Tadamasa Sawada

The Ames room illusion is one of the best-known geometrical illusions but its geometrical properties are often misunderstood. This study discusses the differences in the geometrical properties between the original Ames room and what have been often referred to as “Ames rooms” in recent studies.

The evidence for the use of Augmented Reality (AR) in treating specific phobias has been growing. However, issues of accessibility persist, especially in developing countries. The current study examined a novel, but relatively simple therapist guided smartphone-based AR Exposure Treatment (ARET) of spider phobia. Participants who reported symptoms...

Rectangularity and perpendicularity of contours are important properties of 3D shape for thevisual system and the visual system can use them as a priori constraints for perceiving shape veridically.The present article provides a comprehensive review of prior studies of the perception of rectangularityand perpendicularity and it discusses their effe...

Detecting 3D symmetry is important for the human visual system because many objects in our everyday life are 3D symmetrical. Many are 3D mirror-symmetrical and others are 3D rotational-symmetrical. But note that their retinal images are 2D symmetrical only in degenerate views. It has been suggested that a human observer can detect 3D mirror-symmetr...

Yu, Todd, and Petrov (2021, Journal of Vision) and their follow-up study (Yu, Petrov, & Todd, 2021, i-Perception) aimed at evaluating the role of three-dimensional (3D) symmetry in binocular shape perception by comparing their experimental data to predictions they derived from our computational models. We point out in this note that their predictio...

The visual system can recover 3D information from many different types of visual information, e.g., contour-drawings. How well can people navigate in a real dynamic environment with contour-drawings? This question was addressed by developing an AR-device that could show a contour-drawing of a real scene in an immersive manner and by conducting an o...

People can perceive 3D information from contour drawings and some types of configurations of contours in such drawings are important for 3D perception. We know that our visual system is sensitive to these configurations. Koshmanova & Sawada (2019, Vision Research, 154, 97–104) showed that the sensitivity is higher to a parallel configuration of con...

Human beings can perceive depth by using binocular disparity, namely the difference between a stereo-pair of retinal images. It is commonly believed that the visual system requires oculomotor information about the relative orientation between the two eyes to perceive depth on the basis of binocular disparity. Such oculomotor information can be obta...

Data obtained in empirical Psychological studies are almost always analyzed with statistical tests. Many of these statistical tests assume that the distribution of the data is normally distributed. In Psychology, it is often assumed that this property is satisfied because of the Central-limit Theorem. This theorem says that variables always take th...

Understanding the visual stimulus in a psychophysical experiment, theoretically, is critical for controlling the experiment, for interpreting the empirical results of the experiment, and for discussing the mechanisms the visual system used to get these results. This fact encourages visual scientists to use “simple” visual stimuli in their experimen...

Artists can represent a 3D object by using only contours in a 2D drawing. Prior studies have shown that people can use such drawings to perceive 3D shapes reliably, but it is not clear how useful this kind of contour information actually is in a real dynamical scene in which people interact with objects. To address this issue, we developed an Augme...

An object is 3D centro-symmetrical if the object can be segmented into two halves and the relationship between them can be represented by a combination of reflection about a plane and a rotation through 180° about an axis that is normal to the plane. A 2D orthographic image of the 3D centro-symmetrical object is always 2D rotation-symmetrical. Note...

Artists can represent a 3D object by using only contours in a 2D drawing. Prior studies have shown that people can use such drawings to perceive 3D shapes reliably, but it is not clear how useful this kind of contour information actually is in a real dynamical scene in which people interact with objects. To address this issue, we developed an Augme...

Bishop Berkeley suggested that the distance of an object can be estimated if the object’s size is familiar to the observer. It has been suggested that humans can perceive the distance of the object by using such “familiarity” information, but most or many of the prior experiments that found an effect of familiarity were not designed to minimize or...

The autostereogram (ASG) was discovered in the 1840s and again in the 1960s. It is acknowledged that Pete Stephens rediscovered the ASG serendipitously when he constructed an image with a repetitive pattern manually in the late 1960s. But, the principle and application of the ASG were described by Lev Mogilev from Irkutsk State University earlier i...

