Holistic processing is modulated by the probability that parts contain task-congruent information.

Holistic processing of face and non-face stimuli has been framed as a perceptual strategy, with classic hallmarks of holistic processing, such as the composite effect, reflecting a failure of selective attention, which is a consequence of this strategy. Further, evidence that holistic processing is impacted by training different patterns of attentional prioritization suggest that it may be a result of learned attention to the whole, which renders it difficult to attend to only part of a stimulus. If so, holistic processing should be modulated by the same factors that shape attentional selection, such as the probability that distracting or task-relevant information will be present. In contrast, other accounts suggest that it is the match to an internal face template that triggers specialized holistic processing mechanisms. Here we probed these accounts by manipulating the probability, across different testing sessions, that the task-irrelevant face part in the composite face task will contain task-congruent or -incongruent information. Attentional accounts of holistic processing predict that when the probability that the task-irrelevant part contains congruent information is low (25%), holistic processing should be attenuated compared to when this probability is high (75%). In contrast, template-based accounts of holistic face processing predict that it will be unaffected by manipulation given the integrity of the faces remains intact. Experiment 1 found evidence consistent with attentional accounts of holistic face processing and Experiment 2 extends these findings to holistic processing of non-face stimuli. These findings are broadly consistent with learned attention accounts of holistic processing.

Backward masking implicates cortico-cortical recurrent processes in convex figure context effects and cortico-thalamic recurrent processes in resolving figure-ground ambiguity.

Introduction: Previous experiments purportedly showed that image-based factors like convexity were sufficient for figure assignment. Recently, however, we found that the probability of perceiving a figure on the convex side of a central border was only slightly higher than chance for two-region displays and increased with the number of display regions; this increase was observed only when the concave regions were homogeneously colored. These convex figure context effects (CEs) revealed that figure assignment in these classic displays entails more than a response to local convexity. A Bayesian observer replicated the convex figure CEs using both a convexity object prior and a new, homogeneous background prior and made the novel prediction that the classic displays in which both the convex and concave regions were homogeneous were ambiguous during perceptual organization. Methods: Here, we report three experiments investigating the proposed ambiguity and examining how the convex figure CEs unfold over time with an emphasis on whether they entail recurrent processing. Displays were shown for 100 ms followed by pattern masks after ISIs of 0, 50, or 100 ms. The masking conditions were designed to add noise to recurrent processing and therefore to delay the outcome of processes in which they play a role. In Exp. 1, participants viewed two- and eight-region displays with homogeneous convex regions (homo-convex displays; the putatively ambiguous displays). In Exp. 2, participants viewed putatively unambiguous hetero-convex displays. In Exp. 3, displays and masks were presented to different eyes, thereby delaying mask interference in the thalamus for up to 100 ms. Results and discussion: The results of Exps. 1 and 2 are consistent with the interpretation that recurrent processing is involved in generating the convex figure CEs and resolving the ambiguity of homo-convex displays. The results of Exp. 3 suggested that corticofugal recurrent processing is involved in resolving the ambiguity of homo-convex displays and that cortico-cortical recurrent processes play a role in generating convex figure CEs and these two types of recurrent processes operate in parallel. Our results add to evidence that perceptual organization evolves dynamically and reveal that stimuli that seem unambiguous can be ambiguous during perceptual organization.

Understanding the encoding of object locations in small-scale spaces during free exploration using eye tracking.

Navigation is instrumental to daily life and is often used to encode and locate objects, such as keys in one's house. Yet, little is known about how navigation works in more ecologically valid situations such as finding objects within a room. Specifically, it is not clear how vision vs. body movements contribute differentially to spatial memory in such small-scale spaces. In the current study, participants encoded object locations by viewing them while standing (stationary condition) or by additionally being guided by the experimenter while blindfolded (walking condition) after viewing the objects. They then retrieved the objects from the same or different viewpoint, creating a 2 × 2 within subject design. We simultaneously recorded participant eye movements throughout the experiment using mobile eye tracking. The results showed no statistically significant differences among our four conditions (stationary, same viewpoint as encoding; stationary, different viewpoint; walking, same viewpoint; walking, different viewpoint), suggesting that in a small real-world space, vision may be sufficient to remember object locations. Eye tracking analyses revealed that object locations were better remembered next to landmarks and that participants encoded items on one wall together, suggesting the use of local wall coordinates rather than global room coordinates. A multivariate regression analysis revealed that the only significant predictor of object placement accuracy was average looking time. These results suggest that vision may be sufficient for encoding object locations in a small-scale environment and that such memories may be formed largely locally rather than globally.

