Information integration without awareness

Lack of social interaction advantage: A domain-general cognitive alteration in schizophrenia

People with schizophrenia (PSZ) showed preserved ability to unconsciously process simple social information (e.g., face and gaze), but not in higher-order cognition (e.g., memory). It is yet unknown how PSZ process social interactions across different cognitive domains. This study systematically investigated the cognitive characteristics of PSZ during social interaction processing from bottom-up perception to top-down memory, and established correlations with schizophrenic symptoms. In two experiments, social interactions were consistently displayed by face-to-face or back-to-back dyads. Experiment 1 enrolled 30 PSZ and 30 healthy control subjects (HCS) with a breaking continuous flash suppression (b-CFS) paradigm. Experiment 2 recruited 36 PSZ and 36 HCS for two memory tasks, wherein participants restored the between-model distance (working memory task) and recalled the socially bound pairs (long-term memory task). Results indicated that HCS showed advantageous processing of socially interactive stimuli against non-interactive stimuli throughout two experiments, including faster access to visual consciousness, closer spatial distance held in working memory and higher recollection accuracy in long-term memory. However, PSZ did not show any of these advantages, with significant interaction effects for all three tasks (task one: p = .018, ηp2 = .092; task two: p = .021, ηp2 = .074; task three: p = .015, ηp2 = .082). Moreover, correlation analyses indicated that PSZ with more severe negative symptoms (r = -.344, p = .040) or higher medication dosages (r = -.334, p = .046) showed fewer advantages in memorizing socially interactive information. Therefore, social interaction is not prioritized in schizophrenia from bottom-up perception to top-down memory, and the magnitude of such a domain-general cognitive alteration is clinically relevant to symptom severity and medication.

When alertness fades: Drowsiness-induced visual dominance and oscillatory recalibration in audiovisual integration

Multisensory integration allows the brain to align inputs from different sensory modalities, enhancing perception and behavior. However, transitioning into drowsiness, a state marked by decreased attentional control and altered cortical dynamics, offers a unique opportunity to examine adaptations in these multisensory processes. In this study, we investigated how drowsiness influences reaction times (RTs) and neural oscillations during audiovisual multisensory integration. Participants performed a task where auditory and visual stimuli were presented either in a coordinated manner or with temporal misalignment (visual-first or auditory-first uncoordinated conditions). Behavioral results showed that drowsiness slowed RTs overall but revealed a clear sensory dominance effect: visual-first uncoordination facilitated RTs compared to auditory-first uncoordination, reflecting vision's dominant role in recalibrating sensory conflicts. In contrast, RTs in coordinated conditions remained stable across alert and drowsy states, suggesting that multisensory redundancy compensates for reduced cortical integration during drowsiness. At the neural level, distinct patterns of oscillatory activity emerged. Alpha oscillations supported attentional realignment and temporal alignment in visual-first conditions, while Gamma oscillations were recruited during auditory-first uncoordination, reflecting heightened sensory-specific processing demands. These effects were state-dependent, becoming more pronounced during drowsiness. Our findings demonstrate that drowsiness fundamentally reshapes multisensory integration by amplifying sensory dominance mechanisms, particularly vision. Compensatory neural mechanisms involving Alpha and Gamma oscillations maintain perceptual coherence under conditions of reduced cortical interaction. These results provide critical insights into how the brain adapts to sensory conflicts during states of diminished awareness, with broader implications for performance and decision-making in real-world drowsy states.

Semantic audio-visual congruence modulates visual sensitivity to biological motion across awareness levels

Whether cross-modal interaction requires conscious awareness of multisensory information or whether it can occur in the absence of awareness, is still an open question. Here, we investigated if sounds can enhance detection sensitivity of semantically matching visual stimuli at varying levels of visual awareness. We presented biological motion stimuli of human actions (walking, rowing, sawing) during dynamic continuous flash suppression (CFS) to 80 participants and measured the effect of co-occurring, semantically matching or non-matching action sounds on visual sensitivity (d'). By individually thresholding stimulus contrast, we distinguished participants who detected motion either above or at chance level. Participants who reliably detected visual motion above chance showed higher sensitivity to upright versus inverted biological motion across all experimental conditions. In contrast, participants detecting visual motion at chance level, i.e. during successful suppression, demonstrated this upright advantage exclusively during trials with semantically congruent sounds. Across the whole sample, the impact of sounds on visual sensitivity increased as participants' visual detection performance decreased, revealing a systematic trade-off between auditory and visual processing. Our findings suggest that semantic congruence between auditory and visual information can selectively modulate biological motion perception when visual awareness is minimal or absent, while more robust visual signals enable perception of biological motion independent of auditory input. Thus, semantically congruent sounds may impact visual representations as a function of the level of visual awareness.

Object relations are processed with, but not without, awareness

The scope of unconscious integration is widely debated. Here, we examined this question, focusing specifically on deciphering the relations between two associatively related objects, in a set of five behavioral and electrophysiological experiments. Participants were presented with masked pairs of related and unrelated objects and were asked to judge their relatedness. When the masked pairs were visible, we found both a behavioral priming effect and a difference in the magnitude of the electrophysiological N400 component for unrelated compared with related pairs. In sharp contrast, when the pairs were invisible (validated using both subjective and objective awareness measures), no convincing evidence was found for relatedness processing: with electroencephalography, no difference in N400 amplitude nor above-chance decoding of pair relations was found in two separate experiments. Based on these results, we conclude that the data do not support unconscious relatedness processing, suggesting that consciousness might have a prominent role in enabling relational integration beyond the single object level, which is in line with leading theories of consciousness.

