Contrary to popular lore, optimal visual acuity is typically better than 20/20. Could correcting acuity beyond 20/20 offer any benefit? An affirmative answer could present new confounds in studies of aging, development, psychiatric illness, neurodegenerative disorders, or any other population where refractive error might be more likely. An affirmative answer would also offer a novel explanation of inter-observer variability in visual performance. To address the question, we had individuals perform two well-studied visual tasks, once with 20/20 vision and once with optical correction, so that observers could see one line better on an eye chart. In the contour integration task, observers sought to identify the screen quadrant location of a sparsely defined (integrated) shape embedded in varying quantities of randomly oriented “noise” elements. In the collinear facilitation task, observers sought to detect a low-contrast element flanked by collinear or orthogonal high-contrast elements. In each case, displays were scaled in size to modulate element visibility and spatial frequency (4-12 cycles/deg). We found that improving acuity beyond 20/20 improved contour integration for the high spatial frequency displays. Although improving visual acuity did not affect collinear facilitation, it did improve detection of the central low-contrast target, especially at high spatial frequencies. These results, which were large in magnitude, suggest that optically correcting beyond 20/20 improves the detection and integration of contour elements, especially those that are smaller and of higher spatial frequency. Refractive blur within the normal range may confound special population studies, explain inter-observer differences, and meaningfully impact performance in low-visibility environments.

Abstract The hollow-mask illusion is an optical illusion where a concave face is perceived as convex. It has been demonstrated that individuals with schizophrenia and anxiety are less susceptible to the illusion than controls. Previous research has shown that the P300 and P600 event-related potentials (ERPs) are affected in individuals with schizophrenia. Here, we examined whether individual differences in neuroticism and anxiety scores, traits that have been suggested to be risk factors for schizophrenia and anxiety disorders, affect ERPs of healthy participants while they view concave faces. Our results confirm that the participants were susceptible to the illusion, misperceiving concave faces as convex. We additionally demonstrate significant interactions of the concave condition with state anxiety in central and parietal electrodes for P300 and parietal areas for P600, but not with neuroticism and trait anxiety. The state anxiety interactions were driven by low-state anxiety participants showing lower amplitudes for concave faces compared to convex. The P300 and P600 amplitudes were smaller when a concave face activated a convex face memory representation, since the stimulus did not match the active representation. The opposite pattern was evident in high-state anxiety participants in regard to state anxiety interaction and the hollow-mask illusion, demonstrating larger P300 and P600 amplitudes to concave faces suggesting impaired late information processing in this group. This could be explained by impaired allocation of attentional resources in high-state anxiety leading to hyperarousal to concave faces that are unexpected mismatches to standard memory representations, as opposed to expected convex faces.

Background: Depth-inversion illusions (DII) involve stimuli for which physically distant points are perceived to be closer to observers than physically near points. Schizophrenia (SZ) patients are less likely to perceive DII as strongly as controls. In particular, there is a negative correlation between the tendency to obtain DII and positive SZ symptoms (Keane et al. 2013). Objectives: First, to test the hypothesis that the tendency to obtain DII correlates negatively with delusional ideation in healthy controls, since delusion is an important positive SZ symptom. Second, to ascertain the frequency with which individuals in the general population perceive DII. Methods: We developed a test in psiTurk to obtain data from hundreds of participants. We assess DII tendency by testing performance with DII stimuli, and we measure delusional ideation adapting Peters Delusions Inventory (PDI; Peters et al. 1999) into an online version. We used two classes of 3D objects: perceptually stable unambiguous objects that serve as “catches”: banana, apple, toy, etc.; and bistable objects that can exhibit DII but can also be perceived without depth inversion: human hollow mask, monkey hollow mask and a reverse-perspective scene. To obtain depth from motion, each object was rotated clockwise or counterclockwise around a vertical axis. We used 3-D probes embedded in strategic locations of the objects to infer whether participants obtained the veridical or illusory depth percept. Results: We conducted a pilot study with 9 participants that validated our approach of using probes to assess the perceptual state of participants. Results from large-scale psiTurk sessions are forthcoming. Discussion: Using the depth-from-motion approach is justified in light of results from a study that obtained evidence for its validity in DII experiments with SZ patients and controls (Keane et al. 2013). Our crowd sourcing experiments can study useful unexplored correlations that require large numbers of participants.

