Continuous Flash Suppression Research Articles

Evidence for visual simulation during sign language processing.

What are the mental processes that allow us to understand the meaning of words? A large body of evidence suggests that when we process speech, we engage a process of perceptual simulation whereby sensorimotor states are activated as a source of semantic information. But does the same process take place when words are expressed with the hands and perceived through the eyes? To date, it is not known whether perceptual simulation is also observed in sign languages, the manual-visual languages of deaf communities. Continuous flash suppression is a method that addresses this question by measuring the effect of language on detection sensitivity to images that are suppressed from awareness. In spoken languages, it has been reported that listening to a word (e.g., "bottle") activates visual features of an object (e.g., the shape of a bottle), and this in turn facilitates image detection. An interesting but untested question is whether the same process takes place when deaf signers see signs. We found that processing signs boosted the detection of congruent images, making otherwise invisible pictures visible. A boost of visual processing was observed only for signers but not for hearing nonsigners, suggesting that the penetration of the visual system through signs requires a fully fledged manual language. Iconicity did not modulate the effect of signs on detection, neither in signers nor in hearing nonsigners. This suggests that visual simulation during language processing occurs regardless of language modality (sign vs. speech) or iconicity, pointing to a foundational role of simulation for language comprehension. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Hidden intentions: Visual awareness prioritizes perceived attention even without eyes or faces

Eye contact is a powerful social signal, and it readily captures attention. Recent work has suggested that direct gaze is prioritized even unconsciously: faces rendered invisible via interocular suppression enter awareness faster when they look directly at (vs. away from) you. Such effects may be driven in a relatively low level way by the special visual properties of eyes, per se, but here we asked whether they might instead arise from the perception of a deeper property: being the focus of another agent's attention and/or intentions. We report five experiments which collectively explore whether visual awareness also prioritizes distinctly non-eye-like stimuli that nevertheless convey directedness. We first showed that directed (vs. averted) ‘mouth’ shapes also break through into awareness faster, after being rendered invisible by continuous flash suppression — a direct ‘gaze’ effect without any eyes. But such effects could still be specific to faces (if not eyes), so we next asked whether the prioritization of directed intentions would still occur even for stimuli that have no faces at all. In fact, even simple geometric shapes can be seen as intentional, as when numerous randomly scattered cones are all consistently pointing at you. And indeed, even such directed (vs. averted) cones entered awareness faster — a direct ‘gaze’ effect without any facial cues. Additional control experiments ruled out effects of both symmetry and response biases. We conclude that the perception of directed intentions is sufficient to boost objects into awareness, and that putative eye-contact effects might instead reflect more general phenomena of ‘mind contact’.

Feature-CoAlignment Between Mask and Stimulus Affects Suppression Depth in Continuous Flash Suppression

Feature-CoAlignment Between Mask and Stimulus Affects Suppression Depth in Continuous Flash Suppression

Content-Based Interaction Between Mask and Target in Continuous Flash Suppression

Content-Based Interaction Between Mask and Target in Continuous Flash Suppression

Which comes first? Examining breaking continuous flash suppression time of high-calorie and low-calorie foods

Which comes first? Examining breaking continuous flash suppression time of high-calorie and low-calorie foods

