The informal heuristic practices of the fine arts have much to offer to our understanding of the appearance of phenomenological reality. One interesting example is the use of exaggeration to enhance the illusion of liveliness in both living and nonliving subjects. This further eases the uncomfortable sense that the motion is somehow uncanny - especially with inanimate objects. We performed a series of experiments to test the effects of exaggeration on the phenomenological perception of simple animated objects - bouncing balls. A physically plausible model of a bouncing ball was augmented with a frequently used form of exaggeration known as squash and stretch. Observers were shown a series of animated balls, depicted using systematic parameterizations of the exaggeration model, and asked to rate their plausibility. A range of rendering styles provided varying levels of information as to the type of ball. In all cases, balls with small amounts of exaggeration were seen as plausible as those without any exaggeration (e.g., with veridical motion). Furthermore, when the type of ball was not specified, observers tolerated a large amount of exaggeration before judging them as implausible. When the type of ball was indicated, observers narrowed the range of acceptable exaggeration somewhat but still tolerated exaggeration well beyond that which would be physically possible. We contend that, in this case, exaggeration acts to bridge the so-called uncanny valley for artificial depictions of physical reality.

Previous studies have demonstrated that engaging in graphomotor activity for creating graphemes can enhance their subsequent visual discrimination. This suggests a positive influence of the motor system on visual learning. However, existing studies have emphasized the dominant hand, which is superiorly dexterous in fine-motor movements. This near-exclusive focus prompts the inquiry of whether the observed perceptual facilitation is a general characteristic of the motor system, or specific to pathways controlling the skilled over-trained dominant hand. Furthermore, the mechanistic underpinning of visual facilitation from graphomotor training (i.e., the individual contribution of motor activity, temporal evolution of the visual trace, variability of visual output) remain unclear. To address these questions, we assessed visual discrimination capabilities of healthy right-handed participants (N = 60) before and after graphomotor or visual training. Contrary to our initial expectation, graphomotor engagement with the non-dominant hand did not yield additional benefits to visual learning beyond those attainable through visual training alone. Moreover, graphomotor training with the non-dominant hand resulted in visual discrimination improvements comparable to those of dominant hand training, despite the inherent differences between hands in motor performance and in the amount of improvement in shape tracing throughout training. We conclude that the motor components of graphomotor activity may not be critical for visual learning of shapes through tracing activity. Instead, our results are in agreement with the symbolic theoretical account, suggesting that basic shape features required for discrimination can be acquired through visual inspection alone, providing a perspective on the improvements observed in prior studies.

Introduction: Vision plays a crucial role in social cognition. Humans anthropomorphize and attribute causality even to minimal stimuli. This was demonstrated compellingly by Heider and Simmel (1944) using a simple animation comprising dynamic geometric primitives devoid of any social cues such as speech, body pose and facial expressions. Neurodevelopmental studies have utilized the animation to study social attribution, particularly in Autism Spectrum Disorders (ASD), whereby individuals with good verbal IQ fail to derive social contexts and to attribute personality traits to shape movements. In the present study, we test the Heider and Simmel animation on an unusual group of children, those who were born blind and received sight surgeries late in childhood. Methods: We presented a couple runs of the Heider and Simmel animation to patient groups treated for congenital blindness and to age-matched controls (n=6). One of the patient groups consisted of newly sighted children (n=5) and the other of children operated over two years ago (n=8). Participants later provided descriptive responses to a few narrative questions. We also presented selected excerpts from the animation and recorded their responses. Results: Our data revealed striking differences in subjective responses between the patients and control groups. While most patients were able to recognize different shapes and simple movements (Such as, running around), they could not draw out social narratives, attribute personality traits to individual shapes or assign social meaning to movements. Controls on the other hand described goal-directed inter-shape interactions, sequence of movements and were able to anthropomorphize dynamic scenes. Discussion: Our findings reveal no innate ability for social attribution in perception of simple dynamic sequences, indicating that early visual deprivation compromises the development of mentalizing and attribution capabilities in the patient group. This suggests that there may be a critical period for learning to assign social meaning to dynamic forms.

