Anorthoscopic Perception Research Articles

Aging and temporal integration in the visual perception of object shape

It has been known for more than 160 years that highly occluded objects that would normally be visually unrecognizable can be successfully identified when they move. This anorthoscopic perception relies on the visual system’s ability to integrate information over time to complete the perception of an entire object’s shape. In this experiment, 16 younger and older adults (mean ages were 20.5 and 74.6 years, respectively) were familiarized with the (unoccluded) shapes of five naturally-shaped objects (bell peppers, Capsicum annuum) until they could be easily identified (i.e., with accuracies of at least 90 percent correct). All observers then viewed the stimulus objects anorthoscopically as they moved behind narrow slits; only small object fragments could be seen at any given time, because the objects were almost totally occluded from view. Even though the object identification performance for all observers was equivalent when whole object shapes were visible, a large age-related deficit in object identification emerged during anorthoscopic viewing such that the younger adults’ identification performance was 45.4 percent higher than that of the older adults. This first ever study of aging and anorthoscopic perception demonstrates that there is an age-related deficit in performing the temporal integration needed for successful object recognition.

Neurodynamical model for IT responses during the anorthoscopic perception of bodies

Neurodynamical model for IT responses during the anorthoscopic perception of bodies

On the Spatiotemporal Nature of Vision, as Revealed by Covered Bridges and Puddles: A Dispatch from Vermont.

Retinal painting, anorthoscopic perception and amodal completion are terms to describe visual phenomena that highlight the spatiotemporal integrative mechanisms that underlie primate vision. Although commonly studied using simplified lab-friendly stimuli presented on a computer screen, this is a report of observations made in a novel real-world context that highlight the rich contributions the mechanisms underlying these phenomena make to naturalistic vision.

The role of low spatial frequencies in facial emotion processing: A study on anorthoscopic perception

ABSTRACT We examined the interaction among emotions, spatial frequencies (SF) and holistic analysis using an anorthoscopic paradigm, which is supposed to alter the holistic processing. Emotional and neutral faces were presented sliding behind a narrow aperture (anorthoscopy), or statically in the centre of the screen (whole-face presentation) as broadband images (Experiment 1), filtered at low-SF (Experiment 2), and “hybrids” (emotional low-SF superimposed to neutral high-SF of the same face; Experiment 3). Participants were required to evaluate how “friendly” each stimulus appeared (an indirect measure of emotion processing). These manipulations were aimed at investigating holistic accounts of emotional faces. Friendliness judgments decreased when low-SF and hybrid faces were presented anorthoscopically, possibly due to the impoverished presentation, in which a part-based analysis prevails on a global-based analysis. Although anorthoscopy does not prevent emotion processing, it alters holistic processing of emotional stimuli, confirming the complex interaction among emotions, SF and stimulus presentation.

Moving a Shape behind a Slit: Partial Shape Representations in Inferior Temporal Cortex.

Current models of object recognition are based on spatial representations build from object features that are simultaneously present in the retinal image. However, one can recognize an object when it moves behind a static occlude, and only a small fragment of its shape is visible through a slit at a given moment in time. Such anorthoscopic perception requires spatiotemporal integration of the successively presented shape parts during slit-viewing. Human fMRI studies suggested that ventral visual stream areas represent whole shapes formed through temporal integration during anorthoscopic perception. To examine the time course of shape-selective responses during slit-viewing, we recorded the responses of single inferior temporal (IT) neurons of rhesus monkeys to moving shapes that were only partially visible through a static narrow slit. The IT neurons signaled shape identity by their response when that was cumulated across the duration of the shape presentation. Their shape preference during slit-viewing equaled that for static, whole-shape presentations. However, when analyzing their responses at a finer time scale, we showed that the IT neurons responded to particular shape fragments that were revealed by the slit. We found no evidence for temporal integration of slit-views that result in a whole-shape representation, even when the monkey was matching slit-views of a shape to static whole-shape presentations. These data suggest that, although the temporally integrated response of macaque IT neurons can signal shape identity in slit-viewing conditions, the spatiotemporal integration needed for the formation of a whole-shape percept occurs in other areas, perhaps downstream to IT.SIGNIFICANCE STATEMENT One recognizes an object when it moves behind a static occluder and only a small fragment of its shape is visible through a static slit at a given moment in time. Such anorthoscopic perception requires spatiotemporal integration of the successively presented partial shape parts. Human fMRI studies suggested that ventral visual stream areas represent shapes formed through temporal integration. We recorded the responses of inferior temporal (IT) cortical neurons of macaques during slit-viewing conditions. Although the temporally summated response of macaque IT neurons could signal shape identity under slit-viewing conditions, we found no evidence for a whole-shape representation using analyses at a finer time scale. Thus, the spatiotemporal integration needed for anorthoscopic perception does not occur within IT.

