Size Constancy Research Articles

Ensemble size judgments account for size constancy.

The natural environment is full of redundant information that the visual system compresses into an ensemble representation by averaging features of groups of items. Ensemble perception has been shown to operate with remarkable flexibility, efficiently integrating information across a variety of visual domains. In the current set of experiments, we tested whether average size representations reflect the physical size of objects displayed on a screen or perceptual transformations due to size constancy. We induced a perceptual change by presenting sets of triangles with linear perspective cues - lines converging at the horizon. Assuming a constant size, these cues cause individual objects "in the distance" to appear larger than objects without distance cues, due to size constancy heuristics. Observers viewed sets of triangles with and without linear perspective cues and judged whether a subsequently presented test triangle was larger or smaller than the average size of the preceding set. Results revealed ensemble size representations took size constancy into account, reflecting the perceived size of the triangles rather than their absolute size. Interestingly, the amount of bias exhibited was well characterized by the summed bias associated with each of the three triangles presented individually. Other pictorial cues to depth, such as occlusion and height-in-field, did not elicit the same bias when those were the only depth cues available. Overall, our results complement and extend other work showing that average size reflects the perceptual size of individual items in a set.

What’s behind the curtain? Visual priming by draped objects

Perhaps the most foundational assumption in perception research is that our experience of the world goes beyond the light reaching our eyes. This principle is familiar from visual illusions, perceptual constancies, and amodal completion — as when we perceive the continuity of an object behind an occluding surface. What is the limit to such phenomena? In particular, could we ever experience objects that are occluded completely? In fact, we frequently do: When a cloth or other fabric is draped over an object, we can often appreciate which properties the draped object might have, even when no part of the object is directly visible (Yildirim et al., 2016) — e.g., when a car is placed under a weather-protective covering, or when a child wears a bedsheet to dress up as a ghost. What is the nature of this experience? Do we only infer such hidden properties through thought and reflection? Or might we see such properties as part of automatic visual processing? Here, we investigate this latter possibility using visual priming. On each trial, one of two volumetric shapes (e.g., a cube or sphere) appeared suddenly, and subjects indicated which shape was shown. Crucially, each shape was preceded by a brief ‘cue’: A rendering of one of the shapes with a cloth draped over it. There were thus two types of trials: congruent-cued and incongruent-cued. Even though this cue was completely invalid and task-irrelevant, it facilitated subjects’ responses: They were faster to report the identity of the displayed shape when its draped cue was congruent vs. when it was incongruent. We suggest that the mind automatically represents objects even when they reflect no light whatsoever onto our eyes, such that visual processing computes the properties of completely occluded objects.

A Comparison Between the Use of Afterimages and Physical Stimuli in the Examination of Size Constancy

A Comparison Between the Use of Afterimages and Physical Stimuli in the Examination of Size Constancy

Perceptual constancy and the dimensions of perceptual experience

Perceptual constancy, often defined as the perception of stable features under changing conditions, goes hand in hand with variation in how things look. A white wall in the orange afternoon sun still looks white, though its whiteness looks different compared with the same wall in the noon sun. Historically, this variation has often been explained in terms of our experience of “merely sensory” or subjective properties – an approach at odds with the fact that the variation does track objective features of the perceptual situation, such as illumination (in the case of colour constancy). One approach, becoming more common, is to account for the variation in terms of further “dimensions” to perceptual experience. Especially in colour perception, this is a natural thought to have but the idea is often left vague. In this paper I argue that the “dimensional” strategy has problems of its own, but is useful in drawing out some interesting complications in the way perceptual experience is structured. Specifically, the structure of “constancy spaces” brings out the different ways in which there is stability and instability in the experience of constancy, without the need for novel or merely subjective features. Instability arises in a contingent structural feature of perceptual experience.

Mental geometry of three-dimensional size perception

Judging the poses, sizes, and shapes of objects accurately is necessary for organisms and machines to operate successfully in the world. Retinal images of three-dimensional objects are mapped by the rules of projective geometry and preserve the invariants of that geometry. Since Plato, it has been debated whether geometry is innate to the human brain, and Poincare and Einstein thought it worth examining whether formal geometry arises from experience with the world. We examine if humans have learned to exploit projective geometry to estimate sizes and aspects of three-dimensional shape that are related to relative lengths and aspect ratios.Numerous studies have examined size invariance as a function of physical distance, which changes scale on the retina. However, it is surprising that possible constancy or inconstancy of relative size seems not to have been investigated for object pose, which changes retinal image size differently along different axes. We show systematic underestimation of length for extents pointing toward or away from the observer, both for static objects and dynamically rotating objects. Observers do correct for projected shortening according to the optimal back-transform, obtained by inverting the projection function, but the correction is inadequate by a multiplicative factor. The clue is provided by the greater underestimation for longer objects, and the observation that they seem to be more slanted toward the observer. Adding a multiplicative factor for perceived slant in the back-transform model provides good fits to the corrections used by observers. We quantify the slant illusion with two different slant matching measurements, and use a dynamic demonstration to show that the slant illusion perceptually dominates length nonrigidity.In biological and mechanical objects, distortions of shape are manifold, and changes in aspect ratio and relative limb sizes are functionally important. Our model shows that observers try to retain invariance of these aspects of shape to three-dimensional rotation by correcting retinal image distortions due to perspective projection, but the corrections can fall short. We discuss how these results imply that humans have internalized particular aspects of projective geometry through evolution or learning, and if humans assume that images are preserving the continuity, collinearity, and convergence invariances of projective geometry, that would simply explain why illusions such as Ames’ chair appear cohesive despite being a projection of disjointed elements, and thus supplement the generic viewpoint assumption.

