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Gazes are of central relevance for people. They are crucial for navigating the world and communicating with others. Nevertheless, research in recent years shows that many findings from experimental research on gaze behavior cannot be transferred from the laboratory to everyday behavior. For example, the frequency with which conspecifics are looked at is considerably higher in experimental contexts than what can be observed in daily behavior. In short: findings from laboratories cannot be generalized into general statements. This thesis is dedicated to this matter. The dissertation describes and documents the current state of research on social attention through a literature review, including a meta-analysis on the /gaze cueing/ paradigm and an empirical study on the robustness of gaze following behavior. In addition, virtual reality was used in one of the first studies in this research field. Virtual reality has the potential to significantly improve the transferability of experimental laboratory studies to everyday behavior. This is because the technology enables a high degree of experimental control in naturalistic research designs. As such, it has the potential to transform empirical research in the same way that the introduction of computers to psychological research did some 50 years ago. The general literature review on social attention is extended to the classic /gaze cueing/ paradigm through a systematic review of publications and a meta-analytic evaluation (Study 1). The cumulative evidence supported the findings of primary studies: Covert spatial attention is directed by faces. However, the experimental factors included do not explain the surprisingly large variance in the published results. Thus, there seem to be further, not well-understood variables influencing these social processes. Moreover, classic /gaze cueing/ studies have limited ecological validity. This is discussed as a central reason for the lack of generalisability. Ecological validity describes the correspondence between experimental factors and realistic situations. A stimulus or an experimental design can have high and low ecological validity on different dimensions and have different influences on behavior. Empirical research on gaze following behavior showed that the /gaze cueing/ effect also occurs with contextually embedded stimuli (Study 2). The contextual integration of the directional cue contrasted classical /gaze cueing/ studies, which usually show heads in isolation. The research results can thus be transferred /within/ laboratory studies to higher ecologically valid research paradigms. However, research shows that the lack of ecological validity in experimental designs significantly limits the transferability of experimental findings to complex situations /outside/ the laboratory. This seems to be particularly the case when social interactions and norms are investigated. However, ecological validity is also often limited in these studies for other factors, such as contextual embedding /of participants/, free exploration behavior (and, thus, attentional control), or multimodality. In a first study, such high ecological validity was achieved for these factors with virtual reality, which could not be achieved in the laboratory so far (Study 3). Notably, the observed fixation patterns showed differences even under /most similar/ conditions in the laboratory and natural environments. Interestingly, these were similar to findings also derived from comparisons of eye movement in the laboratory and field investigations. These findings, which previously came from hardly comparable groups, were thus confirmed by the present Study 3 (which did not have this limitation). Overall, /virtual reality/ is a new technical approach to contemporary social attention research that pushes the boundaries of previous experimental research. The traditional trade-off between ecological validity and experimental control thus becomes obsolete, and laboratory studies can closely inherit an excellent approximation of reality. Finally, the present work describes and discusses the possibilities of this technology and its practical implementation. Within this context, the extent to which this development can still guarantee a constructive classification of different laboratory tests in the future is examined.
Humans spontaneously blink several times a minute. These blinks are strongly modulated during various cognitive task. However, the precise function of blinking and the reason for their modulation has not been fully understood. In the present work, I investigated the function of spontaneous blinks through various perceptual and cognitive tasks. Previous research has revealed that blinks rates decrease during some tasks but increase during others. When trying to understand these seemingly contradictory results, I observed that blink reduction occurs when one engages with an external input. For instance, a decrease has been observed due to the onset of a stimulus, sensory input processing and attention towards sensory input. However, for activities that do not involve such an engagement, e.g. imagination, daydreaming or creativity, the blink rate has been shown to increase. To follow up on the proposed hypothesis, I distinguished tasks that involve the processing of an external stimulus and tasks that involve disengagement.
In the first part of the project, I explored blinking during stimulus engagement. If the probability of blinking is low when engaging with the stimulus, then one should find a reduction in blinks specifically during the time period of processing but not during sensory input per se. To this end, in study 1, I tested the influence of task-relevant information duration on blink timing and additionally manipulated the overall sensory input using a visual and an auditory temporal simultaneity judgement task. The results showed that blinks were suppressed longer for longer periods of relevant information or in other words, blinks occurred at the end of relevant information processing for both the visual and the auditory modality. Since relevance is mediated through top-down processes, I argue that the reduction in blinks is a top-down driven suppression. In studies 2 and 3, I again investigated stimulus processing, but in this case, processing was triggered internally and not based on specific changes in the external input. To this end, I used bistable stimuli, in which the actual physical stimulus remains constant but their perception switches between different interpretations. Studies on the involvement of attention in such bistable perceptual changes indicate that the sensory input is reprocessed before the perceptual switch. The results revealed a reduction in eye blink rates before the report of perceptual switches. Importantly, I was able to decipher that the decrease was not caused by the perceptual switch or the behavioral response but likely started before the internal switch. Additionally, periods between a blink and a switch were longer than interblink intervals, indicating that blinks were followed by a period of stable percept. To conclude, the first part of the project revealed that there is a top-down driven blink suppression during the processing of an external stimulus.
