Can you perceive ensembles without perceiving individuals?: The role of statistical perception in determining whether awareness overflows access

More than words: can free reports adequately measure the richness of perception?

The question of the richness (or sparseness) of conscious experience has evoked ongoing debate and discussion. Claims for both richness and sparseness are supported by empirical data, yet they are often indirect, and alternative explanations have been put forward. Recently, it has been suggested that current experimental methods limit participants' responses, thereby preventing researchers from assessing the actual richness of perception. Instead, free verbal reports were presented as a possible way to overcome this limitation. As part of this approach, a novel paradigm of freely reported words was developed using a new metric, intersubjective agreement (IA), with experimental results interpreted as capturing aspects of conscious perception. Here, we challenge the validity of freely reported words as a tool for studying the richness of conscious experience. We base our claims on two studies (each composed of three experiments), where we manipulated the richness of percepts and tested whether IA changed accordingly. Five additional control experiments were conducted to validate the experimental logic and examine alternative explanations. Our results suggest otherwise, presenting four challenges to the free verbal report paradigm: first, impoverished stimuli did not evoke lower IA scores. Second, the IA score was correlated with word frequency in English. Third, the original positive relationship between IA scores and rated confidence was not found in any of the six experiments. Fourth, a high rate of nonexisting words was found, some of which described items that matched the gist of the scene but did not appear in the image. We conclude that a metric based on freely reported words might be better explained by vocabulary conventions and gist-based reports than by capturing the richness of perception.

Variance aftereffect within and between sensory modalities for visual and auditory domains

We can grasp various features of the outside world using summary statistics efficiently. Among these statistics, variance is an index of information homogeneity or reliability. Previous research has shown that visual variance information in the context of spatial integration is encoded directly as a unique feature, and currently perceived variance can be distorted by that of the preceding stimuli. In this study, we focused on variance perception in temporal integration. We investigated whether any variance aftereffects occurred in visual size and auditory pitch. Furthermore, to examine the mechanism of cross-modal variance perception, we also investigated whether variance aftereffects occur between different modalities. Four experimental conditions (a combination of sensory modalities of adaptor and test: visual-to-visual, visual-to-auditory, auditory-to-auditory, and auditory-to-visual) were conducted. Participants observed a sequence of visual or auditory stimuli perturbed in size or pitch with certain variance and performed a variance classification task before and after the variance adaptation phase. We found that in visual size, within modality adaptation to small or large variance, resulted in a variance aftereffect, indicating that variance judgments are biased in the direction away from that of the adapting stimulus. In auditory pitch, within modality adaptation to small variance caused variance aftereffect. For cross-modal combinations, adaptation to small variance in visual size resulted in variance aftereffect. However, the effect was weak, and variance aftereffect did not occur in other conditions. These findings indicate that the variance information of sequentially presented stimuli is encoded independently in visual and auditory domains.

A signal-detection account of item-based and ensemble-based visual change detection: A reply to Harrison, McMaster, and Bays

Growing empirical evidence shows that ensemble information (e.g., the average feature or feature variance of a set of objects) affects visual working memory for individual items. Recently, Harrison, McMaster, and Bays (2021) used a change detection task to test whether observers explicitly rely on ensemble representations to improve their memory for individual objects. They found that sensitivity to simultaneous changes in all memorized items (which also globally changed set summary statistics) rarely exceeded a level predicted by the so-called optimal summation model within the signal-detection framework. This model implies simple integration of evidence for change from all individual items and no additional evidence coming from ensemble. Here, we argue that performance at the level of optimal summation does not rule out the use of ensemble information. First, in two experiments, we show that, even if evidence from only one item is available at test, the statistics of the whole memory set affect performance. Second, we argue that optimal summation itself can be conceptually interpreted as one of the strategies of holistic, ensemble-based decision. We also redefine the reference level for the item-based strategy as the so-called "minimum rule," which predicts performance far below the optimum. We found that that both our and Harrison et al. (2021)'s observers consistently outperformed this level. We conclude that observers can rely on ensemble information when performing visual change detection. Overall, our work clarifies and refines the use of signal-detection analysis in measuring and modeling working memory.

Remembering Sets: Capacity Limit and Time Limit of Ensemble Representations in Working Memory

In a constantly changing visual environment, the ability to extract and store ensemble representations plays a crucial role in efficiently processing and remembering complex visual information. However, how working memory maintains these ensemble representations remains unclear. Therefore, the present study aimed to investigate the limits and characteristics of ensemble representations in working memory using a change detection paradigm. Participants were presented with multiple sets of circles grouped by spatial proximity and were asked to memorize the mean diameter of the circles in each set. Results showed that working memory could stably maintain mean sizes of approximately two sets for at least four seconds. Moreover, the memory performance of ensembles was not affected by the number of circles within a set, suggesting that individual details were not stored in working memory. These results suggest that the visual system can effectively store ensembles in working memory without preserving detailed individual information.

