Human Prosocial Preferences Are Related to Slow-Wave Activity in Sleep.

Prosocial behavior is crucial for the smooth functioning of the society. Yet, individuals differ vastly in the propensity to behave prosocially. Here, we try to explain these individual differences under normal sleep conditions without any experimental modulation of sleep. Using a portable high-density EEG, we measured the sleep data in 54 healthy adults (28 females) during a normal night's sleep at the participants' homes. To capture prosocial preferences, participants played an incentivized public goods game in which they faced real monetary consequences. The whole-brain analyses showed that a higher relative slow-wave activity (SWA, an indicator of sleep depth) in a cluster of electrodes over the right temporoparietal junction (TPJ) was associated with increased prosocial preferences. Source localization and current source density analyses further support these findings. Recent sleep deprivation studies imply that sleeping enough makes us more prosocial; the present findings suggest that it is not only sleep duration, but particularly sufficient sleep depth in the TPJ that is positively related to prosociality. Because the TPJ plays a central role in social cognitive functions, we speculate that sleep depth in the TPJ, as reflected by relative SWA, might serve as a dispositional indicator of social cognition ability, which is reflected in prosocial preferences. These findings contribute to the emerging framework explaining the link between sleep and prosocial behavior by shedding light on the underlying mechanisms.

Face coverings increase apparent honesty and cooperativeness.

People readily make inferences about trait-like characteristics of another person's face. Since the recent global COVID-19 pandemic, the widespread use of hygienic face masks has led to large proportions of the face being covered. We investigated the effect of face masks on the inference of prosocially relevant characteristics, namely cooperativeness and honesty. Portraits of participants of previous studies from which we knew their "true" prosocial tendencies served as stimuli. These facial stimuli were presented once with and once without a hygienic face mask to 60 naïve participants who rated the faces for cooperativeness and honesty. Results revealed that wearing face masks made people generally appear more cooperative and more honest than without a mask, but that these ratings were unrelated to the true prosocial tendencies of these people. Together, these findings have important implications for social interactions, particularly in contexts where nonverbal communication is essential, such as in healthcare settings, job interviews, and social gatherings.

I spy with my little eye: The detection of changes in emotional faces and the influence of facial feedback in Parkinson disease.

BACKGROUND AND PURPOSE: Parkinson disease (PD) is a progressive neurodegenerative disorder that affects the motor system but also involves deficits in emotional processing such as facial emotion recognition. In healthy participants, it has been shown that facial mimicry, the automatic imitation of perceived facial expressions, facilitates the interpretation of the emotional states of our counterpart. In PD patients, recent studies revealed reduced facial mimicry and consequently reduced facial feedback, suggesting that this reduction might contribute to the prominent emotion recognition deficits found in PD. METHODS: We investigated the influence of facial mimicry on facial emotion recognition. Twenty PD patients and 20 healthy controls (HCs) underwent a classical facial mimicry manipulation (holding a pen with the lips, teeth, or nondominant hand) while performing an emotional change detection task with faces. RESULTS: As expected, emotion recognition was significantly influenced by facial mimicry manipulation in HCs, further supporting the hypothesis of facial feedback and the related theory of embodied simulation. Importantly, patients with PD, generally and independent from the facial mimicry manipulation, were impaired in their ability to detected emotion changes. Our data further show that PD patients' facial emotional recognition abilities are completely unaffected by mimicry manipulation, suggesting that PD patients cannot profit from an artificial modulation of the already impaired facial feedback. CONCLUSIONS: These findings suggest that it is not the hypomimia and the absence of facial feedback per se, but a disruption of the facial feedback loop, that leads to the prominent emotion recognition deficit in PD patients.

Face masks have a limited effect on the feeling of being looked at.

