Perceptual organization and visual awareness: the case of amodal completion.

We investigated the involvement of visual awareness in amodal completion, and specifically, whether visual awareness plays a differential role in local versus global completion, using a primed shape discrimination paradigm and the color-opponent flicker technique to render the prime invisible. In four experiments, participants discriminated the shape of a target preceded by a partly occluded or a neutral prime. All primes were divergent occlusion patterns in which the local completion is based on good continuation of the contours at the point of occlusion and the global completion is based on maximum symmetry. The target corresponded to the shape that could arise as a result of local or global completion of the occluded prime. For each experiment with an invisible prime we conducted a version with a visible prime. Our results suggest that local completion, but not global completion, of a partly occluded shape can take place in the absence of visual awareness, but apparently only when the visible occluded shape generates a single, local completion. No completion, either local or global, appears to take place in the absence of visual awareness when the visible occluded shape generates multiple completions. The implications of these results to the differential role of visual awareness in local and global completions and to the relationship between multiple completions and unconscious amodal completions are discussed.

The competition between grouping cues can be resolved under inattention.

We investigated whether attention is required for the resolution of the competition between conflicting grouping cues. Participants performed a demanding change-detection task on a small matrix presented on a backdrop composed of two organizations that could change or stay the same between two consecutive displays independently from changes in the target. We hypothesized that if the competition between the backdrop organizations can be resolved without attention, congruency effects should emerge between changes in the target and changes in the organization that won the competition, but not for the other organization. Three trial types were examined: no-conflict trials, where the two grouping cues formed the same organization (e.g., columns by proximity and by color similarity); conflict trials, where the two cues formed conflicting organizations (e.g., columns by proximity and rows by color similarity); and mixed trials, where one backdrop display depicted no conflict while the other depicted conflicting organizations. Congruency effects were elicited by one organization (Experiment 1-proximity, Experiment 2-common region) but not by the other (color similarity, Experiments 1-2), in the no-conflict and mixed trials, suggesting that if one display in a trial was well organized it facilitated the resolution of the competition in the other display. However, when resolving the competition was required for both displays within a trial, it was not accomplished without attention. Thus, this study shows novel results revealing some of the conditions in which the competition between grouping cues can be resolved without attention.

A divergent effect of stimulus perceptual details on affective and semantic representations of valence.

The current work investigated the potential dissociation between two modes of valence: affective valence (valence of the emotional response) and semantic valence (stored knowledge about the valence of an object/event). A series of six experiments systematically examined the divergent effect of manipulating the amount of perceptual details on affective valence and semantic knowledge about valence. We predicted that affective valence, more than semantic valence, will be affected by manipulating the amount of stimulus perceptual details. Experiment 1a manipulated the amount of perceptual details by presenting the same stimulus content with different quantity of perceptual details. We compared three conditions: a very short movie clip, a still picture that was taken from the movie clip, and a blurred version of the picture from the movie clip. Experiment 1b replicated Experiment 1a using a stronger filter for blurring the picture. Experiment 2 used different manipulation of filtering out visual perceptual details by comparing still pictures to outlined images. Experiment 3 generalized the results of Experiments 1 and 2 by comparing pictures and written words. Experiments 4a and 4b examined the hypothesis regarding the divergent effect of the amount of perceptual details on semantic and affective valence, using physiological signals and a reaction time task, measures that do not rely on self-reports. Results suggest that affective valence is more sensitive to the change in the amount of perceptual details of the stimulus than semantic valence. The psychological mechanism that might underlie this effect and the theoretical implications of the findings are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Mixture-modeling approach reveals global and local processes in visual crowding.

Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on various perceptual tasks such as reading and facial recognition. While prevailing models suggest that crowding is a unitary phenomenon occurring at an early level of processing, recent studies have shown that crowding might also occur at higher levels of representation. Here we investigated whether local and global crowding interference co-occurs within the same display. To do so, we tested the distinctive contribution of local flanker features and global configurations of the flankers on the pattern of crowding errors. Observers (n = 27) estimated the orientation of a target when presented alone or surrounded by flankers. Flankers were grouped into a global configuration, forming an illusory rectangle when aligned or a rectangular configuration when misaligned. We analyzed the error distributions by fitting probabilistic mixture models. Results showed that participants often misreported the orientation of a flanker instead of that of the target. Interestingly, in some trials the orientation of the global configuration was misreported. These results suggest that crowding occurs simultaneously across multiple levels of visual processing and crucially depends on the spatial configuration of the stimulus. Our results pose a challenge to models of crowding with an early single pooling stage and might be better explained by models which incorporate the possibility of multilevel crowding and account for complex target-flanker interactions.

