Umbrella review: Most adolescents experienced no or negligible effects of social media use on mental health

Social media use and its impact on adolescent mental health: An umbrella review of the evidence. Patti M. Valkenburg, Adrian Meier, Ine Beyens. Current Opinion in Psychology, Volume 44, April 2022, Pages 58-68. https://doi.org/10.1016/j.copsyc.2021.08.017

Abstract: Literature reviews on how social media use affects adolescent mental health have accumulated at an unprecedented rate of late. Yet, a higher-level integration of the evidence is still lacking. We fill this gap with an up-to-date umbrella review, a review of reviews published between 2019 and mid-2021. Our search yielded 25 reviews: seven meta-analyses, nine systematic, and nine narrative reviews. Results showed that most reviews interpreted the associations between social media use and mental health as ‘weak’ or ‘inconsistent,’ whereas a few qualified the same associations as ‘substantial’ and ‘deleterious.’ We summarize the gaps identified in the reviews, provide an explanation for their diverging interpretations, and suggest several avenues for future research.

Keywords: Meta-reviewSocial networking sitesSNSFacebookInstagramWell-beingDepressionDepressive symptoms

Discussion

In this umbrella review, we synthesized the results of 25 recent reviews into the effects of SMU on adolescent mental health. Given that adolescents’ SMU is continually changing, it is important to provide regular research updates on this use and its potential effects. In addition to the many important future directions raised in earlier reviews, we discuss three crucial avenues for future research.

Defining SMU, defining mental health

First, future research needs to consistently define the predictors and outcomes under investigation. Several reviews regularly switched between terms such as digital media use, technology use, and SMU without specifying to which media activities these terms refer. In some studies, emailing and gaming were part of the definitions of SMU, whereas others covered only time spent on SNSs. Such imprecise definitions may greatly hinder our understanding of the effects of SMU on mental health because different types of SMU may lead to different effects on mental health outcomes. For example, time spent on SNS is associated with higher levels of depression [17], whereas emotional connectedness to SNS (‘intensity of use’) [15] and the number of friends on SNS [16] are unrelated to depression. In the world of SM, everything is rapidly new and rapidly old, and, therefore, it is all the more important to define the specific types of SMU under investigation and to hypothesize how and why these types of SMU could affect mental health outcomes.

Likewise, in several reviews, both mental health and well-being were used as catchall terms that were left undefined, which sometimes led to the discussion of a potpourri of cognitive and affective outcomes that each deserve to be investigated in their own right. Our umbrella review confirmed that similar types of SMU can lead to opposite associations with different mental health outcomes [17]. Both SMU and mental health are highly complex constructs. Although most studies have focused on the associations of SMU with depression or depressive symptoms, all other constituent mental health outcomes, including their risk (e.g. loneliness) and resilience factors (e.g. self-esteem), also deserve our full research attention, provided that they are clearly defined and demarcated from other mental health outcomes.

Capturing the content and quality of SM interactions

Several reviews have pointed at a need to move away from possibly biased self-report measures toward more objective measures of SMU use, such as log-based measures of time spent with SM. Indeed, self-report measures of time spent with SM correlate only moderately with similar log-based measures [42,43]. However, although log-based measures are often seen as the gold standard, they have their own validity threats, such as technical errors and the erroneous tracing of SM apps running in the background when the screen is turned off [42,43]. This means that the modest correlations between self-reports and log-based measures could be due to validity issues of self-reports but also of objective measures. More importantly, though, most log-based measures only capture time spent with SM apps, which is just as crude a predictor of mental health as comparable self-report measures. If logging measures only reiterate the ‘screen time’ approach of most self-report research, they provide only a limited way forward.

