Feature-invariant processing of spatial segregation based on temporal asynchrony.

Temporal asynchrony is a cue for the perceptual segregation of spatial regions. Past research found attribute invariance of this phenomenon such that asynchrony induces perceptual segmentation regardless of the changing attribute type, and it does so even when asynchrony occurs between different attributes. To test the generality of this finding and obtain insights into the underlying computational mechanism, we compared the segmentation performance for changes in luminance, color, motion direction, and their combinations.

Generalized Gaussian signal detection theory: A unified signal detection framework for confidence data analysis.

Human decision behavior entails a graded awareness of its certainty, known as a feeling of confidence. Until now, considerable interest has been paid to behavioral and computational dissociations of decision and confidence, which has raised an urgent need for measurement frameworks that can quantify the efficiency of confidence rating relative to decision accuracy (metacognitive efficiency). As a unique addition to such frameworks, we have developed a new signal detection theory paradigm utilizing the generalized Gaussian distribution (GGSDT).

Psychophysical measurement of perceived motion flow of naturalistic scenes.

The neural and computational mechanisms underlying visual motion perception have been extensively investigated over several decades, but little attempt has been made to measure and analyze, how human observers perceive the map of motion vectors, or optical flow, in complex naturalistic scenes. Here, we developed a psychophysical method to assess human-perceived motion flows using local vector matching and a flash probe. The estimated perceived flow for naturalistic movies agreed with the physically correct flow (ground truth) at many points, but also showed consistent deviations from the ground truth (flow illusions) at other points.

Coarse-to-fine interaction on perceived depth in compound grating.

To encode binocular disparity, the visual system uses a pair of left eye and right eye bandpass filters with either a position or a phase offset between them. Such pairs are considered to exit at multiple scales to encode a wide range of disparity. However, local disparity measurements by bandpass mechanisms can be ambiguous, particularly when the actual disparity is larger than a half-cycle of the preferred spatial frequency of the filter, which often occurs in fine scales.

Does training with blurred images bring convolutional neural networks closer to humans with respect to robust object recognition and internal representations?

It has been suggested that perceiving blurry images in addition to sharp images contributes to the development of robust human visual processing. To computationally investigate the effect of exposure to blurry images, we trained convolutional neural networks (CNNs) on ImageNet object recognition with a variety of combinations of sharp and blurred images. In agreement with recent reports, mixed training on blurred and sharp images (B+S training) brings CNNs closer to humans with respect to robust object recognition against a change in image blur.

On the assumptions behind metacognitive measurements: Implications for theory and practice.

Theories of visual confidence have largely been grounded in the gaussian signal detection framework. This framework is so dominant that idiosyncratic consequences from this distributional assumption have remained unappreciated. This article reports systematic comparisons of the gaussian signal detection framework to its logistic counterpart in the measurement of metacognitive accuracy.

Visual discrimination of optical material properties: A large-scale study.

Complex visual processing involved in perceiving the object materials can be better elucidated by taking a variety of research approaches. Sharing stimulus and response data is an effective strategy to make the results of different studies directly comparable and can assist researchers with different backgrounds to jump into the field. Here, we constructed a database containing several sets of material images annotated with visual discrimination performance.

An Android for Emotional Interaction: Spatiotemporal Validation of Its Facial Expressions.

Android robots capable of emotional interactions with humans have considerable potential for application to research. While several studies developed androids that can exhibit human-like emotional facial expressions, few have empirically validated androids' facial expressions. To investigate this issue, we developed an android head called Nikola based on human psychology and conducted three studies to test the validity of its facial expressions.

The roles of lower- and higher-order surface statistics in tactile texture perception.

Humans can haptically discriminate surface textures when there is a significant difference in the statistics of the surface profile. Previous studies on tactile texture discrimination have emphasized the perceptual effects of lower-order statistical features such as carving depth, inter-ridge distance, and anisotropy, which can be characterized by local amplitude spectra or spatial-frequency/orientation subband histograms. However, the real-world surfaces we encounter in everyday life also differ in the higher-order statistics, such as statistics about correlations of nearby spatial-frequencies/orientations.

Motion Direction Discrimination with Tactile Random-Dot Kinematograms.

Motion detection is a fundamental sensory function for multiple modalities, including touch, but the mechanisms underlying tactile motion detection are not well understood. While previous findings supported the existence of high-level feature tracking, it remains unclear whether there also exist low-level motion sensing that directly detects a local spatio-temporal correlation in the skin-stimulation pattern. To elucidate this mechanism, we presented, on braille displays, tactile random-dot kinematograms, similar to those widely used in visual motion research, which enables us to independently manipulate feature trackability and various parameters of local motion.

Describing the Sensation of the 'Velvet Hand Illusion' in Terms of Common Materials.

When sandwiching two moving parallel metallic wires between both hands, one often experiences an unexpected tactile sensation known as the "velvet hand illusion" (VHI). Researchers have revealed the optimal conditions for inducing VHI, while the subjective nature of VHI remains obscure. In this article, we conducted a psychophysical experiment to investigate the quality and magnitude of the illusory sensation felt during VHI.

Visual perception of liquids: Insights from deep neural networks.

Visually inferring material properties is crucial for many tasks, yet poses significant computational challenges for biological vision. Liquids and gels are particularly challenging due to their extreme variability and complex behaviour. We reasoned that measuring and modelling viscosity perception is a useful case study for identifying general principles of complex visual inferences.