Introduction: Wearing face masks has been promoted as an effective measure to reduce the spread of COVID-19. Because face masks cover a major part of the face, they have detrimental effects on various aspects of social cognition. Yet, a highly important feature of the face is not occluded by face masks: the eyes. The eyes play an important role in social interactions: knowing where another person is looking is of central importance when interacting with others. Recent research has reported an attentional shift toward the eye region as a consequence of the widespread exposure to face masks. However, no study has yet investigated the influence of face masks on the perception of eye gaze direction. Here we investigated whether face masks have an effect on the feeling of being looked at. Assuming an attentional shift toward the eyes, we might expect more accurate gaze perception in faces wearing face masks. Methods: Sixty-five participants decided for a series of realistic avatar faces whether each face was making eye contact or not. Half of the faces wore face masks, the other half did not. For each participant and separately for each condition (mask vs. no mask), we calculated the cone of direct gaze (CoDG), a commonly used measure to quantify the range of gaze angles within which an observer assumes mutual gaze. Results: Contrary to our expectations, results show that mutual gaze is not recognized more accurately in masked faces. Rather, the CoDG was, on average, slightly wider for faces wearing masks compared to faces without masks. Discussion: Notwithstanding the relatively small effect of face mask, these findings potentially have implications on our social interactions. If we inadvertently feel looked at by an onlooker, we may react inappropriately by reciprocating the alleged approach orientation.

The Cone of Direct Gaze: A Stable Trait.

Direct eye gaze is a potent stimulus in social interactions and is often associated with interest and approach orientation. Yet, there is remarkable variability in the range of gaze lines that people accept as being direct. A measure that is frequently used to quantify the range of gaze angles within which an observer assumes mutual gaze is the cone of direct gaze (CoDG). While individual differences in CoDG have often been examined, studies that systematically investigate the stability of an observers' CoDG over time are scarce. In two experiments, we measured the CoDG using an established paradigm and repeated the measurement after 5 min and/or after 1 week. We found high inter-individual variation, but high agreement within participants (ICCs between 0.649 and 0.855). We conclude that the CoDG can be seen as a rather stable measure, much like a personality trait.

Feeling of guilt explains why people react differently to resource depletion warnings.

Despite insistent warnings from climate scientists, the global environmental situation is further deteriorating. To date, only very few studies have investigated the impact of warnings on sustainable decision-making in controlled laboratory settings. Moreover, the few existing studies mainly looked at average warning reactions rather than taking individual differences into account. Here, we investigated individual differences in the reaction to resource depletion warnings and scrutinized the impact of emotions on behavioural changes by applying a resource dilemma task with warnings. Data-driven and model-free cluster analyses identified four different types of consumption behaviour. Importantly, guilt was positively related to sustainable decision-making after warnings. In contrast, a lack of guilt was associated with no behavioural change or even worse with more unsustainable behaviour after warnings. These findings contribute to the debate over effective climate change communication by demonstrating that issuing warnings about the climate crisis only leads to the intended behavioural changes if people experience guilt.

Effects of posed smiling on memory for happy and sad facial expressions.

The perception and storage of facial emotional expressions constitutes an important human skill that is essential for our daily social interactions. While previous research revealed that facial feedback can influence the perception of facial emotional expressions, it is unclear whether facial feedback also plays a role in memory processes of facial emotional expressions. In the present study we investigated the impact of facial feedback on the performance in emotional visual working memory (WM). For this purpose, 37 participants underwent a classical facial feedback manipulation (FFM) (holding a pen with the teeth-inducing a smiling expression vs. holding a pen with the non-dominant hand-as a control condition) while they performed a WM task on varying intensities of happy or sad facial expressions. Results show that the smiling manipulation improved memory performance selectively for happy faces, especially for highly ambiguous facial expressions. Furthermore, we found that in addition to an overall negative bias specifically for happy faces (i.e. happy faces are remembered as more negative than they initially were), FFM induced a positivity bias when memorizing emotional facial information (i.e. faces were remembered as being more positive than they actually were). Finally, our data demonstrate that men were affected more by FFM: during induced smiling men showed a larger positive bias than women did. These data demonstrate that facial feedback not only influences our perception but also systematically alters our memory of facial emotional expressions.

Content matters: Cyclic effects on women's voices depend on social context.