BOLD activation on the groundside of figures: More suppression of grounds that competed more for figural status.

A fundamental aspect of object detection is assigning a border to one (figure) side but not the other (ground) side. Figures are shaped; grounds appear shapeless near the figure border. Accumulating evidence supports the view that the mechanism of figure assignment is inhibitory competition with the figure perceived on the winning side. Suppression has been observed on the groundside of figure borders. One prediction is that more suppression will be observed when the groundside competes more for figural status. We tested this prediction by assessing BOLD activation on the groundside of two types of stimuli with articulated borders: AEnov and AEfam stimuli. In both stimulus types, multiple image-based priors (symmetry, closure, small area, enclosure by a larger region) favored the inside as the figure. In AEfam but not AEnov stimuli, the figural prior of familiar configuration present on the outside competes for figural status. Observers perceived the insides of both types of stimuli as novel figures and the outsides as shapeless grounds. Previously, we observed lower BOLD activation in early visual areas representing the grounds of AEfam than AEnov stimuli, although unexpectedly, activation was above baseline. With articulated borders, it can be difficult to exclude figure activation from ground ROIs. Here, our ground ROIs better excluded figure activation; we also added straight-edge (SE) control stimuli and increased the sample size. In early visual areas representing the grounds, we observed lower BOLD activation on the groundside of AEfam than AEnov stimuli and below-baseline BOLD activation on the groundside of SE and AEfam stimuli. These results, indicating that greater suppression is applied to groundsides that competed more for figural status but lost the competition, support a Bayesian model of figure assignment in which proto-objects activated at both low and high levels where image features and familiar configurations are represented, respectively, compete for figural status.

Semantic Expectation Effects on Object Detection: Using Figure Assignment to Elucidate Mechanisms.

Recent evidence suggesting that object detection is improved following valid rather than invalid labels implies that semantics influence object detection. It is not clear, however, whether the results index object detection or feature detection. Further, because control conditions were absent and labels and objects were repeated multiple times, the mechanisms are unknown. We assessed object detection via figure assignment, whereby objects are segmented from backgrounds. Masked bipartite displays depicting a portion of a mono-oriented object (a familiar configuration) on one side of a central border were shown once only for 90 or 100 ms. Familiar configuration is a figural prior. Accurate detection was indexed by reports of an object on the familiar configuration side of the border. Compared to control experiments without labels, valid labels improved accuracy and reduced response times (RTs) more for upright than inverted objects (Studies 1 and 2). Invalid labels denoting different superordinate-level objects (DSC; Study 1) or same superordinate-level objects (SSC; Study 2) reduced accuracy for upright displays only. Orientation dependency indicates that effects are mediated by activated object representations rather than features which are invariant over orientation. Following invalid SSC labels (Study 2), accurate detection RTs were longer than control for both orientations, implicating conflict between semantic representations that had to be resolved before object detection. These results demonstrate that object detection is not just affected by semantics, it entails semantics.

Task set and instructions influence the weight of figural priors: A psychophysical study with extremal edges and familiar configuration.

In figure-ground organization, the figure is defined as a region that is both "shaped" and "nearer." Here we test whether changes in task set and instructions can alter the outcome of the cross-border competition between figural priors that underlies figure assignment. Extremal edge (EE), a relative distance prior, has been established as a strong figural prior when the task is to report "which side is nearer?" In three experiments using bipartite stimuli, EEs competed and cooperated with familiar configuration, a shape prior for figure assignment in a "which side is shaped?" task." Experiment 1 showed small but significant effects of familiar configuration for displays sketching upright familiar objects, although "shaped-side" responses were predominantly determined by EEs. In Experiment 2, instructions regarding the possibility of perceiving familiar shapes were added. Now, although EE remained the dominant prior, the figure was perceived on the familiar-configuration side of the border on a significantly larger percentage of trials across all display types. In Experiment 3, both task set (nearer/shaped) and the presence versus absence of instructions emphasizing that familiar objects might be present were manipulated within subjects. With familiarity thus "primed," effects of task set emerged when EE and familiar configuration favored opposite sides as figure. Thus, changing instructions can modulate the weighing of figural priors for shape versus distance in figure assignment in a manner that interacts with task set. Moreover, we show that the influence of familiar parts emerges in participants without medial temporal lobe/ perirhinal cortex brain damage when instructions emphasize that familiar objects might be present.

Learned value and predictiveness affect gaze but not figure assignment.