In the second part of the project, I extended the idea of blinks marking the disengagement from external processing and tested if blinking is associated with better performance during internally directed processes. Specifically, I investigated divergent thinking, an aspect of creativity, and the link between performance and blink rates as well as the effect of motor restriction. While I could show that motor restriction was the main factor influencing divergent thinking, the relationship between eye blink rates and creative output also depended on restriction. Results showed that higher blink rates were associated with better performance during free movement, but only between subjects. In other words, subjects who had overall higher blink rates scored better in the task, but when they were allowed to sit or walk freely. Within a single subject, trial with higher blink rates were not associated with better performance. Therefore, possibly, people who are able to disengage easily, as indicated by an overall high blink rate, perform better in divergent thinking tasks. However, the link between blink rate and internal tasks is not clear at this point. Indeed, a more complex measurement of blink behavior might be necessary to understand the relationship.
In the final part of the project, I aimed to further understand the function of blinks through their neural correlates. I extracted the blink-related neural activity in the primary visual cortex (V1) of existing recordings of three rhesus monkeys during different sensory processing states. I analyzed spike related multi-unit responses, frequency dependent power changes, local field potentials and laminar distribution of activity while the animal watched a movie compared to when it was shown a blank screen. The results showed a difference in blink-related neural activity dependent on the processing state. This difference suggests a state dependent function of blinks.
Taken altogether, the work presented in this thesis suggests that eye blinks have an important function during cognitive and perceptual processes. Blinks seem to facilitate a disengagement from the external world and are therefore suppressed during intended processing of external stimuli.
Anxiety patients overgeneralize fear, also because of an inability to perceptually discriminate threat and safety signals. Therefore, some studies have developed discrimination training that successfully reduced the occurrence of fear generalization. The present work is the first to take a treatment-like approach by using discrimination training after generalization has occurred. Therefore, two studies were conducted with healthy participants using the same fear conditioning and generalization paradigm, with two faces as conditioned stimuli (CSs), and four facial morphs between CSs as generalization stimuli (GSs). Only one face (CS+) was followed by a loud scream (unconditioned stimulus, US). In Study 1, participants underwent either fear-relevant (discriminating faces) or fear-irrelevant discrimination training (discriminating width of lines) or a non-discriminative control training between the two generalization tests, each with or without feedback (n = 20 each). Generalization of US expectancy was reduced more effectively by fear-relevant compared to fear-irrelevant discrimination training. However, neither discrimination training was more effective than non-discriminative control training. Moreover, feedback reduced generalization of US expectancy only in discrimination training. Study 2 was designed to replicate the effects of the discrimination-training conditions in a large sample (N = 244) and examine their benefits in individuals at risk for anxiety disorders. Again, feedback reduced fear generalization particularly well for US expectancy. Fear relevance was not confirmed to be particularly fear-reducing in healthy participants, but may enhance training effects in individuals at risk of anxiety disorder. In summary, this work provides evidence that existing fear generalization can be reduced by discrimination training, likely involving several (higher-level) processes besides perceptual discrimination (e.g., motivational mechanisms in feedback conditions). Its use may be promising as part of individualized therapy for patients with difficulty discriminating similar stimuli.
This dissertation highlights various aspects of basic social attention by choosing versatile approaches to disentangle the precise mechanisms underlying the preference to focus on other human beings. The progressive examination of different social processes contrasted with aspects of previously adopted principles of general attention. Recent research investigating eye movements during free exploration revealed a clear and robust social bias, especially for the faces of depicted human beings in a naturalistic scene. However, free viewing implies a combination of mechanisms, namely automatic attention (bottom-up), goal-driven allocation (top-down), or contextual cues and inquires consideration of overt (open exploration using the eyes) as well as covert orienting (peripheral attention without eye movement). Within the scope of this dissertation, all of these aspects have been disentangled in three studies to provide a thorough investigation of different influences on social attention mechanisms.