Perceptual and attentional impairments of conscious access involve distinct neural mechanisms despite equal task performance

This study investigates failures in conscious access resulting from either weak sensory input (perceptual impairments) or unattended input (attentional impairments). Participants viewed a Kanizsa stimulus with or without an illusory triangle within a rapid serial visual presentation of distractor stimuli. We designed a novel Kanizsa stimulus that contained additional ancillary features of different complexity (local contrast and collinearity) that were independently manipulated. Perceptual performance on the Kanizsa stimulus (presence vs. absence of an illusion) was equated between the perceptual (masking) and attentional (attentional blink) manipulation to circumvent common confounds related to conditional differences in task performance. We trained and tested classifiers on electroencephalogram (EEG) data to reflect the processing of specific stimulus features, with increasing levels of complexity. We show that late stages of processing (~200-250 ms), reflecting the integration of complex stimulus features (collinearity, illusory triangle), were impaired by masking but spared by the attentional blink. In contrast, decoding of local contrast (the spatial arrangement of stimulus features) was observed early in time (~80 ms) and was left largely unaffected by either manipulation. These results replicate previous work showing that feedforward processing is largely preserved under both perceptual and attentional impairments. Crucially, however, under matched levels of performance, only attentional impairments left the processing of more complex visual features relatively intact, likely related to spared lateral and local feedback processes during inattention. These findings reveal distinct neural mechanisms associated with perceptual and attentional impairments and thus contribute to a comprehensive understanding of distinct neural stages leading to conscious access.

Modulation of thermal perception by VR-based visual stimulation to the embodied virtual body

Visual stimulation to the embodied virtual body could modulate human perception, however the associated neurophysiological mechanisms have not elucidated yet. The present study aimed to reveal the underlying neurophysiological mechanisms from a neurophysiological viewpoint. Fifteen healthy participants were subjected to three visual conditions (i.e., fire, water, and non-visual effect conditions) and psychological pain stimulation (thermal grill stimulation). Oscillatory neural activities during stimulation were measured with electroencephalogram. The association between accessory visual stimulation applied to the embodied virtual body, induced by virtual reality, and perception was examined through neuronal oscillatory analysis using electroencephalogram data. Regression analysis was performed to obtain data on brain regions contributing to sensory modulation with body illusion. The results of subjective measures under the fire and water conditions showed that thermal perception were modulated by a visual stimulus to the virtual hand. Furthermore, we found that the insula was commonly associated with thermal perception under the fire and water conditions. This result indicate that the insula may control sensory information as a gatekeeper as well as facilitate the access to human attention and cognition as a hub, suggesting the influence on perception and cognition.

The impact of weak inertial stimulation on visual-vestibular bimodal heading perception

Perception of self-motion involves the integration of visual and vestibular sensory information. Currently, there is limited research exploring visual-vestibular interactions under weak vestibular stimulation. This study investigates the impact of weak inertial stimulation on visual-vestibular bimodal heading perception. A translational XY-axis motion platform equipped with a 46-inch LCD TV was utilized to generate synchronized visual and inertial stimuli. The heading perception was examined under visual-only, vestibular-only, and bimodal conditions using three levels of inertial stimuli (9 mg, 14 mg, and 19 mg). In each condition, participants were tested at nine angles (±16°, ±9.2°, ±3°, ±1.7°, and 0° where 0° represents forward movement), to discern left-forward or right-forward motion. The heading discrimination threshold (HDT) was derived from participants' rightward response proportions across all angles. Our findings reveal that the HDT under 14 mg bimodal conditions is significantly higher than that under visual-only conditions (with marginal significance in the 9 mg and 19 mg conditions), indicating that the presence of weak vestibular signals might decrease the precision of bimodal heading discrimination. These results contradict the prediction of Bayesian model theory that perception is more precise under bimodal compared with unimodal conditions. The results may be explained by neurological biases during Bayesian integration, the "reduced visual precision" theory, or increased task complexity in bimodal heading discrimination. Further research with larger sample size, extending the study to varied inertial stimuli and visual coherence levels, will be beneficial for clarifying its underlying mechanisms.

Markers of consciousness in infants: Towards a 'cluster-based' approach

As recently as the 1980s, it was not uncommon for paediatric surgeons to operate on infants without anaesthesia. Today, the same omission would be considered criminal malpractice, and there is an increased concern with the possibility of consciousness in the earliest stage of human infancy. This concern reflects a more general trend that has characterised science since the early 1990s of taking consciousness seriously. While this attitude shift has opened minds towards the possibility that our earliest experiences predate our first memories, convincing demonstrations of infant consciousness remain challenging given that infants cannot report on their experiences. Furthermore, while many behavioural and neural markers of consciousness that do not rely on language have been validated in adults, no one specific marker can be confidently translated to infancy. For this reason, we have proposed the 'cluster-based' approach, in which a consensus of evidence across many markers, all pointing towards the same developmental period, could be used to argue convincingly for the presence of consciousness. CONCLUSION: We review the most promising markers for early consciousness, arguing that consciousness is likely to be in place by 5 months of age if not earlier.

The UnconTrust Database for Studies of Unconscious Semantic Processing and Attentional Allocation

The question of what processes can take place without conscious awareness has generated extensive research. Yet there is still no consensus regarding the extent and scope of unconscious processing, and past research abounds with conflicting results. A possible reason for this lack of consensus is the diversity of methods in the field, as the methodological choices might influence the results. Thus far, such possible influence of methods, measures, and analyses has not been systematically investigated and mapped. Here, we present the UnconTrust database for studies of unconscious processing focusing on two major domains - semantic and attentional processing. The database allows researchers to explore potential influences and obtain a bird's eye view on the field with respect to these domains. Currently, the database includes information about the methods and findings of 426 experiments (though notably, the data collected in these experiments is not included). The database is also presented as an interactive website.

In Search of an Integrative Method to Study Unconscious Processing: An Application of Bayesian and General Recognition Theory Models to the Processing of Hierarchical Patterns in the Absence of Awareness

The dissociation between conscious and unconscious perception is one of the most relevant issues in the study of human cognition. While there is evidence suggesting that some stimuli might be unconsciously processed up to its meaning (e.g., high-level stimulus processing), some authors claim that most results on the processing of subliminal stimuli can be explained by a mixture of methodological artefacts and questionable assumptions about what can be considered non-conscious. Particularly, one of the most controversial topics involves the method by which the awareness of the stimuli is assessed. To address this question, we introduced an integrative approach to assess the extent to which masked hierarchical stimuli (i.e., global shapes composed of local elements) can be processed in the absence of awareness. We combined a priming task where participants had to report global or local shapes, with the use of subjective and objective awareness measures collected either in a separate block (offline), or trial-by-trial during the main task (online). The unconscious processing of the masked primes was then evaluated through two different novel model-based methods: a Bayesian and a General Recognition Theory modeling approach. Despite the high correlation between awareness measures, our results show that the use of alternative approaches based on different theoretical assumptions leads to diverging conclusions about the extent of the unconscious processing of the masked primes.