Bishop Berkeley suggested that the distance of an object can be estimated if the object’s size is familiar to the observer. The distance can be computed by comparing the size of the retinal image of the object to the memorized size of the object. It has been suggested that humans can perceive the distance of the object by using such “familiarity” i...

A 3D shape of an object is N-fold rotational-symmetric if the shape is invariant for 360/N degree rotations about an axis. Human observers are sensitive to the 2D rotational-symmetry of a retinal image, but they are less sensitive than they are to 2D mirror-symmetry, which involves invariance to reflection across an axis. Note that perception of th...

The perception of a pair of contours in a retinal image cannot be understood simply by adding up the perceptions of the individual contours, especially when they form a perpendicular junction, or are parallel to one another. It is the relationship among the contours that determines what is perceived. Note that it is hard to actually compare the per...

The human visual system uses priors to convert an ill-posed inverse problem of 3D shape recovery into a well-posed one. In previous studies, we have demonstrated the use of priors like symmetry, compactness and minimal surface in the perception of 3D symmetric shapes. We also showed that binocular perception of symmetric shapes can be well modeled...

The physiological responses of simple and complex cells in the primary visual cortex (V1) have been studied extensively and modeled at different levels. At the functional level, the divisive normalization model (DNM, Heeger, 1992) has accounted for a wide range of single-cell recordings in terms of a combination of linear filtering, nonlinear recti...

The physiological responses of simple and complex cells in the primary visual cortex (V1) have been studied extensively and modeled at different levels. At the functional level, the divisive normalization model (DNM, Heeger, 1992) has accounted for a wide range of single-cell recordings in terms of a combination of linear filtering, nonlinear recti...

This study, which was influenced a lot by Gestalt ideas, extends our prior work on the role of a priori constraints in the veridical perception of 3D shapes to the perception of 3D scenes. Our experiments tested how human subjects perceive the layout of a naturally-illuminated indoor scene that contains common symmetrical 3D objects standing on a h...

A 3D shape is N-fold rotational-symmetric if the shape is invariant for 360/N degree rotations about an axis. Mach pointed out that human observers are sensitive to rotational-symmetry in a 2D image, but less sensitive than to mirror-symmetry, which involves invariance to reflection across an axis. We have previously shown that observers are also s...

In this paper, we take up the long-standing problem of how to recover 3-D shapes represented by a 2-D image, such as the image on the retina of the eye, or in a video camera. Our approach is biologically grounded in a theory of how the human visual system solves this problem, focusing on shapes that are mirror symmetrical in 3-D. A 3-D mirror-symme...

The response properties of neurons in V1 have been explored in many empirical studies and modeled in quantitative detail. However, the data are scattered across dozens of articles and the models employ idiosyncratic parameterization schemes tailored to fit specific data sets. Here we consolidate the fragmented results of the prior studies in terms...

A system processes 2D images of 2D or 3D objects, creating a model of the object that is consistent with the image and as veridical as the perception of the 2D image by humans. Vertices of the object that are hidden in the image are recovered by using planarity and symmetry constraints. The 3D shape is recovered by maximizing 3D compactness of the...

Three-dimensional (3D) shape has been studied for centuries despite the absence of a commonly accepted definition of this property. The absence of a useful definition has been a major obstacle in making progress towards understanding the mechanisms that are responsible for the perception of shape. Today, in the absence of the needed new definition,...

Conventionally, Figure-Ground Organization (FGO) has been studied by asking the subject to decide whether a 2D region in a picture looks more like a figure or ground. The main assumption behind these studies was that, from a computational point of view, FGO is a 2D operation. Two years ago we reported that performance in a FGO task was somewhat hig...

This tutorial has two purposes: (i) it provides an example of a computational model that emulates what human beings see in natural environments, and (ii) it explains why, as well as how, each computation can be done.

Symmetry has been shown to be a very effective a priori constraint in solving a 3D shape recovery problem. Symmetry is useful in 3D recovery because it is a form of redundancy. There are, however, some fundamental limits to the effectiveness of symmetry. Specifically, given two arbitrary curves in a single 2D image, one can always find a 3D mirror-...

Background / Purpose: We have shown that the shape of a 3D object can be accurately recovered from a single 2D orthographic or perspective image. The key to a successful recovery is the operation of prior constraints: 3D symmetry, 3D compactness, and planarity of contours. Once the entire 3D shapes in the scene are recovered, it is possible to re...

