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Two experiments are described, the purpose of which was to investigate the presence of a misalignment illusion caused by Poggendorff-like conditions in two paintings by Peter Paul Rubens, both depicting the Descent from the Cross, one located in Antwerp (Belgium), the other in Lille (France). The first shows a geometrical misalignment made by Rubens in a minor detail, which is considered proof that the artist observed the Poggendorff illusion. The second painting, instead, shows a perfect geometrical alignment in a similar detail. In experiment 1, participants were asked to align a top segment to a lower one in two types of stimuli: a full-size digitally manipulated reproduction of the painting and a Poggendorff-like configuration that recalled the painting's lines displacement and tilt. Adjustments were performed from two distances, one up close (painting distance) and one from below and far (observation distance). Results confirmed the presence of the Poggendorff illusion, but mean adjustments significantly differed from the misalignment perpetrated by Rubens. Experiment 2 was set up in a similar fashion with the Lille painting. Results confirmed the presence of the Poggendorff illusion also in this painting; however, the alignment by Rubens coincides with the geometrical one. Results from both experiments do not support the claim that Rubens observed the Poggendorff illusion and therefore corrected for it in the Antwerp painting. An alternative account is discussed, which relates to the structural layout of the painting.

This work concerns the subjective impression of perceived illumination. The purpose of the study is to test attributes expressing qualitative experiences referring to ambient lighting that can be applied as descriptors. Seventy participants viewed an actual model room, with the fourth wall removed (viewing booth). Walls, floor, and ceiling were achromatic. Two achromatic cubes were placed inside the room: One was a reflectance increment to the walls, the other a decrement. The room was illuminated by two different light sources, Artificial Daylight (D65) or Tungsten Filament (F), the order of which was randomized across participants. The participants’ task was to evaluate ambient illumination for each light source. A semantic differential method was employed with 27 pairs of adjectives on 1 to 7 rating scales, categorized in three groups: characteristics of atmosphere, time, and cross-modal. Only the ratings of nine pairs of adjectives were not influenced by the type of illumination. The most differentiated couples under different illuminants were hot/cold and modern/old, but large differences also appeared with the following couples: hard/soft, technological/primitive, summery/wintry, warm/cool, sensual/frigid, natural/artificial, and hospitable/inhospitable. The hypothesis that there would be consistency among the subjects in evaluations of the characteristics tested and that these would be differently perceived under different illuminants was confirmed. The results show that it is possible to identify subjective perceived illumination as a phenomenon endowed with specific filling-in qualities and that as a perceptual experience it can be categorized, with implications for application in architecture and design.

The glare effect is a brightness illusion that has captured the attention of the vision community since its discovery. However, its photometrical reversal, which we refer to here as photometrical reversed glare (PRG) stimuli, remained relatively unexplored. We presented three experiments that sought to examine the perceived brightness of a target area surrounded by luminance gradients in PRG stimuli and compare them with conventional glare effect configurations. Experiment 1 measured the brightness of the central target area of PRG stimuli through an adjustment task; the results showed that the target appeared brighter than similar, comparative areas not surrounded by luminance gradients. This finding was unexpected given the recent report that PRG stimuli cause pupil dilation. Meanwhile, Experiments 2 and 3 implemented a rating task to further test the findings in Experiment 1. Again, the study found a robust brightening illusion in the target area of PRG stimuli in a wide range of target and background luminance. The results are discussed in comparison with the brightness enhancement of the glare effect.

The purpose of this research is to present the employment of a simple-to-use crossmodal method for measuring haptic size illusions. The method, that we call See what you feel, was tested by employing Uznadze’s classic haptic aftereffect in which two spheres physically identical (test spheres) appear different in size after that the hands holding them underwent an adaptation session with other two spheres (adapting spheres), one bigger and the other smaller than the two test spheres. To measure the entity of the illusion, a three-dimensional visual scale was created and participants were asked to find on it the spheres that corresponded in size to the spheres they were holding in their hands out of sight. The method, tested on 160 right-handed participants, is robust and easily understood by participants.

Pupil diameters were recorded with an eye-tracker while participants observed cruciform patterns of gray-scale gradients that evoked illusions of enhanced brightness ( glare ) or of enhanced darkness. The illusions were either presented as static images or as dynamic animations which initially appeared as a pattern of filled squares that—in a few seconds—gradually changed into gradients until the patterns were identical to the static ones. Gradients could either converge toward the center, resulting in a central region of enhanced, illusory, brightness or darkness, or oriented toward each side of the screen, resulting in the perception of a peripheral ring of illusory brightness or darkness. It was found that pupil responses to these illusions matched both the direction and intensity of perceived changes in light: Glare stimuli resulted in pupil constrictions, and darkness stimuli evoked dilations of the pupils. A second experiment found that gradients of brightness were most effective in constricting the pupils than isoluminant step-luminance, local, variations in luminance. This set of findings suggest that the eye strategically adjusts to reflect in a predictive manner, given that these brightness illusions only suggest a change in luminance when none has occurred, the content within brightness maps of the visual scene.

Three experiments investigated the role of physical illumination on lightness perception in simultaneous lightness contrast (SLC). Four configurations were employed: the classic textbook version of the illusion and three configurations that produced either enhanced or reduced SLC. Experiment 1 tested the effect of ambient illumination on lightness perception. It simulated very dark environmental conditions that nevertheless still allowed perception of different shades of gray. Experiment 2 tested the effect of the intensity of Gelb lighting on lightness perception. Experiment 3 presented two conditions that integrated illumination conditions from Experiments 1 and 2. Our results demonstrated an illumination effect on both lightness matching and perceived SLC contrast: As the intensity of illumination increased, the target on the black background appeared lighter, while the target on the white background was little affected. We hypothesize the existence of two illumination ranges that affect lightness perception differently: low and normal. In the low range, the SLC contrast was reduced and targets appeared darker. In the normal range, the SLC contrast and lightness matchings for each background were little changed across illumination intensities.