Frontal engagement in perceptual integration under low subjective visibility

We investigated how spatiotemporal neural dynamics underlying perceptual integration changed with the degree of conscious access to a set of backward-masked pacman-shaped inducers that generated the percept of an illusory triangle. We kept the stimulus parameters at a fixed near-threshold level throughout the experiment and recorded electroencephalography from participants who reported the orientation and subjective visibility of the illusory triangle on each trial. Our multivariate pattern analysis revealed that posterior and central areas initially used dynamic neural code and later switched to stable neural code. The transition from dynamic to stable neural code in posterior area occurred increasingly later and eventually disappeared with decreasing conscious access. Anterior area primarily used stable neural code which waned with decreasing conscious access, but increased at below-median visibility and remained even when stimulus awareness was minimal. These results demonstrate differential spatiotemporal neural dynamics underlying perceptual integration depending on conscious access and emphasize a unique role of anterior area in processing integrated shape information especially under low subjective visibility.

Multiple sources of unconscious-information processing affect a single response: independent unconscious priming effects

At present there is little knowledge on whether and how multiple pieces of unconscious information can simultaneously affect a single conscious response. In the present study, we manipulated the congruency relation between a masked prime arrow and the target arrow, as well as that between masked flankers and the target arrow. The results demonstrated that the masked prime and flankers produced independent unconscious priming effects on the response to the target. In the process of studying the above phenomenon, two secondary findings were made. First, although the prime congruency effect was obtained, the flanker congruency effect was smaller when the flankers were displayed simultaneously with the target than when they were displayed sequentially before the target. This suggested that priming stimulation required enough time to be processed to a sufficient extent to produce an unconscious priming effect. Second, when the prime stimulus was removed, leaving only the flankers, the flanker priming effect increased, suggesting that the attention attracted to the prime and its conscious mask could also reduce the flanker congruency effect. These results observed across several experiments were replicated in one within-subjects experiment. We proposed an "independent unconscious influence hypothesis" for the phenomenon. This hypothesis was further integrated into a more comprehensive unconscious information processing model. The possible causes of the observed phenomena were discussed.

Auditory guidance of eye movements toward threat-related images in the absence of visual awareness

The human brain is sensitive to threat-related information even when we are not aware of this information. For example, fearful faces attract gaze in the absence of visual awareness. Moreover, information in different sensory modalities interacts in the absence of awareness, for example, the detection of suppressed visual stimuli is facilitated by simultaneously presented congruent sounds or tactile stimuli. Here, we combined these two lines of research and investigated whether threat-related sounds could facilitate visual processing of threat-related images suppressed from awareness such that they attract eye gaze. We suppressed threat-related images of cars and neutral images of human hands from visual awareness using continuous flash suppression and tracked observers' eye movements while presenting congruent or incongruent sounds (finger snapping and car engine sounds). Indeed, threat-related car sounds guided the eyes toward suppressed car images, participants looked longer at the hidden car images than at any other part of the display. In contrast, neither congruent nor incongruent sounds had a significant effect on eye responses to suppressed finger images. Overall, our results suggest that only in a danger-related context semantically congruent sounds modulate eye movements to images suppressed from awareness, highlighting the prioritisation of eye responses to threat-related stimuli in the absence of visual awareness.

Unconscious multisensory integration: behavioral and neural evidence from subliminal stimuli

Introduction

The prevailing theories of consciousness consider the integration of different sensory stimuli as a key component for this phenomenon to rise on the brain level. Despite many theories and models have been proposed for multisensory integration between supraliminal stimuli (e.g., the optimal integration model), we do not know if multisensory integration occurs also for subliminal stimuli and what psychophysical mechanisms it follows.

Methods

To investigate this, subjects were exposed to visual (Virtual Reality) and/or haptic stimuli (Electro-Cutaneous Stimulation) above or below their perceptual threshold. They had to discriminate, in a two-Alternative Forced Choice Task, the intensity of unimodal and/or bimodal stimuli. They were then asked to discriminate the sensory modality while recording their EEG responses.

Results

We found evidence of multisensory integration for supraliminal condition, following the classical optimal model. Importantly, even for subliminal trials participant's performances in the bimodal condition were significantly more accurate when discriminating the intensity of the stimulation. Moreover, significant differences emerged between unimodal and bimodal activity templates in parieto-temporal areas known for their integrative role.

Discussion

These converging evidences - even if preliminary and needing confirmation from the collection of further data - suggest that subliminal multimodal stimuli can be integrated, thus filling a meaningful gap in the debate about the relationship between consciousness and multisensory integration.

Unconsciously triggered cognitive conflict influences perceptual choice in active and sedentary individuals

Introduction

People who regularly exercise and receive training perform better when actioning unconscious cognitive tasks. The information flow triggered by a single unconscious visual stimulus has been extensively investigated, but it remains unclear whether multiple unconscious visual stimuli interact. This study aimed to explore the relationship between three simultaneous subliminal arrow stimuli (pointing in same or different directions), focusing on how they interact with each other and the subsequent priming effect on the target arrow in active and sedentary groups.

Methods

We used a priming paradigm combining flanker task to test the hypothesis. A total of 42 participants were recruited. Of these, 22 constituted the active group and 20 constituted the sedentary group.

Results

Behavioral data results revealed that the main effects of group and prime-target compatibility were significant. In the neurophysiological data, prime-target compatibility significantly influenced the latency of PP1. The amplitude of TP1 and TN2 mainly influenced the prime-flanker congruency. The prime-flanker congruency and groups interacted when the prime-target showed sufficient compatibility. The prime-flanker congruency, and the prime-target compatibility considerably influenced the TP3 amplitude in the anterior central frontal region (CZ electrode point).

Conclusion

Event-related potentials revealed the interactions between conscious processing and subliminal conflict in the early stages of perceptual and attention processing (target-related P1 potential component). These results suggest that exercise is helpful for coping with unconscious cognitive conflict.

A global neuronal workspace model of functional neurological disorders

We introduce here a general model of Functional Neurological Disorders based on the following hypothesis: a Functional Neurological Disorder could correspond to a consciously initiated voluntary top-down process causing involuntary lasting consequences that are consciously experienced and subjectively interpreted by the patient as involuntary. We develop this central hypothesis according to Global Neuronal Workspace theory of consciousness, that is particularly suited to describe interactions between conscious and non-conscious cognitive processes. We then present a list of predictions defining a research program aimed at empirically testing their validity. Finally, this general model leads us to reinterpret the long-debated links between hypnotic suggestion and functional neurological disorders. Driven by both scientific and therapeutic goals, this theoretical paper aims at bringing closer the psychiatric and neurological worlds of functional neurological disorders with the latest developments of cognitive neuroscience of consciousness.

