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We report a novel visual illusion that is present in the natural environment. In attempting to cut a banana in half, many people make the side adjacent to the stem shorter, because they see it as longer than it is. This study tested the presence of the banana bisection illusion with outline drawings and a 3D realistic-looking plastic banana. According to Gibson (1966) illusions are the consequence of artificial and impoverished stimuli, such as line drawings. However, the banana bisection illusion was found with naturalistic-looking 3D stimuli. A second experiment with solid 3D plastic bananas found the illusion with and without the stem, but the illusion was larger with the stem present. [ABSTRACT FROM AUTHOR]

Ambiguous patterns have a tendency to appear to point up. This bias makes sense as most objects are on the ground, pointing up. However, we discover that the source of the up bias is the preference for seeing depth receding from the lower to the upper visual field. [ABSTRACT FROM AUTHOR]

With the continued growth of digital device use, a greater portion of the visual world experienced daily by many people has shifted towards digital environments. The "oblique effect" denotes a bias for horizontal and vertical (canonical) contours over oblique contours, which is derived from a disproportionate exposure to canonical content. Carpentered environments have been shown to possess proportionally more canonical than oblique contours, leading to perceptual bias in those who live in "built" environments. Likewise, there is potential for orientation sensitivity to be shaped by frequent exposure to digital content. The potential influence of digital content on the oblique effect was investigated by measuring the degree of orientation anisotropy from a range of digital scenes using Fourier analysis. Content from popular cartoons, video games, and social communication websites was compared to real-life nature, suburban, and urban scenes. Findings suggest that digital content varies widely in orientation anisotropy, but pixelated video games and social communication websites were found to exhibit a degree of orientation anisotropy substantially exceeding that observed in all measured categories of real-world environments. Therefore, the potential may exist for digital content to induce an even greater shift in orientation bias than has been observed in previous research. This potential, and implications of such a shift, is discussed. [ABSTRACT FROM AUTHOR]

Illusory displacements in depth may be perceived in simple geometric configurations devoid of cues for spatial computation but also in real-world images where there is no shortage of information of this kind. Two of these different contexts drew the attention of vision scientists as sources of depth illusions: the Kanizsa square and the images of statues that Catalano's created with a part missing. Similar depth alterations occur in both cases: the portions of the background surrounded by "inducers" (pacmen or body parts) are perceived as coming to the foreground. These illusory effects appear more vivid and diverse in the real-world context leading to hypothesize an involvement of the figural complexity in the misperception. A check was carried out by testing the effects of the background articulation on the depth perception of the illusory Kanizsa square. It was confirmed that both background and inducers articulation enhance the phenomenon. A large set of Catalano's images was analyzed, looking for basic distorting sources along the torn contours. Several basic factors were found, but not enough to account for the complexity of this variegated, often paradoxical phenomenon. [ABSTRACT FROM AUTHOR]

In his extensive writing about pictures, James J. Gibson offered perspective formulae for square tiles projecting trapezoids onto a picture plane, foreshortening to zero height with distance. I reverse the claim: as distance decreases, the trapezoids increase to infinite height, in marginal distortion, or forelengthening. I also reverse the direction of projection. Usually considered to be incoming, from the distant tile to the picture plane, in reverse—outgoing—the tiles have directions from the center of projection, with implications for haptics and people who are blind. A drawing of a cube illustrates the argument. It is by an adult who is blind. It includes foreshortening, and shows directions of surfaces from a vantage point. [ABSTRACT FROM AUTHOR]

J. J. Gibson's ground theory of space perception is contrasted with Descartes' theory, which reduces all of space perception to the perception of distance and angular direction, relative to an abstract viewpoint. Instead, Gibson posits an embodied perceiver, grounded by gravity, in a stable layout of realistically textured, extended surfaces and more delimited objects supported by these surfaces. Gibson's concept of optical contact ties together this spatial layout, locating each surface relative to the others and specifying the position of each object by its location relative to its surface of support. His concept of surface texture—augmented by perspective structures such as the horizon—specifies the scale of objects and extents within this layout. And his concept of geographical slant provides surfaces with environment-centered orientations that remain stable as the perceiver moves around. Contact-specified locations on extended environmental surfaces may be the unattended primitives of the visual world, rather than egocentric or allocentric distances. The perception of such distances may best be understood using Gibson's concept of affordances. Distances may be perceived only as needed, bound through affordances to the particular actions that require them. [ABSTRACT FROM AUTHOR]

