Invisibility concentrator based on van der Waals semiconductor α-MoO3

By combining transformation optics and van der Waals layered materials, an invisibility concentrator with a thin layer of α-MoO3 wrapping around a cylinder is proposed. It inherits the effects of invisibility and energy concentration at Fabry–Pérot resonance frequencies, with tiny scattering. Due to the natural in-plane hyperbolicity in α-MoO3, the challenges of experimental complexity and infinite dielectric constant can be resolved perfectly. Through analytical calculation and numerical simulations, the relevant functionalities including invisibility, energy concentration and illusion effect of the designed device are confirmed, which provides guidelines for the subsequent experimental verification in future.

Processing of the Mandarin polarity item renhe ‘any’

The Mandarin renhe is similar to the English any in terms of polarity sensitivity (Wang 1993; Wang & Hsieh 1996; Kuo 2003; Cheng & Giannakidou 2013; Shyu 2016). However, the following phenomena regarding any in relative clause environments have not been surveyed with respect to renhe: (a) the NPI illusion effect reported in studies like Parker & Phillips (2011; 2016); (b) the subtrigging effect discussed in LeGrand (1975) and Dayal (1998; 2004). We conducted two untimed, offline acceptability judgment experiments and the results suggest that: (i) NPI illusion does not appear in Mandarin in untimed offline processing, (ii) the subtrigging effect of renhe holds, and (iii) renhe can be licensed by certain types of declarative verbs like tongyi ‘agree’ and zancheng ‘approve’. The results confirm the strict structural requirement of the c-commanding relation between a negation licensor and renhe (Wang 1993) and the licensing of renhe in non-veridical contexts (Cheng & Giannakidou 2013), and further suggest additional licensing environments for renhe: relative clauses and declarative verbs. This requires reconsideration of positing non-veridicality as a necessary licensing condition for renhe and calls for future research on how renhe is licensed under these two licensing environments.

Illusory size perception with stimuli from animal experiments of surround modulation

Visual illusions have long been studied because the illusory effect they induce is believed to tell us something important on how the visual system processes visual information. Here, we modified a classic visual illusion, the Delboeuf illusion, so that it resembled a type of stimulus commonly used in experiments investigating surround modulation. We then performed a small set of psychophysical experiments in order to determine if the classical Delboeuf illusion effect, i.e. a change in the perceived size of an object, could be observed in these altered stimuli. In four conditions, we created stimuli that either had a high or low frequency surround in addition to being presented with a proximal thin surround or a distal thick surround. We found a significant difference in perceived object size for all four conditions compared to control indicating the presence of an illusion, and we discuss these findings in relation to existing literature from electrophysiological animal studies.

The effect of the Müller–Lyer configuration on saccadic eye movements is not fully due to illusory perception

The Müller–Lyer illusion affects both perception and oculomotor control, but it is unknown whether these effects arise from the same or different underlying mechanisms. We developed a modified version of the Müller–Lyer configuration, which largely reduced the perceptual illusion effect compared with the typical configuration but reduced the saccadic effect to a much less extent. Such difference indicates that influence of the Müller–Lyer configuration on saccadic eye movements is not fully mediated by illusory perception.

Learning to see the Ebbinghaus illusion in the periphery reveals a top-down stabilization of size perception across the visual field

Our conscious visual perception relies on predictive signals, notably in the periphery where sensory uncertainty is high. We investigated how such signals could support perceptual stability of objects’ size across the visual field. When attended carefully, the same object appears slightly smaller in the periphery compared to the fovea. Could this perceptual difference be encoded as a strong prior to predict the peripheral perceived size relative to the fovea? Recent studies emphasized the role of foveal information in defining peripheral size percepts. However, they could not disentangle bottom-up from top-down mechanisms. Here, we revealed a pure top-down contribution to the perceptual size difference between periphery and fovea. First, we discovered a novel Ebbinghaus illusion effect, inducing a typical reduction of foveal perceived size, but a reversed increase effect in the periphery. The size percept was similar at both retinal locations and deviated from the classic perceptual difference. Then through an updating process of successive peripheral-foveal viewing, the unusual peripheral perceived size decreased. The classic perceptual eccentricity difference was restored and the peripheral illusion effect changed into a fovea-like reduction. Therefore, we report the existence of a prior that actively shapes peripheral size perception and stabilizes it relative to the fovea.

Ventriloquist Illusion Produced With Virtual Acoustic Spatial Cues and Asynchronous Audiovisual Stimuli in Both Young and Older Individuals

Ventriloquist illusion, the change in perceived location of an auditory stimulus when a synchronously presented but spatially discordant visual stimulus is added, has been previously shown in young healthy populations to be a robust paradigm that mainly relies on automatic processes. Here, we propose ventriloquist illusion as a potential simple test to assess audiovisual (AV) integration in young and older individuals. We used a modified version of the illusion paradigm that was adaptive, nearly bias-free, relied on binaural stimulus representation using generic head-related transfer functions (HRTFs) instead of multiple loudspeakers, and tested with synchronous and asynchronous presentation of AV stimuli (both tone and speech). The minimum audible angle (MAA), the smallest perceptible difference in angle between two sound sources, was compared with or without the visual stimuli in young and older adults with no or minimal sensory deficits. The illusion effect, measured by means of MAAs implemented with HRTFs, was observed with both synchronous and asynchronous visual stimulus, but only with tone and not speech stimulus. The patterns were similar between young and older individuals, indicating the versatility of the modified ventriloquist illusion paradigm.