Visual Detection and Decoding Skills of Aerial Photography by Adults with Autism Spectrum Disorder (ASD).

Despite challenges in social communication skills people with ASD often display strengths in visual processing. Aerial photography analysis is an occupation reliant on strong visual processing skills that matches this unique profile. We investigated basic-vision and "real-life" visual tasks in 20 cognitively-able young adults with ASD and 20 typically-developed (TD) "gamers". Basic-vision tests included Visual-Search, Embedded-Figures, and Vigilance; "real-life" tests included aerial-photograph detection and identification. Groups performed equally well, and did not differ significantly on any tasks. The study demonstrates strong visual skills in people with ASD in basic and "real-life" settings, and supports the idea that they may be well suited for employment in occupations that demand high visual perception skills such as aerial photography analysis.

Functional involvement of subcortical structures in global-local processing.

The present study examined the involvement of subcortical structures in the processing of global and local information. To this end, we used a stereoscope to present hierarchical stimuli (global shapes composed of local elements) in a dichoptic or a monocular fashion, such that global and local information was either presented to the same eye (same-eye condition) or segregated between the eyes (different-eyes condition). In Experiment 1, the typical global advantage and global-to-local interference were observed for the same-eye presentation condition. On the other hand, no indication of a global advantage or of global-to-local interference emerged in the different-eyes presentation condition. In Experiment 2 we replicated these results, ruling out a possible alternative explanation that the pattern of results observed for the different-eyes presentation condition resulted merely from segregation of the stimulus between the eyes. Rather, the experiment demonstrated that the global-to-local interference was eliminated only when global and local information was segregated between the eyes. Taken together, these findings suggest that processing the global aspect of hierarchical stimuli involves subcortical regions indexed by monocular portions of the visual system.

The role of visual awareness in processing of global structure: Evidence from the perceptual organization of hierarchical patterns.

We examined whether the perceptual organization of hierarchical structure, and specifically, the integration of local elements into a global shape, requires visual awareness, using a masked priming paradigm, sandwich masking to render the prime invisible, and two types of primes, many-element hierarchical patterns composed of many relatively small elements (Experiment 1) and few-element hierarchical patterns composed of a few relatively large elements (Experiment 2). A significant response priming of the local elements of many-element patterns was observed for invisible primes, whereas a significant response priming of the global shape was found only for the visible primes. For the few-element patterns, only significant response priming of the local elements was observed, as expected, for both visible and invisible primes. Our results suggest that local elements are represented in the absence of visual awareness, regardless of their number and relative size. Visual awareness, however, can be essential for grouping local elements into a global shape. The critical role of awareness in deriving global structure implies that global perception, which characterizes much of our early perception of objects and scenes, is likely to depend on visual awareness.

Perceptual organization of line configurations: Is visual awareness necessary?

We examined whether configuring, which determines the appearance of grouped elements as a global shape, requires visual awareness, using a priming paradigm and two invisibility-inducing methods, CFS and sandwich masking. The primes were organized into configurations based on closure, collinearity, and symmetry (collinear primes), or on closure and symmetry (noncollinear primes). The prime-target congruency could be in configuration or in elements. During CFS, no significant response-priming was observed for invisible primes. When masking induced invisibility, a significant configuration response-priming was found for collinear and noncollinear primes, visible and invisible, with larger magnitude for the former. An element response-priming of equal magnitude was evident for visible and invisible noncollinear primes. Our results suggest that configuring can be accomplished in the absence of visual awareness when stimuli are rendered invisible by sandwich masking, but it benefits from visual awareness. Our results also suggest sensitivity to the available grouping cues in unconscious processing.

Can perceptual grouping unfold in the absence of awareness? Comparing grouping during continuous flash suppression and sandwich masking.

In this study we examined whether grouping by luminance similarity and grouping by connectedness can occur in the absence of visual awareness, using a priming paradigm and two methods to render the prime invisible, CFS and sandwich masking under matched conditions. For both groupings, significant response priming effects were observed when the prime was reported invisible under sandwich masking, but none were obtained under CFS. These results provide evidence for unconscious grouping, converging with previous findings showing that visual awareness is not essential for certain perceptual organization processes to occur. They are also consistent with findings indicating that processing during CFS is limited, and suggest the involvement of higher visual areas in perceptual organization. Moreover, these results demonstrate that whether a process can occur without awareness is dependent on the level at which the suppression induced by the method used for rendering the stimulus inaccessible to awareness takes place.

Attention enhances apparent perceptual organization.

