Where there is no object formation, there is no perceptual organization: Evidence from the configural superiority effect.

Object formation is considered the aim of perceptual organization, but such a proposition has been neglected in empirical studies. In the current study, we investigated the role of object formation in configural superiority. Essentially, discrimination on bar orientations was enhanced by adding a right angle to each of the bars. Such facilitation is due to the emergent feature (EF) of closure formed by combining the bars with right angles. To study object formation, visual stimuli were generated by random dot stereograms to form objects or holes in 3D. Behaviorally, we found that the EF of closure facilitated oddball discrimination on objects, as demonstrated by previous studies, but did not facilitate oddball discrimination on holes with the same shape as objects. Multivariate pattern analysis of functional magnetic resonance imaging (fMRI) data showed that the EF of closure increased the object classification accuracy compared to the holes in the lateral occipital cortex (LOC), where object information is encoded, but not in the early visual cortex (EVC). The neural representations of objects and holes with and without EFs were further investigated using representational similarity analysis. The results demonstrate that in the LOC, the neural representations of objects with EFs showed a greater difference than those of the other three, that is, objects without EFs and holes with or without EFs. However, the uniqueness of objects with EFs was not observed in the EVC. Thus, our results suggest that the EF of closure, which leads to the configural superiority effect, only emerges for objects but not for holes, and only in the LOC but not the EVC. Our study provides the first empirical evidence suggesting that object formation plays an indispensable role in perceptual organization.

Perceptual Gains and Losses in Synesthesia and Schizophrenia.

Individual differences in perception are widespread. Considering inter-individual variability, synesthetes experience stable additional sensations; schizophrenia patients suffer perceptual deficits in, eg, perceptual organization (alongside hallucinations and delusions). Is there a unifying principle explaining inter-individual variability in perception? There is good reason to believe perceptual experience results from inferential processes whereby sensory evidence is weighted by prior knowledge about the world. Perceptual variability may result from different precision weighting of sensory evidence and prior knowledge. We tested this hypothesis by comparing visibility thresholds in a perceptual hysteresis task across medicated schizophrenia patients (N = 20), synesthetes (N = 20), and controls (N = 26). Participants rated the subjective visibility of stimuli embedded in noise while we parametrically manipulated the availability of sensory evidence. Additionally, precise long-term priors in synesthetes were leveraged by presenting either synesthesia-inducing or neutral stimuli. Schizophrenia patients showed increased visibility thresholds, consistent with overreliance on sensory evidence. In contrast, synesthetes exhibited lowered thresholds exclusively for synesthesia-inducing stimuli suggesting high-precision long-term priors. Additionally, in both synesthetes and schizophrenia patients explicit, short-term priors-introduced during the hysteresis experiment-lowered thresholds but did not normalize perception. Our results imply that perceptual variability might result from differences in the precision afforded to prior beliefs and sensory evidence, respectively.

Bouba and Kiki inside objects: Sound-shape correspondence for objects with a hole.

Visual holes (cutouts in a surface) have recently intrigued vision scientists as interesting and useful stimuli in the studies of shape perception and as a perceptual conundrum regarding figure/ground organization. Adopting the Bouba/Kiki paradigm, this study addressed a controversial issue of whether the perceived shape of a closed region alters when the region changes from a solid object to an empty hole, in a more direct manner than previous studies did. Observers were presented with two doughnut-like cardboard cutouts, one with a flower-shaped hole and the other with a star-shaped hole, and then matched them with two nonsense words. The curvature profile of the hole boundary was manipulated so that the shape of the interior region (i.e., a hole) and that of the exterior region (i.e., material edges) give rise to opposite shape impressions (i.e., one rounded and the other spiky). The results of Experiment 1 revealed that shape-name matching for holed objects is based on the interior shapes of holes, but not those of materially defined inner edges. The following three experiments replicated the same pattern of results even when holes appeared like oral apertures in animal character faces (Experiments 2-3) and when they were irregular, non-symmetric, and low in semantic association with familiar real-world objects (Experiment 4). Lastly, Experiment 5 showed that shape-name matching for "C"-shaped, negative-part stimuli is also interior-shape-based if the opening of the interior region is relatively small. These findings suggest that the interior shapes of holes are automatically accessible. I conclude with a discussion of my hypothesis that the only global-level, unitary shape representation of a bounded region of a single connected surface is that of the interior region for both objects and holes, imposing an important constraint in visual shape processing.

