Do conscious perception and unconscious processing rely on independent mechanisms? A meta-contrast study

There is currently no consensus regarding what measures are most valid to demonstrate perceptual processing without awareness. Likewise, whether conscious perception and unconscious processing rely on independent mechanisms or lie on a continuum remains a matter of debate. Here, we addressed these issues by comparing the time courses of subjective reports, objective discrimination performance and response priming during meta-contrast masking, under similar attentional demands. We found these to be strikingly similar, suggesting that conscious perception and unconscious processing cannot be dissociated by their time course. Our results also demonstrate that unconscious processing, indexed by response priming, occurs, and that objective discrimination performance indexes the same conscious processes as subjective visibility reports. Finally, our results underscore the role of attention by showing that how much attention the stimulus receives relative to the mask, rather than whether processing is measured by conscious discrimination or by priming, determines the time course of meta-contrast masking.     

Fear detection and visual awareness in perceiving bodily expressions

Many research reports have concluded that emotional information can be processed without observers being aware of it. The case for perception without awareness has almost always been made with the use of facial expressions. In view of the similarities between facial and bodily expressions for rapid perception and communication of emotional signals, we conjectured that perception of bodily expressions may also not necessarily require visual awareness. Our study investigates the role of visual awareness in the perception of bodily expressions using a backward masking technique in combination with confidence ratings on a trial-by-trial basis. Participants had to detect in three separate experiments masked fearful, angry and happy bodily expressions among masked neutral bodily actions as distractors and subsequently the participants had to indicate their confidence. The onset between target and mask (Stimulus Onset Asynchrony, SOA) varied from -50 to +133 ms. Sensitivity measurements (d-prime) as well as the confidence of the participants showed that the bodies could be detected reliably in all SOA conditions. In an important finding, a lack of covariance was observed between the objective and subjective measurements when the participants had to detect fearful bodily expressions, yet this was not the case when participants had to detect happy or angry bodily expressions.     

Increased cardiac awareness in panic disorder.

We investigated cardiac perception in panic disorder with both self-report and objective measures. In Study 1, 120 patients with panic disorder, 86 infrequent panickers, and 38 patients with other anxiety disorders reported greater cardiac and gastrointestinal awareness than 62 normal control subjects. Subjects with panic attacks reported greater cardiac awareness, but not gastrointestinal awareness, than those with other anxiety disorders. Studies 2 and 3 included a test of heart rate perception in which subjects silently counted their heart-beats without taking their pulse. In Study 2, 65 panic disorder patients showed better performance than 50 infrequent panickers, 27 patients with simple phobias, and 46 normal control subjects. No group differences were found in ability to estimate time intervals. In Study 3, 13 patients with panic disorder and 15 with generalized anxiety disorder showed better heart rate perception than 16 depressed patients.     

Visual expectations change subjective experience without changing performance

It is widely believed that visual expectations can change the subjective experiences of humans. We investigated how visual expectations in a recognition task affected objective performance and subjective perception. Using a 2-alternative-forced-choice task based on digit recognition of briefly presented and visually masked digits, we found over two experiments that expectations changed the quality of the experiences without changing the performance capabilities associated with the quality of experience. Expectations were manipulated by providing a cue indicating the set of possible digits that might appear on each trial.The results also inform the debate about whether subjective experiences can be categorized in a dichotomous manner or in a graded manner. We found that subjective experiences were graded near the objective threshold and more dichotomous away from the threshold. Furthermore, distinct expectations resulted in a more dichotomous distribution of subjective experience.We also provide evidence of an interesting relationship between stimulus duration, objective performance and subjective ratings. Only experiences that were rated as evoking some degree of perception showed systematic improvements in objective performance as a function of stimulus duration.These findings suggest that subjective experience cannot be understood without considering the broader cognitive context, namely that the quality of subjective experiences is dependent on a multitude of factors such as attention, task requirements and cognitive expectations.     

Different subjective awareness measures demonstrate the influence of visual identification on perceptual awareness ratings

We compare four subjective awareness measures in the context of a visual identification task and investigate quantitative differences in terms of scale use and correlation with task performance. We also analyse the effect of identification task decisions on subsequent subjective reports. Results show that awareness ratings strongly predict accuracy for all scale types, although the type of awareness measure may influence the reported level of perceptual awareness. Surprisingly, the overall relationship between awareness ratings and performance was weaker when participants rated their awareness before providing identification responses. Furthermore, the Perceptual Awareness Scale was most exhaustive only when used after the identification task, whereas confidence ratings were most exhaustive when used before the identification task. We conclude that the type of subjective measure applied may influence the reports on visual awareness. We also propose that identification task decisions may affect subsequent awareness ratings.     