In the first study (section 2.1), we implemented top-down manipulations targeting non-social features in a social scene to test competing resources. Interestingly, attention towards social aspects prevailed, even though this was detrimental to completing the requirements. Furthermore, the tendency of this bias was evident for overall fixation patterns, as well as fixations occurring directly after stimulus onset, suggesting sustained as well as early preferential processing of social features. Although the introduction of tasks generally changes gaze patterns, our results imply only subtle variance when stimuli are social. Concluding, this experiment indicates that attention towards social aspects remains preferential even in light of top-down demands.
The second study (section 2.2) comprised of two separate experiments, one in which we investigated reflexive covert attention and another in which we tested reflexive as well as sustained overt attention for images in which a human being was unilaterally located on either the left or right half of the scene. The first experiment consisted of a modified dot-probe paradigm, in which peripheral probes were presented either congruently on the side of the social aspect, or incongruently on the non-social side. This was based on the assumption that social features would act similar to cues in traditional spatial cueing paradigms, thereby facilitating reaction times for probes presented on the social half as opposed to the non-social half. Indeed, results reflected such congruency effect. The second experiment investigated these reflexive mechanisms by monitoring eye movements and specifying the location of saccades and fixations for short as well as long presentation times. Again, we found the majority of initial saccades to be congruently directed to the social side of the stimulus. Furthermore, we replicated findings for sustained attention processes with highest fixation densities for the head region of the displayed human being.
The third study (section 2.3), tackled the other mechanism proposed in the attention dichotomy, the bottom-up influence. Specifically, we reduced the available contextual information of a scene by using a gaze-contingent display, in which only the currently fixated regions would be visible to the viewer, while the remaining image would remain masked. Thereby, participants had to voluntarily change their gaze in order to explore the stimulus. First, results revealed a replication of a social bias in free-viewing displays. Second, the preference to select social features was also evident in gaze-contingent displays. Third, we find higher recurrent gaze patterns for social images compared to non-social ones for both viewing modalities. Taken together, these findings imply a top-down driven preference for social features largely independent of contextual information.
Importantly, for all experiments, we took saliency predictions of different computational algorithms into consideration to ensure that the observed social bias was not a result of high physical saliency within these areas. For our second experiment, we even reduced the stimulus set to those images, which yielded lower mean and peak saliency for the side of the stimulus containing the social information, while considering algorithms based on low-level features, as well as pre-trained high-level features incorporated in deep learning algorithms.
Our experiments offer new insights into single attentional mechanisms with regard to static social naturalistic scenes and enable a further understanding of basic social processing, contrasting from that of non-social attention. The replicability and consistency of our findings across experiments speaks for a robust effect, attributing social attention an exceptional role within the general attention construct, not only behaviorally, but potentially also on a neuronal level and further allowing implications for clinical populations with impaired social functioning.
In daily life, olfactory stimuli are potential generators of affective states, but also have a strong influence on social interaction. Pleasant odors have been shown to increase perceived attractiveness and pro-social behavior, whereas unpleasant body odors are often associated with negative personality traits. Since both pleasant odors and positive affective state facilitate pro-social behavior, it is conceivable that the influence of the odors on social interaction is mediated by the induced affective state elicited by the odor itself. The present thesis aims at exploring the impact of hedonic, i.e., pleasant or unpleasant, odors on the processing and evaluation of social stimuli as assessed by verbal, physiological, and behavioral indices. First, I investigate the effects of initially neutral odors which gained threatening value through an aversive conditioning procedure on social stimuli (Study 1). Second, I study the influence of naturally hedonic odors on social interaction. Third, this thesis aims at disentangling differences in the effects of an odor attributed to either a social interaction partner or the environment where the social encounter takes place (Study 2, 3, and 4).
In the first study, a context conditioning procedure was applied, during which one out of two long-lasting neutral odors was paired with an unpredictable aversive unconditioned stimulus (US, i.e., white noise). This odor (CTX+) thereby gained threatening value, while another odor (CTX-) remained unpaired and therefore signaled safety. During a test session, facial stimuli were presented within both conditioned olfactory contexts. Results indicate that autonomic arousal was increased to faces when presented in the threatening odor context. Additionally, participants rated facial stimuli as more aversive when presented in the threatening odor as compared to the safety odor, indicating that faces acquire hedonic value from the odor they were presented in. Strikingly, angry facial expressions received additional processing resources when presented within a threatening olfactory context, as reflected on verbal reports and electrodermal activity (EDA). This latter finding suggests that threat-related stimuli, here angry faces, are preferentially processed within an olfactory context where a threat might happen.
