In this paper, an optical illusion is described in which purple elements are perceived as purple at the point of fixation, while surrounding elements of the same purple color are perceived toward a blue hue. As the viewing distance increases, a greater number of purple elements revert to a purple appearance.

We challenge the conventional notion that symmetry perception requires positional correspondence between image elements by demonstrating that symmetry can be perceived solely through spatial variations in image statistics in the absence of direct element correspondence (i.e., second-order symmetry, in contrast to the traditional "first-order symmetry" concept characterized by explicit element matching). One example of the second-order symmetry patterns is constructed by modulating random dot carriers with low-pass symmetrical envelopes. Additional instances can be generated via symmetric modulation of dot density, orientation statistics, dot-pair statistics, binocular disparity, and motion flow. These patterns elicit robust symmetry percepts despite lacking local feature correspondence, challenging current models of symmetry detection. Instead, the implication is that the visual system infers a surface structure before symmetry assessment.

This study examined how background context and athletic experience influence peripheral colour detection. Twenty-six participants - outdoor athletes, indoor athletes and non-athletes - completed a colour detection task with human figure or circle stimuli on sport-specific indoor and outdoor scenes. Outdoor athletes showed superior detection across conditions. Crucially, this advantage was not restricted to sport-specific stimuli or backgrounds, suggesting that perceptual learning in athletes generalises across contexts. This quasi-experimental study compared naturally occurring sport groups rather than assigning participants to conditions, allowing investigation of experience-related differences in peripheral processing. The findings provide evidence that perceptual expertise in sport reflects more than reaction speed, highlighting improvements in low-level perception. They also demonstrate that visual plasticity persists beyond critical developmental periods: repeated exposure to complex, unpredictable outdoor environments appears sufficient to shape perceptual abilities later in life.

Faces are critical stimuli used for many social cognitive processes, believed to be served by specialised neural processes in the visual system. A recently described face size illusion shows that upright faces are perceived as physically smaller than inverted faces, and may provide insight into the neurocognitive mechanisms underlying human face perception. In this study, we investigated whether the face size illusion is specific to whole faces or whether it occurs as well for isolated face parts. The results provided a clear replication of the face size illusion for whole faces. In striking contrast, no comparable illusion was found for isolated noses, mouths, and eyes. For eyes, there was in fact an illusion in the opposite direction. These results provide further evidence for the specificity of the face size illusion and suggest that it may arise from the holistic processing of the face as an entire unit, rather than localised processing of individual face parts.

This study investigated the role of perceptual learning in the composite face effect (CFE), which is characterized by reduced accuracy in recognizing the top half of a face when it is combined with the bottom half of another face, particularly when the composite is upright and aligned, compared to when the two halves are laterally offset (misaligned). The misalignment disrupts configural/holistic processing, affecting recognition performance. Experiment 1a (n = 96) employed prototype-defined checkerboards to investigate the presence of the composite effect. The advantage of using these stimuli is that expertise can be precisely controlled. Experiment 1b (n = 96) aimed to replicate the composite effect using face stimuli, serving as a control and enabling direct comparison of the effect between face and checkerboard stimuli. Both experiments employed a full design that included congruent and incongruent, aligned and misaligned composites to measure the composite effect. Results from Experiment 1a indicated that the composite effect could not be obtained with checkerboard composites, whereas Experiment 1b confirmed the robust presence of the CFE in face stimuli. Based on these findings, we can interpret that perceptual learning does not significantly contribute to the CFE.

The sound-induced flash illusion (SIFI) is a classic phenomenon in audiovisual integration research, reflecting the interactive mechanisms in multimodal information processing. This study aimed to recruit 30 healthy participants to explore the effects of sound and flash presentation frequencies and spatial location of stimuli on the perceptual decision-making. Previous studies have used illusion rate or accuracy as the core measurement indices, which fail to reflect the underlying cognitive processes of perceptual decision-making and thus have certain limitations. Therefore, this study aims to model the process of behavioral responses in the task. Among the perceptual decision-making models-Only the Hierarchical Drift Diffusion Model (HDDM) is suitable for the experimental task in this study. We used the drift rate, which reflects the speed of perceptual information accumulation in the model, as the core indicator. The results showed that both the sound-flash combinations and spatial location information significantly influenced evidence accumulation. Furthermore, the overall drift rate for right-side spatial presentation conditions was higher than for left-side conditions. The left-side advantage in B1F1 may reflect the right hemisphere's superiority in spatial attention, while the right-side advantage in B2F1 may reflect hemispheric differences in audiovisual integration. This study is the first to introduce HDDM in analyzing the spatial modulation mechanism within the SIFI paradigm, confirming that spatial location information not only has an independent main effect but can also interact with sensory combination factors to dynamically influence perceptual decision-making.

The colors and lines that compose perceptual experience result from the interplay between visual processing pathways and the light that hits the retina. So it is striking that many individuals seem to also experience these visual properties even in the absence of explicit sensory cues-as in the phenomenon of "scaffolded attention." When observing a uniform grid of squares, people report perceiving the squares as grouped into shapes or patterns, where the squares sometimes appear brighter or colored (for "shaders"), or bolded or outlined (for "bolders"). With 100 observers, we used an interactive grid to characterize the prevalence and magnitude of these experiences. Results showed that people's experiences could be modulated by grid contrast, that is, 89% of hallucinators reporting "bolding" on a black grid, while only 36% on a white one. Thus, stimulus factors may influence what gets selected-the squares (for shaders) or the lines (for bolders)-as the raw material for "everyday hallucinations" in scaffolded attention.

Previous research has demonstrated that words associated with brightness (e.g., "sun") elicit smaller pupil diameters than those related to darkness (e.g., "night"). The present study aimed to determine whether these language-induced pupillary responses are driven by the luminance of the mentally simulated content-referred to here as sensory interpretation-or by the conceptual brightness linked to the words' emotional valence, termed emotional interpretation. To address this question, we utilized the Japanese adjectives akarui and kurai, which can denote both luminance, as in the noun phrase akarui/kurai gamen ("bright/dark screen"), and emotional valence, as in akarui/kurai seikaku ("cheerful/gloomy personality"). Participants were presented with noun phrases composed of these adjectives and various nouns (akarui/kurai + noun). A significant main effect of the adjective indicated that phrases containing akarui yielded smaller pupil diameters than those containing kurai. Furthermore, although the interaction effect did not reach significance, the adjective effect was observed only when the adjectives conveyed luminance, not when they conveyed emotional valence. These findings suggest that sensory, rather than emotional, interpretation better explains language-induced changes in pupil size. The use of pupillometry as a measure of perceptual simulation offers more direct and compelling evidence in support of the central claim of embodied language theories: that during language comprehension, readers and listeners spontaneously generate sensorimotor simulations of the described content. Future studies are warranted to examine whether these findings extend to sentence- and discourse-level processing, as well as to simulations of information conveyed implicitly or indirectly through language.