To arrive at a true understanding of the effects of SMU on mental health, future research needs to adopt measures that capture adolescents' responses to specific content or qualities of SM interactions. In experimental settings, this can be realized by using mock SM sites, such as the Truman Platform (https://socialmedialab.cornell.edu/) or the mock SM site developed by Shaw et al. [44]. In non-experimental settings, there are three approaches that can be combined with survey or experience sampling studies: (1) The ‘Screenomics’ approach developed by Reese et al. [45], which entails end-to-end software that randomly collects screenshots of adolescents’ smartphones, and extracts text and images; (2) phone-based mobile sensing [46], which captures sound via the microphone and text entered via the keyboard; and (3) analysis of SM ‘data download packages’ [47], the archives of SM interactions that each SM user is allowed to download. While each of these methods is promising, they require sophisticated technical skills and specific expertise. Therefore, they can best be achieved in collaborative interdisciplinary projects, which are also better equipped to realize larger samples.

Understanding inconsistent interpretations

Although the majority of the reviews concluded that the reported associations of SMU with mental health were small to moderate, some others interpreted these associations as serious [30], substantial [48] or detrimental [25]. Such disagreeing interpretations can also be witnessed in three recent publications on SMU and mental health by Twenge et al. [49], Orben and Przybylski [3], and Kreski et al. [50], all relying on the same UK-based data set. Such divides in interpretations of the same modest effect sizes are certainly not new in the media effects field. For example, as of the 1980s, there has been a fierce debate among scholars about the effects of game violence on aggression (e.g. see the dispute in Psychological Bulletin about whether this effect is trivial or meaningful [51,52]). Oftentimes, the involved scholars do not disagree that much about the size of the reported effects but just on how to interpret them.

What has often been ignored in such debates is that the effect sizes are just what they are: statistics observed at the aggregate level. Such statistics are typically derived from heterogeneous samples of adolescents who may differ greatly in their susceptibilities to the effects of environmental influences in general [53] and media influences in particular [54]. After all, each adolescent is subject to unique dispositional, social-context, and situational factors that guide their SMU and moderate its effects [55]. Such person-specific antecedents and effects of SMU cannot be captured by the aggregate-level statistics that have been reported in the majority of empirical studies and reviews, including the current one.

If we accept the propositions of media-specific susceptibility theories [54], it is plausible to assume that both optimistic and pessimistic conclusions about the effects of SMU are valid — they just refer to different adolescents. In fact, recent studies that have adopted an idiographic (i.e. N = 1 or person-specific) media effects paradigm [56] have found that a small group of adolescents experienced negative effects of SMU on well-being (around 10–15%) and another small group experienced positive effects (also around 10%–15%). Reassuringly though, most adolescents experienced no or negligible effects [57].

A person-specific approach to media effects requires a large number of respondents and a large number of within-person observations per respondent. Indeed, statistical power is expensive. However, due to rapidly advancing technological (e.g. phone-based experience sampling methods) and methodological developments (e.g. N = 1 time series analyses), such approaches are increasingly within everyone's reach, especially when researchers pool resources in interdisciplinary teams. A person-specific media effects paradigm may not only help academics resolve controversies between optimistic and pessimistic interpretations of aggregate-level effect sizes, but it may also help us understand when, why, and for whom SMU can lead to positive or negative effects on mental health. And above all, it may help us facilitate personalized prevention and intervention strategies to help adolescents maintain or improve their mental health.

Politically-motivated reasoning is similar for both men and women, but only men find it particularly attractive to believe that they outperform others

Gender differences in motivated reasoning. Michael Thaler. Journal of Economic Behavior & Organization, Volume 191, November 2021, Pages 501-518. https://doi.org/10.1016/j.jebo.2021.09.016

Highlights

• I experimentally study whether there are gender differences in motivated reasoning.

• I find that there are significant gender differences in motivated reasoning about performance on a knowledge task: men systematically motivatedly reason to think they outperformed others, while women do not.

• I also find that there are sizeable gender differences in overconfidence in the same direction as motivated reasoning.

• I find that gender differences in motivated reasoning is only observed on the question about performance, and that there are no differences in politically-motivated reasoning.

