Are perspectival shapes seen or imagined? An experimental approach

Abstract

This paper proposes a novel experimental approach that would help to determine whether perspectival shapes, such as the elliptical profile of a tilted plate or coin, are part of perceptual experience. If they are part of perceptual experience, then it should be possible to identify these shapes simply by attending appropriately to them. Otherwise, in order to identify perspectival shapes they must first be constructed in the visual imagination. We propose that these accounts of perspectival identification can be tested by measuring the interference between visual and verbal working memory load, respectively, and the identification of perspectival shapes in the appearance of a 3D object. * Both authors contributed equally to this work. 1 We use "perspectival shape" instead of "apparent shape" since there is a clear sense in which the object shape is also apparent: e.g. the white face of the cube in Figure 1 clearly looks square, and the billiards rack looks like an equilateral triangle, etc. 2 The properties of distance and slant (in 3D) are viewer-relative but do not count as perspectival properties for our purposes. That is because we consider them instead to be part of our experience of the 3D world around us. For example, the rim of a cup, when viewed obliquely, looks circular, slanted in depth, and located some distance away. What we call "perspectival properties" are (roughly) those that a painter would draw on a 2D canvas, i.e., those that 3D objects project onto a flat medium, perpendicular to the line of sight. These do not include 3D slant and distance.

A "living" supplement to: Morales, Bax, & Firestone (2020) Sustained Representation of Perspectival Shape. PNAS

“…Incidentally, this is the same reason Linton's own proposed experiment couldn't decide the present issues. Our claims, like those ofSmith (2002),Schwitzgebel (2006),Kelly (2008),Schellenberg (2008),Cohen (2010),Schwenkler and Weksler (2019) and evenLocke (1975), are about how ordinary objects look in ordinary circumstances -not how specks of light look under cueimpoverished viewing conditions.…”

Reply to Linton: Perspectival interference up close

“…For example, Kelly (4) suggests that photographs of rotated pennies wouldn't prime responses to ellipses. Furthermore, Schwenkler and Weksler (5) propose experiments using 2D images of Rubik's cubes. The core aim of our interdisciplinary project is to meet this philosophical literature on its terms; since (some of) that literature concerns 2D images, (some of) our experiments do, too.…”

Spatial representations in sensory modalities

“…These two opposing theses nicely epitomises the debate Green and Schellenberg (2018) describes in the context of the distance‐and‐slant view. What is the proposal made by Schwenkler and Weksler (2019)? Their proposal, in a nutshell, is this:

If [the elliptical profiles of a tilted coin] are part of perceptual experience, then it should be possible to identify these shapes simply by attending appropriately to them.

…”

“…A recent substantive attempt in this regard is Schwenkler and Weksler (2019). In their terminology, ‘perspectivalism’ is the thesis that ‘visual experience has these two aspects’, that is:

One of these aspects corresponds to the objective shape of visible objects as they exist in the environment at a distance from the viewer: for example, the rectangular shape of the surface of a desk, or the circular shape of a coin.

…”

“…The other aspect concerns what we will call the perspectival shape of an object, i.e., to the viewer‐relative, 2D shape that would outline or occlude an object from a given point of view. (Schwenkler & Weksler, 2019, p. 856; my emphasis)By contrast, anti‐perspectivalism is the thesis that ‘we do not literally see perspectival shapes, nor does the ability to recognize , draw , or describe the 2D shape that would occlude an object in one's line of sight depend on a visual experience of any such shape’ (p. 856). These two opposing theses nicely epitomises the debate Green and Schellenberg (2018) describes in the context of the distance‐and‐slant view.…”