Consistent metacognitive efficiency and variable response biases in peripheral vision.

Across the visual periphery, perceptual and metacognitive abilities differ depending on the locus of visual attention, the location of peripheral stimulus presentation, the task design, and many other factors. In this investigation, we aimed to illuminate the relationship between attention and eccentricity in the visual periphery by estimating perceptual sensitivity, metacognitive sensitivity, and response biases across the visual field. In a 2AFC detection task, participants were asked to determine whether a signal was present or absent at one of eight peripheral locations (±10°, 20°, 30°, and 40°), using either a valid or invalid attentional cue. As expected, results revealed that perceptual sensitivity declined with eccentricity and was modulated by attention, with higher sensitivity on validly cued trials. Furthermore, a significant main effect of eccentricity on response bias emerged, with variable (but relatively unbiased) c'a values from 10° to 30°, and conservative c'a values at 40°. Regarding metacognitive sensitivity, significant main effects of attention and eccentricity were found, with metacognitive sensitivity decreasing with eccentricity, and decreasing in the invalid cue condition. Interestingly, metacognitive efficiency, as measured by the ratio of meta-d'a/d'a, was not modulated by attention or eccentricity. Overall, these findings demonstrate (1) that in some circumstances, observers have surprisingly robust metacognitive insights into how performance changes across the visual field and (2) that the periphery may be subject to variable detection biases that are contingent on the exact location in peripheral space.

Tuned inhibition in perceptual decision-making circuits can explain seemingly suboptimal confidence behavior.

Current dominant views hold that perceptual confidence reflects the probability that a decision is correct. Although these views have enjoyed some empirical support, recent behavioral results indicate that confidence and the probability of being correct can be dissociated. An alternative hypothesis suggests that confidence instead reflects the magnitude of evidence in favor of a decision while being relatively insensitive to the evidence opposing the decision. We considered how this alternative hypothesis might be biologically instantiated by developing a simple neural network model incorporating a known property of sensory neurons: tuned inhibition. The key idea of the model is that the level of inhibition that each accumulator unit receives from units with the opposite tuning preference, i.e. its inhibition 'tuning', dictates its contribution to perceptual decisions versus confidence judgments, such that units with higher tuned inhibition (computing relative evidence for different perceptual interpretations) determine perceptual discrimination decisions, and units with lower tuned inhibition (computing absolute evidence) determine confidence. We demonstrate that this biologically plausible model can account for several counterintuitive findings reported in the literature where confidence and decision accuracy dissociate. By comparing model fits, we further demonstrate that a full complement of behavioral data across several previously published experimental results-including accuracy, reaction time, mean confidence, and metacognitive sensitivity-is best accounted for when confidence is computed from units without, rather than units with, tuned inhibition. Finally, we discuss predictions of our results and model for future neurobiological studies. These findings suggest that the brain has developed and implements this alternative, heuristic theory of perceptual confidence computation by relying on the diversity of neural resources available.

Superior colliculus neuronal ensemble activity signals optimal rather than subjective confidence.

Recent studies suggest that neurons in sensorimotor circuits involved in perceptual decision-making also play a role in decision confidence. In these studies, confidence is often considered to be an optimal readout of the probability that a decision is correct. However, the information leading to decision accuracy and the report of confidence often covaried, leaving open the possibility that there are actually two dissociable signal types in the brain: signals that correlate with decision accuracy (optimal confidence) and signals that correlate with subjects' behavioral reports of confidence (subjective confidence). We recorded neuronal activity from a sensorimotor decision area, the superior colliculus (SC) of monkeys, while they performed two different tasks. In our first task, decision accuracy and confidence covaried, as in previous studies. In our second task, we implemented a motion discrimination task with stimuli that were matched for decision accuracy but produced different levels of confidence, as reflected by behavioral reports. We used a multivariate decoder to predict monkeys' choices from neuronal population activity. As in previous studies on perceptual decision-making mechanisms, we found that neuronal decoding performance increased as decision accuracy increased. However, when decision accuracy was matched, performance of the decoder was similar between high and low subjective confidence conditions. These results show that the SC likely signals optimal decision confidence similar to previously reported cortical mechanisms, but is unlikely to play a critical role in subjective confidence. The results also motivate future investigations to determine where in the brain signals related to subjective confidence reside.

Should a Few Null Findings Falsify Prefrontal Theories of Conscious Perception?