Illusory sound texture reveals multi-second statistical completion in auditory scene analysis.

Sound sources in the world are experienced as stable even when intermittently obscured, implying perceptual completion mechanisms that "fill in" missing sensory information. We demonstrate a filling-in phenomenon in which the brain extrapolates the statistics of background sounds (textures) over periods of several seconds when they are interrupted by another sound, producing vivid percepts of illusory texture. The effect differs from previously described completion effects in that 1) the extrapolated sound must be defined statistically given the stochastic nature of texture, and 2) the effect lasts much longer, enabling introspection and facilitating assessment of the underlying representation. Illusory texture biases subsequent texture statistic estimates indistinguishably from actual texture, suggesting that it is represented similarly to actual texture. The illusion appears to represent an inference about whether the background is likely to continue during concurrent sounds, providing a stable statistical representation of the ongoing environment despite unstable sensory evidence.

The role of temporal integration in auditory stream segregation.

Grouping distinct, temporally separated sounds is assumed to follow Gestalt principles, such as similarity or proximity. In the auditory streaming paradigm, the probability of perceiving all sounds as part of the same repeating pattern (the integrated percept) increases when the interstimulus interval (ISI) is increased from medium to long intervals. However, ISIs shorter than 50 ms have not been systematically explored. Here we show that below ca. 60-ms intervals the direction of the effect of ISI on perception is reversed compared to longer ISIs: Decreasing the ISI increases the probability of the integrated percept. This suggests that temporal proximity plays a different role in auditory stream segregation at very short than at longer ISIs. As the effect of temporal proximity may vary among individuals, we tested whether the proportion of the integrated reports with short ISIs could be associated with individual differences in the temporal resolution of the central auditory system. We found that individual differences in the temporal integration threshold (as measured by a temporal order judgment task) correlated with the percentage of integrated percept reports in some of the short-ISI regions. Although this result cannot be regarded as strong evidence, it is compatible with the notion that temporal integration plays a role in auditory stream segregation at short ISIs. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Neuro-cognitive mechanisms of global Gestalt perception in visual quantification.

Recent neuroimaging studies identified posterior regions in the temporal and parietal lobes as neuro-functional correlates of subitizing and global Gestalt perception. Beyond notable overlap on a neuronal level both mechanisms are remarkably similar on a behavioral level representing both a specific form of visual top-down processing where single elements are integrated into a superordinate entity. In the present study, we investigated whether subitizing draws on principles of global Gestalt perception enabling rapid top-down processes of visual quantification. We designed two functional neuroimaging experiments: a task identifying voxels responding to global Gestalt stimuli in posterior temporo-parietal brain regions and a visual quantification task on dot patterns with magnitudes within and outside the subitizing range. We hypothesized that voxels activated in global Gestalt perception should respond stronger to dot patterns within than those outside the subitizing range. The results confirmed this prediction for left-hemispheric posterior temporo-parietal brain areas. Additionally, we trained a classifier with response patterns from global Gestalt perception to predict neural responses of visual quantification. With this approach we were able to classify from TPJ Gestalt ROIs of both hemispheres whether a trial requiring subitizing was processed. The present study demonstrates that mechanisms of subitizing seem to build on processes of high-level visual perception.

Temporal properties of amodal completion: Influences of knowledge.

We studied the influence of knowledge in the interpretation of partly occluded objects. In the past decades, amodal completion has often been studied by using abstract, meaningless outlines of rather stylistic, geometric shapes. It has been recognized that smooth continuation of partly occluded contours behind an occluding surface is a strong completion tendency. In the current study we contrast this structurally driven completion tendency with knowledge driven tendencies. We used a set of partly occluded well-known objects for which structure-based completions and knowledge-based completions resulted in either the same or different interpretations. We adopted the behavioural primed matching paradigm to measure differential priming effects due to these completion tendencies. Our results implied differential temporal properties for structure-based and knowledge-based effects during perception of partly occluded objects. Interestingly, knowledge has an influence as early as 150 ms after the onset of the prime.

The effects of Kanizsa contours on temporal integration and attention in rapid serial visual presentation.

