Verbal instructions override the meaning of facial expressions

Additive effects of emotional expression and stimulus size on the perception of genuine and artificial facial expressions: an ERP study

Seeing an angry individual in close physical proximity can not only result in a larger retinal representation of that individual and an enhanced resolution of emotional cues, but may also increase motivation for rapid visual processing and action preparation. The present study investigated the effects of stimulus size and emotional expression on the perception of happy, angry, non-expressive, and scrambled faces. We analyzed event-related potentials (ERPs) and behavioral responses of N = 40 participants who performed a naturalness classification task on real and artificially created facial expressions. While the emotion-related effects on accuracy for recognizing authentic expressions were modulated by stimulus size, ERPs showed only additive effects of stimulus size and emotional expression, with no significant interaction with size. This contrasts with previous research on emotional scenes and words. Effects of size were present in all included ERPs, whereas emotional expressions affected the N170, EPN, and LPC, irrespective of size. These results imply that the decoding of emotional valence in faces can occur even for small stimuli. Supra-additive effects in faces may necessitate larger size ranges or dynamic stimuli that increase arousal.

Incidental learning of faces during threat: No evidence for enhanced physiological responses to former threat identities

Remembering an unfamiliar person and the contextual conditions of that encounter is important for adaptive future behavior, especially in a potentially dangerous situation. Initiating defensive behavior in the presence of former dangerous circumstances can be crucial. Recent studies showed selective electrocortical processing of faces that were previously seen in a threat context compared to a safety context, however, this was not reflected in conscious recognition performance. Here, we investigated whether previously seen threat-faces, that could not be remembered, were capable to activate defensive psychophysiological response systems. During an encoding phase, 50 participants with low to moderate levels of anxiety viewed 40 face pictures with neutral expressions (6 s each), without an explicit learning instruction (incidental learning task). Each half of the faces were presented with contextual background colors that signaled either threat-of-shock or safety. In the recognition phase, all old and additional new faces (total of 60) were presented intermixed without context information. Participants had to decide whether a face was new or had been presented previously in a threatening or a safe context. Results show moderate face recognition independent of context conditions. Startle reflex and skin conductance responses (SCR) were more pronounced for threat compared to safety during encoding. For SCR, this differentiation was enhanced with higher levels of depression and anxiety. There were no differential startle reflex or SCR effects during recognition. From a clinical perspective, these findings do not support the notion that perceptual biases and physiological arousal directly relate to threat-associated identity recognition deficits in healthy and clinical participants with anxiety and trauma-related disorders.

Threat shapes visual context sensitivity selectively through low-spatial-frequency channels

Threat has long been supposed to affect human cognitive processing including visual size perception. Whether such threat-related modulation effect varies as a function of spatial frequency is largely unexplored. Here we used low- or high-pass filtered threatening animal and fearful face images as primes and measured their effects on the processing of the Ebbinghaus illusion. Results showed that threatening-animal primes relative to neutral ones significantly decreased the illusion magnitude in low-spatial-frequency rather than in high-spatial-frequency ranges. However, fearful- and neutral-face primes had a comparable effect on the illusion magnitude in both spatial frequency ranges. Notably, when inhibitory transcranial magnetic stimulation was applied to the left temporo-parietal junction (TPJ), fearful-face primes significantly decreased the illusion magnitude in low-spatial-frequency rather than in high-spatial-frequency ranges. However, the opposite pattern of results was observed with right TPJ stimulation. The findings suggest that threat shapes basic aspects of visual perception in a spatial frequency-specific manner, possibly via magnocellular projections from both subcortical and cortical fear-processing systems to early visual cortex.