Taking consciousness for real: Increasing the ecological validity of the study of conscious vs. unconscious processes

The study of consciousness has developed well-controlled, rigorous methods for manipulating and measuring consciousness. Yet, in the process, experimental paradigms grew farther away from everyday conscious and unconscious processes, which raises the concern of ecological validity. In this review, we suggest that the field can benefit from adopting a more ecological approach, akin to other fields of cognitive science. There, this approach challenged some existing hypotheses, yielded stronger effects, and enabled new research questions. We argue that such a move is critical for studying consciousness, where experimental paradigms tend to be artificial and small effect sizes are relatively prevalent. We identify three paths for doing so-changing the stimuli and experimental settings, changing the measures, and changing the research questions themselves-and review works that have already started implementing such approaches. While acknowledging the inherent challenges, we call for increasing ecological validity in consciousness studies.

A new 'CFS tracking' paradigm reveals uniform suppression depth regardless of target complexity or salience

When the eyes view separate and incompatible images, the brain suppresses one image and promotes the other into visual awareness. Periods of interocular suppression can be prolonged during continuous flash suppression (CFS) - when one eye views a static 'target' while the other views a complex dynamic stimulus. Measuring the time needed for a suppressed image to break CFS (bCFS) has been widely used to investigate unconscious processing, and the results have generated controversy regarding the scope of visual processing without awareness. Here, we address this controversy with a new 'CFS tracking' paradigm (tCFS) in which the suppressed monocular target steadily increases in contrast until breaking into awareness (as in bCFS) after which it decreases until it again disappears (reCFS), with this cycle continuing for many reversals. Unlike bCFS, tCFS provides a measure of suppression depth by quantifying the difference between breakthrough and suppression thresholds. tCFS confirms that (i) breakthrough thresholds indeed differ across target types (e.g. faces vs gratings, as bCFS has shown) - but (ii) suppression depth does not vary across target types. Once the breakthrough contrast is reached for a given stimulus, all stimuli require a strikingly uniform reduction in contrast to reach the corresponding suppression threshold. This uniform suppression depth points to a single mechanism of CFS suppression, one that likely occurs early in visual processing because suppression depth was not modulated by target salience or complexity. More fundamentally, it shows that variations in bCFS thresholds alone are insufficient for inferring whether the barrier to achieving awareness exerted by interocular suppression is weaker for some categories of visual stimuli compared to others.

Unconscious Integration of Categorical Relationship of Two Subliminal Numbers in Comparison with "5"

Many studies have shown that the brain can process subliminal numerals, i.e., participants can categorize a subliminal number into two categories: greater than 5 or less than 5. In the context of many studies on the unconscious integration of multiple subliminal stimuli, the issue of whether multiple subliminal numbers can be integrated is contentious. The same-different task is regarded as a perfect tool to explore unconscious integration. In the two experiments reported, we used a same-different task in which a pair of masked prime numbers was followed by a pair of target numbers, and participants were asked to decide whether the two target numbers were on the same (both smaller or larger than 5) or different sides (one smaller, the other larger than 5) of 5 in magnitude. The results indicated that the prime numbers could be categorized unconsciously, which was reflected by the category priming effect, and that the unconscious category relationship of the two prime numbers could affect the judgment on the category relationship of the two target numbers, as reflected by the response priming effect. The duration of the prime-to-target interstimulus interval (ISI) was also manipulated, showing a positive compatibility effect (PCE) of category priming and a negative compatibility effect (NCE) of response priming no matter whether the ISI was short (50 ms) or long (150 ms). The NCE, which occurred when the prime-to-target ISI was relatively short in this study, contradicted the conventional view but was consistent with previous results of unconscious integration based on an attention modulation mechanism. Importantly, this study provided evidence for the still-under-debate issue of numerical information integration.

Awareness is needed for contextual effects in ambiguous object recognition

Despite its centrality to human experience, the functional role of conscious awareness is not yet known. One hypothesis suggests that consciousness is necessary for allowing high-level information to refine low-level processing in a "top-down" manner. To test this hypothesis, in this work we examined whether consciousness is needed for integrating contextual information with sensory information during visual object recognition, a case of top-down processing that is automatic and ubiquitous to our daily visual experience. In three experiments, 137 participants were asked to determine the identity of an ambiguous object presented to them. Crucially, a scene biasing the interpretation of the object towards one option over another (e.g., a picture of a tree when the object could equally be perceived as a fish or a leaf) was presented either before, after, or alongside the ambiguous object. In all three experiments, the scene biased perception of the ambiguous object when it was consciously perceived, but not when it was processed unconsciously. The results therefore suggest that conscious awareness may be needed for top-down contextual processes.

Using virtual reality to induce multi-trial inattentional blindness despite trial-by-trial measures of awareness

Unconscious processing has been widely examined using diverse and well-controlled methodologies. However, the extent to which these findings are relevant to real-life instances of information processing without awareness is limited. Here, we present a novel inattentional blindness (IB) paradigm in virtual reality (VR). In three experiments, we managed to repeatedly induce IB while participants foveally viewed salient stimuli for prolonged durations. The effectiveness of this paradigm demonstrates the close relationship between top-down attention and subjective experience. Thus, this method provides an ecologically valid setup to examine processing without awareness.

Extrapolating animal consciousness

I argue that the question of animal consciousness is an extrapolation problem and, as such, is best tackled by deploying currently accepted methodology for validating experimental models of a phenomenon of interest. This methodology relies on an assessment of similarities and dissimilarities between experimental models, the partial replication of findings across complementary models, and evidence from the successes and failures of explanations, technologies and medical applications developed by extrapolating and aggregating findings from multiple models. Crucially important, this methodology does not require a commitment to any particular theory or construct of consciousness, thus avoiding theory-biased reinterpretations of empirical findings rampant in the literature.