Perceptual organization and selective attention are two crucial processes that influence how we perceive visual information. The former structures complex visual inputs into coherent units, whereas the later selects relevant information. Attention and perceptual organization can modulate each other, affecting visual processing and performance in various tasks and conditions. Here, we tested whether attention can alter the way multiple elements appear to be perceptually organized. We manipulated covert spatial attention using a rapid serial visual presentation task, and measured perceptual organization of two multielements arrays organized by luminance similarity as rows or columns, at both the attended and unattended locations. We found that the apparent perceptual organization of the multielement arrays is intensified when attended and attenuated when unattended. We ruled out response bias as an alternative explanation. These findings reveal that attention enhances the appearance of perceptual organization, a midlevel vision process, altering the way we perceive our visual environment.

Attention to distinguishing features in object recognition: An interactive-iterative framework.

This article advances a framework that casts object recognition as a process of discrimination between alternative object identities, in which top-down and bottom-up processes interact-iteratively when necessary-with attention to distinguishing features playing a critical role. In two experiments, observers discriminated between different types of artificial fish. In parallel, a secondary, variable-SOA visual-probe detection task was used to examine the dynamics of visual attention. In Experiment 1, the fish varied in three distinguishing features: one indicating the general category (saltwater, freshwater), and one of the two other features indicating the specific type of fish within each category. As predicted, in the course of recognizing each fish, attention was allocated iteratively to the distinguishing features in an optimal manner: first to the general category feature, and then, based on its value, to the second feature that identified the specific fish. In Experiment 2, two types of fish could be discriminated on the basis of either of two distinguishing features, one more visually discriminable than the other. On some of the trials, one of the two alternative distinguishing features was occluded. As predicted, in the course of recognizing each fish, attention was directed initially to the more discriminable distinguishing feature, but when this feature was occluded, it was then redirected to the less discriminable feature. The implications of these findings, and the interactive-iterative framework they support, are discussed with regard to several fundamental issues having a long history in the literatures on object recognition, object categorization, and visual perception in general.

Perceptual completion of partly occluded contours during childhood.

An early functional onset of perceptual completion has been extensively documented during the first several months after birth. However, there is no indication for the developmental time periods at which these skills become fully developed. We used a version of an object-based attention task in which children and adults performed a same-different size judgment of two features appearing at two of four possible ends of overlapping objects. Single-object over two-object superiority (i.e., faster judgments when the features appeared on the same object than when they appeared on different objects) was observed for a complete object as early as at 4 years of age. However, it is only at 5 years of age that such a single-object advantage was obtained also for an occluded object, and even then the advantage of the single-object and occluded-object conditions over the two-object condition was observed only when the two features in the two-object condition were spatially distant, demonstrating the critical role of spatial proximity in perceptual organization during childhood. The results suggest that perceptual completion during infancy and early childhood demonstrates some rudimentary perceptual skills that become more firmly established with age.

Crowding and perceptual organization: Target's objecthood influences the relative strength of part-level and configural-level crowding.

In visual crowding, identification of a peripheral object is impaired by nearby objects. Recent studies have demonstrated that crowding is not limited only to interaction between low-level features or parts, as presumed by most models of crowding, but can also occur between high-level, configural representations of objects. In this study we show that the relative strength of crowding at the part level versus the configural level is dependent on the strength of the target's perceptual organization. The target's strength of organization was manipulated by presence or absence of closure and good continuation or by proximity between the target's parts. The flankers were similar either to the target parts or to the target configuration. The stronger the target's organization was, the weaker the crowding was by part flankers (Experiments 1 and 2). Most importantly, the target's strength of organization interacted with target-flanker similarity, such that crowding by target-flanker similarity in configuration was greater than that by target-flanker similarity in parts for strongly organized targets, but lesser for weakly organized targets (Experiments 3 and 4). These results provide strong evidence that perceptual-organization processes play an important role in crowding.

Erratum to: Attention enhances apparent perceptual organization.

This paper originally published with graphical errors in Figures 1 and 4; it has been corrected.

Attentional requirements in perceptual grouping depend on the processes involved in the organization.

Previous studies on the role of attention in perceptual grouping have yielded contradicting findings, some suggesting that grouping requires attention and others indicating that it does not. Kimchi and Razpurker-Apfeld (Psychonomic Bulletin and Review, 11(4), 687-696, 2004) showed that attentional demands in grouping could vary according to the processes involved. The current study expanded on this, examining whether attentional demands vary for (a) different grouping principles and (b) as a function of contingent processing of element segregation and shape formation. We used the inattention paradigm with an online measure, in which participants engaged in an attentionally demanding change-detection task on a small matrix presented on a task-irrelevant backdrop of grouped elements. The backdrop grouping changed or stayed the same independently of any change in the target. Congruency effects produced by changes in backdrop grouping on target-change judgments indicate that the backdrop grouping was accomplished under inattention. The results showed congruency effects when grouping formed columns/rows by proximity but not by shape similarity, and when grouping into a distinct shape by collinearity did not involve element segregation. No congruency effects were found when grouping into a shape by collinearity or connectedness involved element segregation, except when connectedness was combined with color similarity. These results suggest that attentional demands depend on the combination of grouping principles and the complexity of the processes involved in the organization. These findings provide further support for the view that perceptual organization is a multiplicity of processes that vary in attentional demands.