Nasal visual field of origin contributes to interocular competition strength

During binocular rivalry (BR), perceptual dominance alternates between the inputs of the eyes, meaning that (at any time) the non-dominating input is suppressed, despite being projected on a retina. It has been proposed that BR is the result of interocular competition (IOC), where the input that 'wins' the competition becomes the dominant percept. Both top-down factors (e.g., attention, working memory content) and bottom-up factors (e.g., saliency, eye dominance) have been shown to affect IOC. One factor has remained largely disregarded, however: the input’s visual field of origin. The lack of attention to this factor is surprising, since the visual field of origin is known to affect performance in various contexts outside of BR. Exploratory analyses on previously gathered data using a breaking continuous flash suppression (b-CFS) paradigm suggested that nasally presented targets (i.e., presented in the nasal visual hemifield (VHF)) broke through suppression faster than temporally presented targets. We confirmed this exploratory observation in a reanalysis of five independent b-CFS datasets. Strikingly, we found that the effect of VHF was even larger (by 25%) than the well-established effect of eye dominance, as measured by response time differences in the b-CFS paradigm. Importantly, the magnitude of the VHF effect depended on the strength of IOC, both within-observers (recessive > dominant eye), and across-observers (weak > strong eye-dominance). These findings show that the VHF effect reported here is specific to IOC, rather than reflecting a generic visual field anisotropy. Lastly, we simulated 10.000 datasets to show that our findings did not spuriously emerge from our analysis pipeline. Taken together, we demonstrate a substantial advantage for visual input from the nasal VHF during IOC. These findings have broad implications for augmented/virtual reality applications and yield important methodological considerations for researchers utilizing IOC-based paradigms to investigate the contents and functions of human consciousness.

Dimensions of Perception: 3D Real-Life Objects Are More Readily Detected Than Their 2D Images

Most of our interactions with our environment involve manipulating real 3D objects. Accordingly, 3D objects seem to enjoy preferential processing compared with 2D images, for example, in capturing attention or being better remembered. But are they also more readily perceived? Thus far, the possibility of preferred detection for real 3D objects could not be empirically tested because suppression from awareness has been applied only to on-screen stimuli. Here, using a variant of continuous flash suppression (CFS) with augmented-reality goggles (“real-life” CFS), we managed to suppress both real 3D objects and their 2D representations. In 20 healthy young adults, real objects broke suppression faster than their photographs. Using 3D printing, we also showed in 50 healthy young adults that this finding held only for meaningful objects, whereas no difference was found for meaningless, novel ones (a similar trend was observed in another experiment with 20 subjects, yet it did not reach significance). This suggests that the effect might be mediated by affordances facilitating detection of 3D objects under interocular suppression.

Oxygen Metabolism-induced Stress Response Underlies Heart-brain Interaction Governing Human Consciousness-breaking and Attention.

Neuroscientists have emphasized visceral influences on consciousness and attention, but the potential neurophysiological pathways remain under exploration. Here, we found two neurophysiological pathways of heart-brain interaction based on the relationship between oxygen-transport by red blood cells (RBCs) and consciousness/attention. To this end, we collected a dataset based on the routine physical examination, the breaking continuous flash suppression (b-CFS) paradigm, and an attention network test (ANT) in 140 immigrants under the hypoxic Tibetan environment. We combined electroencephalography and multilevel mediation analysis to investigate the relationship between RBC properties and consciousness/attention. The results showed that RBC function, via two independent neurophysiological pathways, not only triggered interoceptive re-representations in the insula and awareness connected to orienting attention but also induced an immune response corresponding to consciousness and executive control. Importantly, consciousness played a fundamental role in executive function which might be associated with the level of perceived stress. These results indicated the important role of oxygen-transport in heart-brain interactions, in which the related stress response affected consciousness and executive control. The findings provide new insights into the neurophysiological schema of heart-brain interactions.

Supplemental Material for Biological Motion Gains Preferential Access to Awareness During Continuous Flash Suppression: Local Biological Motion Matters

Supplemental Material for Biological Motion Gains Preferential Access to Awareness During Continuous Flash Suppression: Local Biological Motion Matters

No effect of value learning on awareness and attention for faces: Evidence from continuous flash suppression and the attentional blink.