Considering that the hedonic value of an odor may be quite subjective, I conducted a pilot study in order to identify odors with pleasant vs. unpleasant properties for most participants. Seven odors (four pleasant and three unpleasant) were rated with respect to their valence (pleasant vs. unpleasant), arousal (arousing vs. calm), and intensity. Additionally, EDA was measured. Two pleasant (Citral and Eucalyptol) and two unpleasant (“Animalis” and Isobutyraldehyde) odors were chosen from the original seven. The unpleasant odors were rated as more negative, arousing, and intense than the positive ones, but no differences were found regarding EDA.
These four odors were subsequently used in a virtual reality (VR) paradigm with two odor attribution groups. Participants of the social attribution group (n = 59) were always passively guided into the same room (an office) towards one out of two virtual agents who were either paired with the pleasant or the unpleasant odor. Participants of the contextual attribution group (n = 58) were guided into one out of two rooms which were either paired with the pleasant or the unpleasant odor and where they always met the same agent. For both groups, the agents smiled, frowned or remained with a neutral facial expression. This design allowed evaluating the influence of odor valence as a within-subjects factor and the influence of odor attribution as a between-subjects factor. Unpleasant odors facilitated the processing of social cues as reflected by increased verbal and physiological arousal as well as reduced active approach behavior. Specific influence of odor valence on emotional facial expressions was found for ratings, EDA, and facial mimicry, with the unpleasant odor causing a levelling effect on the differences between facial expressions. The social attribution group exhibited larger differences between odors than the contextual group with respect to some variables (i.e., ratings and EDA), but not to others (i.e., electrocortical potentials – ERPs – and approach behavior). In sum, unpleasant in comparison to pleasant odors diminished emotional responses during social interaction, while an additional enhancing effect of the social attribution was observed on some variables. Interestingly, the awareness that an interaction partner would smell (pleasantly or unpleasantly) boosted the emotional reactivity towards them.
In Study 3, I adapted the VR paradigm to a within-subjects design, meaning that the different attribution conditions were now manipulated block-wise. Instead of an approach task, participants had to move away from the virtual agent (withdrawal task). Results on the ratings were replicated from Study 2. Specifically, the difference between pleasant and unpleasant odors on valence, arousal, and sympathy ratings was larger in the social as compared to the contextual attribution condition. No effects of odor or attribution were found on EDA, whereas heart rate (HR) showed a stronger acceleration to pleasant odors while participants were passively guided towards the agent. Instead of an approach task, I focused on withdrawal behavior in this study. Interestingly, independently of the attribution condition, participants spent more time withdrawing from virtual agents, when an unpleasant odor was presented. In sum, I demonstrated that the attribution of the odors to the social agent itself had an enhancing effect on their influence on social interaction.
In the fourth and last study, I applied a similar within-subjects protocol as in Study 3 with an additional Ultimatum Game task as a measure of social interaction. Overall findings replicated the results of Study 3 with respect to HR and EDA. Strikingly, participants offered less money to virtual agents in the bad smelling room than in the good smelling room. In contrast to Study 3, no effects of odor attribution were found in Study 4. In sum, again I demonstrated that unpleasant odor may lessen social interaction not only when the interaction partner smells badly, but also in more complex interaction situations.
In conclusion, I demonstrated that hedonic odors in general influence social interaction. Thus, pleasant odors seem to facilitate, while unpleasant odors seem to reduce interpersonal exchanges. Therefore, the present thesis extends the body of literature on the influence of odors on the processing of social stimuli. Although I found a direct influence of odors on social preferences as well as on the physiological and behavioral responses to social stimuli, I did not disentangle impact of odor per se from the impact of the affective state. Interestingly, odor attribution might play an additional role as mediator of social interactions such as odor effects in social interactions might be boosted when the smell is attributed to an individual. However, the results in this regard were less straightforward, and therefore further investigations are needed. Future research should also take into account gender or other inter-individual differences like social anxiety.
The Role of Attentional Control and Fear Acquisition and Generalization in Social Anxiety Disorder
(2020)
Although Social Anxiety Disorder (SAD) is one of the most prevalent mental disorders, still little is known about its development and maintenance. Cognitive models assume that deviations in attentional as well as associative learning processes play a role in the etiology of SAD. Amongst others, deficits in inhibitory attentional control as well as aberrations during fear generalization, which have already been observed in other anxiety disorders, are two candidate mechanisms that might contribute to the onset and retention of SAD. However, a review of the literature shows that there is a lack of research relating to these topics. Thus, the aim of the present thesis was to examine in which way individuals with SAD differ from healthy controls regarding attentional control and generalization of acquired fear during the processing of social stimuli.