A quantitative model of ensemble perception as summed activation in feature space

Ensemble perception is a process by which we summarize complex scenes. Despite the importance of ensemble perception to everyday cognition, there are few computational models that provide a formal account of this process. Here we develop and test a model in which ensemble representations reflect the global sum of activation signals across all individual items. We leverage this set of minimal assumptions to formally connect a model of memory for individual items to ensembles. We compare our ensemble model against a set of alternative models in five experiments. Our approach uses performance on a visual memory task for individual items to generate zero-free-parameter predictions of interindividual and intraindividual differences in performance on an ensemble continuous-report task. Our top-down modelling approach formally unifies models of memory for individual items and ensembles and opens a venue for building and comparing models of distinct memory processes and representations.

Role of facial familiarity and emotional expression intensity in ensemble emotion perception

When looking at groups of people, we can extract information from the different faces to derive properties of the group, such as its average facial emotion, although how this average is computed remains a matter of debate. Here, we examined whether our participants' personal familiarity with the faces in the group, as well as the intensity of the facial expressions, biased ensemble perception. Participants judged the average emotional expression of ensembles of four different identities whose expressions depicted either neutral, angry, or happy emotions. For the angry and happy expressions, the intensity of the emotion could be either low (e.g., slightly happy) or high (very happy). When all the identities in the ensemble were unfamiliar, the presence of any high intensity emotional face biased ensemble perception towards its emotion. However, when a familiar face was present in the ensemble, perception was biased towards the familiar face's emotion regardless of its intensity. These findings reveal that how we perceive the average emotion of a group is influenced by both the emotional intensity and familiarity of the faces comprising the group, supporting the idea that different faces may be weighted differently in ensemble perception. These findings have important implications for the judgements we make about a group's overall emotional state may be biased by individuals within the group.

Keeping quantifier meaning in mind: Connecting semantics, cognition, and pragmatics

A complete theory of the meaning of linguistic expressions needs to explain their semantic properties, their links to non-linguistic cognition, and their use in communication. Even though in principle interconnected, these areas are generally not pursued in tandem. We present a novel take on the semantics-cognition-pragmatics interface. We propose that formal semantic differences in expressions' meanings lead those meanings to activate distinct cognitive systems, which in turn have downstream effects on when speakers prefer to use those expressions. As a case study, we focus on the quantifiers "each" and "every", which can be used to talk about the same state of the world, but have been argued to differ in meaning. In particular, we adopt a mentalistic proposal about these quantifiers on which "each" has a purely individualistic meaning that interfaces with the psychological system for representing object-files, whereas "every" has a meaning that implicates a group and interfaces with the psychological system for representing ensembles. In seven experiments, we demonstrate that this account correctly predicts both known and newly-observed constraints on how "each" and "every" are pragmatically used. More generally, this integrated approach to semantics, cognition, and pragmatics suggests that canonical patterns of language use can be affected in predictable ways by fine-grained differences in semantic meanings and the cognitive systems to which those meanings connect.

Color diversity judgments in peripheral vision: Evidence against "cost-free" representations

Is visual perception "rich" or "sparse?" One finding supporting the "rich" hypothesis shows that a specific visual summary representation, color diversity, is represented "cost-free" outside focally-attended regions in dual-task paradigms [1]. Here, we investigated whether this "cost-free" phenomenon for color diversity perception extends to peripheral vision. After replicating previous findings and verifying that color diversity is represented "cost-free" in central vision, we performed two experiments: in our first experiment, we extended the paradigm to peripheral vision and found that in minimally-attended regions of space, color diversity perception was impaired. In a second and final experiment, we added confidence judgments to our task, and found that participants maintained high levels of metacognitive awareness of impaired performance in minimally-attended visual areas in the periphery. These findings provide evidence that color perception may be partially attention-dependent in peripheral vision, and challenge previous views on both sides of the rich vs. sparse debate.

On the relation between crowding and ensemble perception: Examining the role of attention

Ensemble perception of a crowd of stimuli is very accurate, even when individual stimuli are invisible due to crowding. The ability of high-precision ensemble perception can be an evolved compensatory mechanism for the limited attentional resolution caused by crowding. Thus the relationship of crowding and ensemble coding is like two sides of the same coin wherein attention may play a critical factor for their coexistence. The present study investigated whether crowding and ensemble coding were similarly modulated by attention, which can promote our understanding of their relation. Experiment 1 showed that diverting attention away from the target harmed the performance in both crowding and ensemble perception tasks regardless of stimulus density, but crowding was more severely harmed. Experiment 2 showed that directing attention toward the target bar enhanced the performance of crowding regardless of stimulus density. Ensemble perception of high-density bars was also enhanced but to a lesser extent, while ensemble perception of low-density bars was harmed. Together, our results indicate that crowding is strongly modulated by attention, whereas ensemble perception is only moderately modulated by attention, which conforms to the adaptive view.

