Placebo treatment facilitates social trust and approach behavior

Distinct computational mechanisms of uncertainty processing explain opposing exploratory behaviors in anxiety and apathy

Decision-making in uncertain environments often leads to varied outcomes. Understanding how individuals interpret the causes of unexpected feedback is crucial for adaptive behavior and mental well-being. Uncertainty can be broadly categorized into two components: volatility and stochasticity. Volatility is about how quickly conditions change, impacting results. Stochasticity, on the other hand, refers to outcomes affected by random chance or "luck". Understanding these factors enables individuals to have more effective environmental analysis and strategy implementation (explore or exploit) for future decisions. This study investigates how anxiety and apathy, two prevalent affective states, influence the perceptions of uncertainty and exploratory behavior. Participants (N = 1001) completed a restless three-armed bandit task that was analyzed using latent state models. Anxious individuals perceived uncertainty as more volatile, leading to increased exploration and learning rates, especially after reward omission. Conversely, apathetic individuals viewed uncertainty as more stochastic, resulting in decreased exploration and learning rates. The perceived volatility-to-stochasticity ratio mediated the anxiety-exploration relationship post-adverse outcomes. Dimensionality reduction showed exploration and uncertainty estimation to be distinct but related latent factors shaping a manifold of adaptive behavior that is modulated by anxiety and apathy. These findings reveal distinct computational mechanisms for how anxiety and apathy influence decision-making, providing a framework for understanding cognitive and affective processes in neuropsychiatric disorders.

Systematic manipulation of experimenters' non-verbal behaviors for the investigation of pain reports and placebo effects

Objective

Non-verbal behaviors (NBs) of caregivers affect pain reports and placebo effects. However, little experimental research has systematically examined the caregivers' NBs. This study protocol and preparatory study report a systematic manipulation of experimenters' NBs to investigate pain report and placebo effects.

Methods

We propose an experiment in which videotaped experimenters (VEs) conduct a pain stimulation and a placebo treatment study. The VEs express one positively enhanced NB and keep the other NBs neutral. Participants will be randomized to either the positive facial expressions (+FE), tone of voice (+TV), body movement (+BM), or neutral NBs (i.e., neutral condition; NC) of the VEs. As a preparatory study for proof of concept, two groups of NB coders from Norway and the USA separately rated the degree of NBs (eye contact, body postures and movements, and tone of voice), and impressions of dominance and being in charge, positivity, and expressivity from each NB video. The NB videos had construct validity and reliability. The +BM and +FE were rated as more dominant and in charge than the +TV and the NC. The +FE and +BM were rated as the most positive and expressive NBs, respectively.

Expected results

+FE will have the largest placebo effects on pain and stress levels. However, transmitting the NBs to patients by VEs is challenging. Moreover, controlling for the effects of research assistants present in the testing room is challenging.

Discussion

We propose that caregivers' NBs affect pain reports and placebo effects. Moreover, different NBs elicit different impressions, and a better understanding of the role of caregiver NBs requires more rigorous investigations. Lastly, aiming to investigate the caregiver NBs, the varying degrees of micro-NBs and their effects on the formation of impressions should be considered.

Oxytocin attenuates racial categorization in 14-month-old infants

Intergroup bias - the preferential attitudes one holds towards one's social group - is a ubiquitous socio-cognitive phenomenon. In fact, studies show that already in the first months of life, infants manifest a preference for members of their own social group. This points to the possibility of inborn mechanisms involved in social group cognition. Here we assess the effect of a biological activation of infants' affiliative motivation on their social categorization capacity. In a first visit to the lab, mothers self-administered either Oxytocin (OT) or placebo (PL) via a nasal spray and then engaged in a face-to-face interaction with their 14-month-old infants, a procedure previously shown to increase OT levels in infants. Infants then performed a racial categorization task presented on an eye-tracker. Mothers and infants returned a week later and repeated the procedure while self-administering the complementary substance (i.e., PL or OT, respectively). In total, 24 infants completed the two visits. We found that whereas infants in the PL condition on the first visit exhibited racial categorization, infants in the OT condition in their first visit did not. Moreover, these patterns remained a week later despite the change in substance. Thus, OT inhibited racial categorization when infants first encountered the to-be-categorized faces. These findings highlight the role of affiliative motivation in social categorization, and suggest that the neurobiology of affiliation may provide insights on mechanisms that may be involved in the downstream prejudicial consequences of intergroup bias.