Assessing the commensurability of theories of consciousness: On the usefulness of common denominators in differentiating, integrating and testing hypotheses

How deep is the current diversity in the panoply of theories to define consciousness, and to what extent do these theories share common denominators? Here we first examine to what extent different theories are commensurable (or comparable) along particular dimensions. We posit logical (and, when applicable, empirical) commensurability as a necessary condition for identifying common denominators among different theories. By consequence, dimensions for inclusion in a set of logically and empirically commensurable theories of consciousness can be proposed. Next, we compare a limited subset of neuroscience-based theories in terms of commensurability. This analysis does not yield a denominator that might serve to define a minimally unifying model of consciousness. Theories that seem to be akin by one denominator can be remote by another. We suggest a methodology of comparing different theories via multiple probing questions, allowing to discern overall (dis)similarities between theories. Despite very different background definitions of consciousness, we conclude that, if attention is paid to the search for a common methological approach to brain-consciousness relationships, it should be possible in principle to overcome the current Babylonian confusion of tongues and eventually integrate and merge different theories.

Stimulus awareness is necessary for both instrumental learning and instrumental responding to previously learned stimuli

Instrumental conditioning is a crucial part of adaptive behaviour, allowing agents to selectively interact with stimuli in their environment. Recent evidence suggests that instrumental conditioning cannot proceed without stimulus awareness. However, whether accurate unconscious instrumental responding can emerge from consciously acquired knowledge of the stimulus-action-outcome contingencies is unknown. We studied this question using instrumental trace conditioning, where participants learned to make approach/avoid decisions in two within-subject modes: conscious (stimuli in plain view) and unconscious (visually masked). Both tasks were followed by an unconscious-only instrumental performance task. We show that even when the contingencies are reliably learned in the conscious mode, participants fail to act upon them in the unconscious responding task. We also replicate the previous results that no instrumental learning occurs in the unconscious mode. Consequently, the absence of stimulus awareness not only precludes instrumental conditioning, but also precludes any kind of instrumental responding to already known stimuli. This suggests that instrumental behaviour is entirely supported by conscious awareness of the world, and corroborates the proposals that consciousness may be necessary for adaptive behaviours requiring selective action.

Temporal integration by multi-level regularities fosters the emergence of dynamic conscious experience

The relationship between integration and awareness is central to contemporary theories and research on consciousness. Here, we investigated whether and how information integration over time, by incorporating the underlying regularities, contributes to our awareness of the dynamic world. Using binocular rivalry, we demonstrated that structured visual streams, constituted by shape, motion, or idiom sequences containing perceptual- or semantic-level regularities, predominated over their nonstructured but otherwise matched counterparts in the competition for visual awareness. Despite the apparent resemblance, a substantial dissociation of the observed rivalry advantages emerged between perceptual- and semantic-level regularities. These effects stem from nonconscious and conscious temporal integration processes, respectively, with the former but not the latter being vulnerable to perturbations in the spatiotemporal integration window. These findings corroborate the essential role of structure-guided information integration in visual awareness and highlight a multi-level mechanism where temporal integration by perceptually and semantically defined regularities fosters the emergence of continuous conscious experience.

The place of Free Will: the freedom of the prisoner

Debates about the concept of Free Will date back to ancient times. About 40 years ago, Benjamin Libet designed an experiment showing that the conscious intention to move is preceded by a specific pattern of brain activation. His finding suggested that unconscious processes determine our decisions. Libet-style experiments have continued to dominate the debate about Free Will, pushing some authors to argue that the existence of Free Will is a mere illusion. We believe that this dispute is because we often measure Free Will using arbitrary human decisions rather than deliberate actions. After reviewing the definition of Free Will and the related literature, we conclude that the scientific evidence does not disprove the existence of Free Will. However, our will encounters several constraints and limitations that should be considered when evaluating our deeds' personal responsibility.

Consciousness in the cradle: on the emergence of infant experience

Although each of us was once a baby, infant consciousness remains mysterious and there is no received view about when, and in what form, consciousness first emerges. Some theorists defend a 'late-onset' view, suggesting that consciousness requires cognitive capacities which are unlikely to be in place before the child's first birthday at the very earliest. Other theorists defend an 'early-onset' account, suggesting that consciousness is likely to be in place at birth (or shortly after) and may even arise during the third trimester. Progress in this field has been difficult, not just because of the challenges associated with procuring the relevant behavioral and neural data, but also because of uncertainty about how best to study consciousness in the absence of the capacity for verbal report or intentional behavior. This review examines both the empirical and methodological progress in this field, arguing that recent research points in favor of early-onset accounts of the emergence of consciousness.

When philosophical nuance matters: safeguarding consciousness research from restrictive assumptions

In this paper, we revisit the debate surrounding the Unfolding Argument (UA) against causal structure theories of consciousness (as well as the hard-criteria research program it prescribes), using it as a platform for discussing theoretical and methodological issues in consciousness research. Causal structure theories assert that consciousness depends on a particular causal structure of the brain. Our claim is that some of the assumptions fueling the UA are not warranted, and therefore we should reject the methodology for consciousness science that the UA prescribes. First, we briefly survey the most popular philosophical positions in consciousness science, namely physicalism and functionalism. We discuss the relations between these positions and the behaviorist methodology that the UA assumptions express, despite the contrary claim of its proponents. Second, we argue that the same reasoning that the UA applies against causal structure theories can be applied to functionalist approaches, thus proving too much and deeming as unscientific a whole range of (non-causal structure) theories. Since this is overly restrictive and fits poorly with common practice in cognitive neuroscience, we suggest that the reasoning of the UA must be flawed. Third, we assess its philosophical assumptions, which express a restrictive methodology, and conclude that there are reasons to reject them. Finally, we propose a more inclusive methodology for consciousness science, that includes neural, behavioral, and phenomenological evidence (provided by the first-person perspective) without which consciousness science could not even start. Then, we extend this discussion to the scope of consciousness science, and conclude that theories of consciousness should be tested and evaluated on humans, and not on systems considerably different from us. Rather than restricting the methodology of consciousness science, we should, at this point, restrict the range of systems upon which it is supposed to be built.