Study 1 tested whether impairment in the inhibitory control of attention is a feature of SAD, and how it might be influenced by emotional expression and gaze direction of an interactional partner. For this purpose, individuals with SAD and healthy controls (HC) participated in an antisaccade task with faces displaying different emotional expressions (angry, neutral and happy) and gaze directions (direct and averted) serving as target stimuli. While the participants performed either pro- or antisaccades in response to the peripherally presented faces, their gaze behavior was recorded via eye-tracking, and ratings of valence and arousal were obtained. Results revealed that both groups showed prolonged latencies and increased error rates in trials with correct anti- compared to prosaccades. However, there were no differences between groups with regard to response latency or error rates, indicating that SAD patients did not exhibit impairment on inhibitory attentional control in comparison to HC during eye-tracking. Possible explanations for this finding could be that reduced inhibitory attentional control in SAD only occurs under certain circumstances, for example, when these individuals currently run the risk of being negatively evaluated by others and not in the mere presence of phobic stimuli, or when the cognitive load of a task is so high that it cannot be unwound by compensatory strategies, such as putting more effort into a task.
As not only deviations in attentional, but also associative learning processes might be pathogenic markers of SAD, these mechanisms were further addressed in the following experiments. Study 2 is the first that attempted to investigate the generalization of conditioned fear in patients with SAD. To this end, patients with SAD and HC were conditioned to two neutral female faces serving as conditioned stimuli (CS+: reinforced; CS-: non-reinforced) and a fearful face paired with a loud scream serving as unconditioned stimulus (US). Fear generalization was tested by presenting morphs of the two faces (GS: generalization stimuli), which varied in their similarity to the original faces. During the whole experiment, self-report ratings, heart rate (HR) and skin conductance responses (SCR) were recorded. Results demonstrated that SAD patients rated all stimuli as less pleasant and more arousing, and overestimated the occurrence of the US compared to HC, indicating a general hyperarousal in individuals with SAD. In addition, ratings and SCR indicated that both groups generalized their acquired fear from the CS+ to intermediate GSs as a function of their similarity to the CS+. However, except for the HR data, which indicated that only SAD patients but not HC displayed a generalization response in this measure, most of the results did not support the hypothesis that SAD is characterized by overgeneralization. A plausible reason for this finding could be that overgeneralization is just a key characteristic of some anxiety disorders and SAD is not one of them. Still, other factors, such as comorbidities in the individuals with SAD, could also have had an influence on the results, which is why overgeneralization was further examined in study 3.
The aim of study 3 was to investigate fear generalization on a neuronal level. Hence, high (HSA) and low socially anxious participants (LSA) underwent a conditioning paradigm, which was an adaption of the experimental design used study 2 for EEG. During the experiment, steady-state visually evoked potentials (ssVEPs) and ratings of valence and arousal were recorded. Analyses revealed significant generalization gradients in all ratings with highest fear responses to the CS+ and a progressive decline of these reactions with increasing similarity to the CS-. In contrast, the generalization gradient on a neuronal level showed highest amplitudes for the CS+ and a reduction in amplitude to the most proximal, but not distal GSs in the ssVEP signal, which might be interpreted as lateral inhibition in the visual cortex. The observed dissociation among explicit and implicit measures points to different functions of behavioral and sensory cortical processes during fear generalization: While the ratings might reflect an individual’s consciously increased readiness to react to threat, the lateral inhibition pattern in the occipital cortex might serve to maximize the contrast among stimuli with and without affective value and thereby improve adaptive behavior. As no group differences could be observed, the finding of study 2 that overgeneralization does not seem to be a marker of SAD is further consolidated.
In sum, the conducted experiments suggest that individuals with SAD are characterized by a general hyperarousal during the exposition to disorder-relevant stimuli as indicated by enhanced arousal and reduced valence ratings of the stimuli compared to HC. However, the hypotheses that reduced inhibitory attentional control and overgeneralization of conditioned fear are markers of SAD were mostly not confirmed. Further research is required to elucidate whether they only occur under certain circumstances, such as high cognitive load (e.g. handling two tasks simultaneously) or social stress (e.g. before giving a speech), or whether they are not characteristics of SAD at all. With the help of these findings, new interventions for the treatment of SAD can be developed, such as attentional bias modification or discrimination learning.