Is activity in prefrontal cortex (PFC) critical for conscious perception? Major theories of consciousness make distinct predictions about the role of PFC, providing an opportunity to arbitrate between these views empirically. Here we address three common misconceptions: (1) PFC lesions do not affect subjective perception; (2) PFC activity does not reflect specific perceptual content; and (3) PFC involvement in studies of perceptual awareness is solely driven by the need to make reports required by the experimental tasks rather than subjective experience per se. These claims are incompatible with empirical findings, unless one focuses only on studies using methods with limited sensitivity. The literature highlights PFC's essential role in enabling the subjective experience in perception, contra the objective capacity to perform visual tasks; conflating the two can also be a source of confusion.Dual Perspectives Companion Paper: Are the Neural Correlates of Consciousness in the Front or in the Back of the Cerebral Cortex? Clinical and Neuroimaging Evidence, by Melanie Boly, Marcello Massimini, Naotsugu Tsuchiya, Bradley R. Postle, Christof Koch, and Giulio Tononi.

Limited Cognitive Resources Explain a Trade-Off between Perceptual and Metacognitive Vigilance.

Why do experimenters give subjects short breaks in long behavioral experiments? Whereas previous studies suggest it is difficult to maintain attention and vigilance over long periods of time, it is unclear precisely what mechanisms benefit from rest after short experimental blocks. Here, we evaluate decline in both perceptual performance and metacognitive sensitivity (i.e., how well confidence ratings track perceptual decision accuracy) over time and investigate whether characteristics of prefrontal cortical areas correlate with these measures. Whereas a single-process signal detection model predicts that these two forms of fatigue should be strongly positively correlated, a dual-process model predicts that rates of decline may dissociate. Here, we show that these measures consistently exhibited negative or near-zero correlations, as if engaged in a trade-off relationship, suggesting that different mechanisms contribute to perceptual and metacognitive decisions. Despite this dissociation, the two mechanisms likely depend on common resources, which could explain their trade-off relationship. Based on structural MRI brain images of individual human subjects, we assessed gray matter volume in the frontal polar area, a region that has been linked to visual metacognition. Variability of frontal polar volume correlated with individual differences in behavior, indicating the region may play a role in supplying common resources for both perceptual and metacognitive vigilance. Additional experiments revealed that reduced metacognitive demand led to superior perceptual vigilance, providing further support for this hypothesis. Overall, results indicate that during breaks between short blocks, it is the higher-level perceptual decision mechanisms, rather than lower-level sensory machinery, that benefit most from rest. SIGNIFICANCE STATEMENT: Perceptual task performance declines over time (the so-called vigilance decrement), but the relationship between vigilance in perception and metacognition has not yet been explored in depth. Here, we show that patterns in perceptual and metacognitive vigilance do not follow the pattern predicted by a previously suggested single-process model of perceptual and metacognitive decision making. We account for these findings by showing that regions of anterior prefrontal cortex (aPFC) previously associated with visual metacognition are also associated with perceptual vigilance. We also show that relieving metacognitive task demand improves perceptual vigilance, suggesting that aPFC may house a limited cognitive resource that contributes to both metacognition and perceptual vigilance. These findings advance our understanding of the mechanisms and dynamics of perceptual metacognition.

The Brain's Tendency to Bind Audiovisual Signals Is Stable but Not General.

Previous studies have shown a surprising amount of between-subjects variability in the strength of interactions between sensory modalities. For the same set of stimuli, some subjects exhibit strong interactions, whereas others exhibit weak interactions. To date, little is known about what underlies this variability. Sensory integration in the brain could be governed by a global mechanism or by task-specific mechanisms that could be either stable or variable across time. We used a rigorous quantitative tool (Bayesian causal inference) to investigate whether integration (i.e., binding) tendencies generalize across tasks and are stable across time. We report for the first time that individuals' binding tendencies are stable across time but are task-specific. These results provide evidence against the hypothesis that sensory integration is governed by a single, global parameter in the brain.

Biases in Visual, Auditory, and Audiovisual Perception of Space.

Localization of objects and events in the environment is critical for survival, as many perceptual and motor tasks rely on estimation of spatial location. Therefore, it seems reasonable to assume that spatial localizations should generally be accurate. Curiously, some previous studies have reported biases in visual and auditory localizations, but these studies have used small sample sizes and the results have been mixed. Therefore, it is not clear (1) if the reported biases in localization responses are real (or due to outliers, sampling bias, or other factors), and (2) whether these putative biases reflect a bias in sensory representations of space or a priori expectations (which may be due to the experimental setup, instructions, or distribution of stimuli). Here, to address these questions, a dataset of unprecedented size (obtained from 384 observers) was analyzed to examine presence, direction, and magnitude of sensory biases, and quantitative computational modeling was used to probe the underlying mechanism(s) driving these effects. Data revealed that, on average, observers were biased towards the center when localizing visual stimuli, and biased towards the periphery when localizing auditory stimuli. Moreover, quantitative analysis using a Bayesian Causal Inference framework suggests that while pre-existing spatial biases for central locations exert some influence, biases in the sensory representations of both visual and auditory space are necessary to fully explain the behavioral data. How are these opposing visual and auditory biases reconciled in conditions in which both auditory and visual stimuli are produced by a single event? Potentially, the bias in one modality could dominate, or the biases could interact/cancel out. The data revealed that when integration occurred in these conditions, the visual bias dominated, but the magnitude of this bias was reduced compared to unisensory conditions. Therefore, multisensory integration not only improves the precision of perceptual estimates, but also the accuracy.