Aim To evaluate the accuracy of magnetic resonance imaging in assessing tumor response following neoadjuvant chemotherapy in patients with locally advanced breast cancer. Materials and Methods Twenty-six patients entered a phase II study of neoadjuvant chemotherapy, undergoing bilateral breast magnetic resonance imaging before therapy and before surgery. Tumor response was classified using RECIST criteria, using tumor size at magnetic resonance imaging. The latter was then compared to residue found at histopathological examination. Results Magnetic resonance imaging showed 6 (23%) complete responses, 17 (65%) partial responses, 3 (11.5%) disease stabilizations and no disease progressions. Twenty-three tumors (88.5%) were considered responsive and 3 (11.5%) unresponsive. Pathological tumor response was: 6 complete responses (23%), 17 partial responses (65%), 2 stable disease (8%), 1 progression (4%). When results of the preoperative magnetic resonance imaging were compared to pathological tumor response, magnetic resonance imaging overestimated tumor size in 12 cases (46%) and underestimated it in 9 (35%). However, preoperative magnetic resonance imaging failed to detect invasive tumor in 2 false-negative cases (8%), 1 of which was multifocal. Mastectomy was performed in 12 cases: 1 case of disease progression even though the neoplasm appeared smaller at magnetic resonance imaging, 3 cases with stable disease, and 4 cases with T3 or T4 disease. The 9th patient was T2N2 with initial retroareolar disease and negative magnetic resonance imaging after chemotherapy. The 10th patient, affected by lobular cancer, was in partial remission but was T3N1. The 11th patient was 57 years old but was not interested in conservative surgery. The 12th patient requested bilateral prophylactic mastectomy due to her positive family history of breast cancer. Conclusions Magnetic resonance imaging of the breast allowed conservative surgery in 54% of the patients. This low value is primarily due to overestimation of tumor size, with a negative predictive value of 67% in our population. However, surgeons were able to choose conservative surgery with relative safety in cases of small residual disease.

The perception of luminosity is thought to depend upon the intensity of the stimulus: a surface begins to appear self-luminous when it emits or reflects a certain amount of light. This is known as the luminosity threshold. It is a common opinion among vision scientists that such a threshold is correlated to the intensity of a perceptually white surface, in the sense that only an area of the visual field with luminance higher than perceived surface-white will appear luminous. Here we show grey colours that appear luminous in virtue of surrounding luminance ramps. These ramps are intended to mimic halos seen around light sources in natural environments. The results of three experiments indicate that the phenomenon is in direct contradiction to the aforementioned assumptions and suggest the existence of separate perceptual pathways for self-luminosity perception and for surface-colour perception.

Three compelling luminance-gradient effects are described. The first effect concerns a brightness enhancement and a luminous mist spreading out from a central area having the same luminance as the white background and surrounded by four rectangular inducers shaded with a linear luminance gradient. The second effect is perceived with a photographically reversed configuration, and concerns what may be considered a brightness reduction or the enhancement of a darkness quality of a target area of the visual scene. The third effect concerns the perception of a self-luminous disk inside a somewhat foggy medium. The effects are worthy of further examination because they challenge current theories of luminosity perception and brightness perception in general.

The impression of glare is caused by a very intense light source. However, here I show that this impression can also be generated with normal light intensities. The strength of the effect depends on the number of elements used to produce it. The elements are 2 cm × 5 cm rectangles. A single horizontal achromatic rectangle is first used on a homogeneous white or black background. From left to right, the brightness of the rectangle varies smoothly from black to white. The left part of the rectangle appears to progressively bend toward the background when the background is black, while the rectangle appears straight and to fade into an apparent white mist near its right side when the background is white. When the background is black, two horizontal rectangles, mirror-shaded from black to white, so that their black ends face each other with a 2 cm gap between them, appear either to bend toward the background or to be straight and to fade into a sort of dark ‘smoke’. When the background is white with the left rectangle varying in brightness from black to white and the right one from white to black, the rectangles look straight with a sort of white glare appearing to come out from the gap. The black ‘smoke’ and the white glare look more compelling when there are four rectangles forming a cross with a central square gap. It can be argued that this and the neon spreading effect are unrelated. Instead, psychophysical experiments suggest that the glare and smoke effects depend on a relation between the grey scale gradient and the background brightness.

Starting from an achromatic display used by Zavagno to study a glare and a ‘smoke’ effect, we show two new dynamic effects that we call (a) ‘light explosion’ and (b) ‘night crash’. On a uniform white or black background four black or white rectangles (inducers, 1 deg × 5.7 deg) were arranged to form an orthogonal cross with a square gap in its centre. (a) When the luminance of black inducers on a white background is transformed into a smooth gray scale gradient with the lighter ends facing the square gap, a luminous mist with a glare effect is seen. When such a transformation is performed dynamically by changing the gradient from outside to inside (with the outside ends remaining black and the inside changing toward white), a sudden explosion of light is seen. (b) When the luminance of white inducers on a black background is transformed into a smooth gray scale gradient with their darker ends facing the square gap, a sort of dark ‘smoke’ is seen. If such a transformation is performed dynamically by changing the gradient from inside to outside (with the outside ends remaining white and the inside changing toward black), a sudden and instantaneous black diffusion (a sort of night crash) is seen. Both the light explosion and the night crash effects have an exponential course followed by an immediate drop. Psychophysical data show that both effects depend on an interaction between the lightness of the background, the lightness of the square gap, and the transformation rate of the gray scale gradient.