Performance in rapid serial visual presentation tasks has been shown to depend on the temporal integration of target stimuli when they are presented in direct succession. Temporal target integration produces a single, combined representation of visually compatible stimuli, which is comparatively easy to identify. It is currently unknown to what extent target compatibility affects this perceptual behavior, because it has not been studied systematically to date. In the present study, the effects of compatibility on temporal integration and attention were investigated by manipulating the Gestalt properties of target features. Of particular interest were configurations in which a global illusory shape was formed when all stimulus features were present; a Kanizsa stimulus, which was expected to have a unifying effect on the perception of the successive targets. The results showed that although the presence of a Kanizsa shape can indeed enhance temporal integration, this also was observed for other good Gestalts, such as due to common fate and closure. Identification accuracy seemed to vary, possibly as a result of masking strength, but this did not seem associated with attentional processing per se. Implications for theories of Gestalt processing and temporal integration are discussed.

Reduced intrinsic visual cortical connectivity is associated with impaired perceptual closure in schizophrenia.

Sensory perceptual processing deficits, such as impaired visual object identification and perceptual closure, have been reported in schizophrenia. These perceptual impairments may be associated with neural deficits in visual association areas, including lateral occipital cortex and inferior temporal areas. However, it remains unknown if such deficits can be found in the intrinsic architecture of the visual system. In the current study, we measured perceptual closure performance and resting-state functional connectivity using functional magnetic resonance imaging (FMRI) in 16 schizophrenia patients and 16 matched healthy controls. We estimated intrinsic functional connectivity using self-organized grouping spatial ICA, which clusters component maps in the subject space according to spatial similarity. Patients performed worse than controls in the perceptual closure task. This impaired closure performance of patients was correlated with increased severity of psychotic symptoms. We also found that intrinsic connectivity of the visual processing system was diminished in patients compared to controls. Lower perceptual closure performance was correlated to lower visual cortical intrinsic connectivity overall. We suggest that schizophrenia is associated with impaired intrinsic connectivity of the visual system, and that it is a potential mechanism leading to impaired visual object perception. These findings contribute to increasing evidence for impairments of higher visual functions in schizophrenia.

Impairment of perceptual closure in autism for vertex- but not edge-defined object images.

One of the characteristics of autism spectrum disorder (ASD) is atypical sensory processing and perceptual integration. Here, we used an object naming task to test the significance of deletion of vertices versus extended contours (edges) in naming fragmented line drawings of natural objects in typically developing and ASD children. The basic components of a fragmented image in perceptual closure need to be integrated to make a coherent visual perception. When vertices were missing and only edges were visible, typically developing and ASD subjects performed similarly. But typically developing children performed significantly better than ASD children when only vertex information was visible. These results indicate impairment of binding vertices but not edges to form a holistic representation of an object in children with ASD.

Differentiating global and local contour completion using a dot localization paradigm.

Competing theories of partially occluded object perception (amodal completion) emphasize either relatively local contour relationships or global factors such as symmetry. These disparate theories may reflect 2 separate processes: a low-level contour interpolation process and a higher-order global recognition process. The 2 could be distinguished experimentally if only the former produces precise representations of occluded object boundaries. Using a dot localization paradigm, we measured the precision and accuracy of perceived object boundaries for participants instructed to complete occluded objects with divergent local and global interpretations. On each trial, a small red dot was flashed on top of an occluder. Participants reported whether the dot fell inside or outside the occluded object's boundaries. Interleaved, 2-up, 1-down staircases estimated points on the psychometric function where the probability was .707 that the dot would be seen as either outside or inside the occluded object's boundaries. The results reveal that local contour interpolation produces precise and accurate representations of occluded contours, and consistency across observers, but completion according to global symmetry does not. These results support a distinction between local, automatic contour interpolation processes and global processes based on recognition from partial information. (PsycINFO Database Record

Gleaning Structure from Sound: The Role of Prosodic Contrast in Learning Non-adjacent Dependencies.