Brain literate: making neuroscience accessible to a wider audience of undergraduates.

The ability to critically evaluate neuroscientific findings is a skill that is rapidly becoming important in non-science professions. As neuroscience research is increasingly being used in law, business, education, and politics, it becomes imperative to educate future leaders in all areas of society about the brain. Undergraduate general education courses are an ideal way to expose students to issues of critical importance, but non-science students may avoid taking a neuroscience course because of the perception that neuroscience is more challenging than other science courses. A recently developed general education cluster course at UCLA aims to make neuroscience more palatable to undergraduates by pairing neuroscientific concepts with philosophy and history, and by building a learning community that supports the development of core academic skills and intellectual growth over the course of a year. This study examined the extent to which the course was successful in delivering neuroscience education to a broader undergraduate community. The results indicate that a majority of students in the course mastered the basics of the discipline regardless of their major. Furthermore, 77% of the non-life science majors (approximately two-thirds of students in the course) indicated that they would not have taken an undergraduate neuroscience course if this one was not offered. The findings also demonstrate that the course helped students develop core academic skills and improved their ability to think critically about current events in neuroscience. Faculty reported that teaching the course was highly rewarding and did not require an inordinate amount of time.

Reality monitoring and metacognitive judgments in a false-memory paradigm.

How well do we distinguish between different memory sources when the information from imagination and perception is similar? And how do metacognitive (confidence) judgments differ across different sources of experiences? To study these questions, we developed a reality monitoring task using semantically related words from the Deese-Roediger-McDermott (DRM) paradigm of false memories. In an orientation phase, participants either perceived word pairs or had to voluntarily imagine the second word of a word pair. In a test phase, participants viewed words and had to judge whether the paired word was previously perceived, imagined, or new. Results revealed an interaction between memory source and judgment type on both response rates and confidence judgments: reality monitoring was better for new and perceived (compared to imagined) sources, and participants often incorrectly reported imagined experiences to be perceived. Individuals exhibited similar confidence between correct imagined source judgments and incorrect imagined sources reported to be perceived. Modeling results indicated that the observed judgments were likely due to an externalizing bias (i.e., a bias to judge the memory source as perceived). Additionally, we found that overall metacognitive ability was best in the perceived source. Together, these results reveal a source-dependent effect on response rates and confidence ratings, and provide evidence that observers are surprisingly prone to externalizing biases when monitoring their own memories.

Common computations in automatic cue combination and metacognitive confidence reports.

Appropriate perceptual decision making necessitates the accurate estimation and use of sensory uncertainty. Such estimation has been studied in the context of both low-level multisensory cue combination and metacognitive estimation of confidence, but it remains unclear whether the same computations underlie both sets of uncertainty estimation. We created visual stimuli with low vs. high overall motion energy, such that the high-energy stimuli led to higher confidence but lower accuracy in a visual-only task. Importantly, we tested the impact of the low- and high-energy visual stimuli on auditory motion perception in a separate task. Despite being irrelevant to the auditory task, both visual stimuli impacted auditory judgments presumably via automatic low-level mechanisms. Critically, we found that the high-energy visual stimuli influenced the auditory judgments more strongly than the low-energy visual stimuli. This effect was in line with the confidence but contrary to the accuracy differences between the high- and low-energy stimuli in the visual-only task. These effects were captured by a simple computational model that assumes common computational principles underlying both confidence reports and multisensory cue combination. Our results reveal a deep link between automatic sensory processing and metacognitive confidence reports, and suggest that vastly different stages of perceptual decision making rely on common computational principles.

Metacognition and Causal Inference in Audiovisual Speech.