Visual perception depends fundamentally on statistical regularities in the environment to make sense of the world. One such regularity is the orientation anisotropy typical of natural scenes; most natural scenes contain slightly more canonical (horizontal and vertical) information than oblique information. This property is likely a primary cause of the oblique effect in which subjects experience greater perceptual fluency with horizontally and vertically oriented content than oblique. Recent changes in the visual environment, including the "carpentered" content in urban scenes and the framed, caricatured content in digital screen media presentations, may have altered the typical (natural) level of orientation anisotropy. The current work evaluated whether digital visual experience, or visual experience with framed digital content, has the potential to alter the magnitude of the oblique effect in visual perception. Experiment 1 successfully established a novel eye-tracking method capable of indexing the visual oblique effect quickly and reliably and demonstrated the oblique effect. Experiment 2 used this method and found that one session of exposure to a specific video game altered visual orientation perception. Taken together, these results indicate that exposure to the realistic, but caricatured scene statistics of digital screen media, can alter visual contour perception in one session. [ABSTRACT FROM AUTHOR]

In 1966, James Gibson first presented his theory of the ambient optic array, and he proposed a new field of ecological optics that he hoped would advance our knowledge on this topic. This study will consider how his ideas have largely come to fruition over the past 50 years. It reviews the research on the visual perception of three-dimensional shape from shading, the effects of ambient light from surface interreflections on observers' perceptions, the perception of the light field, and the perception of surface materials. Finally, it also considers Gibson's impact on these developments. [ABSTRACT FROM AUTHOR]

Binocular disparity can give rise to the perception of open surfaces or closed curved surfaces (volumes) that appear to vary smoothly across discrete depths. Here I build on my recent papers by providing examples where modally completing surfaces not only fill in from one depth layer's visible contours to another layer's visible contours within virtual contours in an analog manner, but where modally completing surface curvature is altered by the interpolation of an abutting object perceived to be connected to or embedded within that modally completing surface. Seemingly minor changes in such an abutting object can flip the interpretation of distal regions, for example, turning a distant edge (where a surface ends) into rim (where a surface bends to occlude itself) or turning an open surface into a closed one. In general, the interpolated modal surface appears to deform, warp, or bend in three-dimensions to accommodate the abutting object. These demonstrations cannot be easily explained by existing models of visual processing or modal completion and drive home the implausibility of localistic accounts of modal or amodal completion that are based, for example, solely on extending contours in space until they meet behind an occluder or in front of "pacmen." These demonstrations place new constraints on the holistic surface and volume generation processes that construct our experience of a three-dimensional world of surfaces and objects under normal viewing conditions. [ABSTRACT FROM AUTHOR]

In 1923, Adhemar Gelb and Ragnar Granit, two prominent researchers in early Gestalt perceptual theory, reported a lower threshold for detection of a target (a small colored dot) on the ground region of an image than on an adjacent figural region. Although their results had a wide influence on the understanding of figure-ground perception, they are at odds with more recent investigations in which figural regions appear to have a processing advantage over ground regions. The two present studies replicated Gelb and Granit's experiment using a similar figure-ground stimulus albeit with a two-alternative forced choice procedure rather than their original method of adjustment. Experiment 1 found that, contrary to Gelb and Granit's findings, a detection advantage was found for the figural over the ground region. Experiment 2 indicated that explicit contours might have played a role in detection. [ABSTRACT FROM AUTHOR]

A wearable 'helmet' version of the S cone isolating technique was constructed to explore vision at equiluminance. For my high school summer science project, I visited parks and streets while wearing the helmet and report that the helmet appears to have captured the main properties described for the large-scale, more cumbersome stage version. [ABSTRACT FROM AUTHOR]

The aims of this paper are twofold: first, to discuss and analyze the concept of binocular disparity and second, to contrast the traditional "air theory" of three-dimensional vision with the much older "ground theory," first suggested by Ibn al-Haytham more than a thousand years ago. The origins of an "air theory" of perception can be traced back to Descartes and subsequently to the philosopher George Berkeley, who claimed that distance "could not be seen" because points lying along the same line of sight (in an empty space) would all project to the same location on the retina. However, Descartes was also aware that the angle of convergence of the two eyes could solve the problem of the "missing" information for the monocular observer and, since then, most visual scientists have assumed that eye vergence plays an important role both in judging absolute distance and for scaling retinal size and binocular disparities. In contrast, al-Haytham's and Gibson's "ground theories," which are based on the geometry of the textured ground plane surface that has surrounded us throughout evolution and during our lifetimes, are not just more ecologically based but they also obviate the need for disparity scaling ., Competing Interests: The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)