Dissociating affective and semantic valence.

We examined the possible dissociation between two modes of valence: affective valence (valence of e emotional response) and semantic valence (stored knowledge about valence of an object or event). In Experiment 1, 50 participants viewed affective pictures that were repeatedly presented while their facial electromyography (EMG) activation and heart rate response were continuously recorded. Half of the participants provided self-report ratings about the valence of their feelings and half about the valence of the stimulus. Next, all participants performed an affective Simon task. In Experiment 2, 30 new participants performed the affective Simon task with the repeated exposure embedded within the task. The results showed that measures related to affective valence (feelings-focused self-reports, heart rate, and facial EMG activations) attenuated with repeated exposure to pleasant and unpleasant pictures, whereas measures related to semantic valence (knowledge-focused self-reports and congruency effect of affective Simon task) did not. These findings strongly suggest that affective and semantic valence represent two distinct psychological constructs. (PsycINFO Database Record

The time course of the competition between grouping organizations.

Previous research on the competition between grouping organizations focused mainly on their relative strength as measured by subjective reports of the final percept. Considerably less is known about the underlying representations of the competing organizations. We hypothesized that when more than 1 organization is possible, multiple representations are constructed for the alternative organizations. We tested this hypothesis using the primed-matching paradigm. Our primes depicted either a single grouping principle (grouping into columns or rows by brightness similarity, connectedness, or proximity) or 2 grouping principles (brightness similarity and connectedness, or brightness similarity and proximity) that led to competing organizations (e.g., grouping into columns by brightness similarity and into rows by connectedness, or vice versa). The time course of representation construction was examined by varying prime duration. Significant priming effects of similar magnitude were found for the individual grouping organizations. These effects were modified when 2 competing organizations were present in the prime, indicating that both organizations were represented and competed for dominancy. (PsycINFO Database Record

Figural properties are prioritized for search under conditions of uncertainty: Setting boundary conditions on claims that figures automatically attract attention.

Nelson and Palmer (2007) concluded that figures/figural properties automatically attract attention, after they found that participants were faster to detect/discriminate targets appearing where a portion of a familiar object was suggested in an otherwise ambiguous display. We investigated whether these effects are truly automatic and whether they generalize to another figural property-convexity. We found that Nelson and Palmer's results do generalize to convexity, but only when participants are uncertain regarding when and where the target will appear. Dependence on uncertainty regarding target location/timing was also observed for familiarity. Thus, although we could replicate and extend Nelson and Palmer's results, our experiments showed that figures do not automatically draw attention. In addition, our research went beyond Nelson and Palmer's, in that we were able to separate figural properties from perceived figures. Because figural properties are regularities that predict where objects lie in the visual field, our results join other evidence that regularities in the environment can attract attention. More generally, our results are consistent with Bayesian theories in which priors are given more weight under conditions of uncertainty.

Perceptual organization, visual attention, and objecthood.

We have previously demonstrated that the mere organization of some elements in the visual field into an object attracts attention automatically. Here, we explored three different aspects of this automatic attentional capture: (a) Does the attentional capture by an object involve a spatial component? (b) Which Gestalt organization factors suffice for an object to capture attention? (c) Does the strength of organization affect the object's ability to capture attention? Participants viewed multi-elements displays and either identified the color of one element or responded to a Vernier target. On some trials, a subset of the elements grouped by Gestalt factors into an object that was irrelevant to the task and not predictive of the target. An object effect - faster performance for targets within the object than for targets outside the object - was found even when the target appeared after the object offset, and was sensitive to target-object distance, suggesting that the capture of attention by an object is accompanied by a deployment of attention to the object location. Object effects of similar magnitude were found for objects grouped by a combination of factors (collinearity, closure, and symmetry, or closure and symmetry) or by a single factor when it was collinearity, but not symmetry, suggesting that collinearity, or closure combined with symmetry, suffices for automatic capture of attention by an object, but symmetry does not. Finally, the strength of grouping in modal completion, manipulated by varying contrast polarity between and within elements, affected the effectiveness of the attentional capture by the induced object.