State anxiety by itself does not change political attitudes: A threat of shock experiment

Previous research suggests that state anxiety may sway political attitudes. However, previous experimental procedures induced anxiety using political contexts (e.g., social or economic threat). In a pre-registered laboratory experiment, we set out to examine if anxiety that is unrelated to political contexts can influence political attitudes. We induced anxiety with a threat of shock paradigm, void of any political connotation. All participants were instructed that they might receive an electric stimulus during specified threat periods and none during safety periods. Participants were randomly assigned to one of two conditions: Political attitudes (implicit and explicit) were assessed under safety in one condition and under threat in the other. Psychometric, as well as physiological data (skin conductance, heart rate), confirmed that anxiety was induced successfully. However, this emotional state did not alter political attitudes. In a Bayesian analytical approach, we confirmed the absence of an effect. Our results suggest that state anxiety by itself does not sway political attitudes. Previously observed effects that were attributed to anxiety may be conditional on a political context of threat.

Aversive anticipations modulate electrocortical correlates of decision-making and reward reversal learning, but not behavioral performance

Predicting the consequences of one's own decisions is crucial for organizing future behavior. However, when reward contingencies vary frequently, flexible adaptation of decisions is likely to depend on the situation. We examined the effects of an instructed threat context on choice behavior (i.e., reversal learning) and its electrocortical correlates. In a probabilistic decision-making task, 30 participants had to choose between two options that were either contingent on monetary gains or losses. Reward contingencies were reversed after reaching a probabilistic threshold. Decision-making and reversal learning were examined with two contextual background colors, which were instructed as signals for threat-of-shock or safety. Self-report data confirmed the threat context as more unpleasant, arousing, and threatening relative to safety condition. However, against our expectations, behavioral performance was comparable during the threat and safety conditions (i.e., errors-to-criterion, number of reversal, error rates, and choice times). Regarding electrocortical activity, feedback processing changed throughout the visual processing stream. The feedback-related negativity (FRN) reflected expectancy-driven processing (unexpected vs. congruent losses and gains), and the threat-selective P3 component revealed non-specific discrimination of gains vs. losses. Finally, the late positive potentials (LPP) showed strongly valence-specific processing (unexpected and congruent losses vs. gains). Thus, regardless of contextual threat, early and late cortical activity reflects an attentional shift from expectation- to outcome-based feedback processing. Findings are discussed in terms of reward, threat, and reversal-learning mechanisms with implications for emotion regulation and anxiety disorders.

What's in a face: Automatic facial coding of untrained study participants compared to standardized inventories

Automatic facial coding (AFC) is a novel research tool to automatically analyze emotional facial expressions. AFC can classify emotional expressions with high accuracy in standardized picture inventories of intensively posed and prototypical expressions. However, classification of facial expressions of untrained study participants is more error prone. This discrepancy requires a direct comparison between these two sources of facial expressions. To this end, 70 untrained participants were asked to express joy, anger, surprise, sadness, disgust, and fear in a typical laboratory setting. Recorded videos were scored with a well-established AFC software (FaceReader, Noldus Information Technology). These were compared with AFC measures of standardized pictures from 70 trained actors (i.e., standardized inventories). We report the probability estimates of specific emotion categories and, in addition, Action Unit (AU) profiles for each emotion. Based on this, we used a novel machine learning approach to determine the relevant AUs for each emotion, separately for both datasets. First, misclassification was more frequent for some emotions of untrained participants. Second, AU intensities were generally lower in pictures of untrained participants compared to standardized pictures for all emotions. Third, although profiles of relevant AU overlapped substantially across the two data sets, there were also substantial differences in their AU profiles. This research provides evidence that the application of AFC is not limited to standardized facial expression inventories but can also be used to code facial expressions of untrained participants in a typical laboratory setting.