Many factors affect figure-ground segregation, but the contributions of attention and reward history to this process is uncertain. We conducted two experiments to investigate whether reward learning influences figure assignment and whether this relationship was mediated by attention. Participants learned to associate certain shapes with a reward contingency: During a learning phase, they chose between two shapes on each trial, with subsets of shapes associated with high-probability win, low-probability win, high-probability loss, and low-probability loss. In a test phase, participants were given a figure-ground task, in which they indicated which of two regions that shared a contour they perceived as the figure (high-probability win and low-probability win shapes were pitted against each other, as were high-probability loss and low-probability loss shapes). The results revealed that participants had learned the reward contingencies and that, following learning, attention was reliably drawn to the optimal stimulus. Despite this, neither reward history nor the resulting attentional allocation influenced figure-ground organization.

Author Correction: Prior Experience Alters the Appearance of Blurry Object Borders.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Normative data for an expanded set of stimuli for testing high-level influences on object perception: OMEFA-II.

We present normative data for an expanded set of stimuli designed to investigate past experience effects on object detection. The stimuli are vertically-elongated "bipartite" displays comprising two equal-area regions meeting at an articulated central border. When the central border is assigned to one side, a shaped figure (i.e., an object) is detected on that side. Participants viewing brief masked exposures typically detect figures more often on the critical side of Intact displays where a common ("familiar") object is depicted than on a matched critical side of Part-Rearranged (PR) displays comprising the same parts arranged in novel configurations. This pattern of results showed that past experience in the form of familiar configuration rather than familiar parts is a prior for figure assignment. Spurred by research implicating a network involving the perirhinal cortex of the medial temporal lobe in these familiar configuration effects, we enlarged the stimulus set from 24 to 48 base stimuli to increase its usefulness for behavioral, neuropsychological, and neuroimaging experiments. We measured the percentage of participants who agreed on a single interpretation for each side of Intact, Upright PR, and Inverted PR displays (144 displays; 288 sides) under long exposure conditions. High inter-subject agreement is taken to operationally define a familiar configuration. This new stimulus set is well-suited to investigate questions concerning how parts and wholes are integrated and how high- and low-level brain areas interact in object detection. This set also allows tests of predictions regarding cross-border competition in figure assignment and assessments of individual differences. The displays, their image statistics, and normative data are available online (https://osf.io/j9kz2/).

Prior Experience Alters the Appearance of Blurry Object Borders.

Object memories activated by borders serve as priors for figure assignment: figures are more likely to be perceived on the side of a border where a well-known object is sketched. Do object memories also affect the appearance of object borders? Memories represent past experience with objects; memories of well-known objects include many with sharp borders because they are often fixated. We investigated whether object memories affect appearance by testing whether blurry borders appear sharper when they are contours of well-known objects versus matched novel objects. Participants viewed blurry versions of one familiar and one novel stimulus simultaneously for 180 ms; then made comparative (Exp. 1) or equality judgments regarding perceived blur (Exps. 2-4). For equivalent levels of blur, the borders of well-known objects appeared sharper than those of novel objects. These results extend evidence for the influence of past experience to object appearance, consistent with dynamic interactive models of perception.

Limitations of Hoerl and McCormack's dual systems model of temporal consciousness.

Hoerl & McCormack's dual systems framework provides a new avenue toward the scientific investigation of temporal cognition. However, some shortcomings of the model should be considered. These issues include their reliance on a somewhat vague consideration of "systems" rather than specific computational processes. Moreover, the model does not consider the subjective nature of temporal experience or the role of consciousness in temporal cognition.

Semantic category priming from the groundside of objects shown in nontarget locations and at unpredictable times.

Previous research demonstrated that familiar objects that are suggested, but not consciously perceived, on the groundside of the contours of a figure activate their semantic category during perceptual organization, at least when the figure appears at fixation at an expected time. Here, we investigate whether evidence for such semantic activation extends to stimuli presented at unpredictable times in peripheral locations. Participants categorized words shown centrally as denoting natural or artificial objects (Experiments 1 and 2a) or positive or negative concepts (Experiment 2b). Prior to the word, two distractor silhouettes appeared above and below fixation; both depicted novel figures. On experimental trials, portions of well-known (familiar) objects were suggested on the groundside of the borders of one (Experiment 1) or both (Experiment 2a and 2b) silhouettes. In Experiment 1, reaction times were slower when targets words were preceded by experimental distractor silhouettes regardless of whether the object suggested on the groundside of their borders was in the same or a different category as the object denoted by the word. Overall slowing may have occurred because (a) semantic category access by objects suggested on the groundside of experimental distractor silhouettes was sufficient to require filtering but not category-specific priming, (b) more competition for object status slowed processing of experimental compared to control silhouettes, or (c) featural differences increased the difficulty of processing the experimental versus the control silhouettes. The use of two identical experimental silhouettes in Experiment 2a allowed a semantic category priming effect to emerge, showing that the categories of objects suggested on the groundside of silhouette borders can be activated at unpredictable times in nontarget locations and in more than one location of the visual field. Experiment 2a suggested that (a) better explains the results of Experiment 1 than (b and c). Experiment 2b further ruled out explanations (b and c) as reasons for the Experiment 1 results by showing that the same pattern is not obtained when the semantic category of the objects suggested on the groundside of the experimental silhouettes borders is not task-relevant and does not require filtering. Thus, spatial prime-target congruence and temporal certainty are not necessary for priming by objects suggested on the groundside of figures. Implications for our understanding of the complex processes involved in perceptual organization are considered.