• Results suggest that men and women are both susceptible to motivated reasoning in general, but that only men find it particularly attractive to believe that they outperform others.

Abstract: Men and women systematically differ in their beliefs about their performance relative to others; in particular, men tend to be more overconfident. This paper provides support for one explanation for gender differences in overconfidence, performance-motivated reasoning, in which people distort how they process new information in ways that make them believe they outperformed others. Using a large online experiment, I find that male subjects distort information processing in ways that favor their performance, while female subjects do not systematically distort information processing in either direction. These statistically-significant gender differences in performance-motivated reasoning mimic gender differences in overconfidence; beliefs of male subjects are systematically overconfident, while beliefs of female subjects are well-calibrated on average. The experiment also includes political questions, and finds that politically-motivated reasoning is similar for both men and women. These results suggest that, while men and women are both susceptible to motivated reasoning in general, men find it particularly attractive to believe that they outperformed others.

Keywords: Motivated reasoningOverconfidenceGender differencesExperimental economics

JEL: J16D83C91D91

Three key ways people/organisms can differ in a trait: Mean averages (personality), how variable they are in trait intraindividually over time/context (predictability), & how reactive/responsive the trait is across differing ecologies/contexts (plasticity)

Unifying individual differences in personality, predictability and plasticity: A practical guide. Rose E. O'Dea, Daniel W. A. Noble, Shinichi Nakagawa. Methods in Ecology and Evolution, November 1 2021. https://doi.org/10.1111/2041-210X.13755

Abstract

Organisms use labile traits to respond to different conditions over short time-scales. When a population experiences the same conditions, we might expect all individuals to adjust their trait expression to the same, optimal, value, thereby minimising phenotypic variation. Instead, variation abounds. Individuals substantially differ not only from each other, but also from their former selves, with the expression of labile traits varying both predictably and unpredictably over time.

A powerful tool for studying the evolution of phenotypic variation in labile traits is the mixed model. Here, we review how mixed models are used to quantify individual differences in both means and variability, and their between-individual correlations. Individuals can differ in their average phenotypes (e.g. behavioural personalities), their variability (known as ‘predictability’ or intra-individual variability), and their plastic response to different contexts.

We provide detailed descriptions and resources for simultaneously modelling individual differences in averages, plasticity and predictability. Empiricists can use these methods to quantify how traits covary across individuals and test theoretical ideas about phenotypic integration. These methods can be extended to incorporate plastic changes in predictability (termed ‘stochastic malleability’).

Overall, we showcase the unfulfilled potential of existing statistical tools to test more holistic and nuanced questions about the evolution, function, and maintenance of phenotypic variation, for any trait that is repeatedly expressed.

Successful blinding is an important feature of double-blind randomized controlled trials, & ensures that the safety and efficacy of treatments are accurately appraised; but blinding is not successful among either patients or investigators

A systematic review and meta-analysis of the success of blinding in antidepressant RCTs. Amelia J Scott, Louise Sharpe, Ben Colagiuri. Psychiatry Research, November 24 2021, 114297. https://doi.org/10.1016/j.psychres.2021.114297

Highlights

• Successful blinding is an important feature of double-blind randomized controlled trials, and ensures that the safety and efficacy of treatments are accurately appraised.

• In a range of fields (e.g. chronic pain, general medicine), few trials report assessing the success of blinding.

• We do not know the frequency or success of blinding assessment among antidepressant RCTs within depression.

• Only 4.7% of RCTs examining antidepressants in depression assess blinding.

• Overall, blinding is not successful among either patients or investigators.

