossiness for the big object images suggests that the texture algorithm used may not have preserved the surface reflectance characteristics of the big objects. Furthermore, statistical investigations of the pixel brightness for the stimulus images provided some evidence that the category level differences in perceived glossiness across object size and image condition may have been driven by differences in factors related to naturally occurring optical artifacts that are introduced when photographing small and big objects. Overall, results of this study are important because they indicate that the real-world spatial properties of objects may be jointly encoded with perceptions of object glossiness.
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