In multisensory environments, our brains perform causal inference to estimate which sources produce specific sensory signals. Decades of research have revealed the dynamics which underlie this process of causal inference for multisensory (audiovisual) signals, including how temporal, spatial, and semantic relationships between stimuli influence the brain's decision about whether to integrate or segregate. However, presently, very little is known about the relationship between metacognition and multisensory integration, and the characteristics of perceptual confidence for audiovisual signals. In this investigation, we ask two questions about the relationship between metacognition and multisensory causal inference: are observers' confidence ratings for judgments about Congruent, McGurk, and Rarely Integrated speech similar, or different? And do confidence judgments distinguish between these three scenarios when the perceived syllable is identical? To answer these questions, 92 online participants completed experiments where on each trial, participants reported which syllable they perceived, and rated confidence in their judgment. Results from Experiment 1 showed that confidence ratings were quite similar across Congruent speech, McGurk speech, and Rarely Integrated speech. In Experiment 2, when the perceived syllable for congruent and McGurk videos was matched, confidence scores were higher for congruent stimuli compared to McGurk stimuli. In Experiment 3, when the perceived syllable was matched between McGurk and Rarely Integrated stimuli, confidence judgments were similar between the two conditions. Together, these results provide evidence of the capacities and limitations of metacognition's ability to distinguish between different sources of multisensory information.

Metacognitive awareness in the sound-induced flash illusion.

Hundreds (if not thousands) of multisensory studies provide evidence that the human brain can integrate temporally and spatially discrepant stimuli from distinct modalities into a singular event. This process of multisensory integration is usually portrayed in the scientific literature as contributing to our integrated, coherent perceptual reality. However, missing from this account is an answer to a simple question: how do confidence judgements compare between multisensory information that is integrated across multiple sources, and multisensory information that comes from a single, congruent source in the environment? In this paper, we use the sound-induced flash illusion to investigate if confidence judgements are similar across multisensory conditions when the numbers of auditory and visual events are the same, and the numbers of auditory and visual events are different. Results showed that congruent audiovisual stimuli produced higher confidence than incongruent audiovisual stimuli, even when the perceptual report was matched across the two conditions. Integrating these behavioural findings with recent neuroimaging and theoretical work, we discuss the role that prefrontal cortex may play in metacognition, multisensory causal inference and sensory source monitoring in general. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

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.

Consensus Goals in the Field of Visual Metacognition.

Despite the tangible progress in psychological and cognitive sciences over the last several years, these disciplines still trail other more mature sciences in identifying the most important questions that need to be solved. Reaching such consensus could lead to greater synergy across different laboratories, faster progress, and increased focus on solving important problems rather than pursuing isolated, niche efforts. Here, 26 researchers from the field of visual metacognition reached consensus on four long-term and two medium-term common goals. We describe the process that we followed, the goals themselves, and our plans for accomplishing these goals. If this effort proves successful within the next few years, such consensus building around common goals could be adopted more widely in psychological science.

An investigation of how relative precision of target encoding influences metacognitive performance.

Detection failures in perceptual tasks can result from different causes: sometimes we may fail to see something because perceptual information is noisy or degraded, and sometimes we may fail to see something due to the limited capacity of attention. Previous work indicates that metacognitive capacities for detection failures may differ depending on the specific stimulus visibility manipulation employed. In this investigation, we measured metacognition while matching performance in two visibility manipulations: phase-scrambling and the attentional blink. As in previous work, metacognitive asymmetries emerged: despite matched type 1 performance, metacognitive ability (measured by area under the ROC curve) for reporting stimulus absence was higher in the attentional blink condition, which was mainly driven by metacognitive ability in correct rejection trials. We performed Signal Detection Theoretic (SDT) modeling of the results, showing that differences in metacognition under equal type I performance can be explained when the variance of the signal and noise distributions are unequal. Specifically, the present study suggests that phase scrambling signal trials have a wider distribution (more variability) than attentional blink signal trials, leading to a larger area under the ROC curve for attentional blink trials where subjects reported stimulus absence. These results provide a theoretical basis for the origin of metacognitive differences on trials where subjects report stimulus absence, and may also explain previous findings where the absence of evidence during detection tasks results in lower metacognitive performance when compared to categorization.

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.

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.

Prior expectation of objects in space is dependent on the direction of gaze.

Many studies of multisensory spatial localization have shown that observers' responses are well-characterized by Bayesian inference, as localization judgments are influenced not only by the reliability of sensory encoding, but expectations about where things occur in space. Here, we investigate the frame of reference for the prior expectation of objects in space. Using an audiovisual localization task, we systematically manipulate fixation position and evaluate whether this prior is encoded in an eye-centered, head-centered, or hybrid frame of reference. Results show that in a majority of participants, this prior is encoded in an eye-centered frame of reference.

Neuroscience: The Key to Consciousness May Not Be under the Streetlight.

Key theories of consciousness predict that the prefrontal cortex (PFC) plays important roles, but there has been relatively little causal evidence showing that manipulation of activity in the region can broadly affect conscious experiences. A new study provides crucial findings to help resolve this issue, showing that direct pharmacological stimulation of PFC restores wakefulness in anesthetized rats.