Women's voices reportedly sound more attractive during the fertile days compared to the non-fertile days of their menstrual cycle. Here we investigated whether the speech content modulates the cyclic changes in women's voices. We asked 72 men and women to rate how interested they were in getting to know the speaker based on her voice. Forty-two naturally cycling women were recorded once during the late follicular phase (high fertility) and once during the luteal phase (low fertility) while speaking sentences of neutral and social content. Listeners were more interested in getting to know the speakers when hearing sentences with social content. Furthermore, raters were more interested in getting to know the speakers when these were recorded in the late follicular than in the luteal phase, but only in sentences with social content. Notably, levels of reproductive hormones (EP ratio) across the cycle phases did not significantly predict the preference for late follicular voices, but echoing the perceptual ratings, there was a significant EP ratio x speech content interaction. Phonetic analyses of mean fundamental frequency (F0) revealed a main effect of menstrual cycle phase and speech content but no interaction. Employing an action-oriented task, the present study extends findings of cycle-dependent voice changes by emphasising that speech content critically modulates fertility effects.

Pleasant body odours, but not genetic similarity, influence trustworthiness in a modified trust game.

Identifying trustworthy partners is an important adaptive challenge for establishing mutually cooperative relationships. Previous studies have demonstrated a marked relationship between a person's attractiveness and his apparent trustworthiness (beauty premium). Kin selection theory, however, suggests that cues to kinship enhance trustworthiness. Here we directly tested predictions of the beauty premium and kin selection theory by using body odours as cues to trustworthiness. Body odours reportedly portray information about an individuals' genotype at the human leucocyte antigen system (HLA) and thus olfactory cues in body odours serve as a promising means for kin recognition. Ninety men played trust games in which they divided uneven sums of monetary units between two male trustees represented by their body odour and rated each body odour for pleasantness. Half of the odours came from HLA-similar men (suggesting closer kin) and half from HLA dissimilar men (suggesting non-kin). We found that the amount of money the players transferred was not related to HLA-similarity, but to the pleasantness of the trustee's body odour. By showing that people with more pleasant body odours are trusted more than people with unpleasant body odour we provide evidence for a "beauty-premium" that overrides any putative effect of kin.

Out of Focus: Facial Feedback Manipulation Modulates Automatic Processing of Unattended Emotional Faces.

Facial expressions provide information about an individual's intentions and emotions and are thus an important medium for nonverbal communication. Theories of embodied cognition assume that facial mimicry and resulting facial feedback plays an important role in the perception of facial emotional expressions. Although behavioral and electrophysiological studies have confirmed the influence of facial feedback on the perception of facial emotional expressions, the influence of facial feedback on the automatic processing of such stimuli is largely unexplored. The automatic processing of unattended facial expressions can be investigated by visual expression-related MMN. The expression-related MMN reflects a differential ERP of automatic detection of emotional changes elicited by rarely presented facial expressions (deviants) among frequently presented facial expressions (standards). In this study, we investigated the impact of facial feedback on the automatic processing of facial expressions. For this purpose, participants (n = 19) performed a centrally presented visual detection task while neutral (standard), happy, and sad faces (deviants) were presented peripherally. During the task, facial feedback was manipulated by different pen holding conditions (holding the pen with teeth, lips, or nondominant hand). Our results indicate that automatic processing of facial expressions is influenced and thus dependent on the own facial feedback.

Increased sensitivity to social exclusion during the luteal phase: Progesterone as resilience factor buffering against ostracism?