Abstract: Successful blinding in double-blind RCTs is crucial for minimizing bias, however studies rarely report information about blinding. Among RCTs for depression, the rates of testing and success of blinding is unknown. We conducted a systematic review and meta-analysis of the rates of testing, predictors, and success of blinding in RCTs of antidepressants for depression. Following systematic search, further information about blinding assessment was requested from corresponding authors of the included studies. We reported the frequency of blinding assessment across all RCTs, and conducted logistic regression analyses to assess predictors of blinding reporting. Participant and/or investigator guesses about treatment allocation were used to calculate Bang's Blinding Index (BI). The BI between RCT arms was compared using meta-analysis. Across the 295 included trials, only 4.7% of studies assessed blinding. Pharmaceutical company sponsorship predicted blinding assessment; unsponsored trials were more likely to assess blinding. Meta-analysis suggested that blinding was unsuccessful among participants and investigators. Results suggest that blinding is rarely assessed, and often fails, among RCTs of antidepressants. This is concerning considering controversy around the efficacy of antidepressant medication. Blinding should be routinely assessed and reported in RCTs of antidepressants, and trial outcomes should be considered in light of blinding success or failure.

Keywords: Randomized controlled trialsBlindingDepressionAntidepressants

Contra Duckworth and Seligman’s seminal work: Only intelligence predicted developmental changes in each measure of academic performance over time, self-control did not

Does Self-control Outdo IQ in Predicting Academic Performance? Alexander T. Vazsonyi, Magda Javakhishvili & Marek Blatny. Journal of Youth and Adolescence, Nov 20 2021. https://link.springer.com/article/10.1007/s10964-021-01539-4

Abstract: Duckworth and Seligman’s seminal work found that self-discipline (self-control) was more salient for academic achievement than intelligence. Very little replication work exists, including in different cultures; the current study addressed these gaps. Data were collected from 6th and 7th grade cohorts of early adolescents (N = 589; age: Mean = 12.34 years, and SD = 0.89; 58% female) over two years. The study tested whether self-control was a stronger predictor than intelligence in explaining academic performance two years later as well as in explaining developmental changes over the course of two years. Path analyses provided evidence that both self-control and intelligence longitudinally predicted teacher-reported academic competence as well as school-reported grades; however, intelligence was a significantly stronger predictor than self-control. In addition, only intelligence predicted developmental changes in each measure of academic performance over time, self-control did not.

Death reminders caused less negative affect and more positive affect than toothache reminders; & reactions to death were quite diverse and did not show signs of being dominated by existential anxiety

Storelv, Sina, and Bjørn Sætrevik. 2021. “Nothing Is Certain Except Taxes and the Other Thing: Searching for Death Anxiety in a Large Online Sample.” PsyArXiv. November 19. doi:10.31234/osf.io/3tkzq

Abstract: Philosophical and psychological literature has suggested that death anxiety has a profound impact on our lives, and is a fundamental aspect of what it means to be human. Based on such claims, we wanted to examine how people expressed their thoughts about death when giving short free-text responses in a large online sample. To do so we explored a qualitative dataset where 803 Americans state their thoughts about either death or physical pain (toothache). Comparing these, we found that death reminders caused less negative affect and more positive affect than toothache reminders. We also observed that reactions to death were quite diverse and did not show signs of being dominated by existential anxiety. Qualitative analyses indicate that psychological defense mechanisms do not seem to sufficiently explain the differences between the two conditions. The article also serves as a companion for the open dataset, to facilitate the exploration and reuse by other researchers.

 

The smaller preferences for sexually dimorphic facial cues in older adults compared to young adults suggest that older adults may shift away from mating-oriented psychology as they become less fertile

The Autumn Years: Age Differences in Preferences for Sexually Dimorphic Faces. Chengyang Han, Xiangqian Li, Xiyue Chen, Xue Lei, Chuanjing Liao, Lingshan Zhang, Bingxin Li, Xian Peng & Edward R. Morrison. Archives of Sexual Behavior, Nov 17 2021. https://link.springer.com/article/10.1007/s10508-021-02168-5