A new source of information is proposed for the perception of three-dimensional (3D) shape from shading that identifies surface concavities from the curvature of the luminance field. Two experiments measured the abilities of human observers to identify concavities on smoothly curved shaded surfaces depicted with several different patterns of illumination and several different material properties. Observers were required to identify any apparent concavities along designated cross sections of the depicted objects and to mark each concavity with an adjustable dot. To analyze the results, we computed both the surface curvature and the luminance curvature along each image cross section. The results revealed that most responses were in concave regions of the luminance profiles, although they were often shifted in phase relative to the curvature of the depicted surfaces. This pattern of performance was surprisingly robust over large changes in the pattern of illumination or surface material properties. Our analysis predicts that observers should make false alarm responses in regions where a luminance concavity does not correspond to a surface concavity, and our empirical results confirm that prediction.

A new model of shape from shading is proposed that estimates the locations of surface concavities based on the curvature of the luminance field. Two experiments measured the abilities of human observers to identify concavities on smoothly curved shaded surfaces depicted with several different patterns of illumination and several different material properties. Observers were required to identify any apparent concavities along designated cross-sections of the depicted objects, and to mark each concavity with an adjustable dot. To analyze the results, we computed both the surface curvature and the luminance curvature along each image cross-section. The results revealed that the vast majority of responses were in concave regions of the luminance profiles, though they were often shifted in phase relative to the curvature of the depicted surfaces. This pattern of performance was surprisingly robust over large changes in the pattern of illumination or surface material properties. Our model predicts that observers should make false alarm responses in regions where a luminance concavity does not correspond to a surface concavity, and our empirical results confirm that prediction.

Two experiments were performed to investigate the visual information by which human observers are able to identify concave and convex regions within shaded images of smoothly curved surfaces. An image of an object was presented on each trial, and a horizontal cross-section through the surface was designated by a row of four small adjustable dots on each side. Observers were required to identify any apparent concavities along the cross-section and to mark their deepest points with the adjustable dots. In Experiment 1, the stimuli included four randomly deformed spheres with Lambertian reflection functions that were rendered with four different patterns of illumination. To analyze the data we computed the curvature in the direction of each cross-section for both the variations in depth and luminance. The hit rate for detecting actual surface concavities was 88%, but there were also a large number of false alarms. Our computational model predicts that most of the responses should be located in concave regions of the luminance profile, but it also allows for responses in convex regions under very specific conditions. The results revealed that 79% of the responses were in concave regions of the luminance profile (as opposed to 43% that would be expected from random responses). The convex responses consistent with the model accounted for 16% of the responses. The same design was used in Experiment 2, except that the displays were rendered with four different reflectance functions, including shiny paint, black velvet, satin and wax, with a single pattern of illumination. The number of false alarms increased relative to Experiment 1, but the model performance was comparable in both studies. The success of this analysis provides strong evidence that using differential geometry for image processing is a powerful tool for better understanding the perception of 3D shape from shading.

Early visual deprivation is known to have profound consequences on the subsequent development of spatial visual processing. However, its impact on temporal processing is not well characterized. We have examined spatial and temporal contrast sensitivity functions following treatment for early and extended bilateral visual deprivation in fifteen children born with congenital cataracts in rural India. The results reveal a marked difference in post-treatment spatial and temporal sensitivities. Whereas spatial processing in newly sighted children is significantly impaired relative to age-matched controls, temporal processing exhibits remarkable resilience and is comparable to that in the control group. This difference in spatial and temporal outcomes is especially surprising given our computational analyses of video sequences which indicate a strong linkage between the spatial and temporal spectral content of natural visual inputs. We consider possible explanations for this discrepancy.