Assessing the presence of face biases by means of anorthoscopic perception

Anorthoscopy is a presentation mode in which an image is shown sliding behind a slit-shaped aperture, so that it is visible only part by part and never in its entirety. With the aims to assess (1) whether the processing of complex stimuli (faces) correctly occurs in anorthoscopy, and (2) whether the Own-Gender Bias (OGB: the better recognition of stimuli belonging to the same gender of the observer: faster and more accurate) and the Left-Face Bias (LFB: the preference to analyze the left half of the face) occur in such a part by part presentation, we presented female and male faces as whole stimuli (Experiment 1) and in anorthoscopy (Experiments 2 and 3), as well as female/male chimeric faces (Experiment 4), during a gender categorization task. Experiment 1 confirmed that participants correctly categorized the gender of faces, but the OGB was not found. In Experiments 2 and 3 we manipulated the direction (Experiment 2: upward/downward; Experiment 3: leftward/rightward), the speed (slow and fast) of the sliding faces, and the width of the aperture (small and large). Both tasks revealed that facial gender was correctly categorized in anorthoscopy. The OGB was found, but only for males/females in Experiments 2/3, respectively. In Experiment 4 the LFB emerged only in the tachistoscopic session, suggesting that this perceptual bias does not extend to anorthoscopy.

Object Representations in Human Visual Cortex Formed Through Temporal Integration of Dynamic Partial Shape Views

We typically recognize visual objects using the spatial layout of their parts, which are present simultaneously on the retina. Therefore, shape extraction is based on integration of the relevant retinal information over space. The lateral occipital complex (LOC) can represent shape faithfully in such conditions. However, integration over time is sometimes required to determine object shape. To study shape extraction through temporal integration of successive partial shape views, we presented human participants (both men and women) with artificial shapes that moved behind a narrow vertical or horizontal slit. Only a tiny fraction of the shape was visible at any instant at the same retinal location. However, observers perceived a coherent whole shape instead of a jumbled pattern. Using fMRI and multivoxel pattern analysis, we searched for brain regions that encode temporally integrated shape identity. We further required that the representation of shape should be invariant to changes in the slit orientation. We show that slit-invariant shape information is most accurate in the LOC. Importantly, the slit-invariant shape representations matched the conventional whole-shape representations assessed during full-image runs. Moreover, when the same slit-dependent shape slivers were shuffled, thereby preventing their spatiotemporal integration, slit-invariant shape information was reduced dramatically. The slit-invariant representation of the various shapes also mirrored the structure of shape perceptual space as assessed by perceptual similarity judgment tests. Therefore, the LOC is likely to mediate temporal integration of slit-dependent shape views, generating a slit-invariant whole-shape percept. These findings provide strong evidence for a global encoding of shape in the LOC regardless of integration processes required to generate the shape percept.SIGNIFICANCE STATEMENT Visual objects are recognized through spatial integration of features available simultaneously on the retina. The lateral occipital complex (LOC) represents shape faithfully in such conditions even if the object is partially occluded. However, shape must sometimes be reconstructed over both space and time. Such is the case in anorthoscopic perception, when an object is moving behind a narrow slit. In this scenario, spatial information is limited at any moment so the whole-shape percept can only be inferred by integration of successive shape views over time. We find that LOC carries shape-specific information recovered using such temporal integration processes. The shape representation is invariant to slit orientation and is similar to that evoked by a fully viewed image. Existing models of object recognition lack such capabilities.