Finding meaning in "wrong responses": The multiple object-awareness paradigm shows that visual awareness is probabilistic

Visual information that observers perceive and remember at any given moment guides behavior in daily life. However, binary alternative-forced choice responses, often used in visual research, limit the report of the visual information that observers perceive and remember. We used a new multiple object-awareness paradigm where observers can use multiple clicks to find a target. We calculated visual awareness capacity based on the first-attempt accuracy and the total number of clicks, respectively. Results showed that the capacity estimated by the clicks in guessing from N was significantly greater than that estimated by the first-attempt accuracy. Further, analysis found that if observers could not locate the target in their first attempt, they were more likely to click closer to the target or on stimuli that matched its color. In addition, we found that even when observers used the same number of clicks to find a target (2 or 3), the average distance was shorter when observers reported high-level subjective visibility. The findings are compatible with the partial awareness hypothesis, and the visual ensembles and summary statistics hypothesis, which hold that visual awareness is probabilistic. These results also support the visual short-term memory models where many items are stored but with a resolution or noise level that depends on the number of items in memory.

No effect of spatial attention on the processing of a motion ensemble: Evidence from Posner cueing

The formation of ensemble codes is an efficient means through which the visual system represents vast arrays of information. This has led to the claim that ensemble representations are formed with minimal reliance on attentional resources. However, evidence is mixed regarding the effects of attention on ensemble processing, and researchers do not always make it clear how attention is being manipulated by their paradigm of choice. In this study, we examined the effects of Posner cueing - a well-established method of manipulating spatial attention - on the processing of a global motion stimulus, a naturalistic ensemble that requires the pooling of local motion signals. In Experiment 1, using a centrally presented, predictive attentional cue, we found no effect of spatial attention on global motion performance: Accuracy in invalid trials, where attention was misdirected by the cue, did not differ from accuracy in valid trials, where attention was directed to the location of the motion stimulus. In Experiment 2, we maximized the potential for our paradigm to reveal any attentional effects on global motion processing by using a threshold-based measure of performance; however, despite this change, there was again no evidence of an attentional effect on performance. Together, our results show that the processing of a global motion stimulus is unaffected when spatial attention is misdirected, and speak to the efficiency with which such ensemble stimuli are processed.

Extracting Summary Statistics of Rapid Numerical Sequences

We examine the ability of observers to extract summary statistics (such as the mean and the relative-variance) from rapid numerical sequences of two digit numbers presented at a rate of 4/s. In four experiments (total N = 100), we find that the participants show a remarkable ability to extract such summary statistics and that their precision in the estimation of the sequence-mean improves with the sequence-length (subject to individual differences). Using model selection for individual participants we find that, when only the sequence-average is estimated, most participants rely on a holistic process of frequency based estimation with a minority who rely on a (rule-based and capacity limited) mid-range strategy. When both the sequence-average and the relative variance are estimated, about half of the participants rely on these two strategies. Importantly, the holistic strategy appears more efficient in terms of its precision. We discuss implications for the domains of two pathways numerical processing and decision-making.

Is the n-back task a measure of unstructured working memory capacity? Towards understanding its connection to other working memory tasks

Working memory is fundamental to human cognitive functioning, and it is often measured with the n-back task. However, it is not clear whether the n-back task is a valid measure of working memory. Importantly, previous studies have found poor correlations with measures of complex span, whereas a recent study (Frost et al., 2019) showed that n-back performance was correlated with a transsaccadic memory task but dissociated from performance on the change detection task, a well-accepted measure of working memory capacity. To test whether capacity is involved in the n-back task we correlated a spatial version of the test with different versions of the change detection task. Experiment 1 introduced perceptual and cognitive disruptions to the change detection task. This impacted task performance, however, all versions of the change detection task remained highly correlated with one another whereas there was no significant correlation with the n-back task. Experiment 2 removed spatial and non-spatial context from the change detection task. This produced a correlation with n-back. Our results indicate that the n-back task is supported by faculties similar to those that support change detection, but that this commonality is hidden when contextual information is available to be exploited in a change detection task such that structured representations can form. We suggest that n-back might be a valid measure of working memory, and that the ability to exploit contextual information is an important faculty captured by some versions of the change detection task.