Grip Constancy but Not Perceptual Size Constancy Survives Lesions of Early Visual Cortex

Object constancies are central constructs in theories of visual phenomenology. A powerful example is "size constancy," in which the perceived size of an object remains stable despite changes in viewing distance [1-4]. Evidence from neuropsychology [5], neuroimaging [6-11], transcranial magnetic stimulation [12, 13], single-unit and lesion studies in monkey [14-20], and computational modeling [21] suggests that re-entrant processes involving reciprocal interactions between primary visual cortex (V1) and extrastriate visual areas [22-26] play an essential role in mediating size constancy. It is seldom appreciated, however, that object constancies must also operate for the visual guidance of goal-directed action. For example, when reaching out to pick up an object, the hand's in-flight aperture scales with size of the goal object [27-30] and is refractory to the decrease in retinal-image size with increased viewing distance [31-41] (Figure1), a phenomenon we call "grip constancy." Does grip constancy, like perceptual constancy, depend on V1 or can it be mediated by pathways that bypass it altogether? We tested these possibilities in an individual, M.C., who has bilateral lesions encompassing V1 and much of the ventral visual stream. We show that her perceptual estimates of object size co-vary with retinal-image size rather than real-world size as viewing distance varies. In contrast, M.C. shows near-normal scaling of in-flight grasp aperture to object size despite changes in viewing distance. Thus, although early visual cortex is necessary for perceptual object constancy, it is unnecessary for grip constancy, which is mediated instead by separate visual inputs to dorsal-stream visuomotor areas [42-48].

Size Inflation in Drawing From Mirror and Proportional Accuracy in Observational Drawing.

In three experiments, a bias to inflate in drawing the proportion of an image on a mirror over the mirror itself is demonstrated in a sample (N = 146) of undergraduate students taking introductory psychology classes. The inflation is not confined to the image of one's own head but is likely to occur in depictions of any object from a mirror with the mirror frame included. Having to include in the drawing background objects visible in the mirror is found to reduce the inflation. The inflation also diminishes with a smaller mirror and at a longer viewing distance. An account for the inflation in terms of a mechanism of size constancy contingent on selective attention is offered. The size of the inflation suggests a conflation of the perceived mirror image size with the size of the distal object it signals rather than a complete take-over by the latter. The reduction of the size inflation when participants are asked draw both a target and background objects is more likely a result of the selective attention to proportional relationships in the mirror scene, rather than a manifestation of an evenly scaled visual space under distributed visual spatial attention. The implications of the findings to improving proportional accuracy in observational drawing are discussed.

Size and shape constancy in consumer virtual reality

With the increase in popularity of consumer virtual reality headsets, for research and other applications, it is important to understand the accuracy of 3D perception in VR. We investigated the perceptual accuracy of near-field virtual distances using a size and shape constancy task, in two commercially available devices. Participants wore either the HTC Vive or the Oculus Rift and adjusted the size of a virtual stimulus to match the geometric qualities (size and depth) of a physical stimulus they were able to refer to haptically. The judgments participants made allowed for an indirect measure of their perception of the egocentric, virtual distance to the stimuli. The data show under-constancy and are consistent with research from carefully calibrated psychophysical techniques. There was no difference in the degree of constancy found in the two headsets. We conclude that consumer virtual reality headsets provide a sufficiently high degree of accuracy in distance perception, to allow them to be used confidently in future experimental vision science, and other research applications in psychology.

The nature of perceptual constancies

AbstractPerceptual constancies have been studied by psychologists for decades, but in recent years, they have also become a major topic in the philosophy of mind. One reason for this surge of interest is Tyler Burge’s (2010) influential claim that constancy mechanisms mark the difference between perception and mere sensitivity, and thereby also the difference between organisms with genuine representational capacities and ‘mindless’ beings. Burge’s claim has been the subject of intense debate. It is becoming increasingly clear, however, that we cannot hope to settle this debate (as well as related debates in the philosophy of mind) without a clear and substantive theoretical account of what perceptual constancies are. In the first part of this paper, I argue that the standard definitions in the literature fall short of providing such an account. Still, as I aim to show in the second part of the paper, by taking a closer look at some of the paradigm examples, it is possible to construct a plausible general account of perceptual constancies that is both clear and substantive, and that can serve as a firm foundation for settling debates like the dispute about Burge’s ‘constancy mechanism criterion’ for perception.