Deceptive and open-label placebo effects in experimentally induced guilt: a randomized controlled trial in healthy subjects

Placebos are known to yield significant effects in many conditions. We examined deceptive and open-label placebo effects on guilt, which is important for self-regulation and a symptom of mental disorders. Following an experimental induction of guilt, healthy subjects were randomized to deceptive placebo (DP; n = 35), open-label placebo (OLP; n = 35), or no treatment (NT; n = 39). The primary outcome was guilt responses assessed in area under the curve (AUC). Secondary outcomes were shame, guilt, and affect. We hypothesized that DP and OLP would reduce guilt compared to NT. Guilt responses were higher in the NT group than in the placebo groups (estimate = 2.03, 95% CI = 0.24-3.82, d = 0.53), whereas AUC guilt did not differ significantly between the placebo groups (estimate = -0.38, 95% CI = -2.52-1.76, d = -0.09). Placebos are efficacious in reducing acute guilt responses, regardless of the placebo administration (i.e., open vs. deceptive). Furthermore, we observed narrative-specific effects with significant changes of guilt but not shame, pride, or affect. These results indicate not only that guilt is amenable to placebos but also that placebos can be administered in an ethical and potentially emotion-specific manner.

Default beliefs as a basis of social decision-making

Default beliefs are implicit assumptions about the future existence of oneself, others, and the environment. They differ from individual and cultural beliefs in that they are held universally, implicitly, and with high confidence. What is the content of default beliefs? How are they represented in the brain? And what is their role in social decision-making?

Can placebos reduce intrusive memories?

After traumatic experiences, intrusive memories can flash back and evoke significant distress. Here, we investigated whether the frequency and severity of intrusions can be reduced by the provision of placebo. After the (online) exposure to the trauma-film paradigm, healthy participants (N = 112) received deceptive placebo (DP), open-label placebo (OLP), or no treatment. In the DP group, participants were led to believe to receive a dopamine-modulating drug, which was supposed to disrupt the consolidation of traumatic memories, although they in fact received the same placebo tablets as the OLP group for one week. The results show that the groups did not differ in the frequency of intrusive memories after one week. However, participants receiving OLP reported a significantly reduced intensity of intrusions as compared to DP. Across groups, negative expectations about the intensity and controllability of intrusions were associated with a higher frequency of intrusions, higher distress, higher burden, and more negative appraisal. The results suggest that expectations play an important role in the emergence of intrusive memories and that some of the disabling aspects of intrusive memories can be reduced by placebo. This may carry clinical potential because placebos are an accessible, cost-effective intervention to reduce the risk of intrusive memories.

Social incentive factors in interventions promoting sustainable behaviors: A meta-analysis

Based on a meta-analysis, this paper highlights the strength and relevance of several social incentive factors concerning pro-environmental behaviors, including social influence, network factors (like network size, network connection and leadership), trust in others, and trust in institutions. Firstly, our results suggest that social influence is necessary for the emergence of pro-environmental behaviors. More specifically, an internal social influence (i.e., motivating people to change their perceptions and attitudes) is essential to promote pro-environmental behaviors. Secondly, network connection encourages pro-environmental behaviors, meaning that the effectiveness of a conservation policy can be improved if connections among individuals are increased. Finally, trust in institutions can dictate individual behaviors to shape policy design and generate desired policy outcomes.

Makeup and Its Application Simulation Affect Women's Self-Perceptions

Appearance modification is ancient, universal and influences other and self-perceptions. It has been rarely addressed how expectation of appearance modification would affect women's self-perception. We analyzed self-assessments of women without makeup and after having makeup professionally applied at four increasing levels (light, moderate, heavy 1, and heavy 2 makeup). In the simulation phase, women were treated with colorless cosmetics. Fifty Brazilian women (M_age = 24.26 years; SD = 5.53) rated themselves on attractiveness, health, self-esteem, femininity, satisfaction with appearance, age, dominance, confidence, and competence in all experimental conditions. Women in the simulation phase considered themselves more feminine, healthier, and with higher self-esteem than without makeup. In the real makeup phases, these ratings were higher than in the simulation phase. Appearance satisfaction and attractiveness did not differ between simulation and the real makeup phases, both being higher than without makeup. Confidence increased only in real makeup phases, but there was no effect on competence. Thus, real appearance modification and/or an expectation thereof can differently affect specific domains of self-evaluation.