The ability to detect non-adjacent dependencies (i.e. between a and b in aXb) in spoken input may support the acquisition of morpho-syntactic dependencies (e.g. The princess is kiss ing the frog). Functional morphemes in morpho-syntactic dependencies are often marked by perceptual cues that render them distinct from lexical elements. We use an artificial grammar learning experiment with adults to investigate the role of perceptual cues in non-adjacent dependency learning, by manipulating the perceptual/prosodic properties of the a / b elements in aXb strings and testing participants' incidental learning of these dependencies. Our results show that non-adjacent dependencies are learned both when the dependent elements are perceptually prominent, and when they are perceptually reduced compared to the intervening material (in the same way that functional words are reduced compared to lexical words), but only if integrated into a natural prosodic contour. This result supports the idea that the prosodic properties of natural languages facilitate non-adjacent dependency learning.

Organization principles in visual working memory: Evidence from sequential stimulus display.

Although the mechanisms of visual working memory (VWM) have been studied extensively in recent years, the active property of VWM has received less attention. In the current study, we examined how VWM integrates sequentially presented stimuli by focusing on the role of Gestalt principles, which are important organizing principles in perceptual integration. We manipulated the level of Gestalt cues among three or four sequentially presented objects that were memorized. The Gestalt principle could not emerge unless all the objects appeared together. We distinguished two hypotheses: a perception-alike hypothesis and an encoding-specificity hypothesis. The former predicts that the Gestalt cue will play a role in information integration within VWM; the latter predicts that the Gestalt cue will not operate within VWM. In four experiments, we demonstrated that collinearity (Experiment 1) and closure (Experiment 2) cues significantly improved VWM performance, and this facilitation was not affected by the testing manner (Experiment 3) or by adding extra colors to the memorized objects (Experiment 4). Finally, we re-established the Gestalt cue benefit with similarity cues (Experiment 5). These findings together suggest that VWM realizes and uses potential Gestalt principles within the stored representations, supporting a perception-alike hypothesis.

Disentangling effects of structure and knowledge in perceiving partly occluded shapes: An ERP study.

Using event-related potentials (ERPs) we investigated the influence of object knowledge on perceiving partly occluded shapes. We created stimuli based on well-known objects of which the middle part was occluded. Object completions that were compatible with structure consisted of the connection of the visible fragments by smoothly extending their contours. In contrast, object completions that were incompatible with structure consisted of separate disconnected completions of the fragments. Furthermore, object completions could be in line with, or conflict with expectations based on knowledge. We measured ERPs when hidden parts were revealed by removing the occluder, and observed an early positive ERP peaking around 115-140ms at occipital sites, presumably triggered by physical differences. Most importantly, we observed a positive ERP peaking around 300-400ms at parieto-occipital sites that could be related to influences of both structure and knowledge. An additional analysis controlling for differential stimulus characteristics revealed similar conclusions. All in all, we demonstrate that the interpretation of partly occluded shapes is not solely driven by stimulus structure, but that it can also be influenced by knowledge of objects.

Created unequal: Temporal dynamics of modal and amodal boundary interpolation.

In this study we manipulate the distribution of contrast polarity reversals in inducing configurations to create novel variants of modal and amodal completion. The novel variants, better equated in their geometric and photometric characteristics offer a superior way to probe similarities and differences in the temporal dynamics that underlie different forms of perceptual completion. We use dot localisation to directly compare the spatial characteristics of modally and amodally interpolated contours at presentation durations ranging from 120 to 300ms and find robust differences in the spatiotemporal formation of modally and amodally completed boundaries. Modally completed contours are localised more accurately and with better spatial precision across all presentation durations. Our results challenge the assumption that the boundary interpolation system depends solely on the geometrical relatability of inducing fragments and suggest that boundary interpolation depends on the spatial distribution of local luminance relationships. As an alternative to the strong version of the identity hypothesis, we propose that modal and amodal completion are mediated by different mechanisms, triggered by particular configurations of contrast polarity.

Partial modal completion under occlusion: what do modal and amodal percepts represent?