You see what you avoid: Fear of spiders and avoidance are associated with predominance of spiders in binocular rivalry

What we see is the result of an efficient selection of cues in the visual stream. In addition to physical characteristics this process is also influenced by emotional salience of the cues. Previously, we showed in spider phobic patients that fear-related pictures gain preferential access to consciousness in binocular rivalry. We set out to replicate this in an independent unselected sample and examine the relationship of this perceptual bias with a range of symptom clusters. To this end, we recruited 79 participants with variable degrees of fear of spiders. To induce binocular rivalry, a picture of either a spider or a flower was projected to one eye, and a neutral geometric pattern to the other eye. Participants continuously reported what they saw. We correlated indices of perceptual dominance (first percept, dominance duration) with individual fear of spiders and with scores on specific symptom clusters of fear of spiders (i.e., vigilance, fixation, and avoidance coping). Overall, higher fear of spiders correlates with more predominace of spider pictures. In addition, this perceptual bias is uniquely associated with avoidance coping. Interestingly, this demonstrates that a perceptual bias, which is not intentionally controlled, is linked with an instrumental coping behavior, that has been implicated in the maintenance of pathological fear.

The mere sight of loved ones does not inhibit psychophysiological defense mechanisms when threatened

Looking at pictures of loved ones, such as one's romantic partner or good friends, has been shown to alleviate the experience of pain and reduce defensive reactions. However, little is known about such modulatory effects on threat and safety learning and the psychophysiological processes involved. Here, we explored the hypothesis that beloved faces serve as implicit safety cues and attenuate the expression of fear responses and/or accelerate extinction learning in a threatening context. Thirty-two participants viewed pictures of their loved ones (romantic partner, parents, and best friend) as well as of unknown individuals within contextual background colors indicating threat-of-shock or safety. Focusing on the extinction of non-reinforced threat associations (no shocks were given), the experiment was repeated on two more test days while the defensive startle-EMG, SCR, and threat ratings were obtained. Results confirmed pronounced defensive responding to instructed threat-of-shock relative to safety context (e.g., threat-enhanced startle reflex and SCR). Moreover, threat-potentiated startle response slowly declined across test days indicating passive extinction learning in the absence of shocks. Importantly, neither a main effect of face category (loved vs. unknown) nor a significant interaction with threat/safety instructions was observed. Thus, a long-term learning history of beneficial relations (e.g., with supportive parents) did not interfere with verbal threat learning and aversive apprehensions. These findings reflect the effects of worries and apprehensions that persist despite the repeated experience of safety and the pictorial presence of loved ones. How to counter such aversive expectations is key to changing mal-adaptive behaviors (e.g., avoidance or stockpiling), biased risk perceptions, and stereotypes.

Social threat and safety learning in individuals with adverse childhood experiences: electrocortical evidence on face processing, recognition, and working memory

BACKGROUND

Adverse childhood experiences (ACEs) are often associated with stress and anxiety-related disorders in adulthood, and learning and memory deficits have been suggested as a potential link between ACEs and psychopathology.

OBJECTIVE

In this preregistered study, the impact of social threat learning on the processing, encoding, and recognition of unknown faces as well as their contextual settings was measured by recognition performance and event-related brain potentials.

METHOD

Sixty-four individuals with ACEs encoded neutral faces within threatening or safe context conditions. During recognition, participants had to decide whether a face was new or had been previously presented in what context (item-source memory), looking at old and new faces. For visual working memory, participants had to detect changes in low and high load conditions during contextual threat or safety.

RESULTS

Results showed a successful induction of threat expectation in persons with ACEs. In terms of face and source recognition, overall recognition of safe and new faces was better compared to threatening face-compounds, with more socially anxious individuals having an advantage in remembering threatening faces. For working memory, an effect of task load was found on performance, irrespective of threat or safety context. Regarding electrocortical activity, an old/new recognition effect and threat-selective processing of face-context information was observed during both encoding and recognition. Moreover, neural activity associated with change detection was found for faces in a threatening context, but only at high task load, suggesting reduced capacity for faces in potentially harmful situations when cognitive resources are limited.

CONCLUSION

While individuals with ACE showed intact social threat and safety learning overall, threat-selective face processing was observed for item/source memory, and a threatening context required more processing resources for visual working memory. Further research is needed to investigate the psychophysiological processes involved in functional and dysfunctional memory systems and their importance as vulnerability factors for stress-related disorders.