It is widely believed that the emotional and movtivational value of social signals, such as faces, influences perception and attention. However, effects reported for stimuli with intrinsic affective value, such as emotional facial expressions, can often be explained by differences in low-level stimulus properties. To rule out such low-level effects, here we used a value-learning procedure, in which faces were associated with different probabilities of monetary gain and loss in a choice game. In three experiments involving 149 participants, we tested the influence of affective valence (win- vs. loss-associated faces) and motivational salience (probability of monetary gain or loss) on visual awareness, attention, and memory. Using continuous flash suppression and rapid serial visual presentation, we found no effects of affective valence or motivational salience on visual awareness of faces. Furthermore, in two experiments, there was no evidence for a modulation of the attentional blink, indicating that acquired emotional and motivational value does not influence attentional priority of faces. However, we found that motivational salience boosted recognition memory, and this effect was particularly pronounced for win-associated faces. These results indicate that acquired affective valence and motivational salience affect only later processing of faces related to memory but do not directly affect visual awareness and attention. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Holistic face processing is influenced by non-conscious visual information.

Holistic face processing has been widely implicated in conscious face perception. Yet, little is known about whether holistic face processing occurs when faces are processed unconsciously. The present study used the composite face task and continuous flash suppression (CFS) to inspect whether the processing of target facial information (the top half of a face) is influenced by irrelevant information (the bottom half) that is presented unconsciously. Results of multiple experiments showed that the composite effect was observed in both monocular and CFS conditions, providing the first evidence that the processing of top facial halves is influenced by the aligned bottom halves no matter whether they are presented consciously or unconsciously. However, much of the composite effect for faces without masking was disrupted when bottom facial parts were rendered with CFS. These results suggest that holistic face processing can occur unconsciously, but also highlight the significance of holistic processing of consciously presented faces.

Interaction Between Conscious and Unconscious Information-Processing of Faces and Words.

It is widely acknowledged that holistic processing is a key characteristic of face perception. Although holistic processing implies the automatic integration of face parts, it is unclear whether such processing requires the awareness of face parts. Here, we investigated the interactions between visible face parts and face parts rendered invisible using continuous flash suppression (CFS). In the first experiment with the upper half-face visible and the lower half-face invisible, the results showed that perceived face identity was influenced by the invisible lower half-face, suggesting that integration occurs between the visible and invisible face parts, a variant of the "composite face effect". In the second experiment, we investigated the influence of visible face parts on the processing of invisible face parts, as measured by the time it took for the invisible parts to break out from CFS. The results showed a visible-to-invisible facilitation effect, that the aligned invisible face parts broke through CFS faster than when the visible and invisible face parts were misaligned. Visible eyes had a stronger influence on the invisible nose/mouth than the other way around. Such facilitation of processing from visible to invisible parts was also found when Chinese characters were used as stimuli. These results show that information integration occurs across the consciousness boundary.

Diffusion model-based understanding of subliminal affective priming in continuous flash suppression

Affective states influence our decisions even when processed unconsciously. Continuous flash suppression (CFS) is a new variant of binocular rivalry that can be used to render the prime subliminal. Nonetheless, how prior information from emotional faces suppressed by CFS influences subsequent decision-making remains unclear. Here, we employed a CFS priming task to examine the effect of the two main types of information conveyed by faces, i.e., facial identity and emotion, on the evaluation of target words as positive or negative. The hierarchical diffusion model was used to investigate the underlying mechanisms. A significant interaction effect on response time was observed following the angry face prime but not the happy or neutral face primes. The results of the diffusion model analyses revealed that the priming effects of facial identity were mapped onto the drift rate and erased the ‘positive bias’ (the processing advantage of positive over negative stimuli). Meanwhile, the positive emotional faces increased the nondecision time in response to negative target words. The model-based analysis implies that both facial identity and emotion are processed under CFS.

Sorry, baby: Infant faces reach awareness more slowly than adult faces.