Measures of explicit and implicit in motor learning: what we know and what we don't

Adaptation tasks are a key tool in characterizing the contribution of explicit and implicit processes to sensorimotor learning. However, different assumptions and ideas underlie methods used to measure these processes, leading to inconsistencies between studies. For instance, it is still unclear explicit and implicit combine additively. Cognitive studies of explicit and implicit processes show how non-additivity and bias in measurement can distort results. We argue that to understand explicit and implicit processes in visuomotor adaptation, we need a stronger characterization of the phenomenology and a richer set of models to test it on.

Ensemble perception without attention depends upon attentional control settings

People are able to rapidly extract summary statistical information about common patterns, or ensembles, that may exist in a scene, such as repeated textures or colors. Here we examined the extent to which such an ensemble perception can occur in the absence of focal visual attention using a method that has some advantages over methods previously used to study the issue. In particular, we assessed the extent to which ensembles can be processed without attention by measuring the indirect effect of a to-be-ignored ensemble on judgments of an attended ensemble. The results show that ensembles outside the focus of attention do influence judgments of attended ensembles when the to-be-ignored ensemble contains summary statistics that match a sought-for target category. Thus, an attentional control setting for specific summary statistical information permits the processing of ensembles outside of focal attention, facilitating the rapid perception of visual scenes.

Partial awareness can be induced by independent cognitive access to different spatial frequencies

Partial awareness-an intermediate state between complete consciousness and unconsciousness-has been explained by independent cognitive access to different levels of representation in hierarchical visual processing. This account, however, cannot explain graded visual experiences in low levels. We aimed to explain partial awareness in low levels of visual processing by independent cognitive access to different spatial frequencies. To observe partial awareness stably, we used a novel method. Stimuli were presented briefly (12 ms) and repeatedly with a specific inter-stimulus interval, ranging from 0 to 235 ms. By using various stimuli containing high and low spatial frequencies (superimposed sinusoidal gratings, Navon letters, and scenes), we found that conscious percept was degraded with increasing inter-stimulus intervals. However, the degree of degradation was smaller for low spatial frequency than for high spatial frequency information. Our results reveal that cognitive access to different spatial frequencies can occur independently and this can explain partial awareness in low levels of visual processing.

Variability leads to overestimation of mean summaries

Research on ensemble perception has shown that people can extract both mean and variance information, but much less is understand how these two different types of summaries interact with one another. Some research has argued that people are more erroneous in extracting the mean of displays that have greater variability. In all three experiments, we manipulated the variability in the displays. Participants reported the mean size of a set of circles (Experiment 1) and mean length of horizontally placed (Experiment 2a) and randomly oriented lines (Experiment 2b). In all experiments, we found that mean size estimations were more erroneous for higher than smaller variance displays. More critically, there was a tendency to overestimate the mean, driven by variance in both task-relevant and task-irrelevant features. We discuss these findings in relation to limitations in concurrent summarization ability and outlier discounting in ensemble perception.

Contributions of ensemble perception to outlier representation precision

It is known that the visual system can efficiently extract mean and variance information, facilitating the detection of outliers. However, no research to date has directly investigated whether ensemble perception mechanisms contribute to outlier representation precision. We specifically were interested in how the distinctiveness of outliers impacts their precision. Across two experiments, we compared how accurately viewers represented the orientation of spatial outliers that varied in distinctiveness and found that increased outlier distinctiveness resulted in greater precision. Based on comparisons of our data to simulations reflecting particular selective strategies, we eliminated the possibility that participants were selectively processing the outlier, at the expense of the ensemble. Thus, we argued that participants separately represented distinct outliers along with ensemble summaries of the remaining items in a display. We also found that outlier distinctiveness moderated the precision of how the remaining items were summarized. We discuss these findings in relation to computational capacity and constraints of ensemble perception mechanisms.

Perceived variability reflects the reliability of individual items

When confronted with many visual items, people can compute their variability accurately and rapidly, which facilitates efficient information processing and optimal decision making. However, how the visual system computes variability is still unclear. To investigate this, we implemented situations whereby estimates of variability based on several possible variability measures (e.g., range, standard deviation, and weighted standard deviation) could be differentiated, and then examined which best accounted for human variability perception. In three psychophysical experiments, participants watched two arrays of items with various orientations and judged which had more variable orientations. Results showed that perceived variability was most consistent with the weighted standard deviation based on the reliability of individual items. Specifically, participants gave less consideration to deviant orientations that were likely to be outliers, and greater consideration to salient orientations that were likely to be encoded precisely. This reliability-based weighted standard deviation suggests an efficient and flexible way of representing visual variability.