Color constancy and color term knowledge are positively related during early childhood

The ability to keep perception constant despite environmental changes of illumination, viewing angle, or distance is a key feature of perception. Here, we investigated how “perceptual constancy” relates to language learning by investigating the relationship between color constancy and color term knowledge in 3- and 4-year-old children. We used a novel method to test color constancy where children are required to match colored stimuli under different illuminations. We found a positive relationship between color constancy and color term knowledge; children who knew more color words also had better color constancy. The relationship remained even when accounting for the effect of age and ability to discriminate colors. The findings have implications for understanding the development of perceptual constancy, language learning, and the link between perceptual processing and cognitive development.

The contribution of stereopsis in Emmert's law.

Size constancy is the ability to perceive objects as remaining constant in size regardless of their distance from the observer. Emmert's law demonstrates that viewing distance determines the perceived size of afterimages according to the amount of depth cues that are available. Using an afterimage paradigm, we examined to what extent removing stereopsis and other depth cues affects size-distance scaling. Thirty participants 'projected' afterimages onto a surface presented at different distances under binocular, monocular, and eyes-closed conditions. The perceived size of the afterimages closely followed the size-distance scaling predictions made by Emmert's law under binocular testing conditions, when all depth cues were available. In contrast, monocular testing decreased adherence to Emmert's law, while the eyes-closed condition resulted in a greater breakdown of size-distance scaling. Because we used an afterimage paradigm, this study provides the first demonstration of how perceived size is modulated by the availability of depth cues under conditions with a constant retinal image stimulus.

The Effects of Three-Dimensional Context on Shape Perception

Humans have a unique ability to perceive shape in different ways. Although we naturally estimate objective (physical) shape in our daily interactions with the world, we are also capable of estimating projective (retinal) shape, especially when attempting to accurately draw objects and scenes. In four experiments, we demonstrated robust effects of 3D context on shape perception. Using a binocular stereo paradigm, we presented rectangular surfaces of varying widths alone or embedded in a polyhedron. We investigated how context, judgment type, and angle affected width estimates. We found that the presence of even a small amount of 3D context aids objective judgments but hinders projective judgments, whereas a lack of context had the opposite effect. Context facilitated objective shape assessments by improving estimates of surface orientation. These results demonstrate that the typical presence of 3D context aids shape perception (shape constancy) while simultaneously making the projective judgments necessary for realistic drawing more difficult.

Dynamic Corridor Illusion in Pigeons: Humanlike Pictorial Cue Precedence Over Motion Parallax Cue in Size Perception.

Depth information is necessary for perceiving the real size of objects at varying visual distances. To investigate to what extent this size constancy present in another vertebrate class, we addressed the two questions using pigeons: (a) whether pigeons see a corridor illusion based on size constancy and (b) whether pigeons prioritize pictorial cues over motion parallax cues for size constancy, like humans. We trained pigeons to classify target sizes on a corridor. In addition, we presented a dynamic version of corridor illusion in which the target and corridor moved side by side. Target speed was changed to manipulate motion parallax. With the static corridor, pigeons overestimated the target size when it was located higher, indicating that pigeons see a corridor illusion like humans. With the dynamic corridor, the pigeons overestimated the target size depending on target position, as in the static condition, but target speed did not affect their responses, indicating that the pictorial precedence also applies to pigeons. In a follow-up experiment using the same stimulus, we confirmed that humans perceive object size based on pictorial cues. These results suggest that size constancy characteristics are highly similar between pigeons and humans, despite the differences in their phylogeny and neural systems.

Object contour tracking via adaptive data-driven kernel

We present a novel approach to non-rigid object tracking in this paper by deriving an adaptive data-driven kernel. In contrast with conventional kernel-based trackers which suffer from the constancy of kernel shape as well as scale and orientation selection problem when the tracking targets are changing in size, the adaptive kernel can robustly achieve the adaptation to target variation and act toward the actual target contour simultaneously with the mean shift iterations. Level set technique is novelly introduced to the mean shift sample space to both cope with insufficient low-level information and implement the adaptive kernel evolution and update. Since the active contour model is designed to drive the kernel constantly to the direction that maximizes the appearance similarity, this adaptive kernel can continually seize the target shape to give a better estimation bias and produce accurate shift of the mean. Finally, accurate target region can successfully avoid the performance loss stemmed from pollution of background pixels hiding inside the kernel and qualify the samples fed the next time step. Experimental results on a numer of challenging sequences validate the effectiveness of the technique.