Representational momentum and anisotropies in nearby visual space.

The possibility of anisotropies in visual space in and near the final location of a moving target was examined. Experiments 1 and 2 presented a moving target, and after the target vanished, participants indicated the final location of the leading or trailing edge of the target. Memory for both edges was displaced forward from the actual final locations, and the magnitude of displacement was smaller for the leading edge. Experiments 3 and 4 also presented stationary objects in front of and behind the final location of the target, and participants indicated the location of the nearest or farthest edge of one of the stationary objects. Memory for the near or far edge of an object in front of the target was displaced backward, and memory for the near or far edge of an object behind the target was displaced forward; the magnitude of displacement was larger for objects in front of the target and when the edge was farther away. The findings (a) suggest representational momentum is associated with an anisotropy of visual space that extends across and outward from the moving target and (b) are consistent with previous findings regarding estimation of time-to-contact, anorthoscopic perception, and memory psychophysics.

The maintenance and updating of representations of no longer visible objects and their parts.

When an object partially or completely disappears behind an occluding surface, a representation of that object persists. For example, fragments of no longer visible objects can serve as an input into mid-level constructive visual processes, interacting and integrating with currently visible portions to form perceptual units and global motion signals. Remarkably, these persistent representations need not be static and can have their positions and orientations updated postdictively as new information becomes visible. In this chapter, we highlight historical considerations, behavioral evidence, and neural correlates of this type of representational updating of no longer visible information at three distinct levels of visual processing. At the lowest level, we discuss spatiotemporal boundary formation in which visual transients can be integrated over space and time to construct local illusory edges, global form, and global motion percepts. At an intermediate level, we review how the visual system updates form information seen at one moment in time and integrates it with subsequently available information to generate global shape and motion representations (e.g., spatiotemporal form integration and anorthoscopic perception). At a higher level, when an entire object completely disappears behind an occluder, the object's identity and predicted position can be maintained in the absence of visual information.

The disembodied eye: Consequences of displacing perception from action

In our research, people use actions to expose hidden targets as planar images displayed either in situ or ex situ (displaced remotely). We show that because ex situ viewing impedes relating actions to their perceptual consequences, it impairs localizing targets, including compensating for surface deformation, and directing movement toward them. Using a 3D analogue of anorthoscopic perception, we demonstrate that spatio-temporal integration of contiguous planar slices is possible when action and perception are co-located, but not when they are separated. Ex situ viewing precludes the formation of a spatial frame of reference that supports complex visualization from action.

