Emotional priming depends on the degree of conscious experience

Priming using human and chimpanzee expressions of emotion biases attention toward positive emotions

Perceiving and correctly interpreting emotional expressions is one of the most important abilities for social animals' communication. It determines the majority of social interactions, group dynamics, and cooperation - being highly relevant for an individual's survival. Core mechanisms of this ability have been hypothesised to be shared across closely related species with phylogenetic similarities. This study explored homologies in human processing of species-specific facial expressions using eye-tracking. Introducing a prime-target paradigm, we tested the influences on human attention elicited by priming with differently valenced emotional stimuli depicting human and chimpanzee faces. We demonstrated an attention shift towards the conspecific (human) target picture that was congruent with the valence depicted in the primer picture. We did not find this effect with heterospecific (chimpanzee) primers and ruled out that this was due to participants interpreting them incorrectly. Implications about the involvement of related emotion-processing mechanisms for human and chimpanzee facial expressions are discussed. Systematic cross-species-investigations of emotional expressions are needed to unravel how emotion representation mechanisms can extend to process other species' faces. Through such studies, we can better understand the implications of humans' and apes' shared evolutionary ancestry and better understand "Where our emotions come from".

Ultrahigh Field fMRI Reveals Different Roles of the Temporal and Frontoparietal Cortices in Subjective Awareness

A central question in consciousness theories is whether one is dealing with a dichotomous ("all-or-none") or a gradual phenomenon. In this 7T fMRI study, we investigated whether dichotomy or gradualness in fact depends on the brain region associated with perceptual awareness reports. Both male and female human subjects performed an emotion discrimination task (fear vs neutral bodies) presented under continuous flash suppression with trial-based perceptual awareness measures. Behaviorally, recognition sensitivity increased linearly with increased stimuli awareness and was at chance level during perceptual unawareness. Physiologically, threat stimuli triggered a slower heart rate than neutral ones during "almost clear" stimulus experience, indicating freezing behavior. Brain results showed that activity in the occipitotemporal, parietal, and frontal regions as well as in the amygdala increased with increased stimulus awareness while early visual areas showed the opposite pattern. The relationship between temporal area activity and perceptual awareness best fitted a gradual model while the activity in frontoparietal areas fitted a dichotomous model. Furthermore, our findings illustrate that specific experimental decisions, such as stimulus type or the approach used to evaluate awareness, play pivotal roles in consciousness studies and warrant careful consideration.

Comparison of Frequentist and Bayesian Statistics for Studying Unconscious Perception: Differences Between Null Awareness Dissociation and Relative Sensitivity Dissociation

For unconscious perception research, Bayesian statistics are more appropriate for assessing null awareness of masked stimuli than traditional (frequentist) statistics. This assertion is based mostly upon the theoretical features of Bayesian statistics and modeling studies. To further assess the potential advantages, we compared frequentist and Bayesian statistical tests in a masked Stroop priming experiment in which the prime stimuli were presented at varying degrees of visibility. A novel contribution was to compare a null awareness dissociation approach (i.e., stimulus awareness = 0) to a relative sensitivity approach (indirect or priming effects > direct effects) for the same data. From a null awareness perspective, the frequentist t-tests for the Stroop effect (i.e., perception) for the briefest display conditions had non-significant outcomes. Similar Bayesian t-tests were inconclusive. In contrast, the relative sensitivity dissociation approach was more interpretable, with strong evidence against unconscious perception from a single Bayesian t test. For the longer display conditions, both statistical approaches suggested large conscious perception effects. We conclude that the utility of Bayesian statistics is highly dependent upon the type of dissociation approach, with a relative sensitivity approach being more straightforward to interpret than a null awareness approach.