A brief tribute to Bela Julesz (1928–2003) is made in words and images. In addition to a conventional stereophotographic portrait, his major contributions to vision research are commemorated by two ‘perceptual portraits’, which try to capture the spirit of his main accomplishments in stereopsis and the perception of texture.

Two major uses of linear perspective are in planar paintings-the flat canvas is incongruent with the painted 3-D scene-and in forced perspectives, such as theater stages that are concave truncated pyramids, where the physical geometry and the depicted scene are congruent. Patrick Hughes pioneered a third major art form, the reverse perspective, where the depicted scene opposes the physical geometry. Reverse perspectives comprise solid forms composed of multiple planar surfaces (truncated pyramids and prisms) jutting toward the viewer, thus forming concave spaces between the solids. The solids are painted in reverse perspective: as an example, the left and right trapezoids of a truncated pyramid are painted as rows of houses; the bottom trapezoid is painted as the road between them and the top forms the sky. This elicits the percept of a street receding away, even though it physically juts toward the viewer. Under this illusion, the concave void spaces between the solids are transformed into convex volumes. This depth inversion creates a concomitant motion illusion: when a viewer moves in front of the art piece, the scene appears to move vividly. Two additional contributions by the artist are discussed, in which he combines reverse-perspective parts with forced and planar-perspective parts on the same art piece. The effect is spectacular, creating objects on the same planar surface that move in different directions, thus "breaking" the surface apart, demonstrating the superiority of objects over surfaces. We conclude with a discussion on the value of these art pieces in vision science.

Introduction: Perhaps the best known depth inversion illusion (DII) is the hollow-face illusion, in which a concave face mask is misperceived as convex; when it rotates, it is perceived rotating in the opposite direction. DII is possible with other concave objects, even with a hollow ovoid surface, but the illusion strength is much weaker. Two possible causes for the hollow-face illusion are a general convexity bias and face-specific stored knowledge that influences the visual input. The current project aimed to look for these effects in the presence of abstract facial and non-facial features. Method: We generated six computer-rendered 3D wire-frame objects that shared the same bounding contour; the bounding contour was a planar closed oblong wire-frame shape that resembled the outline of a frontal view of a face. Each object had a concave and a convex side. The two face-like objects were: (1) FN, with eyebrows and nose contour; (2) FNM, same as FN, with added mouth. The non-face objects were: (3) nFX, with two crossing diagonal contours; (4) nFV, with two nearly vertical non-crossing contours; (5) fNH, with nose, eyebrows and mouth rotated 90° clockwise. The last stimulus, (6) F+nF was the union of FNM and nFX stimuli. To provide kinetic depth information, each object was rotated clockwise or counterclockwise at 10 degrees/second. Results: DII was present for both concave and convex objects, but significantly stronger for concave objects (convexity bias). DII was equally strong for FN and FNM. DII was significantly stronger for face than for non-face stimuli. Performance with F+nF was closer to non-face than to face stimuli. Conclusions: Results suggest that DII is stronger for concave objects for both face and non-face stimuli, providing support for a general convexity bias. The increased frequency of DII occurrence for face-like objects indicates the presence of face-specific influences. Meeting abstract presented at VSS 2018