Neural mechanisms of modulations of empathy and altruism by beliefs of others' pain

Perceived cues signaling others' pain induce empathy which in turn motivates altruistic behavior toward those who appear suffering. This perception-emotion-behavior reactivity is the core of human altruism but does not always occur in real-life situations. Here, by integrating behavioral and multimodal neuroimaging measures, we investigate neural mechanisms underlying modulations of empathy and altruistic behavior by beliefs of others' pain (BOP). We show evidence that lack of BOP reduces subjective estimation of others' painful feelings and decreases monetary donations to those who show pain expressions. Moreover, lack of BOP attenuates neural responses to their pain expressions within 200 ms after face onset and modulates neural responses to others' pain in the insular, post-central, and frontal cortices. Our findings suggest that BOP provide a cognitive basis of human empathy and altruism and unravel the intermediate neural mechanisms.

Determinants and modulators of human social decisions

Social decision making is a highly complex process that involves diverse cognitive mechanisms, and it is driven by the precise processing of information from both the environment and from the internal state. On the one hand, successful social decisions require close monitoring of others' behavior, in order to track their intentions; this can guide not only decisions involving other people, but also one's own choices and preferences. On the other hand, internal states such as own reward or changes in hormonal and neurotransmitter states shape social decisions and their underlying neural function. Here, we review the current literature on modulators and determinants of human social decisions.

Placebo Effects in the Context of Religious Beliefs and Practices: A Resting-State Functional Connectivity Study

Background: Placebos (inert substances or procedures) can positively influence a person’s psychological and physical well-being, which is accompanied by specific changes in brain activity. There are many different types of placebos with different effects on health-related variables. This study investigated placebo effects in the context of religious beliefs and practices. The participants received an inert substance (tap water) along with the verbal suggestion that the water would come from the sanctuary in Lourdes (a major Catholic pilgrimage site with reports of miracle cures). We investigated changes in resting-state functional connectivity (rsFC) in three brain networks (default-mode, salience, cognitive control) associated with the drinking of the placebo water.

Methods: A total of 37 females with the belief that water from the sanctuary in Lourdes has positive effects on their spiritual, emotional, and physical well-being participated in this placebo study with two sessions. The participants drank tap water that was labeled “Lourdes water” (placebo) before a 15-min resting-state scan in one session. In the other (control) session, they received tap water labeled as tap water. The participants rated their affective state (valence, arousal) during the session and were interviewed concerning specific thoughts, feelings, and bodily sensations directly after each of the two sessions.

Results: The placebo reduced rsFC in the frontoparietal cognitive control network and increased rsFC in the salience network (insular-cerebellar connectivity). During the session, the participants rated their affective state as very pleasant and calm. The ratings did not differ between the two conditions. Immediately after the session, the participants reported increased intensity of pleasant bodily sensations (e.g., feelings of warmth, tingling) and feelings (e.g., gratefulness) for the “Lourdes water” condition.

Conclusions: The present findings provide the first evidence that placebos in the context of religious beliefs and practices can change the experience of emotional salience and cognitive control which is accompanied by connectivity changes in the associated brain networks.

A meta-analysis of hormone administration effects on cooperative behaviours: Oxytocin, vasopressin, and testosterone

The hormones oxytocin, vasopressin, and testosterone have been implicated in cooperative behaviours and have attracted increasing research interest for their potential to regulate human cooperation in both healthy and clinical populations. However, the behavioural effects of the administration of these hormones remain to be verified. The current analysis included 41 studies involving 3,269 participants with a narrow age range. We examined the administration effects of these hormones on cooperative behaviour and the regulatory effects of individual characteristics, hormone interventions, and task structure and context. Results revealed a moderate positive effect size of oxytocin intranasal administration, a large negative effect size of vasopressin intranasal administration, and nonsignificant effects of testosterone administration on cooperative behaviours. Participants with mental dysfunctions were less sensitive to oxytocin and vasopressin administration. Oxytocin administration was effective in an in-group situation and for initial choices, corroborating a Tit-for-Tat strategy.

Placebo prevents rumination: An experimental study

BACKGROUND

Rumination is a risk factor for the development and maintenance of depressive symptoms and represents an important target for the treatment of depression. In the present study, we aimed to examine whether rumination can be reduced when participants are led to believe that they would receive medication that would prevent them from ruminating.