In our previous studies, we showed that monocular perception of 3D shapes is based on a priori constraints, such as 3D symmetry and 3D compactness. The present study addresses the nature of perceptual mechanisms underlying binocular perception of 3D shapes. First, we demonstrate that binocular performance is systematically better than monocular per...

Traditionally, the perception of three-dimensional (3D) scenes and objects was assumed to be the result of the reconstruction of 3D surfaces from available depth cues, such as binocular disparity, motion parallax, texture, and shading (Marr, 1982). In this approach, the role of figure-ground organization was kept to a minimum. Figure-ground organiz...

A "transfer-across-depth-cues" method was used to explore the development of the ability to generate and use spatial representations of an object as specified by static pictorial depth cues. Infants were habituated to an object with depth specified by one cue and then presented with the same shape with depth specified by a different cue. Only if an...

We explored the development of infants' ability to perceive the 3-D shape of an object from pictorial depth cues, using a “transfer-across-depth-cues” method. Our participants were habituated to a 3-D shape, specified by one cue, and then presented with the same shape and a novel-shape, both specified by a different depth cue. Under these circumsta...

Many objects in our environment are symmetrical and volumetric. These two constraints are extremely effective in 3D shape recovery (Sawada, 2009). In contrast, the spaces between objects, representing the background, are almost never symmetrical and volumetric. Prior studies of figure-ground organization showed that symmetrical regions are perceive...

The percept of the shape of a 3D object produced by a single 2D image is veridical enough to recognize the object from a different viewpoint (i.e. to achieve shape constancy). Recovering and recognizing 3D shapes are very important tasks for the human visual system. Recovering a 3D shape from a single 2D image is formally an ill-posed problem: infi...

This study tested perception of symmetry of 3D shapes from single 2D images. In Experiment 1, performance in discrimination between symmetric and asymmetric 3D shapes from single 2D line drawings was tested. In Experiment 2, performance in discrimination between different degrees of asymmetry of 3D shapes from single 2D line drawings was tested. Th...

This paper reviews recent progress towards understanding 3D shape perception made possible by appreciating the significant role that veridicality and complexity play in the natural visual environment. The ability to see objects as they really are "out there" is derived from the complexity inherent in the 3D object's shape. The importance of both ve...

The purpose of this study was to explore the infants' ability to perceive 3D shape from pictorial depth cues. While several previous studies showed that infants discriminate between displays which differ in pictorial information for depth and can use this information to direct reaching, it is not clear that infants form a common representation of a...

We present a new computational model for verifying whether a 3D shape is mirror-symmetric based on its single 2D image. First, a psychophysical experiment which tested human performance in detection of 3D symmetry is described. These psychophysical results led to the formulation of a new algorithm for symmetry detection. The algorithm first recover...

This study examined the ability of human observers to discriminate between symmetric and asymmetric planar figures from perspective and orthographic images. The first experiment showed that the discrimination is reliable in the case of polygons, but not dotted patterns. The second experiment showed that the discrimination is facilitated when the pr...

Retinal image of a symmetric object is itself symmetric only for a small set of viewing directions. Interestingly, human subjects have little difficulty in determining whether a given retinal image was produced by a symmetric object, regardless of the viewing direction. We tested perception of planar (2D) symmetric figures (dotted patterns and poly...

Humans can perceive three-dimensional shapes from shading, but reconstructing the original shape of an object from shading alone (luminance distribution) is mathematically impossible. Researchers have used different assumptions and reported that the human visual systems can resolve this difficulty. Here, we propose an assumption for perceiving shap...

INTRODUCTION: Although reconstructing shape from shading is an ill-posed problem which has multiple solutions, human visual system selects a shape from a shading easily. For example, a disk with shading definable either a spherical or saddle shape, is mostly perceived as a spherical shape. This selection is often inconsistent with the assumptions f...

To perceive shape from shading correctly, information about, the direction of illumination is needed. We investigated how the direction from visual information affects perceiving shape from shading and how we estimate the direction of illumination using both visual information and the Light-from-above assumption. The results showed that the informa...