A multinomial modelling approach to face identity recognition during instructed threat

To organise future behaviour, it is important to remember both the central and contextual aspects of a situation. We examined the impact of contextual threat or safety, learned through verbal instructions, on face identity recognition. In two studies (N = 140), 72 face-context compounds were presented each once within an encoding session, and an unexpected item/source recognition task was performed afterwards (including 24 new faces). Hierarchical multinomial processing tree modelling served to estimate individual parameters of item (face identity) and source memory (threat or safety context) as well as guessing behaviour. Results show that language was highly effective in establishing threatening and safe context conditions. In Study 1, a fleeting picture stream (1 s per picture) led to poor item and source recognition. Prolonged presentation times (Study 2 with 6 s per picture) improved face memory but no contextual modulation was observed. Thus, incidental face learning was surprisingly poor and rapidly changing contextual settings might have interfered with the accurate encoding of face identity information and item-source binding.

Verbal threat learning does not spare loved ones

Significant others provide individuals with a sense of safety and security. However, the mechanisms that underlie attachment-induced safety are hardly understood. Recent research has shown beneficial effects when viewing pictures of the romantic partner, leading to reduced pain experience and defensive responding. Building upon this, we examined the inhibitory capacity of loved face pictures on fear learning in an instructed threat paradigm. Pictures of loved familiar or unknown individuals served as signals for either threat of electric shocks or safety, while a broad set of psychophysiological measures was recorded. We assumed that a long-term learning history of beneficial relations interferes with social threat learning. Nevertheless, results yielded a typical pattern of physiological defense activation towards threat cues, regardless of whether threat was signaled by an unknown or a loved face. These findings call into question the notion that pictures of loved individuals are shielded against becoming threat cues, with implications for attachment and trauma research.

Contextual information resolves uncertainty about ambiguous facial emotions: Behavioral and magnetoencephalographic correlates

Environmental conditions bias our perception of other peoples' facial emotions. This becomes quite relevant in potentially threatening situations, when a fellow's facial expression might indicate potential danger. The present study tested the prediction that a threatening environment biases the recognition of facial emotions. To this end, low- and medium-expressive happy and fearful faces (morphed to 10%, 20%, 30%, or 40% emotional) were presented within a context of instructed threat-of-shock or safety. Self-reported data revealed that instructed threat led to a biased recognition of fearful, but not happy facial expressions. Magnetoencephalographic correlates revealed spatio-temporal clusters of neural network activity associated with emotion recognition and contextual threat/safety in early to mid-latency time intervals in the left parietal cortex, bilateral prefrontal cortex, and the left temporal pole regions. Early parietal activity revealed a double dissociation of face-context information as a function of the expressive level of facial emotions: When facial expressions were difficult to recognize (low-expressive), contextual threat enhanced fear processing and contextual safety enhanced processing of subtle happy faces. However, for rather easily recognizable faces (medium-expressive) the left hemisphere (parietal cortex, PFC, and temporal pole) showed enhanced activity to happy faces during contextual threat and fearful faces during safety. Thus, contextual settings reduce the salience threshold and boost early face processing of low-expressive congruent facial emotions, whereas face-context incongruity or mismatch effects drive neural activity of easier recognizable facial emotions. These results elucidate how environmental settings help recognize facial emotions, and the brain mechanisms underlying the recognition of subtle nuances of fear.

Making translation work: Harmonizing cross-species methodology in the behavioural neuroscience of Pavlovian fear conditioning

Translational neuroscience bridges insights from specific mechanisms in rodents to complex functions in humans and is key to advance our general understanding of central nervous function. A prime example of translational research is the study of cross-species mechanisms that underlie responding to learned threats, by employing Pavlovian fear conditioning protocols in rodents and humans. Hitherto, evidence for (and critique of) these cross-species comparisons in fear conditioning research was based on theoretical viewpoints. Here, we provide a perspective to substantiate these theoretical concepts with empirical considerations of cross-species methodology. This meta-research perspective is expected to foster cross-species comparability and reproducibility to ultimately facilitate successful transfer of results from basic science into clinical applications.