Autonomic Nervous System Correlates of Speech Categorization Revealed Through Pupillometry.

Human perception requires the many-to-one mapping between continuous sensory elements and discrete categorical representations. This grouping operation underlies the phenomenon of categorical perception (CP)—the experience of perceiving discrete categories rather than gradual variations in signal input. Speech perception requires CP because acoustic cues do not share constant relations with perceptual-phonetic representations. Beyond facilitating perception of unmasked speech, we reasoned CP might also aid the extraction of target speech percepts from interfering sound sources (i.e., noise) by generating additional perceptual constancy and reducing listening effort. Specifically, we investigated how noise interference impacts cognitive load and perceptual identification of unambiguous (i.e., categorical) vs. ambiguous stimuli. Listeners classified a speech vowel continuum (/u/-/a/) at various signal-to-noise ratios (SNRs [unmasked, 0 and −5 dB]). Continuous recordings of pupil dilation measured processing effort, with larger, later dilations reflecting increased listening demand. Critical comparisons were between time-locked changes in eye data in response to unambiguous (i.e., continuum endpoints) tokens vs. ambiguous tokens (i.e., continuum midpoint). Unmasked speech elicited faster responses and sharper psychometric functions, which steadily declined in noise. Noise increased pupil dilation across stimulus conditions, but not straightforwardly. Noise-masked speech modulated peak pupil size (i.e., [0 and −5 dB] > unmasked). In contrast, peak dilation latency varied with both token and SNR. Interestingly, categorical tokens elicited earlier pupil dilation relative to ambiguous tokens. Our pupillary data suggest CP reconstructs auditory percepts under challenging listening conditions through interactions between stimulus salience and listeners’ internalized effort and/or arousal.

Visual Perception of Space in Multifocal Three-Dimensional Displays Stimulating Accommodation

The influence of a viewing device — a multifocal 3D display — on user’s visual perception and assessment of the depth and size of objects is analyzed. As an experiment model we used the Holway-Boring technique, which has proved that the constancy of size perception plays a decisive role in distance perception. A series of experiments has been performed showing that multifocal 3D displays provide fairly reliable information about the distance and size of objects, making it possible not to violate the law of constancy of perception.

Vowel normalization as perceptual constancy

Vowel normalization as perceptual constancy

Vowel normalization as perceptual constancy

Vowel normalization as perceptual constancy

Spectral contrast effects and auditory enhancement under normal and impaired hearing.

We are generally able to identify sounds and understand speech with ease, despite the large variations in the acoustics of each sound, which occur due to factors such as different talkers, background noise, and room acoustics. This form of perceptual constancy is likely to be mediated in part by the auditory system's ability to adapt to the ongoing environment or context in which sounds are presented. Auditory context effects have been studied under different names, such as spectral contrast effects in speech and auditory enhancement effects in psychoacoustics, but they share some important properties and may be mediated by similar underlying neural mechanisms. This review provides a survey of recent studies from our laboratory that investigate the mechanisms of speech spectral contrast effects and auditory enhancement in people with normal hearing, hearing loss, and cochlear implants. We argue that a better understanding of such context effects in people with normal hearing may allow us to restore some of these important effects for people with hearing loss via signal processing in hearing aids and cochlear implants, thereby potentially improving auditory and speech perception in the complex and variable everyday acoustic backgrounds that surround us.

Susceptibility to Flight Simulator-Induced Spatial Disorientation in Pilots and Non-Pilots

ABSTRACT Objective: This study aimed to investigate whether pilots and non-pilots differ in their susceptibility to spatial disorientation (SD) during a flight in various disorienting scenarios, and in coping with SD. Background: Pilot selection is relevant in assessing pilots’ susceptibility to SD. However, SD-related accidents indicate that it may not be fully effective. Method: A set of 12 flight sequences (six containing an SD conflict, three with vestibular and three with visual illusions) was flown by military pilots (N = 20; age: M = 31.6; SD = 8.22) and non-pilots (N = 20; age: M = 30.95; SD = 7.72) in a flight simulator specially designed for SD research and training. The number and mean magnitude of control reversal errors (CREs) were calculated along with the effects of SD conflict on flight performance. Results: With two exceptions, in all SD-conflict flights, the mean number of CREs increased. For mean magnitudes of CREs, the same effects were not observed. Pilots and non-pilots differed in disorientation conditions (M = 4.5 ± 1.95 vs M = 2.6 ± 2.41) only in one profile (shape constancy illusion). In the other two (false horizon and leans illusions), the applied SD cues significantly affected their flight performance. Conclusion: Although the effects of SD cues on flight performance were observed, the applied disorientation scenario would not be useful in the pilot selection procedure. To provide the criteria to select pilot candidates, other disorientation scenarios, or even a different flight simulator should be considered.