The present study provides evidence that simple manual reaction time (RT) can be shortened by task irrelevant Kanizsa-like illusory figures emerging as completed perceptual units in the observer's visual system. This type of behavioral effect allows to evaluate the role of a perceived figure constituted by brightness enhancement, illusory contours and depth stratification by maintaining constant retinal size and average luminance of the inducers in modulating RT. Using two different versions of the inducers, with the same retinal size and different average luminance, we found that simple RT was shortened by the presence vs absence of the figure with significant faster response in the illusory condition than no-illusory condition in the two versions of the inducers. These results confirm previous works that provide evidence on the relationship between simple RT and perceptual/phenomenal features.

In filmmaking, a neutral face paired with an emotional context can convey a congruent emotion—a phenomenon known as the Kuleshov effect. However, past research has yielded mixed findings on the existence of the Kuleshov effect, possibly due to methodological variability; we therefore implemented a boundary-test paradigm that combined normed static context images with dynamic facial stimuli separated by an explicit context-rating step to examine how visual context shapes the evaluation and categorization of faces under such conditions. We hypothesized that positive context would elevate facial valence ratings (and vice versa), while evoking different-than-neutral emotions in a neutral face when categorized. Thirty-two participants first rated the valence of a context image on a 7-point Likert scale. They then viewed a video of a neutral face, evaluated its valence on the same scale, and explicitly categorized the expression by selecting one of five predefined emotion labels (neutral, angry, happy, sad, disgusted). Analyses using linear mixed-effects models confirmed that positive contexts led to higher facial valence ratings, while negative contexts led to lower ones; by contrast, multinomial regression revealed no effect of context on emotional categorization. Our findings suggest that while visual context can bias evaluative judgments of facial expressions, it does not necessarily alter their emotional categorization under conditions where cinematic continuity is absent, highlighting the boundaries of the Kuleshov effect in line with previous studies.

Visual illusions serve as a window into the altered perceptual experiences of individuals with psychiatric disorders. One such is the induced Roelofs effect, where the perceived position of a small stimulus is shifted toward the midline of a distractor frame surrounding the stimulus, as the shift is more pronounced in individuals with schizophrenia. The present work extends the induced Roelofs effect assessment to bipolar disorder. Healthy controls, patients with bipolar disorder, and patients with schizophrenia were shown a dot stimulus placed inside a frame whose horizontal position could vary, and they were asked to determine whether the dot position was to their left or to their right. The induced Roelofs effect was minimal in healthy controls, large in schizophrenia, and intermediate in bipolar disorder. No association between the effect size and psychotic symptomatology or cognitive abilities was found. Yet, a nonlinear, concave association was found between the total pharmacological load and the illusion size. The results suggest that the illusion is related to alterations in sensory processing, which are common to both bipolar disorder and schizophrenia, hence showing their potential utility in clinical evaluations, which currently tend to overlook the sensory domain.

We report a novel visual illusion, where a 2 × 2 two-colored checkerboard square rotating against an identical background appears to morph into a circle with a size change. This illusion can be categorized as a subtype of the breathing illusion (BI) based on its phenomenological characteristics. However, it also exhibits intriguing features that may offer new insights into BI's underlying mechanisms, not fully captured by existing displays.

The principle of “common fate” tells us that objects that move together, group together. But what happens when physical paths are shared and illusory paths differ? Here, horizontally aligned targets move up and down over columns containing static, oblique gratings. If all columns share the same orientation, the target group appears to drift in that direction, as per the furrow illusion. However, when the two outer “bookend” targets have a different background orientation from the inner “book” targets, group motion is entirely captured by the bookends. This occurs despite the inner books having discriminable features and recoverable relative motion. What is missing is any sense of their opposing illusory path. We suggest that spatial proximity and common vertical motion help create a single grouped object representation. Since rigid objects tend not to move in two directions at once, the salient bookends dominate our perception of where the group is going.

This study investigates how the method used by participants to assess the beauty of pictures influences their preference for the compositional rules of symmetry, balance, and proximity. The hypothesis that production methods (actively arranging picture elements) prompt a local perspective, favoring proximity, while evaluation tasks (rating precomposed pictures) elicit a global perspective, favoring symmetry and balance, was tested in two experiments. Experiment 1 demonstrated that (positional) symmetry was preferred over balance, and balance over proximity, when participants rated precomposed pictures. Experiment 2, employing a production method with movable elements, showed a frequent use of proximity, yet also a tendency toward (positional) symmetry. The combined results indicate that assessment methods substantially impact the preferred composition rules.

