E.J. Green

Many of the objects that we perceive have an important characteristic: When they move, they change shape. For instance, when you watch a person walk across a room, her body constantly deforms. I suggest that we exercise a type of perceptual constancy in response to changes of this sort, which I call structure constancy. In this paper I offer an account of structure constancy. I introduce the notion of compositional structure, and propose that structure constancy involves perceptually representing an object as retaining its compositional structure over time. I argue that compositional structure is represented in visual phenomenology, and I also assemble empirical evidence in support of the claim that compositional structure is recovered by the visual system. Finally, I draw out consequences of this account. I argue that structure constancy has implications for the predictive capacities of perception, and that the phenomenon places important constraints on viable accounts of both the format and reference frame of visual experience.

Many authors have posited an " object file " system, which underlies the perceptual selection and tracking of objects. Several have proposed that this system internalizes principles specifying what counts as an object, and relies on them during tracking. Here I consider a popular view on which the object file system is tuned to entities that satisfy principles of three-dimensionality, cohesion, and boundedness. I argue that the evidence gathered in support of this view is consistent with a more permissive view on which object files select and track according to well-known perceptual organization criteria. Further evidence supplies positive support for the permissive view.

Some philosophers have suggested that certain shifts in perceptual organization are counterexamples to representationalism about phenomenal character. Representationalism about phenomenal character is, roughly, the view that there can be no difference in the phenomenal character of experience without a difference in the representational content of experience. In this paper, I examine three of these alleged counterexamples: the dot array (Peacocke 1983), the intersecting lines (Speaks 2010), and the 3 x 3 grid (Nickel 2007). I identify the two features of their phenomenology that call for explanation: grouping and prominence. I then argue that representationalists can adequately account for both of these features. I also critique some previous treatments of grouping and prominence.

In this study we investigated the conditions under which the visual system treats negative parts as objects. A negative part is a background region mostly surrounded by a region of negative curvature along a figure's contour. Previous work has shown that negative parts can take on a "quasi-figural" status, inducing globally inconsistent judgments of border ownership (Kim & Feldman, 2009). The degree to which a negative part is treated as figural depends on its geometry, including its depth and the narrowness of its opening. We studied apparent motion of negative parts, focusing on whether variation in a region's figural status could modulate the degree to which it could participate in apparent motion with closed figures. We employed a variant of the Ternus display, containing a sequence of motion frames in which the correspondence between frames can be solved in two distinct ways: "group motion," in which a group of elements in the display appear to translate, and "element motion," in which one object translates while the others do not. Displays were constructed so that group motion percept involved motion between a closed figure and a negative part, while element motion did not, so the proportion of group motion percepts reveals the degree to which the negative part had taken on quasi-object status and thus could be placed in motion correspondence with an ordinary closed object. Critically, we manipulated the geometric factors determining the strength of the negative part. We found that the rate of group motion responses varied with negative part strength, i.e., that stronger negative parts are more likely than weaker ones to be treated as distinct objects. This finding sheds light on the mechanisms by which image regions come to be treated as distinct objects on an equal footing with closed figures. Meeting abstract presented at VSS 2015.