Thresholds for detection and awareness of masked facial stimuli

It has been suggested that perception without awareness can be demonstrated by a dissociation between performance in objective (forced-choice) and subjective (yes–no) tasks, and such dissociations have been reported both for simple stimuli and more complex ones including faces. However, signal detection theory (SDT) indicates that the subjective measures used to assess awareness in such studies can be affected by response bias, which could account for the observed dissociation, and this was confirmed by Balsdon and Azzopardi (2015) using simple visual targets. However, this finding may not apply to all types of stimulus, as the detectability of complex targets such as faces is known to be affected by their configuration as well as by their stimulus energy. We tested this with a comparison of forced-choice and yes–no detection of facial stimuli depicting happy or angry or fearful expressions using a backward masking paradigm, and using SDT methods including correcting for unequal variances in the underlying signal distributions, to measure sensitivity independently of response criterion in 12 normal observers. In 47 out 48 comparisons there was no significant difference between sensitivity (d_a) in the two tasks: hence, across the range of expressions tested it appears that the configuration of complex stimuli does not enhance detectability independently of awareness. The results imply that, on the basis of psychophysical experiments in normal observers, there is no reason to postulate that performance and awareness are mediated by separate processes.     

Gradedness of visual awareness depends on attentional scope: Global perception is more graded than local perception

The gradedness or discreteness of our visual awareness has been debated. Here, we investigate the influence of spatial scope of attention on the gradedness of visual awareness. We manipulated scope of attention using hierarchical letter-based tasks (global: broad scope; local: narrow scope). Participants reported the identity of a masked hierarchical letter either at the global level or at the local level. We measured subjective awareness using the perceptual awareness scale ratings and objective performance. The results indicate more graded visual awareness (lesser slope for the awareness rating curve) at the global level compared to the local level. Graded perception was also observed in visibility ratings usage with global level task showing higher usage of the middle PAS ratings. Our results are in line with the prediction of level of processing hypothesis and show that global/local attentional scope and contextual endogenous factors influence the graded nature of our visual awareness.     

Subjective discriminability of invisibility: A framework for distinguishing perceptual and attentional failures of awareness

Conscious visual perception can fail in many circumstances. However, little is known about the causes and processes leading to failures of visual awareness. In this study, we introduce a new signal detection measure termed subjective discriminability of invisibility (SDI) that allows one to distinguish between subjective blindness due to reduction of sensory signals or to lack of attentional access to sensory signals. The SDI is computed based upon subjective confidence in reporting the absence of a target (i.e., miss and correct rejection trials). Using this new measure, we found that target misses were subjectively indistinguishable from physical absence when contrast reduction, backward masking and flash suppression were used, whereas confidence was appropriately modulated when dual task, attentional blink and spatial uncertainty methods were employed. These results show that failure of visual perception can be identified as either a result of perceptual or attentional blindness depending on the circumstances under which visual awareness was impaired.     

Measuring consciousness: Is one measure better than the other?

What is the best way of assessing the extent to which people are aware of a stimulus? Here, using a masked visual identification task, we compared three measures of subjective awareness: The Perceptual Awareness Scale (PAS), through which participants are asked to rate the clarity of their visual experience; confidence ratings (CR), through which participants express their confidence in their identification decisions, and Post-decision wagering (PDW), in which participants place a monetary wager on their decisions. We conducted detailed explorations of the relationships between awareness and identification performance, looking to determine (1) which scale best correlates with performance, and (2) whether we can detect performance in the absence of awareness and how the scales differ from each other in terms of revealing such unconscious processing. Based on these findings we discuss whether perceptual awareness should be considered graded or dichotomous. Results showed that PAS showed a much stronger performance-awareness correlation than either CR or PDW, particularly for low stimulus intensities. In general, all scales indicated above-chance performance when participants claimed not to have seen anything. However, such above-chance performance only showed when we also observed a correlation between awareness and performance. Thus (1) PAS seems to be the most exhaustive measure of awareness, and (2) we find support for above-chance performance in the absence of subjective awareness, but such unconscious knowledge only contributes to performance when we observe conscious knowledge as well. Similarities and differences between scales are discussed in the light of consciousness theories and response strategies.     

Marginally perceptible outcome feedback, motor learning and implicit processes

Participants struck 500 golf balls to a concealed target. Outcome feedback was presented at the subjective or objective threshold of awareness of each participant or at a supraliminal threshold. Participants who received fully perceptible (supraliminal) feedback learned to strike the ball onto the target, as did participants who received feedback that was only marginally perceptible (subjective threshold). Participants who received feedback that was not perceptible (objective threshold) showed no learning. Upon transfer to a condition in which the target was unconcealed, performance increased in both the subjective and the objective threshold condition, but decreased in the supraliminal condition. In all three conditions, participants reported minimal declarative knowledge of their movements, suggesting that deliberate hypothesis testing about how best to move in order to perform the motor task successfully was disrupted by the impoverished disposition of the visual outcome feedback. It was concluded that sub-optimally perceptible visual feedback evokes implicit processes.     