There are various ways to evoke stereopsis without binocular disparities. Closing one eye, or looking through a synopter are well-known methods. Ames (1925) listed nine ways of generating this so-called ‘‘plastic effect,” one of which involves a cylindrically curved lens placed in front of one eye. We investigated qualitative perceptual effects of this particular way of viewing artworks. A total of 38 participants viewed three digitally reproduced paintings. Initially, they were asked to spontaneously report the perceptual effect of the lens. While being naive to the purpose of the experiment, 66% of the participants reported increased depth experience. In addition, participants reported increased contrast, color vibrancy, and material expression (e.g., increased shininess). During a second part of the experiment, we asked to report on seven qualities: depth, color, three-dimensional shape, realism, detail, light, and material. All qualities increased significantly except detail, which seemed to show idiosyncratic results: the majority of the observers experienced a decrease of detail, while a minority reported, surprisingly, an increase of detail. The results agree with previous qualitative accounts on monocular aperture viewing, despite relying on entirely different nonpictorial cues: monocular aperture viewing relies on the absence of vergence and binocular disparities, whereas the Ames’ Glass relies on distorted binocular disparities while keeping vergence unchanged. Together with the synopter, for which qualitative data is lacking, the Ames Glass and monocular aperture viewing are pictorial spacecrafts fit for art gallery viewing.

We discovered a new type of assimilative color induction. An achromatic target with a white background was placed in the center of a concentric chromatic gradient that caused the glare effect. The target frequently appears to be in the same hue as the gradient. We discussed lower-level factors such as lateral inhibition and spatial summation functions, and higher-level factors such as illumination estimation.

The color appearance of #TheDress image varies across individuals. The color of pixels in the image distributes mostly in blue-achromatic-yellow color direction, and so are the perceived color variations. One of the potential causes is differences in the degree of perceiving light-blue pixels as a part of white clothing under a skylight, referred to as “blue bias.” A deep neural network (DNN) application was used to simulate individual differences in blue bias, by varying the percentage of such scenes in the training-image set. A style-transfer DNN was used to simulate a “color naming” procedure by learning pairs of natural images and their color-name labels as pixel-by-pixel maps. The models trained with different ratio of blue-bias scenes were tested using the #TheDress image. The averaged results across trials showed a progressive change from blue/black to white (gray)/gold, indicating that exposure or attention to blue-bias scenes could have caused the individual differences in the color perception of #TheDress image. In an additional experiment, we manipulated the relative number of artificially blue- or yellow-tinted images, instead of varying the ratio of blue-bias scenes, to train the DNN. If the blue-bias scenes are equivalent with blue-tinted images of scenes taken under daylight, this manipulation should yield similar result. However, the resulting outputs did not produce a white/gold image at all. This suggests that exposure to skylight scenes alone is insufficient; the scenes must contain unequivocally white objects (such as snow, white clothing, or white road signs) in order to establish a “blue bias” in human observers.

In dynamic visual scenes, many materials—including cloth, jelly-like bodies, and flowing liquids—undergo non-rigid deformations that convey information about their physical state. Among such cues, we focus on deformation-based motion—defined as the spatial shifts of image deformation. Studying deformation-based motion is essential because it lies at the intersection of motion perception and material perception. This study examines how two fundamental properties—spatial frequency and displacement speed—jointly shape the perception of deformation-based motion. We focused on these parameters because, in luminance-based motion perception, spatial frequency and displacement speed have been shown to critically influence motion sensitivity. Across three experiments using sequentially deformed 1/f noise images as a neutral background, we systematically manipulated the spatial frequency components of the deformation and the speed at which these deformations were displaced. Results showed that direction discrimination performance was strongly modulated by the interaction between spatial frequency and displacement speed. Suppressing local deformation cues improved discrimination at low frequencies, suggesting that local signals may interfere with global motion inference. These findings reveal how the spatial structure and dynamics of image deformation constrain motion perception and provide insights into how the brain interprets dynamic visual information from non-rigid materials.