Past research has found an attentional bias for positive relative to neutral stimuli, with a greater attentional bias for stimuli that are more motivationally relevant. Baby faces are an example of a motivationally relevant stimulus because they elicit caretaking behaviors. Building on previous work demonstrating that baby faces capture attention, the current study used breaking continuous flash suppression (bCFS) to investigate whether infant faces are prioritized for access to awareness. On each trial of the task, a face was shown to one eye and a rapidly changing Mondrian pattern to the other. Participants were asked to report the location of the face as soon as it emerged from suppression. The faces were either infant or adult faces, presented in upright or inverted orientation. Despite evidence suggesting that infant faces might reach awareness more quickly than adult faces, the opposite was found: Adult faces reached awareness more quickly than infant faces. Moreover, a stronger face inversion effect was observed for adult versus infant faces, indicating that the shorter suppression times for adult faces were due to increased expertise with adult faces. A past bCFS study demonstrated an own-age face effect for young adults, but it left open the possibility that this effect was due to the youthful appearance of the young versus old faces. The current results rule out this possibility and provide further support for the idea that experience with faces of one's own social group facilitates the access of those faces to awareness. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Shifting eye balance using monocularly directed attention in normal vision.

In binocular vision, even without conscious awareness of eye of origin, attention can be selectively biased toward one eye by presenting a visual stimulus uniquely to that eye. Monocularly directed visual cues can bias perceptual dominance, as shown by studies using discrete measures of percept changes in continuous-flash suppression. Here, we use binocular rivalry to determine whether eye-based visual cues can modulate eye balance using continuous percept reporting. Using a dual-task versus single-task paradigm, we investigated whether the attentional load of these cues differentially modulates eye balance. Furthermore, both color-based and motion-based cue stimuli, non-overlaid and peripheral to the rivalry grating stimuli, were used to determine whether shifts in eye balance were stimulus specific. Aligned to cue stimulus onset, time series of percept reports were constructed and averaged across trials and participants. Specifically, for the monocular attention conditions, we found a significant shift in eye balance toward the cued eye and a significant difference in the time taken to switch from the dominating percept, regardless of whether the attention stimuli is color based or motion based. Although we did not find a significant main effect of attentional load, we found a significant interaction effect between the attentionally cued eye and attentional load on the shift in eye balance, indicating an influence of monocular attention on the shift in eye balance.

Conscious awareness modulates processing speed in the redundant signal effect

Evidence for the influence of unaware signals on behaviour has been reported in both patient groups and healthy observers using the Redundant Signal Effect (RSE). The RSE refers to faster manual reaction times to the onset of multiple simultaneously presented target than those to a single stimulus. These findings are robust and apply to unimodal and multi-modal sensory inputs. A number of studies on neurologically impaired cases have demonstrated that RSE can be found even in the absence of conscious experience of the redundant signals. Here, we investigated behavioural changes associated with awareness in healthy observers by using Continuous Flash Suppression to render observers unaware of redundant targets. Across three experiments, we found an association between reaction times to the onset of a consciously perceived target and the reported level of visual awareness of the redundant target, with higher awareness being associated with faster reaction times. However, in the absence of any awareness of the redundant target, we found no evidence for speeded reaction times and even weak evidence for an inhibitory effect (slowing down of reaction times) on response to the seen target. These findings reveal marked differences between healthy observers and blindsight patients in how aware and unaware information from different locations is integrated in the RSE.

Overly Strong Priors for Socially Meaningful Visual Signals Are Linked to Psychosis Proneness in Healthy Individuals.

According to the predictive coding theory of psychosis, hallucinations and delusions are explained by an overweighing of high-level prior expectations relative to sensory information that leads to false perceptions of meaningful signals. However, it is currently unclear whether the hypothesized overweighing of priors (1) represents a pervasive alteration that extends to the visual modality and (2) takes already effect at early automatic processing stages. Here, we addressed these questions by studying visual perception of socially meaningful stimuli in healthy individuals with varying degrees of psychosis proneness (n = 39). In a first task, we quantified participants’ prior for detecting faces in visual noise using a Bayesian decision model. In a second task, we measured participants’ prior for detecting direct gaze stimuli that were rendered invisible by continuous flash suppression. We found that the prior for detecting faces in noise correlated with hallucination proneness (r = 0.50, p = 0.001, Bayes factor 1/20.1) as well as delusion proneness (r = 0.46, p = 0.003, BF 1/9.4). The prior for detecting invisible direct gaze was significantly associated with hallucination proneness (r = 0.43, p = 0.009, BF 1/3.8) but not conclusively with delusion proneness (r = 0.30, p = 0.079, BF 1.7). Our results provide evidence for the idea that overly strong high-level priors for automatically detecting socially meaningful stimuli might constitute a processing alteration in psychosis.