视觉情绪知觉需要注意和意识吗？困惑及其原因

一些研究者通过操纵刺激知觉条件或者被试注意资源的分配方式来改变意识水平,他们报告视觉情绪刺激可以在没有进入意识的条件下知觉。但最近采用更为客观的方法揭示先前研究中所用的测量意识觉知的标准并不客观有效,这些以信号检测论为基础的研究显示,视觉情绪知觉离不开注意,注意通过自上而下和自下而上两种方式调控情绪知觉,除此之外还发现,个性变量,比如焦虑特质的差异也会影响到情绪知觉     

Relative blindsight arises from a criterion confound in metacontrast masking: implications for theories of consciousness

Relative blindsight is said to occur when different levels of subjective awareness are obtained at equality of objective performance. Using metacontrast masking, Lau and Passingham (2006) reported relative blindsight in normal observers at the shorter of two stimulus-onset asynchronies (SOAs) between target and mask. Experiment 1 replicated the critical asymmetry in subjective awareness at equality of objective performance. We argue that this asymmetry cannot be regarded as evidence for relative blindsight because the observers' responses were based on different attributes of the stimuli (criterion contents) at the two SOAs. With an invariant criterion content (Experiment 2), there was no asymmetry in subjective awareness across the two SOAs even though objective performance was the same. Experiment 3 examined the effect of criterion level on estimates of relative blindsight. Collectively, the present results question whether metacontrast masking is a suitable paradigm for establishing relative blindsight. Implications for theories of consciousness are discussed.     

Domain-specific and domain-general processes underlying metacognitive judgments

Metacognition and self-awareness are commonly assumed to operate as global capacities. However, there have been few attempts to test this assumption across multiple cognitive domains and metacognitive evaluations. Here, we assessed the covariance between “online” metacognitive processes, as measured by decision confidence judgments in the domains of perception and memory, and error awareness in the domain of attention to action. Previous research investigating metacognition across task domains have not matched stimulus characteristics across tasks raising the possibility that any differences in metacognitive accuracy may be influenced by local task properties. The current experiment measured metacognition in perceptual, memorial and attention tasks that were closely matched for stimulus characteristics. We found that metacognitive accuracy across the three tasks was dissociated suggesting that domain specific networks support an individual’s capacity for accurate metacognition. This finding was independent of objective performance, which was controlled using a staircase procedure. However, response times for metacognitive judgments and error awareness were associated suggesting that shared mechanisms determining how these meta-level evaluations unfold in time may underlie these different types of decision. In addition, the relationship between these laboratory measures of metacognition and reports of everyday functioning from participants and their significant others (informants) was investigated. We found that informant reports, but not self reports, predicted metacognitive accuracy on the perceptual task and participants who underreported cognitive difficulties relative to their informants also showed poorer metacognitive accuracy on the perceptual task. These results are discussed in the context of models of metacognitive regulation and neuropsychological evidence for dissociable metacognitive systems. The potential for the refinement of metacognitive assessment in clinical populations is also discussed.     

The perception of visual emotion: Comparing different measures of awareness

Here, we explore the sensitivity of different awareness scales in revealing conscious reports on visual emotion perception. Participants were exposed to a backward masking task involving fearful faces and asked to rate their conscious awareness in perceiving emotion in facial expression using three different subjective measures: confidence ratings (CRs), with the conventional taxonomy of certainty, the perceptual awareness scale (PAS), through which participants categorize “raw” visual experience, and post-decision wagering (PDW), which involves economic categorization. Our results show that the CR measure was the most exhaustive and the most graded. In contrast, the PAS and PDW measures suggested instead that consciousness of emotional stimuli is dichotomous. Possible explanations of the inconsistency were discussed. Finally, our results also indicate that PDW biases awareness ratings by enhancing first-order accuracy of emotion perception. This effect was possibly a result of higher motivation induced by monetary incentives.     

Perception without awareness: perspectives from cognitive psychology

Four basic approaches that have been used to demonstrate perception without awareness are described. Each approach reflects one of two types of experimental logic and one of two possible methods for controlling awareness. The experimental logic has been either to demonstrate a dissociation between a measure of perception with awareness and a measure that is sensitive to perception without awareness or to demonstrate a qualitative difference between the consequences of perception with and without awareness. Awareness has been controlled either by manipulating the stimulus conditions or by instructing observers on how to distribute their attention. The experimental findings based on all four approaches lead to the same conclusion; namely, stimuli are perceived even when observers are unaware of the stimuli. This conclusion is supported by results of studies in which awareness has been assessed with either objective measures of forced-choice discriminations or measures based on verbalizations of subjective conscious experiences. Given this solid empirical support for the concept of perception without awareness, a direction for future research studies is to assess the functions of information perceived without awareness in determining what is perceived with awareness. The available evidence suggests that information perceived without awareness both biases what stimuli are perceived with awareness and influences how stimuli perceived with awareness are consciously experienced.     