In the occlusion illusion, a partly occluded object is perceived as though it were less occluded than it actually is (Palmer, Brooks, & Lai, 2007). We confirm and extend this finding using a stimulus with a moving occluder. In agreement with Palmer et al.'s (2007) findings and their partial-modal-completion hypothesis, we found that the illusion is indeed related to the sensory evidence for occlusion. Our experiments also confirm their speculation that the occlusion illusion involves an intriguing, seemingly paradoxical percept. In our experiments, subjects viewed an opaque disk with an open sector rotating in front of a background and indicated the perceived angular extent (a) of the occluder and (b) of the part of the background experienced as directly visible through the open sector. While the former was judged quite accurately, the latter was clearly overestimated. Thus, the angular extent of the background experienced as occluded and the extent experienced as directly visible sum to more than 360°, which makes the total percept an impossible figure. We argue that the key to resolving this paradox is to question the seemingly self-evident assumption that occluded and unoccluded portions of a visual scene are represented by amodal and modal percepts, respectively. Instead, we propose that visual percepts are experienced as modal whenever they are based on sufficiently conclusive sensory evidence and are otherwise experienced as amodal. Functionally, this perceptual representation of the conclusiveness of the sensory evidence underlying perceptual inferences might be more useful than estimates about optical visibility.

Size of the foveal blue scotoma related to the shape of the foveal pit but not to macular pigment.

When the eye is covered with a filter that transmits light below 480 nm and a blue field is observed on a computer screen that is modulated in brightness at about 1 Hz, the fovea is perceived as small irregular dark spot. It was proposed that the "foveal blue scotoma" results from the lack of S-cones in the foveal center. The foveal blue scotoma is highly variable among subjects. Possible factors responsible for the variability include differences in S-cone distribution, in foveal shape, and in macular pigment distribution. Nine young adult subjects were instructed to draw their foveal blue scotomas on a clear foil that was attached in front of the computer screen. The geometry of their foveal pit was measured in OCT images in two dimensions. Macular pigment distribution was measured in fundus camera images. Finally, blue scotomas were compared with Maxwell's spot which was visualized with a dichroic filter and is commonly assumed to reflect the macular pigment distribution. The diameters of the foveal blue scotomas varied from 15.8 to 76.4 arcmin in the right eyes and 15.5 to 84.7 arcmin in the left and were highly correlated in both eyes. It was found that the steeper the foveal slopes and the narrower the foveal pit, the larger the foveal blue scotoma. There was no correlation between foveal blue scotoma and macular pigment distribution or Maxwell's spot. The results are therefore in line with the assumption that the foveal blue scotoma is a consequence of the lack of S-cones in the foveal center. Unlike the foveal blue scotoma, Maxwell's spot is based on macular pigment as previously proposed.

Recovering metric properties of objects through spatiotemporal interpolation.

Spatiotemporal interpolation (STI) refers to perception of complete objects from fragmentary information across gaps in both space and time. It differs from static interpolation in that requirements for interpolation are not met in any static frame. It has been found that STI produced objective performance advantages in a shape discrimination paradigm for both illusory and occluded objects when contours met conditions of spatiotemporal relatability. Here we report psychophysical studies testing whether spatiotemporal interpolation allows recovery of metric properties of objects. Observers viewed virtual triangles specified only by sequential partial occlusions of background elements by their vertices (the STI condition) and made forced choice judgments of the object's size relative to a reference standard. We found that length could often be accurately recovered for conditions where fragments were relatable and formed illusory triangles. In the first control condition, three moving dots located at the vertices provided the same spatial and timing information as the virtual object in the STI condition but did not induce perception of interpolated contours or a coherent object. In the second control condition oriented line segments were added to the dots and mid-points between the dots in a way that did not induce perception of interpolated contours. Control stimuli did not lead to accurate size judgments. We conclude that spatiotemporal interpolation can produce representations, from fragmentary information, of metric properties in addition to shape.

An online version of the Mooney Face Test: phenotypic and genetic associations.

The Mooney Face Test is a widely used test of face perception, but was originally designed to be administered by personal interview. We have developed a three-alternative forced-choice version for online testing. We tested 397 healthy adults between the ages of 18 and 42 (M=24 years). There was a wide range of performance (64-100% correct; M=89.6%). We observed a significant sex difference favoring males (.31 standard deviation; p =.004). In addition, independently of sex, higher 2D:4D digit ratios were significantly associated with higher scores (ρ=.14, p=.006). A genome-wide association study (GWAS) for a subset of 370 participants identified an association between Mooney performance and a polymorphism in the RAPGEF5 gene (rs1522280; p=9.68×10(-8)). This association survives a permutation test (p=.031).