Unpredictive linguistic verbal cues accelerate congruent visual targets into awareness in a breaking continuous flash suppression paradigm

One of the most influential ideas within the domain of cognition is that of embodied cognition, in which the experienced world is the result of an interplay between an organism’s physiology, sensorimotor system, and its environment. An aspect of this idea is that linguistic information activates sensory representations automatically. For example, hearing the word ‘red’ would automatically activate sensory representations of this color. But does linguistic information prioritize access to awareness of congruent visual information? Here, we show that linguistic verbal cues accelerate matching visual targets into awareness by using a breaking continuous flash suppression paradigm. In a speeded reaction time task, observers heard spoken color labels (e.g., red) followed by colored targets that were either congruent (red), incongruent (green), or neutral (a neutral noncolor word) with respect to the labels. Importantly, and in contrast to previous studies investigating a similar question, the incidence of congruent trials was not higher than that of incongruent trials. Our results show that RTs were selectively shortened for congruent verbal–visual pairings, and that this shortening occurred over a wide range of cue–target intervals. We suggest that linguistic verbal information preactivates sensory representations, so that hearing the word ‘red’ preactivates (visual) sensory information internally.

Bottom-up processing of fearful and angry facial expressions is intact in schizophrenia

ABSTRACT Introduction Judgments of emotion from faces are reportedly impaired in schizophrenia. However, it is unclear whether this is due to a top-down cognitive deficit in evaluating sensory information or a fundamental bottom-up perturbation in the early stages of face encoding. This study examined whether deficits in emotion processing reflect imprecision in the initial preconscious registration of emotional face expressions within the visual system. Methods Using continuous flash suppression (CFS), we presented participants (18 patients with schizophrenia, 8M/10F; 20 healthy controls, 13M/7F) with fearful and angry faces. Previous CFS research on healthy participants reveals that fearful facial expressions gain privileged access to awareness over angry faces—demonstrating the visual system’s ability to discriminate these emotions at a preconscious level. We used this same approach to probe the integrity of early emotion encoding whilst minimising the potential contribution of any top-down cognitive biases on perceptual judgments. Results In both groups, fearful faces were perceived faster than angry faces, with no differences observed between patients and controls. Conclusions Emotion processing difficulties in schizophrenia are unlikely to reflect an early sensory deficit, but rather a deficit in social cognition that has a top-down impact on the conscious evaluation of facial expressions.

Color Can Shorten Breakthrough Times in Continuous Flash Suppression through Increased Salience and Task Relevance

Color can enhance the perception of relevant stimuli by increasing their salience and guiding visual search towards stimuli that match a task-relevant color. Using Continuous Flash Suppression (CFS), the current study investigated whether color facilitates the discrimination of targets that are difficult to perceive due to interocular suppression. Gabor patterns of two or four cycles per degree (cpd) were shown as targets to the non-dominant eye of human participants. CFS masks were presented at a rate of 10 Hz to the dominant eye, and participants had the task to report the target’s orientation as soon as they could discriminate it. The 2-cpd targets were robustly suppressed and resulted in much longer response times compared to 4-cpd targets. Moreover, only for 2-cpd targets, two color-related effects were evident. First, in trials where targets and CFS masks had different colors, targets were reported faster than in trials where targets and CFS masks had the same color. Second, targets with a known color, either cyan or yellow, were reported earlier than targets whose color was randomly cyan or yellow. The results suggest that the targets’ entry to consciousness may have been speeded by color-mediated effects relating to increased (bottom-up) salience and (top-down) task relevance.