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 Perceptual Awareness Scale-recent controversies and debates

Accurate insight into subjective experience is crucial for the science of consciousness. The Perceptual Awareness Scale (PAS) was created in 2004 as a method for obtaining precise introspective reports for participants in research projects, and since then, the scale has become increasingly popular. This does not mean, of course, that no critiques have been voiced. Here, we briefly recapitulate our main thoughts on the intended PAS usage and the findings of the first decade, and we update this with the latest empirical and theoretical developments. We focus specifically on findings with relevance to whether consciousness is gradual or all-or-none phenomenon, to what should be considered conscious/unconscious, and to whether PAS is preferable to alternative measures of awareness. We respond in detail to some recent, selected articles.

Gender differences in subliminal affective face priming: A high-density ERP study

INTRODUCTION

Subliminal affective priming effects (SAPEs) refer to the phenomenon by which the presentation of an affective prime stimulus influences the subsequent affective evaluation of a target stimulus. Previous studies have reported that unconsciously processed stimuli affect behavioral performance more than consciously processed stimuli. However, the impact of SAPEs on the face-specific N170 component is unclear. We studied how SAPEs for fearful faces affected the N170 for subsequent supraliminal target faces using event-related potentials (ERPs).

METHODS

Japanese adults (n = 44, 20 females) participated in this study. Subliminal prime faces (neutral or fearful) were presented for 17 ms, followed by a backward mask for 283 ms and 800 ms target faces (neutral, emotionally ambiguous, or fearful). 128-channel ERPs were recorded while participants judged the expression of target faces as neutral or fearful. Response rates and response times were also measured for assessing behavioral alterations.

RESULTS

Although the behavioral results revealed no evidence of SAPEs, we found gender-related SAPEs in right N170 amplitude. Specifically, female participants exhibited enhanced right N170 amplitude for emotionally neutral faces primed by fearful faces, while male participants exhibited decreased N170 amplitude in fearful prime trials with fearful target faces. Male participants exhibited significant correlations between N170 amplitude and behavioral response time in the fearful prime-neutral target condition.

CONCLUSIONS

Our ERP results suggest the existence of a gender difference in target-face processing preceded by subliminally presented face stimuli in the right occipito-temporal region.

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

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

Phenomenal consciousness and cognitive access

In consciousness research, it is common to distinguish between phenomenal consciousness and access consciousness. Recently, a number of scientists have attempted to show that phenomenal content can be empirically separated from cognitive access and, accordingly, that the mental content that is accessed is not (always) identical to the content that is experienced. One notable position is that of Ned Block who suggests that phenomenal content overflows cognitive access. I will review the evidence and show that existing data, in fact, do not demonstrate overflow. I will further argue that overflow is theoretically possible-yet highly difficult to empirically demonstrate-under the condition that 'cognitive access' is defined as working memory or attention. However, if 'access' is defined as information becoming 'cognitively available', in a broader sense, I will argue that a separation between subjective experience and access is impossible.This article is part of the theme issue 'Perceptual consciousness and cognitive access'.

Neural Responses to Consciously and Unconsciously Perceived Emotional Faces: A Spinal fMRI Study

Emotional stimuli modulate activity in brain areas related to attention, perception, and movement. Similar increases in neural activity have been detected in the spinal cord, suggesting that this understudied component of the central nervous system is an important part of our emotional responses. To date, previous studies of emotion-dependent spinal cord activity have utilized long presentations of complex emotional scenes. The current study differs from this research by (1) examining whether emotional faces will lead to enhanced spinal cord activity and (2) testing whether these stimuli require conscious perception to influence neural responses. Fifteen healthy undergraduate participants completed six spinal functional magnetic resonance imaging (fMRI) runs in which three one-minute blocks of fearful, angry, or neutral faces were interleaved with 40-s rest periods. In half of the runs, the faces were clearly visible while in the other half, the faces were displayed for only 17 ms. Spinal fMRI consisted of half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences targeting the cervical spinal cord. The results indicated that consciously perceived faces expressing anger elicited significantly more activity than fearful or neutral faces in ventral (motoric) regions of the cervical spinal cord. When stimuli were presented below the threshold of conscious awareness, neutral faces elicited significantly more activity than angry or fearful faces. Together, these data suggest that the emotional modulation of spinal cord activity is most impactful when the stimuli are consciously perceived and imply a potential threat toward the observer.