Global and local interference effects in ensemble encoding are best explained by interactions between summary representations of the mean and the range

Through ensemble encoding, the visual system compresses redundant statistical properties from multiple items into a single summary metric (e.g., average size). Numerous studies have shown that global summary information is extracted quickly, does not require access to single-item representations, and often interferes with reports of single items from the set. Yet a thorough understanding of ensemble processing would benefit from a more extensive investigation at the local level. Thus, the purpose of this study was to provide a more critical inspection of global-local processing in ensemble perception. Taking inspiration from Navon (Cognitive Psychology, 9(3), 353-383, 1977), we employed a novel paradigm that independently manipulates the degree of interference at the global (mean) or local (single item) level of the ensemble. Initial results were consistent with reciprocal interference between global and local ensemble processing. However, further testing revealed that local interference effects were better explained by interference from another summary statistic, the range of the set. Furthermore, participants were unable to disambiguate single items from the ensemble display from other items that were within the ensemble range but, critically, were not actually present in the ensemble. Thus, it appears that local item values are likely inferred based on their relationship to higher-order summary statistics such as the range and the mean. These results conflict with claims that local information is captured alongside global information in summary representations. In such studies, successful identification of set members was not compared with misidentification of items within the range, but which were nevertheless not presented within the set.

Synergy between research on ensemble perception, data visualization, and statistics education: A tutorial review

In the age of big data, we are constantly inventing new data visualizations to consolidate massive amounts of numerical information into smaller and more digestible visual formats. These data visualizations use various visual features to convey quantitative information, such as spatial position in scatter plots, color saturation in heat maps, and area in dot maps. These data visualizations are typically composed of ensembles, or groups of related objects, that together convey information about a data set. Ensemble perception, or one's ability to perceive summary statistics from an ensemble, such as the mean, has been used as a foundation for understanding and explaining the effectiveness of certain data visualizations. However, research in data visualization has revealed some perceptual biases and conceptual difficulties people face when trying to utilize the information in these graphs. In this tutorial review, we will provide a broad overview of research conducted in ensemble perception, discuss how principles of ensemble encoding have been applied to the research in data visualization, and showcase the barriers graphs can pose to learning statistical concepts, using histograms as a specific example. The goal of this tutorial review is to highlight possible connections between three areas of research-ensemble perception, data visualization, and statistics education-and to encourage research in the practical applications of ensemble perception in solving real-world problems in statistics education.

Defending subjective inflation: an inference to the best explanation

In a recent opinion piece, Abid (2019) criticizes the hypothesis that subjective inflation may partly account for apparent phenomenological richness across the visual field and outside the focus of attention. In response, we address three main issues. First, we maintain that inflation should be interpreted as an intraperceptual-and not post-perceptual-phenomenon. Second, we describe how inflation may differ from filling-in. Finally, we contend that, in general, there is sufficient evidence to tip the scales toward intraperceptual interpretations of visibility and confidence judgments.

Ensemble coding of crowd speed using biological motion

The accurate perception of human crowds is integral to social understanding and interaction. Previous studies have shown that observers are sensitive to several crowd characteristics such as average facial expression, gender, identity, joint attention, and heading direction. In two experiments, we examined ensemble perception of crowd speed using standard point-light walkers (PLW). Participants were asked to estimate the average speed of a crowd consisting of 12 figures moving at different speeds. In Experiment 1, trials of intact PLWs alternated with trials of scrambled PLWs with a viewing duration of 3 seconds. We found that ensemble processing of crowd speed could rely on local motion alone, although a globally intact configuration enhanced performance. In Experiment 2, observers estimated the average speed of intact-PLW crowds that were displayed at reduced viewing durations across five blocks of trials (between 2500 ms and 500 ms). Estimation of fast crowds was precise and accurate regardless of viewing duration, and we estimated that three to four walkers could still be integrated at 500 ms. For slow crowds, we found a systematic deterioration in performance as viewing time reduced, and performance at 500 ms could not be distinguished from a single-walker response strategy. Overall, our results suggest that rapid and accurate ensemble perception of crowd speed is possible, although sensitive to the precise speed range examined.

Implicit processing during inattentional blindness: A systematic review and meta-analysis

The occurrence of implicit processing of visual stimuli during inattentional blindness is still a matter of debate. To assess the evidence available in this debate, we conducted a systematic review of articles that explored whether unexpected visual stimuli presented during inattentional blindness are implicitly processed despite not being reported. Additionally, we employed meta-analysis to combine 59 behavioral experiments and investigate the statistical support for such implicit processing across experiments. Results showed that visual stimuli can be processed when unattended and unnoticed. Additionally, we reviewed the measures used to assess participants' awareness of the unexpected stimuli. We also employed meta-analysis to search for differences in awareness of the unexpected stimuli that may result from adopting distinct criteria to categorize participants as aware or unaware. The results showed that the overall effect of awareness changed depending on whether more demanding or less demanding measures of awareness were employed. This suggests that the choice of awareness measure may influence conclusions about whether processing of the US is implicit or explicit. We discuss the implications of these results for the study of implicit processing and the role of attention in visual cognition.