The present dissertation aims to shed light on different mechanisms of socio-emotional feedback in social decision-making situations. The objective is to evaluate emotional facial expressions as feedback stimuli, i.e., responses of interaction partners to certain social decisions. In addition to human faces, artificial emojis are also examined due to their relevance for modern digital communication. Previous research on the influence of emotional feedback suggests that a person's behavior can be effectively reinforced by rewarding stimuli. In the context of this dissertation, the differences in the feedback processing of human photographs and emojis, but also the evaluation of socially expected versus socially unexpected feedback were examined in detail in four studies. In addition to behavioral data, we used the electroencephalogram (EEG) in all studies to investigate neural correlates of social decision-making and emotional feedback.
As the central paradigm, all studies were based on a modified ultimatum game. The game is structured as follows: there is a so-called proposer who holds a specific amount of money (e.g., 10 cents) and offers the responder a certain amount (e.g., 3 cents). The responder then decides whether to accept or reject the offer. In the version of the ultimatum game presented here, different types of proposers are introduced. After the participants have accepted or rejected in the role of the responder, the different proposers react to the participant’s decision with specific emotional facial expressions. Different feedback patterns are used for the individual experiments conducted in the course of this dissertation.
In the first study, we investigated the influence of emotional feedback on decision-making in the modified version of the ultimatum game. We were able to show that a proposer who responds to the acceptance of an offer with a smiling face achieves more accepted offers overall than a control proposer who responds to both accepted and rejected offers with a neutral facial expression. Consequently, the smile served as a positive reinforcement. Similarly, a sad expression in response to a rejected offer also resulted in higher acceptance rates as compared to the control identity, which could be considered an expression of compassion for that proposer. On a neuronal level, we could show that there are differences between simply looking at negative emotional stimuli (i.e., sad and angry faces) and their appearance as feedback stimuli after rejected offers in the modified ultimatum game. The so-called feedback-related negativity was reduced (i.e., more positive) when negative emotions appeared as feedback from the proposers. We argued that these findings might show that the participants wanted to punish the proposers by rejecting an offer for its unfairness and therefore the negative feedback met their expectations. The altered processing of negative emotional facial expressions in the ultimatum game could therefore indicate that the punishment is interpreted as successful. This includes the expectation that the interaction partner will change his behavior in the future and eventually make fairer offers.
In the second study we wanted to show that smiling and sad emojis as feedback stimuli in the modified ultimatum game can also lead to increased acceptance rates. Contrary to our assumptions, this effect could not be observed. At the neural level as well, the findings did not correspond to our assumptions and differed strongly from those of the first study. One finding, however, was that the neural P3 component showed how the use of emojis as feedback stimuli particularly characterizes certain types of proposers. This is supported by the fact that the P3 is increased for the proposer who rewards an acceptance with a smile as well as for the proposer who reacts to rejection with a sad emoji compared to the neutral control proposer.
The third study examined the discrepancy between the findings of the first and second study. Accordingly, both humans and emojis representing the different proposers were presented in the ultimatum game. In addition, emojis were selected that showed a higher similarity to known emojis from common messenger services compared to the second study. We were able to replicate that the proposers in the ultimatum game, who reward an acceptance of the offer with a smile, led to an increased acceptance rate compared to the neutral control proposers. This difference is independent of whether the proposers are represented by emojis or human faces. With regard to the neural correlates, we were able to demonstrate that emojis and human faces differ strongly in their neural processing. Emojis showed stronger activation than human faces in the face-processing N170 component, the feedback-related negativity and the P3 component. We concluded that the results of the N170 and feedback-related negativity could indicate a signal for missing social information of emojis compared to faces. The increased P3 amplitude for emojis might imply that emojis appear unexpectedly as reward stimuli in a social decision task compared to human faces.
The last study of this project dealt with socially unexpected feedback. In comparison to the first three studies, new proposer identities were implemented. In particular, the focus was on a proposer who reacted to the rejection of an offer unexpectedly with a smile and to the acceptance with a neutral facial expression. According to the results, participants approach this unexpected smile through increased rejection, although it is accompanied by financial loss. In addition, as reported in studies one and three, we were able to show that proposers who respond to the acceptance of an offer with a smiling face and thus meet the expectations of the participants have higher offer acceptance rates than the control proposer. At the neuronal level, especially the feedback from the socially unexpected proposer led to an increased P3 amplitude, which indicates that smiling after rejection is attributed a special subjective importance.
The experiments provide new insights into the social influence through emotional feedback and the processing of relevant social cues. Due to the conceptual similarity of the studies, it was possible to differentiate between stable findings and potentially stimulus-dependent deviations, thus creating a well-founded contribution to the current research. Therefore, the novel paradigm presented here, and the knowledge gained from it could also play an important role in the future for clinical questions dealing with limited social competencies.