There is considerable evidence that the visual perception of 3D shape from shading can be influenced by the pattern of illumination. Some experiments have shown that changes in illumination can have dramatic effects on apparent 3D shape, whereas others have shown that these effects are relatively modest. One possible factor that may modulate these results is the 3D geometry of the depicted objects. The central hypothesis of the present experiment is that regions of high curvature on a surface provide perceptual landmarks that can help to stabilize shape perception over changes in illumination or materials. The stimuli were all constructed from plane-faced polyhedra that were subjected to varying degrees of smoothing that reduced the curvature of the polyhedral edges, and these objects were illuminated from either left or right. Their 2D images were judged using two different response tasks: a gauge-figure adjustment task, in which observers estimated the local surface orientation at designated probe points; and a near-point task, in which they marked points on the surface that appeared to be the nearest points in depth. The results suggest that regions of high curvature do indeed stabilize observers' 3D shape perceptions. As the curvature of the polyhedral edges decreased, this produced increased perceptual distortions relative to the ground truth, and the effect of illumination direction on perceived shape was magnified as well.

The present research was designed to examine how patterns of illumination influence the perceptual categorization of metal, shiny black, and shiny white materials. The stimuli depicted three possible objects that were illuminated by five possible high-dynamic-range imaging light maps, which varied in their overall distributions of illuminant directions and intensities. The surfaces included a low roughness chrome material, a shiny black material, and a shiny white material with both diffuse and specular components. Observers rated each stimulus by adjusting four sliders to indicate their confidence that the depicted material was metal, shiny black, shiny white, or something else, and these adjustments were constrained so that the sum of all four settings was always 100%. The results revealed that the metal and shiny black categories are easily confused. For example, metal materials with low intensity light maps or a narrow range of illuminant directions are often judged as shiny black, whereas shiny black materials with high intensity light maps or a wide range of illuminant directions are often judged as metal. To discover the visual information on which these judgements are based, we measured several possible image statistics, and we found two that were highly correlated with the observers’ confidence ratings in appropriate contexts. We also performed a spherical harmonic analysis on the different light maps to quantitatively predict how they would bias observers’ judgments of metal and shiny black surfaces.

Three-dimensional (3D) shape perception is one of the most important functions of vision. It is crucial for many tasks, from object recognition to tool use, and yet how the brain represents shape remains poorly understood. Most theories focus on purely geometrical computations (e.g., estimating depths, curvatures, symmetries). Here, however, we find that shape perception also involves sophisticated inferences that parse shapes into features with distinct causal origins. Inspired by marble sculptures such as Strazza's The Veiled Virgin (1850), which vividly depict figures swathed in cloth, we created composite shapes by wrapping unfamiliar forms in textile, so that the observable surface relief was the result of complex interactions between the underlying object and overlying fabric. Making sense of such structures requires segmenting the shape based on their causes, to distinguish whether lumps and ridges are due to the shrouded object or to the ripples and folds of the overlying cloth. Three-dimensional scans of the objects with and without the textile provided ground-truth measures of the true physical surface reliefs, against which observers' judgments could be compared. In a virtual painting task, participants indicated which surface ridges appeared to be caused by the hidden object and which were due to the drapery. In another experiment, participants indicated the perceived depth profile of both surface layers. Their responses reveal that they can robustly distinguish features belonging to the textile from those due to the underlying object. Together, these findings reveal the operation of visual shape-segmentation processes that parse shapes based on their causal origin.