Direction of Apparent Motion During Smooth Pursuit Is Determined Using a Mixture of Retinal and Objective Proximities.

Many studies have investigated various effects of smooth pursuit on visual motion processing, especially the effects related to the additional retinal shifts produced by eye movement. In this article, we show that the perception of apparent motion during smooth pursuit is determined by the interelement proximity in retinal coordinates and also by the proximity in objective world coordinates. In Experiment 1, we investigated the perceived direction of the two-frame apparent motion of a square-wave grating with various displacement sizes under fixation and pursuit viewing conditions.

Perceptually Based Adaptive Motion Retargeting to Animate Real Objects by Light Projection.

A recently developed light projection technique can add dynamic impressions to static real objects without changing their original visual attributes such as surface colors and textures. It produces illusory motion impressions in the projection target by projecting gray-scale motion-inducer patterns that selectively drive the motion detectors in the human visual system. Since a compelling illusory motion can be produced by an inducer pattern weaker than necessary to perfectly reproduce the shift of the original pattern on an object's surface, the technique works well under bright environmental light conditions.

Deformation-induced transparency resolves color scission.

Dynamic image deformation produces the perception of a transparent material that appears to deform the background image by light refraction. Since past studies on this phenomenon have mainly used subjective judgment about the presence of a transparent layer, it remains unsolved whether this is a real perceptual transparency effect in the sense that it forms surface representations, as do conventional transparency effects. Visual computation for color and luminance transparency, induced mainly by surface-contour information, can be decomposed into two components: surface formation to determine foreground and background layers, and scission to assign color and luminance to each layer.

Motion Perception: From Detection to Interpretation.

Visual motion processing can be conceptually divided into two levels. In the lower level, local motion signals are detected by spatiotemporal-frequency-selective sensors and then integrated into a motion vector flow. Although the model based on V1-MT physiology provides a good computational framework for this level of processing, it needs to be updated to fully explain psychophysical findings about motion perception, including complex motion signal interactions in the spatiotemporal-frequency and space domains.

Estimating Tactile Perception by Observing Explorative Hand Motion of Others.

When we acquire tactile information about an object's surface, we actively move our hands. Past studies have shown a correlation between participants' (i.e.

Material and shape perception based on two types of intensity gradient information.

Visual estimation of the material and shape of an object from a single image includes a hard ill-posed computational problem. However, in our daily life we feel we can estimate both reasonably well. The neural computation underlying this ability remains poorly understood.

Human tactile detection of within- and inter-finger spatiotemporal phase shifts of low-frequency vibrations.

When we touch an object, the skin copies its surface shape/texture, and this deformation pattern shifts according to the objects movement. This shift pattern directly encodes spatio-temporal "motion" information of the event, and has been detected in other modalities (e.g.

Reduction of Flicker in Four-Stroke Motion of Color Images.

When two sequential video frames extracted from a single video clip are followed by the negative of the two frames, a viewer often experiences a visual illusion whereby a scene in the frames continuously moves in a single direction (four-stroke apparent motion). To create a four-stroke apparent motion display, the image intensities of the whole of the second pair of images are reversed. However, this intensity reversal creates a strong impression of flicker that can be undesirable for comfortable viewing.

Contour junctions defined by dynamic image deformations enhance perceptual transparency.

The majority of work on the perception of transparency has focused on static images with luminance-defined contour junctions, but recent work has shown that dynamic image sequences with dynamic image deformations also provide information about transparency. The present study demonstrates that when part of a static image is dynamically deformed, contour junctions at which deforming and nondeforming contours are connected facilitate the deformation-based perception of a transparent layer. We found that the impression of a transparent layer was stronger when a dynamically deforming area was adjacent to static nondeforming areas than when presented alone.

Grouping by feature of cross-modal flankers in temporal ventriloquism.

Signals in one sensory modality can influence perception of another, for example the bias of visual timing by audition: temporal ventriloquism. Strong accounts of temporal ventriloquism hold that the sensory representation of visual signal timing changes to that of the nearby sound. Alternatively, underlying sensory representations do not change.

A new analytical method for characterizing nonlinear visual processes with stimuli of arbitrary distribution: Theory and applications.

Characterization of the functional relationship between sensory inputs and neuronal or observers' perceptual responses is one of the fundamental goals of systems neuroscience and psychophysics. Conventional methods, such as reverse correlation and spike-triggered data analyses are limited in their ability to resolve complex and inherently nonlinear neuronal/perceptual processes because these methods require input stimuli to be Gaussian with a zero mean. Recent studies have shown that analyses based on a generalized linear model (GLM) do not require such specific input characteristics and have advantages over conventional methods.

Integration of vibrotactile frequency information beyond the mechanoreceptor channel and somatotopy.

A wide variety of tactile sensations arise from the activation of several types of mechanoreceptor-afferent channels scattered all over the body, and their projections create a somatotopic map in the somatosensory cortex. Recent findings challenge the traditional view that tactile signals from different mechanoreceptor-channels/locations are independently processed in the brain, though the contribution of signal integration to perception remains obscure. Here we show that vibrotactile frequency perception is functionally enriched by signal integration across different mechanoreceptor channels and separate skin locations.

Visual wetness perception based on image color statistics.

Color vision provides humans and animals with the abilities to discriminate colors based on the wavelength composition of light and to determine the location and identity of objects of interest in cluttered scenes (e.g., ripe fruit among foliage).