Age-Related Changes in Perirhinal Cortex Sensitivity to Configuration and Part Familiarity and Connectivity to Visual Cortex.

The perirhinal cortex (PRC) is a medial temporal lobe (MTL) structure known to be involved in assessing whether an object is familiar (i.e., meaningful) or novel. Recent evidence shows that the PRC is sensitive to the familiarity of both whole object configurations and their parts, and suggests the PRC may modulate part familiarity responses in V2. Here, using functional magnetic resonance imaging (fMRI), we investigated age-related decline in the PRC's sensitivity to part/configuration familiarity and assessed its functional connectivity to visual cortex in young and older adults. Participants categorized peripherally presented silhouettes as familiar ("real-world") or novel. Part/configuration familiarity was manipulated via three silhouette configurations: Familiar (parts/configurations familiar), Control Novel (parts/configurations novel), and Part-Rearranged Novel (parts familiar, configurations novel). "Real-world" judgments were less accurate than "novel" judgments, although accuracy did not differ between age groups. The fMRI data revealed differential neural activity, however: In young adults, a linear pattern of activation was observed in left hemisphere (LH) PRC, with Familiar > Control Novel > Part-Rearranged Novel. Older adults did not show this pattern, indicating age-related decline in the PRC's sensitivity to part/configuration familiarity. A functional connectivity analysis revealed a significant coupling between the PRC and V2 in the LH in young adults only. Older adults showed a linear pattern of activation in the temporopolar cortex (TPC), but no evidence of TPC-V2 connectivity. This is the first study to demonstrate age-related decline in the PRC's representations of part/configuration familiarity and its covariance with visual cortex.

Effects of aging on figure-ground perception: Convexity context effects and competition resolution.

We examined age-related differences in figure-ground perception by exploring the effect of age on Convexity Context Effects (CCE; Peterson & Salvagio, 2008). Experiment 1, using Peterson and Salvagio's procedure and black and white stimuli consisting of 2 to 8 alternating concave and convex regions, established that older adults exhibited reduced CCEs compared to younger adults. Experiments 2 and 3 demonstrated that this age difference was found at various stimulus durations and sizes. Experiment 4 compared CCEs obtained with achromatic stimuli, in which the alternating convex and concave regions were each all black or all white, and chromatic stimuli in which the concave regions were homogeneous in color but the convex regions varied in color. We found that the difference between CCEs measured with achromatic and colored stimuli was larger in older than in younger adults. Our results are consistent with the hypothesis that the senescent visual system is less able to resolve the competition among various perceptual interpretations of the figure-ground relations among stimulus regions.

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.

A behavioral task sets an upper bound on the time required to access object memories before object segregation.

Traditional theories of vision assume that object segregation occurs before access to object memories. Yet, behavioral evidence shows that familiar configuration is a prior for segregation, and electrophysiological experiments demonstrate these memories are accessed rapidly. A behavioral index of the speed of access is lacking, however. Here we asked how quickly behavior is influenced by object memories that are accessed in the course of object segregation. We investigated whether access to object memories on the groundside of a border can slow behavior during a rapid categorization task. Participants viewed two silhouettes that depicted a real-world and a novel object. Their task was to saccade toward the real-world object as quickly as possible. Half of the nontarget novel objects were ambiguous in that a portion of a real-world object was suggested, but not consciously perceived, on the groundside of their borders. The rest of the nontargets were unambiguous. We tested whether saccadic reaction times were perturbed by the real-world objects suggested on the groundside of ambiguous novel silhouettes. In Experiments 1 and 2, saccadic reaction times were slowed when nontargets were ambiguous rather than unambiguous. Experiment 2 set an upper limit of 190 ms on the time required for object memories in grounds to influence behavior. Experiment 3 ruled out factors that could have produced longer latencies other than access to object memories. These results provide the first behavioral index of how quickly memories of objects suggested in grounds can influence behavior, placing the upper limit at 190 ms.