A woman's social behaviour reportedly varies across the menstrual cycle. In this study, we estimated changes in sensitivity to social exclusion across the menstrual cycle and scrutinized the related role of progesterone. Forty-nine naturally cycling women played a virtual ball-tossing game (Cyberball) to manipulate social inclusion. All participants underwent inclusion and exclusion conditions during the late follicular and the luteal phase. We assessed salivary progesterone concentrations at each cycle phase. After each Cyberball session we measured positive/negative mood using the Multidimensional Mood State Questionnaire (MDMQ). Multilevel analyses indicated that women showed worse mood following exclusion as compared to inclusion conditions (p = 0.014). Notably, this exclusion effect was more pronounced during the luteal phase than the late follicular phase (p = 0.029). As expected, progesterone concentrations were higher during the luteal phase as compared to the late follicular phase, but interestingly, progesterone concentrations were negatively associated with exclusion effects. When accounting for mediation via progesterone, direct cycle-phase related differences in social exclusion effects even increased as compared to the model without mediator. These findings suggest that progesterone may function as buffer against negative feelings that result from being socially excluded. The relevance of these findings for Premenstrual Dysphoric Disorder (PMDD) are discussed, and we conclude that social exclusion may represent an important research domain criterion (RDoC) of relevance for PMDD, with progesterone pointing to new potential pharmacological targets.

TV vs. YouTube: TV Advertisements Capture More Visual Attention, Create More Positive Emotions and Have a Stronger Impact on Implicit Long-Term Memory.

In an experiment, effects of commercials that are either shown within a TV program or embedded in YouTube videos were compared. These two media environments have not yet been compared empirically in terms of their advertising impact. A within-subjects design and a multi-method approach were used (N = 36). Eye tracking data show that more attention is allocated to advertisements that appear within a TV program compared to the YouTube-condition and the viewing experience elicited more positive emotions in the TV-condition. Two days after reception, no difference in recognition, likeability, and purchase intention occurred, but in terms of implicit long-term memory: In the TV condition, brands that were previously advertised but no longer remembered elicited stronger skin conductance change than brands for which no advertisements had previously been shown. In terms of advertising impact, TV seems to still be the better choice for advertisers. Presentation mode should be considered in future evaluation of advertisement potential.

Compassionate faces: Evidence for distinctive facial expressions associated with specific prosocial motivations.

Compassion is a complex cognitive, emotional and behavioural process that has important real-world consequences for the self and others. Considering this, it is important to understand how compassion is communicated. The current research investigated the expression and perception of compassion via the face. We generated exemplar images of two compassionate facial expressions induced from two mental imagery tasks with different compassionate motivations (Study 1). Our kind- and empathic compassion faces were perceived differently and the empathic-compassion expression was perceived as best depicting the general definition of compassion (Study 2). Our two composite faces differed in their perceived happiness, kindness, sadness, fear and concern, which speak to their underling motivation and emotional resonance. Finally, both faces were accurately discriminated when presented along a compassion continuum (Study 3). Our results demonstrate two perceptually and functionally distinct facial expressions of compassion, with potentially different consequences for the suffering of others.

The scent of attractiveness: levels of reproductive hormones explain individual differences in women's body odour.

Individuals are thought to have their own distinctive body odour which reportedly plays an important role in mate choice. In the present study we investigated individual differences in body odours of women and examined whether some women generally smell more attractive than others or whether odour preferences are a matter of individual taste. We then explored whether levels of reproductive hormones explain women's body odour attractiveness, to test the idea that body odour attractiveness may act as a chemosensory marker of reproductive fitness. Fifty-seven men rated body odours of 28 healthy, naturally cycling women of reproductive age. We collected all odours at peak fertility to control for menstrual cycle effects on body odour attractiveness. Women's salivary oestradiol, progesterone, testosterone and cortisol levels were assessed at the time of odour collection to test whether hormone levels explain body odour attractiveness. We found that the men highly agreed on how attractive they found women's body odours. Interestingly, women's body odour attractiveness was predicted by their oestradiol and progesterone levels: the higher a woman's levels of oestradiol and the lower her levels of progesterone, the more attractive her body odour was rated. In showing that women's body odour attractiveness is explained by levels of female reproductive hormones, but not by levels of cortisol or testosterone, we provide evidence that body odour acts as a valid cue to potential fertility.

Timing is crucial: Some critical thoughts on using LH tests to determine women's current fertility.