Symposia introduction

Due to the movements of the eyes and those of the objects in the environment, natural vision is highly dynamic. An understanding of how the visual system can cope with such complex inputs requires an understanding of reference frames, used in the computations of various stimulus attributes. It is well known that the early visual system has a retinotopic organization. It is generally thought that the retinotopic organization of the early visual system is insufficient to support the fusion of visual images viewed at different eye positions. Moreover, metacontrast masking and anorthoscopic perception show that a retinotopic image is neither sufficient nor necessary for the perception of spatially extended form. How retinotopic representations are transformed into more complex non-retinotopic representations has been long-standing and often controversial question. The classical paradigm to study this question has been the study of memory across eye movements. As we shift our gaze from one fixation to another one, the retinotopic representation of the environment undergoes drastic shifts, yet phenomenally our environment appears stable. How is this phenomenal stability achieved? Does the visual system integrate information across eye movements and if so how? A variety of theories ranging from purely retinotopic representations without information integration to detailed spatiotopic representations with point-by-point information integration have been proposed. Talks in this symposium (Crawford, Melcher, Cavanagh) will address the nature of trans-saccadic memory, the role of extra-retinal signals, retinotopic, spatiotopic, and objectopic representations for information processing and integration during and across eye movements. In addition to the challenge posed by eye movements on purely retinotopic representations, recent studies suggest that, even under steady fixation, computation of moving form requires non-retinotopic representations. This is because objects in the environment often move with complex trajectories and do not stimulate sufficiently retinotopically anchored receptive fields. Moreover, occlusions can ‘blank out’ retinotopic information for a significant time period. These failures to activate sufficiently retinotopically anchored neurons, in turn, suggest that some form of non-retinotopic information analysis and integration should take place. Talks in this symposium (Nishida, Herzog) will present recent findings that show how shape and color information for moving objects can be integrated according to non-retinotopic reference frames. Taken together, the talks at the symposium aim to provide a recent perspective to the fundamental problem of reference frames utilized by the visual system and present techniques to study these representations during both eye movement and fixation periods. The recent convergence of a variety of techniques and stimulus paradigms in elucidating the roles of non-retinotopic representations provides timeliness for the proposed symposium. Since non-retinotopic representations have implications for a broad range of visual functions, we expect our symposium to be of interest to the general VSS audience including students and faculty.

(Mis)Perception of motion and form after occlusion: Anorthoscopic perception revisited

(Mis)Perception of motion and form after occlusion: Anorthoscopic perception revisited

Shape distortions and Gestalt grouping in anorthoscopic perception.

When a figure moves behind a stationary narrow slit, observers often report seeing the figure as a whole, a phenomenon called slit viewing or anorthoscopic perception. Interestingly, in slit viewing, the figure is perceived compressed along the axis of motion. As with other perceptual distortions, it is unclear whether the perceptual space in the vicinity of the slit or the representation of the figure itself undergoes compression. In a psychophysical experiment, we tested these two hypotheses. We found that the percept of a stationary bar, presented within the slit, was not distorted even when at the same time a circle underwent compression by moving through the slit. This result suggests that the compression of form results from figural rather than from space compression. In support of this hypothesis, we found that when the bar was perceptually grouped with the circle, the bar appeared compressed. Our results show that, in slit viewing, the distortion occurs at a non-retinotopic level where grouped objects are jointly represented.

Perceived speed differences explain apparent compression in slit viewing

When a figure moves behind a stationary narrow slit, observers often report seeing the figure as an integrated whole, a phenomenon known as slit viewing or anorthoscopic perception. Interestingly, in slit viewing, the figure is perceived compressed along the axis of motion, e.g., a circle is perceived as an ellipse. Underestimation of the speed of the moving object was offered as an explanation for this apparent compression. We measured perceived speed and compression in anorthoscopic perception and found results that are inconsistent with this hypothesis. We found evidence for an alternative hypothesis according to which apparent compression results from perceived speed differences between different parts of the figure, viz., the trailing parts are perceived to move faster than the leading parts. These differences in the perceived speeds of the trailing and the leading edges may be due to differences in the visibilities of the leading and trailing parts. We discuss our findings within a non-retinotopic framework of form analysis for moving objects.

An Examination of An Anorthoscopic Perception Focused on A Delay and A Generation Rate of Smooth Pursuit Eye Movement

In the observation through the slit, we can observe only the part of the object in some moments. However, we can perceive the whole image, when the object moves behind the slit. Then, it is perceived to be shorter than the length of actual object. This causes “Anorthoscopic perception.” This phenomenon indicates the mechanism for perceiving the whole image which temporarily stores the fragments of the image. The mechanism is not yet investigated in detail. In this paper, we propose the technique in which we quantitatively measure the shortening effect using multiple slits. We carried out the psychology experiment using this technique. Then, we obtained the result which indicated the possibility with the relation between the effect and eye movements. So, we measured the eye movements in observing through slits for verification of this possibility by the EOG-method. We are focuced on the delay and generation rate of smooth pursuit eye movement.As a considering this factor, we predicted the shortening rate. The predicted curve was matched experimental result.Finally, it was indicated that the delay and generation rate of smooth pursuit eye movement played important role in the shortening effect of an anorthoscopic perception.