Introduction: Depth-inversion illusions (DII) offer examples in which stored knowledge overcomes visual cues and causes 3D objects to be perceived in opposite depth: points located physically closer appear to be behind points located physically further, thus transforming convexities into perceived concavities and vice versa. Viewers moving in front of DII stimuli perceive them to move (illusory DII motion). We manipulated the binocular disparity (BD) cue to study its role in DII. Methods: We used large (height > 80 cm) realistically painted hollow masks (HM) and reverse-perspectives (RP) as DII stimuli (DIIS); painted cues and the 3D geometry were incongruent. We also used their depth-opposites: a normal 3D mask (NM) and a proper-perspective (PP) that are normally not depth-inverted stimuli (nDIIS). Subjects viewed DIIS (HF and RP) and nDIIS (NM and PP) from 3 meters, monocularly and binocularly, as well as using a synopter (identical eyes' views, BD=0) and a pseudoscope (left and right eye views swapped; BD is the negative of its value under normal viewing). Results: DII was strongest under pseudoscopic viewing and weakest under binocular viewing, with synoptic and monocular viewing yielding intermediate strengths as expected, for both DIIS. DI was impossible for nDIIS under all conditions. It was nearly impossible when viewers saw only the top or only the bottom parts of nDIIS for all conditions, but it became possible under pseudoscopic viewing. Illusory motion was always present when DII was present. Conclusions: BD opposes DII under binocular viewing, because it signals veridical depth. As expected, DII strength increases under monocular or synoptic viewing (BD=0), reaching its maximum under pseudoscopic viewing, because BD signals illusory depth under pseudoscopy. The above confirms BD as a strong cue for recovering 3D shape. However, BD's weak effect on nDIIS indicates its limits as a cue for 3D shape recovery. Meeting abstract presented at VSS 2018

Abstract The main goal of this chapter is to present the relatively new art form of reverspectives, invented and refined by Patrick Hughes. Reverspectives are painted on nonplanar surfaces that jut out of the wall, yet the painted scenery contains strong reverse-perspective cues that cause depth reversal: convex and concave parts are perceived as concave and convex, respectively. Reverspectives also appear to move vividly as viewers move past them. The chapter presents a wide variety of reverspectives, as well as a related class of illusions that are painted on large spheres, producing depth inversion and illusory motion. The chapter provides a plausible explanation for the percepts obtained with these types of stimuli.

This chapter presents a brief history of the Ames window illusion, in which a trapezoid with its long and short sides in a vertical position rotates continuously in the same direction about a vertical axis. It creates the illusion of oscillating back and forth. An explanation is offered that is based on humans’ tendency to perceive a trapezoid as a slanted rectangle; according to this explanation, when the long base of the trapezoid is behind the short base, viewers perceive it to be in front, thus reversing depth and, consequently, reversing the direction of rotation. The chapter tries to see this illusion in a broader perspective and includes many compelling variations of the Ames window illusion.

The effects of higher than recommended vitamin D doses on bone mineral density (BMD) and quality are not known. In this study, higher intakes, in postmenopausal women undergoing weight control over 1 year, had no effect on areal or volumetric BMD but prevented the deterioration in cortical bone geometry.

Background: The vast majority of studies that examine visual processing in schizophrenia ensure that subjects have normal or corrected-to-normal vision without also reporting whether subject groups are matched on visual acuity (VA) within the normal range. This is problematic because individuals with schizophrenia typically have impaired VA and because optimal VA among healthy adults is better than 20/20. Therefore, we ask: Could VA be a confounding variable even when all subjects have normal or corrected-to-normal vision? Methods: The question was addressed in 2 separate investigations of healthy adults. In the first, we measured binocular VA with a logarithmic eye chart, and compared individuals with 20/20 vision (N = 14) to those with better-than 20/20 vision (“SharpPerceivers”, N = 30) on 3 behavioral tasks. In the contour integration (CI) task, subjects located an integrated shape embedded in varying quantities of randomly-oriented noise elements; in the collinear facilitation (CF) task, subjects detected a low-contrast element flanked by collinear or orthogonal high-contrast elements; in the orientation discrimination task, subjects discerned the orientation of 4 briefly-presented, high-contrast pac-man elements. Spatial frequency was modulated in the CI and CF tasks (4–12 cycles/deg) by scaling the entire display. In the second study, 13 healthy adults with 20/20 uncorrected binocular VA performed the same 3 tasks as above—once without eyeglasses and once with eyeglasses so that they could read an additional line (0.11 logMAR units) on the eye chart. Results: In the first study, the SharpPerceivers integrated contours under noisier conditions (P < .001), had higher contrast sensitivity (P = .01), and discriminated orientation more accurately than the 20/20 group (P = .02). In the second study, optical correction enabled observers to integrate contours under noisier conditions (P = .001), detect elements of lower contrast (P = .001) but did not quite improve orientation discrimination ability (P = .14). When elements were composed of high (rather than lower) spatial frequency, optical correction conferred a greater benefit for contour integration (P < .01) and contrast sensitivity (P < .05). Conclusion: Previous schizophrenia studies reporting contour integration, contrast sensitivity, or perhaps orientation discrimination deficits may need to be re-evaluated if they did not match for VA within the normal range. Our results also show that modest reductions in refractive blur strongly improve visual perception and that fitting patients with appropriate eyewear even in cases of questionable impairment may offer a host of benefits for normal visual functioning.