Age-related deficits in inhibition in figure-ground assignment.

We assessed age differences in the ability to resolve competition for figural status in stationary displays using small, enclosed, symmetrical silhouettes that participants classified as depicting "novel" or "familiar" shapes. The silhouettes were biased such that the inside was perceived as the shaped figure, and the outside was perceived as a shapeless ground. The critical manipulation was whether a portion of a meaningful object was suggested on the outside of the border of some of the novel silhouettes but not others (M+Ground and M-Ground novel silhouettes, respectively). This manipulation was intended to induce greater inhibitory competition for figural status from the groundside in M+Ground silhouettes than M-Ground silhouettes. In previous studies, young adults classified M+Ground silhouettes as "novel" faster than M-Ground silhouettes (Trujillo, Allen, Schnyer, & Peterson, 2010), suggesting that young adults may recruit more inhibition to resolve figure-ground when there is more competition. We replicated this effect with young adults in the present study, but older adults showed the opposite pattern and were less accurate in classifying M+Ground than M-Ground silhouettes. These results extend the evidence for inhibitory deficits in older adults to figure assignment in stationary displays. The (M+Ground - M-Ground) RT differences were evident in observers' longest responses, consistent with the hypothesis that inhibitory deficits are evident when the need for inhibition is substantial.

Increased alpha band activity indexes inhibitory competition across a border during figure assignment.

Figure-ground assignment is thought to entail inhibitory competition between potential objects on opposite sides of a shared border; the winner is perceived as the figure, and the loser as the shapeless ground. Computational models and response time measures support this understanding but to date no online measure of inhibitory competition during figure-ground assignment has been reported. The current study assays electroencephalogram (EEG) alpha power as a measure of inhibitory competition during figure-ground assignment. Activity in the EEG alpha band has been linked to functional inhibition in the brain, and it has been proposed that increased alpha power reflects increased inhibition. In 2 experiments participants viewed silhouettes designed so that the insides would be perceived as figures. Real-world silhouettes depicted namable objects. Novel silhouettes depicted novel objects on the insides of their borders, but varied in the amount of hypothesized cross-border competition for figural status: In "Low-Competition" silhouettes, the borders suggested novel objects on the outside as well as on the inside. In "High-Competition" silhouettes the borders suggested portions of real-world objects on the outside; these compete with the figural properties favoring the inside as figure. Participants accurately categorized both types of novel silhouettes as "novel" objects and were unaware of the real world objects suggested on the outside of the High-Competition silhouettes. In both experiments, we observed more alpha power while participants viewed High- rather than Low-Competition novel silhouettes. These are the first results to show via an online index of neural activity that figure assignment entails inhibitory competition.

Neural evidence for competition-mediated suppression in the perception of a single object.

Multiple objects compete for representation in visual cortex. Competition may also underlie the perception of a single object. Computational models implement object perception as competition between units on opposite sides of a border. The border is assigned to the winning side, which is perceived as an object (or "figure"), whereas the other side is perceived as a shapeless ground. Behavioral experiments suggest that the ground is inhibited to a degree that depends on the extent to which it competed for object status, and that this inhibition is relayed to low-level brain areas. Here, we used fMRI to assess activation for ground regions of task-irrelevant novel silhouettes presented in the left or right visual field (LVF or RVF) while participants performed a difficult task at fixation. Silhouettes were designed so that the insides would win the competition for object status. The outsides (grounds) suggested portions of familiar objects in half of the silhouettes and novel objects in the other half. Because matches to object memories affect the competition, these two types of silhouettes operationalized, respectively, high competition and low competition from the grounds. The results showed that activation corresponding to ground regions was reduced for high- versus low-competition silhouettes in V4, where receptive fields (RFs) are large enough to encompass the familiar objects in the grounds, and in V1/V2, where RFs are much smaller. These results support a theory of object perception involving competition-mediated ground suppression and feedback from higher to lower levels. This pattern of results was observed in the left hemisphere (RVF), but not in the right hemisphere (LVF). One explanation of the lateralized findings is that task-irrelevant silhouettes in the RVF captured attention, allowing us to observe these effects, whereas those in the LVF did not. Experiment 2 provided preliminary behavioral evidence consistent with this possibility.