Awareness and Stimulus-Driven Spatial Attention as Independent Processes

To investigate the relation between attention and awareness, we manipulated visibility/awareness and stimulus-driven attention capture among metacontrast-masked visual stimuli. By varying the time interval between target and mask, we manipulated target visibility measured as target discrimination accuracies (ACCs; Experiments 1 and 2) and as subjective awareness ratings (Experiment 3). To modulate stimulus-driven attention capture, we presented the masked target either as a color-singleton (the target stands out by its unique color among homogeneously colored non-singletons), as a non-singleton together with a distractor singleton elsewhere (an irrelevant distractor has a unique color, whereas the target is colored like the other stimuli) or without a singleton (no stimulus stands out; only in Experiment 1). As color singletons capture attention in a stimulus-driven way, we expected target visibility/discrimination performance to be best for target singletons and worst with distractor singletons. In Experiments 1 and 2, we confirmed that the masking interval and the singleton manipulation influenced ACCs in an independent way and that attention capture by the singletons, with facilitated performance in target-singleton compared to distractor-singleton conditions, was found regardless of the interval-induced (in-)visibility of the targets. In Experiment 1, we also confirmed that attention capture was the same among participants with worse and better visibility/discrimination performance. In Experiment 2, we confirmed attention capture by color singletons with better discrimination performance for probes presented at singleton position, compared to other positions. Finally, in Experiment 3, we found that attention capture by target singletons also increased target awareness and that this capture effect on subjective awareness was independent of the effect of the masking interval, too. Together, results provide new evidence that stimulus-driven attention and awareness operate independently from one another and that stimulus-driven attention capture can precede awareness.

Adaptation to mean and variance: Interrelationships between mean and variance representations in orientation perception

When there are many visual items, the visual system could represent their summary statistics (e.g., mean, variance) to process them efficiently. Although many previous studies have investigated the mean or variance representation itself, a relationship between these two ensemble representations has not been investigated much. In this study, we tested the potential interaction between mean and variance representations by using a visual adaptation method. We reasoned that if mean and variance representations interact with each other, an adaptation aftereffect to either mean or variance would influence the perception of the other. Participants watched a sequence of orientation arrays containing a specific statistical property during the adaptation period. To produce an adaptation aftereffect specific to variance or mean, one property of the adaptor arrays (variance or mean) had a fixed value while the other property was randomly varied. After the adaptation, participants were asked to discriminate the property of the test array that was randomly varied during the adaptation. We found that the adaptation aftereffect of orientation variance influenced the sensitivity of mean orientation discrimination (Experiment 1), and that the adaptation aftereffect of mean orientation influenced the bias of orientation variance discrimination (Experiment 2). These results suggest that mean and variance representations do closely interact with each other. Considering that mean and variance reflect the representative value and dispersion of multiple items respectively, the interactions between mean and variance representations may reflect their complementary roles to summarize complex visual information effectively.

Relating categorization to set summary statistics perception

Two cognitive processes have been explored that compensate for the limited information that can be perceived and remembered at any given moment. The first parsimonious cognitive process is object categorization. We naturally relate objects to their category, assume they share relevant category properties, often disregarding irrelevant characteristics. Another scene organizing mechanism is representing aspects of the visual world in terms of summary statistics. Spreading attention over a group of objects with some similarity, one perceives an ensemble representation of the group. Without encoding detailed information of individuals, observers process summary data concerning the group, including set mean for various features (from circle size to face expression). Just as categorization may include/depend on prototype and intercategory boundaries, so set perception includes property mean and range. We now explore common features of these processes. We previously investigated summary perception of low-level features with a rapid serial visual presentation (RSVP) paradigm and found that participants perceive both the mean and range extremes of stimulus sets, automatically, implicitly, and on-the-fly, for each RSVP sequence, independently. We now use the same experimental paradigm to test category representation of high-level objects. We find participants perceive categorical characteristics better than they code individual elements. We relate category prototype to set mean and same/different category to in/out-of-range elements, defining a direct parallel between low-level set perception and high-level categorization. The implicit effects of mean or prototype and set or category boundaries are very similar. We suggest that object categorization may share perceptual-computational mechanisms with set summary statistics perception.