The relation between implicit statistical learning and proactivity as revealed by EEG

Environmental events often occur on a probabilistic basis but can sometimes be predicted based on specific cues and thus approached proactively. Incidental statistical learning enables the acquisition of knowledge about probabilistic cue-target contingencies. However, the neural mechanisms of statistical learning about contingencies (SLC), the required conditions for successful learning, and the role of implicit processes in the resultant proactive behavior are still debated. We examined changes in behavior and cortical activity during an SLC task in which subjects responded to visual targets. Unbeknown to them, there were three types of target cues associated with high-, low-, and zero target probabilities. About half of the subjects spontaneously gained explicit knowledge about the contingencies (contingency-aware group), and only they showed evidence of proactivity: shortened response times to predictable targets and enhanced event-related brain responses (cue-evoked P300 and contingent negative variation, CNV) to high probability cues. The behavioral and brain responses were strictly associated on a single-trial basis. Source reconstruction of the brain responses revealed activation of fronto-parietal brain regions associated with cognitive control, particularly the anterior cingulate cortex and precuneus. We also found neural correlates of SLC in the contingency-unaware group, but these were restricted to post-target latencies and visual association areas. Our results document a qualitative difference between explicit and implicit learning processes and suggest that in certain conditions, proactivity may require explicit knowledge about contingencies.

Experiencing without knowing? Empirical evidence for phenomenal consciousness without access

Can one have a phenomenal experience to which one does not have access? That is, can you experience something without knowing? The dissociation between phenomenal (P) and access (A) consciousness is widely debated. A major challenge to the supporters of this dissociation is the apparent inability to experimentally demonstrate that P-without-A consciousness exists; once participants report having a P-experience, they already have access to it. Thus, all previous empirical support for this dissociation is indirect. Here, using a novel paradigm, we create a situation where participants (Experiment 1, N = 40) lack online access to the stimulus yet are nevertheless able to retrospectively form judgements on its phenomenal, qualitative aspects. We further show that their performance cannot be fully explained by unconscious processing or by a response to stimulus offset (Experiment 2, N = 40). This suggests that P and A consciousness are not only conceptually distinct, but might also be teased apart empirically. STATEMENT OF RELEVANCE: A critical question in the scientific quest towards solving the problem of consciousness focuses on the ability to isolate conscious experiences at their purity, without any accompanying cognitive processes. This challenge has been augmented by a highly influential - yet controversial - dissociation suggested by the philosopher Ned Block between Phenomenal consciousness, or the "what it is like" to have an experience, and Access consciousness, indexing the ability to report that one has that experience. Critically, these two types of consciousness most typically go together, making it highly difficult - if not impossible - to isolate Phenomenal consciousness. Our work shows that the dissociation between phenomenal and access consciousness is not merely conceptual, but can also be empirically demonstrated. It further opens the gate to future studies pinpointing the neural correlates of the two types of consciousness.

Only visible flicker helps flutter: Tactile-visual integration breaks in the absence of visual awareness

Combining information from multiple senses enhances our perception of the world. Whether we need to be aware of all stimuli to benefit from multisensory integration, however, is still under investigation. Here, we tested whether tactile frequency perception benefits from the presence of congruent visual flicker even if the flicker is so rapid that it is perceptually fused into a steady light and therefore invisible. Our participants completed a tactile frequency discrimination task given either unisensory tactile or congruent tactile-visual stimulation. Tactile and tactile-visual test frequencies ranged from far below to far above participants' flicker fusion threshold (determined separately). For frequencies distinctively below their flicker fusion threshold, participants performed significantly better given tactile-visual stimulation than when presented with only tactile stimuli. Yet, for frequencies above their flicker fusion threshold, participants' tactile frequency perception did not profit from the presence of congruent but likely fused and thus invisible visual flicker. The results matched the predictions of an ideal-observer model in which tactile-visual integration is conditional on awareness of both stimuli. In contrast, it was impossible to reproduce the observed results with a model that assumed tactile-visual integration proceeds irrespective of stimulus awareness. In sum, we revealed that the benefits of congruent visual stimulation for tactile flutter frequency perception depend on the visibility of the visual flicker, suggesting that multisensory integration requires awareness.

Hand Motions Reveal Attentional Status and Subliminal Semantic Processing: A Mouse-Tracking Technique

Theories of embodied cognition suggest that hand motions and cognition are closely interconnected. An emerging technique of tracking how participants move a computer mouse (i.e., the mouse-tracking technique) has shown advantages over the traditional response time measurement to detect implicit cognitive conflicts. Previous research suggests that attention is essential for subliminal processing to take place at a semantic level. However, this assumption is challenged by evidence showing the presence of subliminal semantic processing in the near-absence of attention. The inconsistency of evidence could stem from the insufficient sensitivity in the response time measurement. Therefore, we examined the role of attention in subliminal semantic processing by analyzing participants' hand motions using the mouse-tracking technique. The results suggest that subliminal semantic processing is not only enhanced by attention but also occurs when attention is disrupted, challenging the necessity of facilitated top-down attention for subliminal semantic processing, as claimed by a number of studies. In addition, by manipulating the color of attentional cues, our experiment shows that the cue color per se could influence participants' response patterns. Overall, the current study suggests that attentional status and subliminal semantic processing can be reliably revealed by temporal-spatial features extracted from cursor motion trajectories.

Perceptual and semantic same-different processing under subliminal conditions

Although other types of subliminal integrative processing are widely refuted by recent studies, subliminal same-different processing (SSDP) remains unchallenged to this day. Using shapes, categorical images, and Chinese characters as stimuli, the current study assessed whether SSDP can occur on a perceptual and semantic basis. Although some significant results were found, the effects are much weaker than previous studies, with Bayes factors suggesting that these effects are not reliable. It is therefore concluded that substantiating claims of SSDP requires more reliable evidence than currently available.

Effects of invisible lip movements on phonetic perception

We investigated whether 'invisible' visual information, i.e., visual information that is not consciously perceived, could affect auditory speech perception. Repeated exposure to McGurk stimuli (auditory /ba/ with visual [ga]) temporarily changes the perception of the auditory /ba/ into a 'da' or 'ga'. This altered auditory percept persists even after the presentation of the McGurk stimuli when the auditory stimulus is presented alone (McGurk aftereffect). We used this and presented the auditory /ba/ either with or without (No Face) a masked face articulating a visual [ba] (Congruent Invisible) or a visual [ga] (Incongruent Invisible). Thus, we measured the extent to which the invisible faces could undo or prolong the McGurk aftereffects. In a further control condition, the incongruent faces remained unmasked and thus visible, resulting in four conditions in total. Visibility was defined by the participants' subjective dichotomous reports ('visible' or 'invisible'). The results showed that the Congruent Invisible condition reduced the McGurk aftereffects compared with the other conditions, while the Incongruent Invisible condition showed no difference with the No Face condition. These results suggest that 'invisible' visual information that is not consciously perceived can affect phonetic perception, but only when visual information is congruent with auditory information.