Naturally cycling women reportedly go through a variety of psychological and behavioural changes over menstrual cycle. Evolutionary informed scholars have interpreted such changes as maximising reproductive success. However, concerns have been raised regarding this ovulatory shift hypothesis, since recent studies have yielded inconsistent findings. We suggest that the inconsistent findings regarding the ovulatory shift hypothesis may result from a too simplistic definition of the fertile window. Presently, most studies use LH tests to determine the fertile window. The problem with this "gold standard" is that it builds on the misconception that fertility peaks with ovulation and that ovulation regularly occurs 24 to 48 hours after the LH surge. While commercially available urinary LH test strips are a cheap and easy way to reliably detect LH surges, the LH surge itself marks the impending end of the fertile window. So if women are invited to the laboratory after the LH surge (as is often done for practical reasons) there is a high probability of misclassifying women as fertile when in fact the fertile window has already closed. We discuss possible advancements that may help to increase the accuracy and reliability of determining a woman's individual fertile window, during which any adaptive changes that increase the chance of reproduction should be best observable.

Reactive aggression tracks within-participant changes in women's salivary testosterone.

The relation between testosterone and aggression has been relatively well documented in men, but it is less well understood in women. Here we assessed the relationship between salivary testosterone and reactive aggression (i.e., rejection rate for unfair offers) in the Ultimatum Game. Forty naturally cycling women were tested twice, once in the late follicular phase (around ovulation) and once during the luteal phase. Ovulation was determined using urine test strips measuring luteinizing hormone levels. Salivary samples were assayed for testosterone, estradiol, progesterone, and cortisol at both test sessions. There was no association with the cycle, but multilevel modeling revealed a significant within-participant association between testosterone and rejection rate for extremely unfair offers (i.e., high reactive aggression), indicating that women showed greater reactive aggression when their testosterone levels were higher. Additionally, we found that women with relatively high individual concentrations of testosterone were more likely to reject extremely unfair offers than women with relatively low concentrations of testosterone. This study is the first to demonstrate that women react more aggressively in response to provocation when their testosterone level is high than when their testosterone is low, suggesting that testosterone plays an important role in the regulation of women's aggressive behavior following social provocation.

Theta resting EEG in TPJ/pSTS is associated with individual differences in the feeling of being looked at.

Direct eye gaze is a powerful stimulus in social interactions, yet people vary considerably in the range of gaze lines that they accept as being direct (cone of direct gaze, CoDG). Here, we searched for a possible neural trait marker of these individual differences. We measured the width of the CoDG in 137 healthy participants and related their individual CoDG to their neural baseline activation as measured with resting electroencephalogram. Using a source-localization technique, we found that resting theta current density in the left temporo-parietal junction (TPJ) and adjacent posterior superior temporal sulcus (pSTS) was associated with the width of CoDG. Our findings suggest that the higher the baseline cortical activation in the left TPJ/pSTS, the wider the CoDG and thus the more liberal the individuals' judgments were in deciding whether a looker stimulus was making eye contact or not. This is a first demonstration of the neural signatures underlying individual differences in the feeling of being looked at.

Men's preferences for women's body odours are not associated with human leucocyte antigen.

Body odours reportedly portray information about an individual's genotype at the major histocompatibility complex (MHC, called human leucocyte antigen, HLA, in humans). While there is strong experimental support for MHC-associated mating behaviour in animals, the situation in humans is more complex. A lot of effort has been spent on testing HLA-associated odour preferences of women. To date, only very few studies have looked at HLA-linked olfactory preferences in men and these studies have revealed inconsistent results. Here, we investigate men's HLA-associated preferences for women's body odours. Importantly, and in contrast to previous studies, these odours were gathered at peak fertility (i.e. just before ovulation) when any HLA-associated odour preferences should be strongest. We scrutinized whether men's preference for women's body odours is influenced by (i) the number of shared HLA alleles between men and women, (ii) HLA heterozygosity, and (iii) the frequency of rare HLA alleles. We found that men could readily differentiate between odours they found attractive and odours they found less attractive, but that these preferences were not associated with HLA. Specifically, men did not prefer odours from women who are HLA dissimilar, HLA heterozygous, or who have rare HLA alleles. Together, these findings suggest that HLA has no effect on men's odour preferences.