Shape-deforming processes (e.g., squashing, bending, twisting) can radically alter objects' shapes. After such a transformation, some features are due to the object's original form, while others are due to the transformation, yet it is challenging to separate the two. We tested whether observers can distinguish the causal origin of different features, teasing apart the characteristics of the original shape from those imposed by transformations, a process we call 'shape scission'. Using computer graphics, we created 8 unfamiliar objects and subjected each to 8 transformations (e.g., "twisted", "inflated", "melted"). One group of participants named transformations consistently. A second group arranged cards depicting the objects into classes according to either (i) the original shape or (ii) the type of transformation. They could do this almost perfectly, suggesting that they readily distinguish the causal origin of shape features. Another group used a digital painting interface to indicate which locations on the objects appeared transformed, with responses suggesting they can localise features caused by transformations. Finally, we parametrically varied the magnitude of the transformations, and asked another group to rate the degree of transformation. Ratings correlated strongly with transformation magnitude with a tendency to overestimate small magnitudes. Responses were predicted by both the magnitude and area affected by the transformation. Together, the findings suggest that observers can scission object shapes into original shape and transformation features and access the resulting representational layers at will.

Highly reflective and refractive materials such as gemstones, polished metals, shimmering water, glazed ceramics and the like, act as touchstones of visual wonder for humans. While this might simply be indicative of a “sparkly good!” mechanism of prehistoric origin, the question remains how the human visual system uses this information to identify materials. Since the 15th century, painters (e.g., van Eyck, Heda, Claesz) have been acutely aware of the depiction of these materials. Even contemporary comic illustrators make it a priority to depict this phenomenology via denotative mechanisms like ’lucaflection’ (Mort Walker). It is intuitively tempting to assign the heavy lifting of material perception to the specularity of the material. Indeed, transparency and translucency seem to be special cases of our day-to-day experiences with materials — the vast majority of which that seem relatively opaque. However they are frequently not as opaque as they may seem (grapes, for example) and even those that are completely so still have sub-surface interactions with light that make for complicated depiction. In a series of experiments we show that the spatial composition of the illuminating environment has a strong effect on material perception of non-trivial objects made from ostensibly opaque materials. Broad (i.e., low-frequency dominant) fields of illumination result in fiducially black materials to be perceived as ‘metal’ while sparse fields (small, isolated high frequency information) biased perception of metal toward ‘black plastic’. Preliminary work with transparent and translucent materials suggests the same mechanisms may be at work — The structure of refracted environmental information plays an even more significant role than that of the specular highlights. Finally, multi-scale analysis of the illumination environment shows clustering more consistent with the empirical perceptual impressions of the surface than with the actual surface material.

In three experiments participants haptically discriminated object shape using unimanual (single hand explored two objects) and bimanual exploration (both hands were used, but each hand, left or right, explored a separate object). Such haptic exploration (one versus two hands) requires somatosensory processing in either only one or both cerebral hemispheres; previous studies related to the perception of shape/curvature found superior performance for unimanual exploration, indicating that shape comparison is more effective when only one hemisphere is utilized. The current results, obtained for naturally shaped solid objects (bell peppers, Capsicum annuum) and simple cylindrical surfaces demonstrate otherwise: bimanual haptic exploration can be as effective as unimanual exploration, showing that there is no necessary reduction in ability when haptic shape comparison requires interhemispheric communication. We found that while successive bimanual exploration produced high shape discriminability, the participants' bimanual performance deteriorated for simultaneous shape comparisons. This outcome suggests that either interhemispheric interference or the need to attend to multiple objects simultaneously reduces shape discrimination ability. The current results also reveal a significant effect of age: older adults' shape discrimination abilities are moderately reduced relative to younger adults, regardless of how objects are manipulated (left hand only, right hand only, or bimanual exploration).