Influences of Music Reading on Auditory Chord Discrimination: A Novel Test Bed for Nonconscious Processing of Irrelevant Prime Meaning

The question whether nonconscious processing could involve higher-level, semantic representations is of broad interest. Here, we demonstrate semantic processing of task-relevant and task-irrelevant features of nonconscious primes within a novel, empirical test bed. In two experiments, musicians were visually primed with musical note triads varying in mode (i.e., major vs minor) and position (i.e., the arrangement of notes within a triad). The task required to discriminate only the mode in the following auditory target chord. In two experimental blocks, primes were either consciously visible or masked, respectively. Response times for auditory discrimination of the modes (relevant dimension) of heard triads were measured. Crucially, the targets also varied with respect to mode and position, creating different grades of congruency with the visual primes. Based on the Theory of Event Coding, we expected and found interactions between relevant and irrelevant semantic characteristics of masked primes, illustrating that even irrelevant prime meaning was processed. Moreover, our results indicated that both task-relevant and task-irrelevant prime characteristics are processed in nonconscious conditions only, and that practice in ignoring uninformative conscious primes can be transferred to a subsequent block. In conclusion, this study demonstrates cross-modal, automatic semantic processing using a novel approach to study such effects.

Functional characterization of correct and incorrect feature integration

Our sensory system constantly receives information from the environment and our own body. Despite our impression to the contrary, we remain largely unaware of this information and often cannot report it correctly. Although perceptual processing does not require conscious effort on the part of the observer, it is often complex, giving rise to errors such as incorrect integration of features (illusory conjunctions). In the present study, we use functional magnetic resonance imaging to study the neural bases of feature integration in a dual task that produced ~30% illusions. A distributed set of regions demonstrated increased activity for correct compared to incorrect (illusory) feature integration, with increased functional coupling between occipital and parietal regions. In contrast, incorrect feature integration (illusions) was associated with increased occipital (V1-V2) responses at early stages, reduced functional connectivity between right occipital regions and the frontal eye field at later stages, and an overall decrease in coactivation between occipital and parietal regions. These results underscore the role of parietal regions in feature integration and highlight the relevance of functional occipito-frontal interactions in perceptual processing.

Feasibility of unconscious instrumental conditioning: A registered replication

The extent to which high-level, complex functions can proceed unconsciously has been a topic of considerable debate. While unconscious processing has been demonstrated for a range of low-level processes, from feature integration to simple forms of conditioning and learning, theoretical contributions suggest that increasing complexity requires conscious access. Here, we focus our attention on instrumental conditioning, which has been previously shown to proceed without stimulus awareness. Yet, instrumental conditioning also involves integrating information over a large temporal scale and distinct modalities in order to deploy selective action, constituting a process of substantial complexity. With this in mind, we revisit the question of feasibility of instrumental conditioning in the unconscious domain. Firstly, we address the theoretical and practical considerations relevant to unconscious learning in general. Secondly, we aim to replicate the first study to show instrumental conditioning in the absence of stimulus awareness (Pessiglione et al., 2008), following the original design and supplementing the original crucial analyses with a Bayesian approach (Experiment 1). We found that apparent unconscious learning took place when replicating the original methods directly and according to the tests of awareness used. However, we could not establish that the full sample was unaware in a separate awareness check. We therefore attempted to replicate the effect yet again with improved methods to address the issues related to sensitivity and immediacy (Experiment 2), including an individual threshold-setting task and a trial-by-trial awareness check permitting exclusion of individual aware trials. Here, we found evidence for absence of unconscious learning. This result provides evidence that instrumental conditioning did not occur without stimulus awareness in this paradigm, supporting the view that complex forms of learning may rely on conscious access. Our results provides support for the proposal that perceptual consciousness may be necessary for complex, flexible processes, especially where selective action and behavioural adaptation are required.

Unconscious integration: Current evidence for integrative processing under subliminal conditions

Integrative processing is traditionally believed to be dependent on consciousness. While earlier studies within the last decade reported many types of integration under subliminal conditions (i.e. without perceptual awareness), these findings are widely challenged recently. This review evaluates the current evidence for 10 types of subliminal integration that are widely studied: arithmetic processing, object-context integration, multi-word processing, same-different processing, multisensory integration and 5 different types of associative learning. Potential methodological issues concerning awareness measures are also taken into account. It is concluded that while there is currently no reliable evidence for subliminal integration, this does not necessarily refute 'unconscious' integration defined through non-subliminal (e.g. implicit) approaches.

The functions of consciousness in visual processing

Conscious experiences form a relatively diverse class of psychological phenomena, supported by a range of distinct neurobiological mechanisms. This diversity suggests that consciousness occupies a variety of different functional roles across different task domains, individuals, and species; a position I call functional pluralism. In this paper, I begin to tease out some of the functional contributions that consciousness makes to (human) visual processing. Consolidating research from across the cognitive sciences, I discuss semantic and spatiotemporal processing as specific points of comparison between the functional capabilities of the visual system in the presence and absence of conscious awareness. I argue that consciousness contributes a cluster of functions to visual processing; facilitating, among other things, (i) increased capacities for semantically processing informationally complex visual stimuli, (ii) increased spatiotemporal precision, and (iii) increased capacities for representational integration over large spatiotemporal intervals. This sort of analysis should ultimately yield a plurality of functional markers that can be used to guide future research in the philosophy and science of consciousness, some of which are not captured by popular theoretical frameworks like global workspace theory and information integration theory.

