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Deploying the Mental Eye

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ABSTRACT

Three observers performed a task designed to quantify their “pictorial relief” in visual awareness for a photograph of a piece of sculpture. In separate sessions, they were instructed to assume one of two “mental viewpoints.” The main objective was to investigate whether human observers have such command. All three observers could redirect their “mental view direction” by up to 20°. These observers experience “paradoxical monocular” stereopsis, whereas a sizable fraction of the population does not. Moreover, they had some experience in assuming various “viewing modes.” Whereas one cannot generalize to the population at large, these findings at least prove that it is possible to direct the mental viewpoint actively. This is of importance to the visual arts. For instance, academic drawings require one to be simultaneously aware of a “viewing” (for the drawing) and an “illumination direction” (for the shading). Being able to mentally deploy various vantage points is a crucial step from the “visual field” to the “visual space.”

No MeSH data available.


(a) The tree and the people are in front of the house. (b)The top-right blob is in front of the bottom-left one. There is no need for pictorial space here. (c) The “3D sphere” is actually a 2D circular disk filled with a uniform gradient of gray tone. Some people are aware of the former, some of the latter (Metzger, 1975; Ramachandran, 1988; van Doorn, Koenderink, Todd, & Wagemans, 2012; Wagemans, van Doorn, & Koenderink, 2010). Convex–concave flips are only experienced by the former group.
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fig1-2041669515607710: (a) The tree and the people are in front of the house. (b)The top-right blob is in front of the bottom-left one. There is no need for pictorial space here. (c) The “3D sphere” is actually a 2D circular disk filled with a uniform gradient of gray tone. Some people are aware of the former, some of the latter (Metzger, 1975; Ramachandran, 1988; van Doorn, Koenderink, Todd, & Wagemans, 2012; Wagemans, van Doorn, & Koenderink, 2010). Convex–concave flips are only experienced by the former group.

Mentions: Many, though by no means all, human observers experience “pictorial spaces” when looking into pictures, say holiday snapshots. Probably no one experiences a pictorial space when viewing a picture upside down. This is a common technique used by painters to experience a work as a flat array of pigments, without intrusion of perceptual objects due to stereopsis. Notice that 2D pictures may permit various 3D inferences even when there is no such a thing as “pictorial space.” In Figure 1(a), one immediately “sees” the tree in front of the house. It works just as well for random blobs (Figure 1(b)). No need for 3D phantasms, and a simple 2D algorithm achieves this. The case of Figure 1(c) is perhaps different. It has been used often in vision research (Metzger, 1975; Ramachandran, 1988). Textbooks tell you that you are supposed to “see a sphere,” that is a pictorial, volumetric object. Indeed, many observers do, but some do not (van Doorn et al., 2012; Wagemans et al., 2010). The latter see “a circular disc filled with a linear gradient of gray tone,” as an editor of one of our papers once reminded us. He had never experienced a 3D impression with such stimuli. We would not know how to call him wrong. Various 2D structures allow observers to participate in many “shape from shading” experiments without ever being aware of a 3D shape. We find, however, that persons who experience the 3D impressions have a decisive speed advantage in some paradigms apparently because they simply act on their immediate visual awareness, where the others are faced with a cognitive judgment. Another difference is that the 3D-sensitive observers occasionally experience sudden depth reversals and experience these as remarkable happenings, whereas the 2D observers are never aware of such spooky events. This suggests that one might differentiate between such “viewing modes” (we use “mode” simply to indicate a variety of visual experiences) on objective criteria. Perhaps unfortunately, the 3D observers cannot explain the qualities of awareness experienced by them to the 2D observers because, after all, the picture never changes.Figure 1.


Deploying the Mental Eye
(a) The tree and the people are in front of the house. (b)The top-right blob is in front of the bottom-left one. There is no need for pictorial space here. (c) The “3D sphere” is actually a 2D circular disk filled with a uniform gradient of gray tone. Some people are aware of the former, some of the latter (Metzger, 1975; Ramachandran, 1988; van Doorn, Koenderink, Todd, & Wagemans, 2012; Wagemans, van Doorn, & Koenderink, 2010). Convex–concave flips are only experienced by the former group.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2 - License 3
Show All Figures
getmorefigures.php?uid=PMC5016826&req=5

fig1-2041669515607710: (a) The tree and the people are in front of the house. (b)The top-right blob is in front of the bottom-left one. There is no need for pictorial space here. (c) The “3D sphere” is actually a 2D circular disk filled with a uniform gradient of gray tone. Some people are aware of the former, some of the latter (Metzger, 1975; Ramachandran, 1988; van Doorn, Koenderink, Todd, & Wagemans, 2012; Wagemans, van Doorn, & Koenderink, 2010). Convex–concave flips are only experienced by the former group.
Mentions: Many, though by no means all, human observers experience “pictorial spaces” when looking into pictures, say holiday snapshots. Probably no one experiences a pictorial space when viewing a picture upside down. This is a common technique used by painters to experience a work as a flat array of pigments, without intrusion of perceptual objects due to stereopsis. Notice that 2D pictures may permit various 3D inferences even when there is no such a thing as “pictorial space.” In Figure 1(a), one immediately “sees” the tree in front of the house. It works just as well for random blobs (Figure 1(b)). No need for 3D phantasms, and a simple 2D algorithm achieves this. The case of Figure 1(c) is perhaps different. It has been used often in vision research (Metzger, 1975; Ramachandran, 1988). Textbooks tell you that you are supposed to “see a sphere,” that is a pictorial, volumetric object. Indeed, many observers do, but some do not (van Doorn et al., 2012; Wagemans et al., 2010). The latter see “a circular disc filled with a linear gradient of gray tone,” as an editor of one of our papers once reminded us. He had never experienced a 3D impression with such stimuli. We would not know how to call him wrong. Various 2D structures allow observers to participate in many “shape from shading” experiments without ever being aware of a 3D shape. We find, however, that persons who experience the 3D impressions have a decisive speed advantage in some paradigms apparently because they simply act on their immediate visual awareness, where the others are faced with a cognitive judgment. Another difference is that the 3D-sensitive observers occasionally experience sudden depth reversals and experience these as remarkable happenings, whereas the 2D observers are never aware of such spooky events. This suggests that one might differentiate between such “viewing modes” (we use “mode” simply to indicate a variety of visual experiences) on objective criteria. Perhaps unfortunately, the 3D observers cannot explain the qualities of awareness experienced by them to the 2D observers because, after all, the picture never changes.Figure 1.

View Article: PubMed Central - PubMed

ABSTRACT

Three observers performed a task designed to quantify their “pictorial relief” in visual awareness for a photograph of a piece of sculpture. In separate sessions, they were instructed to assume one of two “mental viewpoints.” The main objective was to investigate whether human observers have such command. All three observers could redirect their “mental view direction” by up to 20°. These observers experience “paradoxical monocular” stereopsis, whereas a sizable fraction of the population does not. Moreover, they had some experience in assuming various “viewing modes.” Whereas one cannot generalize to the population at large, these findings at least prove that it is possible to direct the mental viewpoint actively. This is of importance to the visual arts. For instance, academic drawings require one to be simultaneously aware of a “viewing” (for the drawing) and an “illumination direction” (for the shading). Being able to mentally deploy various vantage points is a crucial step from the “visual field” to the “visual space.”

No MeSH data available.