Mental control and visual illusions: Toward explaining race-biased weapon misidentifications

People are biased to misidentify harmless objects as weapons when the objects are associated with African Americans (Payne, 2001). Two studies examined the processes underlying this bias. The illusory perception hypothesis argues that stereotypes alter the subjective construal of the object. In contrast, the executive failure hypothesis argues that even when perception of the item is intact, misidentifications can result from failures to control responses. Immediately after making an error, participants were able to accurately express that they had made a mistake via confidence ratings (Experiment 1) and by correcting their judgment (Experiment 2). Subjective confidence judgments were extremely well calibrated to accuracy, and participants virtually never believed their own mistakes. Conditions likely to create errors through both illusions and control failures are discussed.     

Individual Difference Correlates of the Experience of Sexual Harassment Among Female University Students1

Individuals often report experiences that conform to objective definitions of sexual harassment, but rarely report the subjective perception that they have been sexually harassed. The present research proposed that individual difference factors may mediate this commonly observed discrepancy. It was hypothesized that erotophobia, sexual inexperience, youth, sex role traditionality, repressing defensive style, and need for social approval have a weak inhibitory effect on reports of objectively defined experiences of sexual harassment, but a strong inhibitory effect on subjective perceptions that one has been sexually harassed. Results showed that individual difference factors including erotophobia, repressing defenses, and need for social approval were associated with fewer reported objective experiences of sexual harassment, while the base rate of subjective perception that one had been sexually harassed was very low, and this subjective perception was generally unassociated with individual difference factors. Discussion focuses on individual difference characteristics and motivation to ignore or to fail to report objective experiences of sexual harassment, and on suggestions for further research into the very high base rate of objectively defined experiences of sexual harassment and the very low base rate of perceived sexual harassment.     

Contingency learning with evaluative stimuli: testing the generality of contingency learning in a performance paradigm

In two experiments, we tested the generality of the learning effects in the recently-introduced color-word contingency learning paradigm. Participants made speeded evaluative judgments to valenced target words. Each of a set of distracting nonwords was presented most often with either positive or negative target words. We observed that participants responded faster on trials that respected these contingencies than on trials that contradicted the contingencies. The contingencies also produced changes in liking: in a subsequent explicit evaluative rating task, participants rated positively-conditioned nonwords more positively than negatively-conditioned nonwords. Interestingly, contingency effects in the performance task correlated with this explicit rating effect in both experiments. In Experiment 2, all effects reported were independent of subjective and objective contingency awareness (which was completely lacking), even when awareness was measured at the item level. Our results reveal that learning in this type of performance task extends to nonword-valence contingencies and to responses different from those emitted during the performance task. We discuss the implications of these findings for theories about the processes that underlie contingency learning in performance tasks and for research on evaluative conditioning.     

The importance of identifying underlying process abnormalities in alexithymia: Implications of the three-process model and a single case study illustration

We present an in-depth case study of a rare individual (whom we will refer to as “Jane”) who reported an inability to experience emotion. Jane completed a range of assessments measuring alexithymia, emotional awareness, and emotion recognition ability. She, along with 22 control participants, also underwent skin conductance (SC) measurement and facial electromyography (EMG) during exposure to affective images, and self reported the valence/arousal of their responses to those images. Jane scored high on alexithymia and low on emotional awareness; yet she performed well on emotion recognition measures and showed a typical pattern of valence ratings. Her SC responses and subjective arousal ratings were atypically low, and some of her EMG responses were also atypical. Jane’s deficit profile highlights the dissociability of self-focused emotional awareness and other-focused emotion recognition ability, as well as the dissociability between the generation and representation of valence and arousal (with both subjective and objective measures).     

Unawareness is more than a chance event: comment on Lovibond and Shanks (2002)

P. F. Lovibond and D. R. Shanks (2002) suggested that expectancy of the unconditional stimulus and emotional ratings are valid indexes of awareness in Pavlovian conditioning and that participants are aware if they can discriminate the conditional stimuli. However, research suggests that processes that are irrelevant to awareness affect these measures. Further, as awareness refers to conscious experience, a valid measures needs to index subjective state rather than discrimination ability. In support, research using subjective measures has demonstrated qualitatively different effects depending on whether participants reported being aware or unaware of the stimuli. In this research, participants reported being unaware of the stimuli even though they were clearly able to discriminate the stimuli. These findings question the validity of Lovibond and Shanks' concept of awareness and their suggestion of a close association between conditioning and awareness.