We experience vivid percepts of objects and materials despite complexities in the way images are structured by the interaction of light with surface properties (3D shape, albedo, and gloss or specularity). Although the perception of gloss (and lightness) has been argued to depend on image statistics (e.g., sub-band skew), studies have shown that perceived gloss depends critically on the structure of luminance variations in images. Here, we found that separately adapting observers to either positive or negative skew generated declines in perceived gloss, contrary to the predictions of theories involving image statistics. We also found similar declines in perceived gloss following adaptation to contours geometrically correlated with sharp specular edges. We further found this aftereffect was stronger when contour adaptors were aligned with specular edges compared with adaptation to the same contours rotated by 90. These findings support the view that the perception of gloss depends critically on the visual system's ability to encode specular edge structure and not image skew. [ABSTRACT FROM AUTHOR]

A novel haptic illusion is described where deformations of the fingertip skin lead to subsequent misperceptions of an object's shape., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)

Disruptive colouration (DC) is a form of camouflage comprised of areas of pigmentation across a target's surface that form false edges, which are said to impede detection by disguising the outline of the target. In nature, many species with DC also exhibit edge enhancement (EE); light areas have lighter edges and dark areas have darker edges. EE DC has been shown to undermine not only localisation but also identification of targets, even when they are not hidden (Sharman, Moncrieff, & Lovell, 2018). We use a novel task, where participants judge which "snake" is more "wiggly," to measure shape discrimination performance for three colourations (uniform, DC, and EE DC) and two backgrounds (leafy and uniform). We show that EE DC impairs shape discrimination even when targets are not hidden in a textured background. We suggest that this mechanism may contribute to misidentification of EE DC targets.

The present article reports a new illusory colour phenomenon. There have been previous reports of illusory colours that spread to an area in contact with a coloured object (e.g., neon-like spreading). However, according to our informal observations as well as the experiments reported here, illusory colour spreads even if the coloured and noncoloured areas are separated by a gap. The contour-based perception account as well as the interaction of some components of surround suppression in the visual cortex were discussed as possibilities to account for the present illusion. The effect reported in the present study may provide suggestions for further understanding of colour perception. [ABSTRACT FROM AUTHOR]

It is popular to attribute the appearance of extended colour fields to a process of filling-in from the differential colour signals at colour edges, where one colour transitions to another. We ask whether such a process can account for the appearance of extended colour fields in natural images. Some form of colour filling-in must underlie the equiluminant colour Craik–O’Brien–Cornsweet effect and the Watercolour Effect, but these effects are too weak to account for the appearance of extended colour fields in natural images. Moreover, the graded colour disappearance effect reported as evidence for colour filling-in does not work under natural viewing conditions. We demonstrate that natural images do not look very colourful when their colour is restricted to edge transitions. Moreover, purely chromatic images with maximally graded (edgeless) transitions look fully colourful. Consequently, we conclude that colour filling-in makes no more than a minor contribution to the appearance of extended colour regions in natural images. [ABSTRACT FROM AUTHOR]

Building on the modal and amodal completion work of Kanizsa, Carman and Welch showed that binocular stereo viewing of two disparate images can give rise to a percept of 3D curved, nonclosed illusory contours and surfaces. Here, it is shown that binocular presentation can also give rise to the percept of closed curved surfaces or volumes that appear to vary smoothly across discrete depths in binocularly fused images, although in fact only two binocular disparities are discretely defined between corresponding contour elements of the inducing elements. Surfaces are filled in from one depth layer’s visible contours to another layer’s visible contours within virtual contours that are interpolated on the basis of good contour continuation between the visible portions of contour. These single depth contour segments are taken not to arise from surface edges, as in Kanizsa’s or Carman and Welch’s examples, but from segments of “rim” where the line of sight just grazes a surface that continues behind and beyond the rim smoothly. When there are two or more surface-propagating contour segments, the propagated surfaces can continue away from the inferred rim, merge, and then close behind the self-occluding visible surface into an everywhere differentiable closed surface or volume. Illusory surfaces can possess a depth and perceived surface curvature that is consistent with all visible contour segments, despite the absence of local disparity cues at interpolated 3D surface locations far from any visible contour. These demonstrations cannot be easily explained by existing models of visual processing. They place constraints on the surface and volume generation processes that construct our 3D world under normal viewing conditions. [ABSTRACT FROM AUTHOR]

A new class of dynamic volume completion is introduced, where image elements (e.g., occluding semi-ellipses placed at the edge of an object) can link across a gap between two or more objects, leading to the perception of illusory volumes that deform as those image elements are set into relative motion. These new demonstrations provide further evidence that volume completion is not dictated solely by contour relatability constraints, but is instead a dynamic process of 3D shape construction that also takes into account dynamic cues to object shape, even in the absence of any contour relatability whatsoever. [ABSTRACT FROM AUTHOR]