Introduction: Recovering depth from stereo image pairs is known to have difficulties (Hoffman et al., 2008; Kim et al., 2012). The main issue: Poor matching of the distance between the two eyes' images and the placement of the eyes' prisms. We describe results with a hardware/software method enabling the precise adjustment of the horizontal position of images and the viewing prisms of the haploscope. Methods: A two-piece apparatus was added to prism-and-mirror haploscope that was initially designed with a fixed interpupillary distance (IPD) suitable most viewers. We added 1) a 3D-printed slider for the precise positioning of the prisms. 2) an eye piece with separate viewing ports to ensure a fixed distance between the eyes and the prisms.The IPD of each observer was used to adjust the distance between the centers of the haploscope prisms. Observers used a program developed in MATLAB to adjust the degree of horizontal displacement of left/right images on the screen.We compared results with the original haploscope and with the improved apparatus. Stimuli included random-dot stereograms (RDS), computer-generated objects and pictures of human faces. In the RDS condition, the task was to decide whether the presented shape was located in front or behind the background. In the 3D object and the face conditions, the task was to report whether the object/face was convex, concave or flat. Results: Data indicates significant improvement in accuracy with RDS images with the customized setup. Surprisingly, even after the improvement, not all viewers were virtually 100% correct in perceiving convex faces as convex, whereas they were all virtually 100% correct with physical masks (Keane et al. 2013). Conclusion: Setting up the haploscope to accommodate the viewer's unique IPD distance improves accuracy of depth perception. Despite the improvement, performance with stereoscopic images is still inferior to that with physical objects. Meeting abstract presented at VSS 2017

Introduction: Two depth-inversion (DI) illusions, where viewers perceive depth structure opposite to the stimulus's physical depth, are hollow masks and reverspectives [Wade & Hughes, 1999]. For faces, one explanation is that face-specific 3D stored knowledge and a general convexity bias overcome data-driven depth cues to produce DI. For reverspectives, stored general perspective rules (e.g., that retinal trapezoids are rectangles slanted in physical space with their long retinal edge closer to viewer) may account for the DI [Gregory, Phil. Trans. R. Soc. B, 2005]. We call such easily obtained DI illusions "Easillusions". Rationale for present study: We investigated whether humans can downplay stored knowledge and rules to obtain DI "hardillusions" for stimuli in which stored knowledge and rules oppose, rather than favor, DI [Papathomas et al. ECVP 2015]. Examples of such stimuli are normal, convex 3-D faces and "proper-perspectives", in which the retinal trapezoids are consistent with the depth of the physical surfaces. However, our 2015 study included only unpainted masks and fragments of reverse-perspectives. Methods: This study included a complete reverspective and realistically painted convex masks. Stimuli were both easillusions (hollow mask, reverspective) and hardillusions (convex mask, proper-perspective). Also, all stimuli were either realistically painted or unpainted. We assessed how long it took 16 subjects to obtain DI. Results: Painted reverspectives tended to produce DI faster than unpainted ones, whereas painted proper perspectives were much slower than unpainted ones. For faces, the difference for obtaining DI between painted and unpainted faces was much smaller both for the hollow and convex masks. The only stimuli that no subject was able to get DI were painted convex masks. Conclusions: Perspective painted cues played a much stronger role than facial painted cues, providing additional evidence that facial 3D geometry plays a larger role than scene 3D geometry. Meeting abstract presented at VSS 2017