Role of visual awareness on semantic integration of sequentially presented words: An fMRI study

Reading comprehension requires the semantic integration of words across space and time. However, it remains unclear whether comprehension requires visual awareness for such semantic integration. Compared to earlier studies that investigated semantic integration indirectly from its priming effect, we used functional magnetic resonance imaging (fMRI) to directly examine the processes of semantic integration with or without visual awareness. Specifically, we manipulated participants' visual awareness by continuous flash suppression (CFS) while they viewed a meaningful sequence of four Chinese words (i.e., an idiom) or its meaningless counterpart (i.e., a random sequence). Behaviorally, participants had better recognition memory for idioms than random sequences only when their visual awareness was interfered rather than blocked by CFS. Neurally, semantics-processing areas, such as the superior temporal gyrus and inferior frontal gyrus, were significantly activated only when participants were aware of word sequences, be they meaningful or meaningless. By contrast, orthography-processing areas, such as the fusiform gyrus and inferior occipital gyrus, were significantly activated regardless of visual awareness or word sequence. Taken together, these results suggest that visual awareness modules the functioning of the semantic neural network in the brain and facilitates reading comprehension.

Inverse forgetting in unconscious episodic memory

Forming memories of experienced episodes calls upon the episodic memory system. Episodic encoding may proceed with and without awareness of episodes. While up to 60% of consciously encoded episodes are forgotten after 10 h, the fate of unconsciously encoded episodes is unknown. Here we track over 10 h, which are filled with sleep or daytime activities, the retention of unconsciously and consciously experienced episodes. The episodes were displayed in cartoon clips that were presented weakly and strongly masked for conscious and unconscious encoding, respectively. Clip retention was tested for distinct clips directly after encoding, 3 min and 10 h after encoding using a forced-choice test that demands deliberate responses in both consciousness conditions. When encoding was conscious, retrieval accuracy decreased by 25% from 3 min to 10 h, irrespective of sleep or wakefulness. When encoding was unconscious, retrieval accuracy increased from 3 min to 10 h and depended on sleep. Hence, opposite to the classic forgetting curve, unconsciously acquired episodic memories strengthen over time and hinge on sleep on the day of learning to gain influence over human behavior.

Assessing tests of animal consciousness

Which animals have conscious experiences? Many different, diverse and unrelated behaviors and cognitive capacities have been proposed as tests of the presence of consciousness in an animal. It is unclear which of these tests, if any, are valid. To remedy this problem, I develop a list consisting of eight desiderata which can be used to assess putative tests of animal consciousness. These desiderata are based either on detailed analogies between consciousness-linked human behavior and non-human behavior, on theories of consciousness or on methods from human consciousness science. If a test or set of tests satisfies more of these desiderata, passing it provides stronger evidence of consciousness. Moreover, one can design future tests of animal consciousness with the intention of satisfying these desiderata to ensure their evidential strength.

Cascaded normalizations for spatial integration in the primary visual cortex of primates

Spatial integration of visual information is an important function in the brain. However, neural computation for spatial integration in the visual cortex remains unclear. In this study, we recorded laminar responses in V1 of awake monkeys driven by visual stimuli with grating patches and annuli of different sizes. We find three important response properties related to spatial integration that are significantly different between input and output layers: neurons in output layers have stronger surround suppression, smaller receptive field (RF), and higher sensitivity to grating annuli partially covering their RFs. These interlaminar differences can be explained by a descriptive model composed of two global divisions (normalization) and a local subtraction. Our results suggest suppressions with cascaded normalizations (CNs) are essential for spatial integration and laminar processing in the visual cortex. Interestingly, the features of spatial integration in convolutional neural networks, especially in lower layers, are different from our findings in V1.

The functional contributions of consciousness

The most widely endorsed philosophical and scientific theories of consciousness assume that it contributes a single functional capacity to an organism's information processing toolkit. However, conscious processes are a heterogeneous class of psychological phenomena supported by a variety of neurobiological mechanisms. This suggests a plurality of functional contributions of consciousness (FCCs), in the sense that conscious experience facilitates different functional capacities in different psychological domains. In this paper, I first develop a general methodological framework for isolating the psychological functions that are associated with conscious experience. I then use this to show that the leading accounts-Global Workspace Theories, Higher Order Thought Theory and Information Integration Theory-all fail to acknowledge this functional pluralism, which limits their applicability as theories of consciousness.

The why of the phenomenal aspect of consciousness: Its main functions and the mechanisms underpinning it

What distinguishes conscious information processing from other kinds of information processing is its phenomenal aspect (PAC), the-what-it-is-like for an agent to experience something. The PAC supplies the agent with a sense of self, and informs the agent on how its self is affected by the agent's own operations. The PAC originates from the activity that attention performs to detect the state of what I define "the self" (S). S is centered and develops on a hierarchy of innate and acquired values, and is primarily expressed via the central and peripheral nervous systems; it maps the agent's body and cognitive capacities, and its interactions with the environment. The detection of the state of S by attention modulates the energy level of the organ of attention (OA), i.e., the neural substrate that underpins attention. This modulation generates the PAC. The PAC can be qualified according to five dimensions: qualitative, quantitative, hedonic, temporal and spatial. Each dimension can be traced back to a specific feature of the modulation of the energy level of the OA.

Neuroscientific Evidence for Processing Without Awareness

The extent to which we are affected by perceptual input of which we are unaware is widely debated. By measuring neural responses to sensory stimulation, neuroscientific data could complement behavioral results with valuable evidence. Here we review neuroscientific findings of processing of high-level information, as well as interactions with attention and memory. Although the results are mixed, we find initial support for processing object categories and words, possibly to the semantic level, as well as emotional expressions. Robust neural evidence for face individuation and integration of sentences or scenes is lacking. Attention affects the processing of stimuli that are not consciously perceived, and such stimuli may exogenously but not endogenously capture attention when relevant, and be maintained in memory over time. Sources of inconsistency in the literature include variability in control for awareness as well as individual differences, calling for future studies that adopt stricter measures of awareness and probe multiple processes within subjects.

Unconscious information integration: A replication and the role of spatial window in masking experiments

Consciousness and high-level information integration have commonly been closely related to each other (Baars, 2002; Dehaene & Naccache, 2001; Tononi, 2004). Different results, however, have challenged this assumption by showing that information integration can occur for stimuli presented outside of conscious awareness. More recently, a re-examination of some of the data and different replication attempts questioned these results thereby again suggesting a close link between consciousness and information integration. The current study aimed at (i) replicating another piece of evidence for unconscious information integration and (ii) investigating if the size of the spatial window in which the information to be integrated is presented could explain why unconscious information integration sometimes fails. Results showed a reliable replication so providing further evidence for unconscious information integration in a subliminal priming paradigm. Furthermore, our results revealed that unconscious integration depends on the size of the spatial window in which the information is presented.