Anxiety research is one of the major psychological research domains and looks back on decades of research activity. Traditionally, novel theories and approaches are tested utilizing animal models. One way to study inherent anxiety in rodents is the elevated plus-maze (EPM). The EPM is a plus-shaped platform with two closed, i.e., walled, arms and two open unwalled arms. If given the opportunity to freely explore the apparatus, rodents instinctively avoid the open arms to protect themselves from predators. Hence, they spent less time on open and more time on closed arms, which is behaviorally associated with general anxiety. In the course of the pharmacological validation, it was found that this exploratory pattern can be reversed by anxiolytic substances, e.g., benzodiazepines, or potentiated by anxiogenics. One of the significant advantages of the EPM is that no prior training session is required in contrast to conditioning studies, thus allowing to observe natural behavior. Therefore, together with the economic and uncomplicated setup, the EPM has become a standard preclinical rodent anxiety test over the decades. In order to validate these rodent anxiety tests, there have recently been attempts to retranslate them to humans. A paramount of cross-species validation is not only the simple transferability of these animal tests but also the observation of anxiety behaviors that are evolutionarily conserved across species. Accordingly, it could be possible to conclude various factors associated with the etiology and maintenance of anxiety disorders in humans. So far, convincing translations of the EPM to humans are still lacking. For that reason, the primary aim of this dissertation is to retranslate the EPM throughout three studies and to evaluate cross-species validity critically. Secondly, the undertaken studies are set out to observe ambulatory activity equivalent to rodent EPM behavior, i.e., open arm avoidance. Thirdly, the undertaken studies aimed to assess the extent to which trait anxiety influences human exploratory activity on the platform to associate it with the assumption that rodent EPM-behavior is a reflection of general anxiety. Finally, virtual reality (VR) was the method of choice to maintain the economic advantage and adjust the EPM size to humans. Study 1 (N = 30) was set up to directly transfer the rodent EPM regarding test design and experimental procedure using a Computer Automatic Virtual Environment (CAVE). The results revealed that humans unlike rodents display a general open arms approach during free exploration. However, open arm avoidance was associated with high trait anxiety and acrophobia (fear of height), which was initially assessed as a control variable due to the virtual platform height. Regression analyses and subjective anxiety ratings hinted at a more significant influence of acrophobia on open arm avoidance. In addition, it was assumed that the open arms approach might have resulted from claustrophobic tendencies experienced in the closed arms due to the high walls. Study 2 (N = 61) sought to differentiate the influence of trait anxiety and acrophobia and adapt the virtual EPM to humans. Therefore, parts of the platform held a semi-transparent grid-floor texture, and the wall height on the closed arms was reduced to standard handrail level. Moreover, participants were priorly screened to exclude clinically significant levels of acrophobia, claustrophobia, and agoraphobia. The data on general exploratory activity showed no arm preference. Regression analyses confirmed that acrophobia is related to open arm avoidance, corroborating the finding of Study 1. Surprisingly, for trait anxiety, the result of Study 1 could not be replicated. Instead, for trait anxiety, no significant effect was found indicating that predominantly fear of heights shapes human EPM behavior even on a subclinical stage. In Study 3 (N = 57), the EPM was embedded into a city setting to 1) create a more natural human environment and 2) eliminate height. Furthermore, a head-mounted display was utilized for VR presentation, and arousal ratings were introduced. Participants were screened for high and low levels of trait anxiety and agoraphobia, and claustrophobia. Replicating the findings of Study 2, no difference in open and closed arm activity was observed, and no effect was found in relationship with trait anxiety. The data on anxiety ratings and claustrophobia suggest a positive correlation indicating that in this city EPM, claustrophobic tendencies might play a role in closed arm avoidance. In summary, this thesis added valuable insights into the retranslation of a well-established standard anxiety test used in rodents. However, it also majorly challenges current findings on the cross-species validity of the EPM. Various explanatory models for the results are critically discussed and associated with clinical implications concerning future research.
This thesis aims for a better understanding of the mechanisms underlying anxiety as well as trauma- and stressor-related disorders and the development of new therapeutic approaches. I was first interested in the associative learning mechanisms involved in the etiology of anxiety disorders. Second, I explored the therapeutic effects of transcutaneous vagus nerve stimulation (tVNS) as a promising new method to accelerate and stabilize extinction learning in humans.
For these purposes, I applied differential anxiety conditioning protocols realized by the implementation of virtual reality (VR). Here, a formerly neutral virtual context (anxiety context, CTX+) is presented whereby the participants unpredictably receive mildly aversive electric stimuli (unconditioned stimulus, US). Another virtual context (safety context, CTX-) is never associated with the US. Moreover, extinction of conditioned anxiety can be modeled by presenting the same contexts without US delivery. When unannounced USs were administered after extinction, i.e. reinstatement, the strength of the “returned” conditioned anxiety can provide information on the stability of the extinction memory.