Reversing Threat to Safety: Incongruence of Facial Emotions and Instructed Threat Modulates Conscious Perception but Not Physiological Responding

Facial expressions inform about other peoples’ emotion and motivation and thus are central for social communication. However, the meaning of facial expressions may change depending on what we have learned about the related consequences. For instance, a smile might easily become threatening when displayed by a person who is known to be dangerous. The present study examined the malleability of emotional facial valence by means of social learning. To this end, facial expressions served as cues for verbally instructed threat-of-shock or safety (e.g., “happy faces cue shocks”). Moreover, reversal instructions tested the flexibility of threat/safety associations (e.g., “now happy faces cue safety”). Throughout the experiment, happy, neutral, and angry facial expressions were presented and auditory startle probes elicited defensive reflex activity. Results show that self-reported ratings and physiological reactions to threat/safety cues dissociate. Regarding threat and valence ratings, happy facial expressions tended to be more resistant becoming a threat cue, and angry faces remain threatening even when instructed as safety cue. For physiological response systems, however, we observed threat-potentiated startle reflex and enhanced skin conductance responses for threat compared to safety cues regardless of whether threat was cued by happy or angry faces. Thus, the incongruity of visual and verbal threat/safety information modulates conscious perception, but not the activation of physiological response systems. These results show that verbal instructions can readily overwrite the intrinsic meaning of facial emotions, with clear benefits for social communication as learning and anticipation of threat and safety readjusted to accurately track environmental changes.

Placebo Manipulations Reverse Pain Potentiation by Unpleasant Affective Stimuli

According to the motivational priming hypothesis, unpleasant stimuli activate the motivational defense system, which in turn promotes congruent affective states such as negative emotions and pain. The question arises to what degree this bottom-up impact of emotions on pain is susceptible to a manipulation of top-down-driven expectations. To this end, we investigated whether verbal instructions implying pain potentiation vs. reduction (placebo or nocebo expectations)-later on confirmed by corresponding experiences (placebo or nocebo conditioning)-might alter behavioral and neurophysiological correlates of pain modulation by unpleasant pictures. We compared two groups, which underwent three experimental phases: first, participants were either instructed that watching unpleasant affective pictures would increase pain (nocebo group) or that watching unpleasant pictures would decrease pain (placebo group) relative to neutral pictures. During the following placebo/nocebo-conditioning phase, pictures were presented together with electrical pain stimuli of different intensities, reinforcing the instructions. In the subsequent test phase, all pictures were presented again combined with identical pain stimuli. Electroencephalogram was recorded in order to analyze neurophysiological responses of pain (somatosensory evoked potential) and picture processing [visually evoked late positive potential (LPP)], in addition to pain ratings. In the test phase, ratings of pain stimuli administered while watching unpleasant relative to neutral pictures were significantly higher in the nocebo group, thus confirming the motivational priming effect for pain perception. In the placebo group, this effect was reversed such that unpleasant compared with neutral pictures led to significantly lower pain ratings. Similarly, somatosensory evoked potentials were decreased during unpleasant compared with neutral pictures, in the placebo group only. LPPs of the placebo group failed to discriminate between unpleasant and neutral pictures, while the LPPs of the nocebo group showed a clear differentiation. We conclude that the placebo manipulation already affected the processing of the emotional stimuli and, in consequence, the processing of the pain stimuli. In summary, the study revealed that the modulation of pain by emotions, albeit a reliable and well-established finding, is further tuned by reinforced expectations-known to induce placebo/nocebo effects-which should be addressed in future research and considered in clinical applications.