Consciousness without report: insights from summary statistics and inattention 'blindness'

We contrast two theoretical positions on the relation between phenomenal and access consciousness. First, we discuss previous data supporting a mild Overflow position, according to which transient visual awareness can overflow report. These data are open to two interpretations: (i) observers transiently experience specific visual elements outside attentional focus without encoding them into working memory; (ii) no specific visual elements but only statistical summaries are experienced in such conditions. We present new data showing that under data-limited conditions observers cannot discriminate a simple relation (same versus different) without discriminating the elements themselves and, based on additional computational considerations, we argue that this supports the first interpretation: summary statistics (same/different) are grounded on the transient experience of elements. Second, we examine recent data from a variant of 'inattention blindness' and argue that contrary to widespread assumptions, it provides further support for Overflow by highlighting another factor, 'task relevance', which affects the ability to conceptualize and report (but not experience) visual elements.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

The methodological puzzle of phenomenal consciousness

Is phenomenal consciousness constitutively related to cognitive access? Despite being a fundamental issue for any science of consciousness, its empirical study faces a severe methodological puzzle. Recent years have seen numerous attempts to address this puzzle, either in practice, by offering evidence for a positive or negative answer, or in principle, by proposing a framework for eventual resolution. The present paper critically considers these endeavours, including partial-report, metacognitive and no-report paradigms, as well as the theoretical proposal that we can make progress by studying phenomenal consciousness as a natural kind. It is argued that the methodological puzzle remains obdurately with us and that, for now, we must adopt an attitude of humility towards the phenomenal.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

The offline stream of conscious representations

When do we become conscious of a stimulus after its presentation? We would all agree that this necessarily takes time and that it is not instantaneous. Here, I would like to propose not only that conscious access is delayed relative to the external stimulation, but also that it can flexibly desynchronize from external stimulation; it can process some information 'offline', if and when it becomes relevant. Thus, in contrast with initial sensory processing, conscious experience might not strictly follow the sequence of events in the environment. In this article, I will review gathering evidence in favour of this proposition. I will argue that it offers a coherent framework for explaining a great variety of observations in the domain of perception, sensory memory and working memory: the psychological refractory period, the attentional blink, post-dictive phenomena, iconic memory, latent working memory and the newly described retro-perception phenomenon. I will integrate this proposition to the global neuronal workspace model and consider possible underlying brain mechanisms. Finally, I will argue that this capacity to process information 'offline' might have made conscious processing evolutionarily advantageous in spite of its sluggishness and capacity limitations.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

Downgraded phenomenology: how conscious overflow lost its richness

Our in-the-moment experience of the world can feel vivid and rich, even when we cannot describe our experience due to limitations of attention, memory or other cognitive processes. But the nature of visual awareness is quite sparse, as suggested by the phenomena of failures of awareness, such as change blindness and inattentional blindness. I will argue that once failures of memory or failures of comparison are ruled out as explanations for these phenomena, they present strong evidence against rich awareness. To accommodate and explain these massive failures of awareness, any theory of phenomenal consciousness must downgrade phenomenology to a degree where it is functionless or, ironically, does not reflect what we experience.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

Perceptual consciousness and cognitive access: an introduction

The problem of perceptual consciousness-the question of how our subjective experiences (colours as we see them; sounds as we hear them; tastes, etc., as we feel them) could be accounted for in terms of brain processes-is often regarded as the greatest unsolved mystery of our times. In recent literature, one of the most pressing questions in this regard is whether the neural basis of perceptual consciousness is independent of the neural basis of cognitive access mechanisms that make reporting and reflecting on conscious experiences possible. The Theme Issue focuses on this central problem of consciousness research and aims to contribute to the field by critically discussing state-of-the-art empirical findings, identifying methodological problems and proposing novel approaches.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

Perceiving set mean and range: Automaticity and precision

To compensate for the limited visual information that can be perceived and remembered at any given moment, many aspects of the visual world are represented as summary statistics. We acquire ensemble representations of element groups as a whole, spreading attention over objects, for which we encode no detailed information. Previous studies found that different features of items (from size/orientation to facial expression/biological motion) are summarized to their mean, over space or time. Summarizing is economical, saving time and energy when the environment is too rich and complex to encode each stimulus separately. We investigated set perception using rapid serial visual presentation sequences. Following each sequence, participants viewed two stimuli, member and nonmember, indicating the member. Sometimes, unbeknownst to participants, one stimulus was the set mean, and or the nonmember was outside the set range. Participants preferentially chose stimuli at/near the mean, a "mean effect," and more easily rejected out-of-range stimuli, a "range effect." Performance improved with member proximity to the mean and nonmember distance from set mean and edge, though they were instructed only to remember presented stimuli. We conclude that participants automatically encode both mean and range boundaries of stimulus sets, avoiding capacity limits and speeding perceptual decisions.