In Study 1, I disentangled the role of elemental and conjunctive context representations in the acquisition of conditioned anxiety. Sequential screenshots of two virtual offices were presented like a flip-book so that I elicited the impression of walking through the contexts. Some pictures of CTX+ were paired with an US (threat elements), but not some other screenshots of the same context (non-threat elements), nor the screenshots depicting CTX- (safety elements). Higher contingency ratings for threat compared to non-threat elements revealed elemental representation. Electro-cortical responses showed larger P100 and early posterior negativity amplitudes elicited by screenshots depicting CTX+ compared to CTX- and suggested conjunctive representation. These results support the dual context representation in anxiety acquisition in healthy individuals.
Study 2 addressed the effects of tVNS on the stabilization of extinction learning by using a context conditioning paradigm. Potentiated startle responses as well as higher aversive ratings in CTX+ compared to CTX- indicate successful anxiety conditioning. Complete extinction was found in startle responses and valence ratings as no differentiation between CTX+ and CTX- suggested. TVNS did not affect extinction or reinstatement of anxiety which may be related to the inappropriate transferability of successful stimulation parameters from epilepsy patients to healthy participants during anxiety extinction.
Therefore, in Study 3 I wanted to replicate the modulatory effects of tVNS on heart rate and pain perception by the previously used parameters. However, no effects of tVNS were observed on subjective pain ratings, on pain tolerance, or on heart rate. This led to the conclusion that the modification of stimulation parameters is necessary for a successful acceleration of anxiety extinction in humans.
In Study 4, I prolonged the tVNS and, considering previous tVNS studies, I applied a cue conditioning paradigm in VR. Therefore, during acquisition a cue (CS+) presented in CTX+ predicted the US, but not another cue (CS-). Both cues were presented in a second context (CTX-) and never paired with the US. Afterward, participants received either tVNS or sham stimulation and underwent extinction learning. I found context-dependent cue conditioning only in valence ratings, which was indicated by lower valence for CS+ compared to CS- in CTX+, but no differential ratings in CTX-. Successful extinction was indicated by equal responses to CS+ and CS-. Interestingly, I found reinstatement of conditioned fear in a context-dependent manner, meaning startle response was potentiated for CS+ compared to CS- only in the anxiety context. Importantly, even the prolonged tVNS had no effect, neither on extinction nor on reinstatement of context-dependent cue conditioning. However, I found first evidence for accelerated physiological contextual extinction due to less differentiation between startles in CTX+ compared to CTX- in the tVNS than in the sham stimulated group.
In sum, this thesis first confirms the dual representation of a context in an elemental and a conjunctive manner. Second, though anxiety conditioning and context-dependent cue conditioning paradigms worked well, the translation of tVNS accelerated extinction from rats to humans needs to be further developed, especially the stimulation parameters. Nevertheless, tVNS remains a very promising approach of memory enhancement, which can be particularly auspicious in clinical settings.
Depressive disorders represent one of the main sources for the loss of healthy years of life. One of the reasons for this circumstance is the recurrent course of these disorders, which can be interrupted by current therapeutic approaches, especially in the shortterm, but seem to be maintained at least in part in the long-term. Subsequently, on one hand, this thesis deals with methodological measurement issues in the longitudinal prediction of depressive courses. On the other hand, it addresses two currently discussed neuroscience-based treatment approaches, which are investigated experimentally in a basic-psychological manner and reviewed in the light of their potential to translate results to the application in patient care. These two approaches each address potential mechanisms that may negatively impact long-term disease trajectories: First, stable endophenotypes for vulnerability factors that could regain control over the organism and reactivate maladaptive experiences, or behaviors with increasing temporal distance from therapeutic methods are focused on. In the studies presented, these were influenced by a recently rediscovered method of neuromodulation (transcranial low-intensity focused ultrasound) which is discussed in light of its unique capability to address even deepest, subcortical regions at a high spatial resolution. Lastly, as a second approach, an experimental design for the use of reconsolidation interference is presented, which could provide a first insight into the applicability of corresponding protocols in the field of depressive disorders and thus contribute to the modification, instead of inhibition, of already mentioned endophenotypes. In sum, methodological considerations for monitoring and predicting long-term courses of depression are deducted before two approaches are discussed that could potentially exert positive influences on the recurrent nature of depressive symptoms on their own, in combination with each other, or as augmentation for existing therapeutic procedures.