As robots become more human-like our appreciation of them increases — up to a crucial point where we find them realistic but not perfectly so. At this point, human preference plummets into the so-called uncanny valley. This phenomenon isn't limited to robotics and has been observed in many other areas. These include the fine arts, especially photorealistic painting, sculpture, computer graphics, and animation. The informal heuristic practices of the fine arts, especially those of traditional animation, have much to offer to our understanding of the appearance of phenomenological reality. One interesting example is the use of exaggeration to mitigate uncanny valley phenomena in animation. Raw rotoscoped imagery (e.g., action captured from live performance) is frequently exaggerated to give the motion 'more life' so as to appear less uncanny. We performed a series of experiments to test the effects of exaggeration on the phenomenological perception of simple animated objects — bouncing balls. A physically plausible model of a bouncing ball was augmented with a frequently used form of exaggeration known as squash and stretch. Subjects were shown a series of animated balls, depicted using systematic parameterizations of the model, and asked to rate their plausibility. A range of rendering styles provided varying levels of information as to the type of ball. In all cases, balls with no exaggeration (e.g., veridically) were seen as significantly less plausible than those with it. Furthermore, when the type of ball was not specified, subjects tolerated a large amount of exaggeration before judging them as implausible. When the type of ball was indicated, subjects narrowed the range of acceptable exaggeration somewhat but still tolerated exaggeration well beyond that which would be physically possible. We contend that, in this case, exaggeration acts to bridge the uncanny valley for artificial depictions of physical reality. Meeting abstract presented at VSS 2018

A growing body of evidence demonstrates that the brain can reorganize dramatically following sensory loss. Although the existence of such neuroplastic crossmodal changes is not in doubt, the functional significance of these changes remains unclear. The dominant belief is that reorganization is compensatory. However, results thus far do not unequivocally indicate that sensory deprivation results in markedly enhanced abilities in other senses. Here, we consider alternative reasons besides sensory compensation that might drive the brain to reorganize after sensory loss. One such possibility is that the cortex reorganizes not to confer functional benefits, but to avoid undesirable physiological consequences of sensory deafferentation. Empirical assessment of the validity of this and other possibilities defines a rich program for future research.

Research on shape perception usually focuses on the estimation of local surface geometry through cues like stereopsis, shading or texture. Here, we argue that observers use these shape estimates to infer other object properties such as material composition and the transformation processes that generated the observed shape from this matter. We call this separation of object shape into intrinsic and extrinsic object properties shape scission. We investigated shape scission in a series of experiments with different groups of participants responding to a set of 8 unfamiliar rendered objects, each transformed by 8 transformations (e.g., "melted", "cut", or "inflated"). Importantly, participants did never see the untransformed versions of objects. First, participants produced adjectives in a free naming task to describe what happened to the transformed objects. Second, participants classified the objects according to either (i) their original shape, or (ii) the transformation that had been applied to them. Third, participants marked those regions of the objects that were transformed away from the original shape. Finally, participants viewed objects at 5 different levels of transformation magnitude and provided perceptual ratings of deformation. We find that participants (i) are consistent in naming the transformations, (ii) can classify unfamiliar objects according to their original shape as well as the applied transformation, (iii) can identify regions of the objects that were transformed, and (iv) can to some extent perceive the magnitude of the transformation (when compared to objective mesh deformations). Thus, we can identify "objects" across transformations and "transformations" across objects, separating observed features by their causal origin (shape scission). We can use this perceptual understanding of the causal processes to make inferences about what other members of the same class might look like and about how objects have been altered by forces in their past. Meeting abstract presented at VSS 2018

Renaissance artists noticed that placing objects on a visible ground plane anchors them stably, making it easy to perceive their depth. Subsequently, they developed methods for geometric calculation of perspective by drawing construction lines defining the ground plane. Thus, the artist constructs the geometry of pictorial space, based on the station point and the view direction, then places objects in it. This practice created a scale for placing and sizing objects on a minimally patterned ground plane. Our experiments, which measure the precision of depth perception in perspective images, hypothesize that spatial perception evolved in the presence of two constancies, vertical gravity and an almost horizontal ground. Human sensitivity to horizontal and vertical orientations exemplifies the important effect that gravity and the ground have on human perception. From them a third constancy emerges, objects in contact with the ground at the same distance lie along a horizontal line, which artists' floor constructions highlight. In psychophysical experiments we measured the response time and accuracy of forced-choice closer/farther judgments between two objects placed in simple scenes based on traditional artist's perspective. The presence or absence of ground constructions and its orientation are varied in SVG images to minimize pixellation artifacts. Among the directions of gravity participants best perceive depth when the ground plane is horizontal and gravity downward, as measured by response time at 97% accuracy. Furthermore, the horizontal construction lines, which abstract the horizontal guides present in Renaissance paintings the tiled floors, improve depth perception substantially. In Renaissance scene paintings feet are usually visible; our experiments show that the feet provide the viewer with an accurate perception of relative depth, configuring the scene elements into clusters. The underlying cause lies in the structure of vision, which privileges the horizontal ground and downward gravity. Meeting abstract presented at VSS 2018