An investigation of detection biases in the unattended periphery during simulated driving

While people often think they veridically perceive much of the visual surround, recent findings indicate that when asked to detect targets such as gratings embedded in visual noise, observers make more false alarms in the unattended periphery. Do these results from psychophysics studies generalize to more ecologically valid settings? We used a modern game engine to create a simulated driving environment where participants (as drivers) had to make judgments about the colors of pedestrians' clothing in the periphery. Confirming our hypothesis based on previous psychophysics studies, we found that subjects showed liberal biases for unattended locations when detecting specific colors of pedestrians' clothing. A second experiment showed that this finding was not simply due to a confirmation bias in decision-making when subjects were uncertain. Together, these results support the idea that in everyday visual experience, there is subjective inflation of experienced detail in the periphery, which may happen at the decisional level.

Subjective inflation: phenomenology's get-rich-quick scheme

How do we explain the seemingly rich nature of visual phenomenology while accounting for impoverished perception in the periphery? This apparent mismatch has led some to posit that rich phenomenological content overflows cognitive access, whereas others hold that phenomenology is in fact sparse and constrained by cognitive access. Here, we review the Rich versus Sparse debate as it relates to a phenomenon called subjective inflation, wherein minimally attended or peripheral visual perception tends to be subjectively evaluated as more reliable than attended or foveal perception when objective performance is matched. We argue that subjective inflation can account for rich phenomenology without invoking phenomenological overflow. On this view, visual phenomenology is constrained by cognitive access, but seemingly inflated above what would be predicted based on sparse sensory content.

Ensemble statistics accessed through proxies: Range heuristic and dependence on low-level properties in variability discrimination

People can quickly and accurately compute not only the mean size of a set of items but also the size variability of the items. However, it remains unknown how these statistics are estimated. Here we show that neither parallel access to all items nor random subsampling of just a few items is sufficient to explain participants' estimations of size variability. In three experiments, we had participants compare two arrays of circles with different variability in their sizes. In the first two experiments, we manipulated the congruency of the range and variance of the arrays. The arrays with congruent range and variability information were judged more accurately, indicating the use of range as a proxy for variability. Experiments 2B and 3 showed that people also are not invariant to low- or mid-level visual information in the arrays, as comparing arrays with different low-level characteristics (filled vs. outlined circles) led to systematic biases. Together, these experiments indicate that range and low- or mid-level properties are both utilized as proxies for variability discrimination, and people are flexible in adopting these strategies. These strategies are at odds with the claim of parallel extraction of ensemble statistics per se and random subsampling strategies previously proposed in the literature.

Ensemble coding remains accurate under object and spatial visual working memory load

A number of studies have provided evidence that the visual system statistically summarizes large amounts of information that would exceed the limitations of attention and working memory (ensemble coding). However the necessity of working memory resources for ensemble coding has not yet been tested directly. In the current study, we used a dual task design to test the effect of object and spatial visual working memory load on size averaging accuracy. In Experiment 1, we tested participants' accuracy in comparing the mean size of two sets under various levels of object visual working memory load. Although the accuracy of average size judgments depended on the difference in mean size between the two sets, we found no effect of working memory load. In Experiment 2, we tested the same average size judgment while participants were under spatial visual working memory load, again finding no effect of load on averaging accuracy. Overall our results reveal that ensemble coding can proceed unimpeded and highly accurately under both object and spatial visual working memory load, providing further evidence that ensemble coding reflects a basic perceptual process distinct from that of individual object processing.

Ensemble Perception

To understand visual consciousness, we must understand how the brain represents ensembles of objects at many levels of perceptual analysis. Ensemble perception refers to the visual system's ability to extract summary statistical information from groups of similar objects-often in a brief glance. It defines foundational limits on cognition, memory, and behavior. In this review, we provide an operational definition of ensemble perception and demonstrate that ensemble perception spans across multiple levels of visual analysis, incorporating both low-level visual features and high-level social information. Further, we investigate the functional usefulness of ensemble perception and its efficiency, and we consider possible physiological and cognitive mechanisms that underlie an individual's ability to make accurate and rapid assessments of crowds of objects.

Are we underestimating the richness of visual experience?

It has been argued that the bandwidth of perceptual experience is low-that the richness of experience is illusory and that the amount of visual information observers can perceive and remember is extremely limited. However, the evidence suggests that this postulated poverty of experiential content is illusory and that visual phenomenology is immensely rich. To properly estimate perceptual content, experimentalists must move beyond the limitations of binary alternative-forced choice procedures and analyze reports of experience more broadly. This will open our eyes to the true richness of experience and to its neuronal substrates.