Classroom Demonstrations in Perception and Cognition Using Presentation Software

Presentation software, notebook computers, and projection equipment are increasingly being used to present lecture material. However, the potential advantages of such presentation over more traditional lecture methods are often underutilized. In this article, I illustrate computer-based classroom demonstrations in perception and cognition that require no computer programming and can be presented with the same standard presentation software used for lecture presentation, thus allowing the demonstrations to fit seamlessly within the lecture. The demonstrations capitalize on the advantages of multimedia lecture presentations because they are interactive and cannot be achieved with more traditional pedagogical methods. Examples include apparent motion, anorthoscopic perception, illusory conjunctions, and the capacity of early visual memory.

Generating Dynamic Projection Images for Scene Representation and Understanding

This paper explores an interesting image projection produced by scanning dynamic scenes with a slit camera. Based on the concept of Anorthoscopic Perception, we investigate how a two-dimensionalDynamic Projection Imageof three-dimensional scenes is generated from consecutive 1-D snapshots taken through a slit, when the relative motion is homogeneous between the viewer and scenes. By moving the camera in the 3-D environment or rotating an object, we can obtain various dynamic projection images. These dynamic projection images contain major spatial and temporal information about 3-D scenes in a small amount of data. Consequently, the projection is suited for the memorization, registration, and indexing of image sequences. The generated images also directly show some of the motion properties in dynamic scenes. If a relative motion between the camera and a subject is planned properly, the dynamic projection image can even provide a texture image of the subject along with some expected photometry characteristics. Therefore, the dynamic projection can facilitate dynamic object recognition, 3-D structure acquisition, and image compression, all for a stable motion between the objects and camera. We outline various applications in vision, robotics, and multimedia and summarize the motion types and the camera setting for generating such dynamic projection images.

What is a crucial determinant in anorthoscopic perception?

There are two important problems in anorthoscopic perception. The first is how a sequence of parts of a figure viewed through a slit is integrated into a whole. The second is how the distortion of an anorthoscopic image along the direction of its motion occurs. To answer the questions, two experiments and two demonstrations were performed by conceiving compound figures of one horizontal and one curvilinear component and a method which permits seeing anorthoscopic and ordinary images at the same time. From the results, the idea of anorthoscopic motion complementary to apparent motion is introduced as a crucial determinant that permits an integration of the parts into a perception of the whole. As regards the distortion of the percept we agree with Rock, et al.'s 1987 assumption but also consider that the distortion depends on the ratio of speed of anorthoscopic motion to real motion.

WHAT IS A CRUCIAL DETERMINANT IN ANORTHOSCOPIC PERCEPTION

There are two important problems in anorthoscopic perception. The first is how a sequence of parts of a figure viewed through a slit is integrated into a whole. The second is how the distortion of an anorthoscopic image along the direction of its motion occurs. To answer the questions, two experiments and two demonstrations were performed by conceiving compound figures of one horizontal and one curvilinear component and a method which permits seeing anorthoscopic and ordinary images at the same time. From the results, the idea of anorthoscopic motion complementary to apparent motion is introduced as a crucial determinant that permits an integration of the parts into a perception of the whole. As regards the distortion of the percept we agree with Rock, et al.'s 1987 assumption but also consider that the distortion depends on the ratio of speed of anorthoscopic motion to real motion.

Three-Dimensional Anorthoscopic Perception

When a rotating 3-D wireframe object passes behind a narrow slit, it is often perceived as a 3-D object, even though only a small portion of it is visible at any one instant. This result constitutes a new finding in connection with both anorthoscopic perception and the perception of structure-from-motion.