Positive social interactions during childhood and adolescence are essential for human neurobehavioral development. All social animals show persistent physiological and behavioral deficits after extended periods of social isolation. Our goal was to determine whether postweaning social isolation negatively impacts adult anxiety and sociability in female Long Evans rats. Additionally, we tested whether administration of the pro-social hormone, oxytocin, could prevent behavioral deficits induced by isolation. On post-natal day (PND) 21, subjects were randomly assigned to social isolation (n = 30) or group housing (n = 30). Half of the subjects in each housing condition received 1 mg/kg oxytocin every three days for thirty days. The other half received saline-vehicle control. On PND 51-52, anxiety was assessed in the elevated-plusmaze (EPM). Subjects were then group housed (“resocialization”) in novel triplets. Due to the potential influence of ovarian hormones on social motivation, daily vaginal cytology was initiated to track subjects’ estrous cycles. On PND 66-67, subjects completed a second EPM test. On PND 70-72, subjects’ social motivation was assessed using a three-chamber sociability apparatus. Isolated subjects exhibited higher anxiety in the first EPM test (immediately following isolation) compared to group housed subjects (p < 0.01). In the second EPM test, however, there were no group differences in anxiety, suggesting that the detrimental effects of post-weaning social isolation on anxiety had been redressed by resocialization. Also as predicted, previously isolated subjects exhibited reduced social motivation compared to group-housed subjects (p < 0.05). These findings suggest that post-weaning isolation leads to persistent social deficits that cannot be explained by an increase in generalized anxiety. Lastly, oxytocin treatment did not prevent the detrimental behavioral effects of post-weaning social isolation, which suggests that the developmental consequences of adolescent social deprivation may not be caused by reduced oxytocin output. Overall, this study substantiates the theory that early social isolation has detrimental effects on adult emotionality and behavior. Future animal research should continue to explore the potential clinical utility of oxytocin in treating social deficits.

When objects are deformed by external forces (e.g. a crushed can or twisted rag), the resulting shape is a complex combination of features from the original shape and those imparted by the transformation. If we observe only the resulting shape, distinguishing the origin of its various features is formally ambiguous. However, in many cases the transformation leaves distinctive signatures that could be used to infer how the object has been transformed. Here we investigated how well observers can identify the type and magnitude of deformations applied to unfamiliar 3D shapes. We rendered objects subjected to physical simulations of 12 shape-transforming processes (e.g., twisting, crushing, stretching). Observers rated the magnitude of object deformation at different stages of the transformation process (e.g., barely twisted vs. strongly twisted). Another group viewed one transformed object at a time and ranked other objects-which were submitted to the same or one of the 11 other transformations-according to their similarity to the test object in terms of the applied transformation. A third group viewed a subset of the objects and painted on the surface to indicate which regions appeared most informative about the type of transformation. We find that observers can estimate the magnitude of deformation of unfamiliar objects without knowing their pre-transformed shapes. They can infer specific causal origins from these deformations, reflected in their ability to identify other objects subjected to the same transformation. We also identify the shape features underlying these inferences by comparing the painting responses to the physical mesh deformations. Our findings show that observers can infer transformations from object shape. This ability to infer the causal origin of objects is potentially useful in estimating their physical properties (e.g., stiffness), predicting their future states, or judging similarity between different objects. Meeting abstract presented at VSS 2017