METHODS

In healthy participants (N= 91), an initial dysphoric state was induced via mood-suggestive music and autobiographic recall. Subsequently, participants were randomly assigned to one of two groups: an experimental group that received a deceptive active placebo via intranasal application accompanied by expectancy-enhancing instructions vs. a no-treatment control group. Then, rumination was induced via a rumination-activating task. The primary outcome was current rumination; experienced sadness was considered a secondary outcome.

RESULTS

Consistent with the hypothesis, participants receiving the placebo reported a significantly lower increase in current rumination (d= 0.57) and a higher decrease in sadness (d= 0.69) after the experimental induction than the control group.

LIMITATIONS

The external validity of this study might be limited due to the highly educated student sample.

CONCLUSIONS

The results suggest that rumination processes as well as experienced sadness can be positively influenced by placebo treatment. To evaluate its clinical potential, placebo-induced expectancy effects in rumination research should be further examined, particularly with clinically depressed patients. Also, the results imply that clinicians might consider the effects of expectations on patients' rumination tendencies, for example by explicitly addressing patients' expectations about rumination, mood, and the treatment in general.

Oxytocin facilitates valence-dependent valuation of social evaluation of the self

People are eager to know the self in other’s eyes even with personal costs. However, what drives people costly to know evaluations remains unknown. Here we tested the hypothesis of placing subjective value on knowing social evaluations. To quantify the subjective value, we developed a pay-to-know choice task where individuals trade off profits against knowing social evaluations. Individuals computed independent unknown aversion towards positive and negative social evaluations and placed higher values on knowing social evaluation on positive than negative aspects. Such a valence-dependent valuation of social evaluation was facilitated by oxytocin, a neuropeptide linked to feedback learning and valuation processes, by decreasing values of negative social evaluation. Moreover, individuals scoring high in depression undervalued positive social evaluation, which was normalized by oxytocin. We reveal the psychological and computational processes underlying self-image formation/update and suggest a role of oxytocin in normalizing hypo-valuation of positive social evaluation in depression.

Danyang Wang and Yina Ma measure the amount of money participants are willing to forgo for the opportunity to access social or non-social evaluations of the self. They show that subjective values on knowing social evaluation is valence-dependent whereas that on non-social evaluation is valence-insensitive. Moreover, oxytocin contributes to valence-dependent valuation on social evaluation.

The placebo and its effects: A psychoneuroendocrinological perspective

Placebos are usually employed deceptively in clinical trials in order to control for non-specific effects. However, since placebos themselves have been found to cause clinically relevant changes and in some cases are indistinguishable from the verum they are tested against, this theoretically inert, but practically effective intervention has become a scientific discipline in its own right. In this review, it is argued that placebos are generic and genuine biopsychosocial interventions and as such are highly interesting candidates for a psychoneuroendocrinological perspective. Yet, despite a considerable conceptual proximity between explanatory models of placebos and their effects with psychoneuroendocrine models and findings, placebos have thus far not been subject to systematic psychoneuroendocrine examination. Consequently, it would be highly interesting and informative to make placebos the target of psychoneuroendocrine scrutiny.

Guided Imagery for Total Knee Replacement: Responses to an Audiobook Placebo Treatment

The use of a placebo is the gold standard for establishing the efficacy of new treatments in randomized controlled trials (RCTs). Placebo treatments are inert; this allows specific effects of the experimental treatment to be separated from nonspecific physiological, psychological, and social effects. The aim of this study was to scrutinize the workings of an audiobook (AB) placebo treatment, which was used in a placebo-controlled, investigator-blinded, RCT of the effect of guided imagery (GI) to improve pain and function in persons undergoing total knee replacement. A secondary analysis of quantitative and narrative data collected during the RCT was performed. The AB treatment provided attention control. Participants in the AB group identified benefits-pleasant get-away, new knowledge, quiet time-out, and inspiration; however, there was also evidence of resentful demoralization, especially in the postoperative period. The use of ABs as a placebo treatment in GI RCTs should be executed with caution.

Oxytocin modulates social value representations in the amygdala

Humans exhibit considerable variation in how they value their own interest relative to the interests of others. Deciphering the neural codes representing potential rewards for self and others is crucial for understanding social decision-making. Here we integrate computational modeling with functional magnetic resonance imaging to investigate the neural representation of social value and the modulation by oxytocin, a nine-amino acid neuropeptide, in participants evaluating monetary allocations to self and other (self-other allocations). We found that an individual's preferred self-other allocation serves as a reference point for computing the value of potential self-other allocations. In more prosocial participants, amygdala activity encoded a social-value-distance signal; that is, the value dissimilarity between potential and preferred allocations. Intranasal oxytocin administration amplified this amygdala representation and increased prosocial behavior in more individualistic participants but not in more prosocial ones. Our results reveal a neurocomputational mechanism underlying social-value representations and suggest that oxytocin may promote prosociality by modulating social-value representations in the amygdala.