Abstract When viewers see a hollow mask, they misperceive it as a regular convex face. This is the basic form of the hollow-mask illusion, but the illusion involves misperceived motion as well. Namely, when stationary observers view a rotating hollow mask, they perceive a convex face that appears to rotate in the opposite direction; in a dual situation, moving observers perceive a stationary hollow mask as a convex face that appears to rotate as if to “follow” them. This chapter reviews the hollow-mask illusion and examines factors that enhance or weaken it, pathological responses to it, developmental and computational issues, some variants of the illusion, as well its significance in brain research.

Background: One of the best-known depth-inversion illusions (DII) that offers strong evidence for the influence of stored knowledge on the visual input [Bar et al. PNAS2006] is the hollow-face illusion [Gregory, "The intelligent eye", 1970; Georgeson, Perception 1979], where a concave face is misperceived as convex. A general explanation is that lifelong familiarity with convex faces overrides data-driven sensory signals. The convexity bias may also play a role in the illusion [Hill & Bruce, Perception 1994]. To isolate the role of the convexity bias we assessed the illusion strength using computer generated 3D convex and concave ovoid objects (results with similar computer generated face stimuli were reported last year [Farkas et al. VSS2015]). Methods: We modeled 14 ovoid "non-face" objects (7 convex, 7 concave), differing in shape, texture and depth structure. Three types of textures were mapped onto the objects, with random black-and-white square textels (texture elements): (1) "Concave texture": Textel size decreased linearly from periphery to center to provide perspective depth cue favoring concavity. (2) "Convex texture": Opposite size variation (increase from periphery to center), favoring convexity. (3) "Neutral texture": Uniform textel size. Each object oscillated around its vertical axis. Observers had to report whether the object was convex or concave. Results: The results indicate that DII strength depends on both structure and texture. The stimuli that produce the most ambiguous percept are the ones in which the textural depth cues compete against depth structure. Using this method we obtained a psychometric function for the DII tendency elicited by a set of virtual "non-face" objects. Conclusions - Discussion: The data show far weaker DII effects with ovoid stimuli as compared to the hollow-face illusion from our previous studies [Farkas et al. VSS2015]. These stimuli will be used to study differences in DII perception between schizophrenia patients and controls. Meeting abstract presented at VSS 2016

Patients with psychosis exhibit a reduced susceptibility to depth inversion illusions (DII) in which a physically concave surface is perceived as convex (e.g., the hollow mask illusion). Here, we examined the extent to which lessened susceptibility to DII characterized youth at ultra high risk (UHR) for psychosis. In this study, 44 UHR participants and 29 healthy controls judged the apparent convexity of face-like human masks, two of which were concave and the other convex. One of the concave masks was painted with realistic texture to enhance the illusion; the other was shown without such texture. Networks involved with top-down and bottom-up processing were evaluated with resting state functional connectivity magnetic resonance imaging (fcMRI). We examined regions associated with the fronto-parietal network and the visual system and their relations with susceptibility to DII. Consistent with prior studies, the UHR group was less susceptible to DII (i.e., they were characterized by more veridical perception of the stimuli) than the healthy control group. Veridical responses were related to weaker connectivity within the fronto-parietal network, and this relationship was stronger in the UHR group, suggesting possible abnormalities of top-down modulation of sensory signals. This could serve as a vulnerability marker and a further clue to the pathogenesis of psychosis.