Effects and Components of Placebos with a Psychological Treatment Rationale - Three Randomized-Controlled Studies

In recent years, placebos have evolved from a mean to control for 'therapeutic chaff' to something that has clinically relevant effects with biological underpinning and that is considered to have clinical as well as scientific potential. However, the wealth of scientific placebo research is conceptualized in a biomedical context, i.e. based on placebos provided with a biomedical treatment rationale, whereas little is known about effects and mechanisms of placebos provided with a psychological treatment rationale. This has important repercussions not only on placebo research, but also on attempts to establish specificity of psychological interventions, such as psychotherapy. Therefore, we set out to assess the effects and possible components of placebos provided with a psychological treatment rationale in three experiments on healthy subjects. We show that placebos provided with a psychological treatment rationale are effective in short- as well as mid-term, but only when provided by a trustworthy, friendly and empathetic experimenter. These findings indicate that placebos are effective outside the medical context and thus need be controlled for in non-medical trials. Furthermore, it highlights and confirms the importance of a plausible psychological treatment rationale in the context of a therapeutic alliance for psychological interventions, such as psychotherapy.

Oxytocin promotes coordinated out-group attack during intergroup conflict in humans

Intergroup conflict contributes to human discrimination and violence, but persists because individuals make costly contributions to their group’s fighting capacity. Yet how group members effectively coordinate their contributions during intergroup conflict remains poorly understood. Here we examine the role of oxytocin for (the coordination of) contributions to group attack or defense in a multi-round, real-time feedback economic contest. In a double-blind placebo-controlled study with N=480 males in an Intergroup Attacker-Defender contest game, we found that oxytocin reduced contributions to attack and over time increased attacker’s within-group coordination of contributions. However, rather than becoming peaceful, attackers given oxytocin better tracked their rival’s historical defense and coordinated their contributions into well-timed and hence more profitable attacks. Our results reveal coordination of contributions as a critical component of successful attacks and subscribe to the possibility that oxytocin enables individuals to contribute to in-group efficiency and prosperity even when doing so implies outsiders are excluded or harmed.

Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Conflict between groups is a recurring theme in human history. We tend to form social bonds with others who share the same characteristics as ourselves, whether that is nationality, ethnicity, or supporting the same football team. Individuals that belong to the same group as us comprise our ‘in-group’. All other individuals make up our ‘out-groups’. Competition and conflict with out-groups – from benign sporting rivalry to warfare – has a key role in shaping human cultures and societies.

Such conflict often requires individuals to act in ways that harm their own self-interests. It also requires them to coordinate their actions with other members of their in-group. How does our biology drive this behavior? When small groups prepare for conflict with other groups, they often perform social bonding routines and rituals. These trigger the brain to release a hormone called oxytocin into the bloodstream. Known as the ‘love hormone’, oxytocin helps promote pair bonding as well as social bonding with in-group members. Studies in both humans and monkeys show that boosting oxytocin levels artificially via a nasal spray makes individuals more trusting and cooperative.

But Zhang et al. now show that the ‘love hormone’ also helps individuals launch more coordinated ‘attacks’ on out-groups. In a study involving a multi-round economic contest game between groups of ‘attackers’ and ‘defenders’, oxytocin did not make attackers less aggressive. Instead it enabled them to better coordinate their attacks. Each contest game involved three attackers individually contributing money to a group pool to outbid the other group and win more money, and three defenders making similar contributions to their own group pool to defend it against the rivals’ attacks and protect themselves from losing all their money. Attackers who used an oxytocin nasal spray were better at tracking their rivals' defensive strategies than attackers whose nasal spray contained a placebo. Under the influence of oxytocin, the attackers timed their strikes to occur when their rivals were vulnerable. Over time, the oxytocin users became better at coordinating their behavior with other members of their in-group. This resulted in more earnings.

Success – and even survival – in intergroup conflicts depends on how willing individuals are to make contributions that incur a personal cost. They also depend on how well individuals coordinate their contributions. Social strategies, such as leading by example, and neurobiological mechanisms such as oxytocin can both help achieve the coordination needed to exploit out-group rivals.