Abstract: Life history theory proposes that it is adaptive for older people to shift investment away from reproductive effort (such as mating) to survivorship. However, it remains unclear whether the shift is also present at the psychological level. We investigated this question by comparing preferences for mate choice-relevant cues, sexually dimorphic facial images, between older (60 years and older, n = 92) and younger adults (18–40 years, n = 86). Results showed that older adults had significantly smaller preferences for sexually dimorphic faces of both sexes than young adults. Specifically, both older men and women showed no significant preferences for sexually dimorphic traits when judging opposite-sex faces, and smaller preferences for masculine male faces and feminine female faces when judging same-sex faces. Young adults generally showed strong preferences for masculine male faces and feminine female faces. In Study 2, we confirmed that the absent/reduced preferences in older adults for sexually dimorphic faces did not result from poor visual ability. The smaller preferences for sexually dimorphic facial cues in older adults compared to young adults suggest that older adults may shift away from mating-oriented psychology as they become less fertile.

Consistent low-to-moderate alcohol consumption in early-to-middle adulthood predicted lower depressive symptoms at age 50; his work offers preliminary evidence that such protective effects may be causal

Visontay, Rachel, Louise Mewton, Tim Slade, Izzuddin M. Aris, and Matthew Sunderland. 2021. “Moderate Alcohol Consumption and Depressive Symptoms: A Marginal Structural Model Approach Promoting Causal Inference.” OSF Preprints. November 19. doi:10.31219/osf.io/e2gcm

Abstract

Importance: Prevention of depressive symptoms and disorders is a key public health priority but requires an improved understanding of modifiable risk and protective factors. A salient unanswered question in this context is whether the apparent protective effect of alcohol against depression may be causal.

Objective: To compare the effects of consistent abstinence, occasional, moderate, and heavy alcohol consumption throughout early-to-middle adulthood on depressive symptoms at age 50.

Design: This secondary analysis of the National Longitudinal Survey of Youth (NLSY79) cohort employed a marginal structural model approach in assessing the relationship between alcohol consumption in early-to-middle adulthood (29-37 through 41-49) and depressive symptoms at age 50. Alcohol consumption was based on measurements at 1994, 2002, and 2006, covariates at 1992, 1994, and age 40 (1998-2006), and outcome at age 50 (2008-2016).

Setting: The NLSY79 is a nationally representative, population-based cohort study.

Participants: 5,667 eligible participants at baseline provided valid data on alcohol consumption, depressive symptoms, and covariates of interest.

Exposure: Alcohol consumption was categorised as either abstinence, occasional, moderate, or heavy drinking in 1994, 2002, and 2006.

Main Outcome and Measure: Depressive symptoms at age 50 as measured by the Centre for Epidemiological Studies-Depression Scale short form (CES-D-SF).

Results: Of the 5,667 eligible participants at baseline, 2,862 [50.50%] were female and the mean age was 30.81 [2.24], with 3,593 participants providing valid outcome data for analysis. Results of linear contrasts from marginal structural models were consistent with a J-shaped relationship, where both consistent occasional (b=-0.84, CI= -1.47, -.11) and consistent moderate (b=-1.08, CI=-1.88, -.20) drinkers had significantly reduced predicted CES-D-SF scores at age 50 compared to consistent abstainers. Consistent heavy drinkers were predicted to have increased depressive symptoms, but this was not statistically significant (b=0.34, CI=-0.62, 1.25). In sex-stratified analyses, results were similar for females and males.

Conclusions and Relevance: In this secondary analysis of longitudinal data accounting for time-varying exposure and confounding, consistent low-to-moderate alcohol consumption in early-to-middle adulthood predicted lower depressive symptoms at age 50, compared with those abstaining from alcohol. This work offers preliminary evidence that such protective effects may be causal.

Rolf Degen summarizing... Comic book bodies are supernormal stimuli that cater to the unrealistic sexual imagination of a predominantly male audience

Burch, R. L., & Widman, D. R. (2021). Comic book bodies are supernormal stimuli: Comparison of DC, Marvel, and actual humans. Evolutionary Behavioral Sciences, Nov 2021. https://doi.org/10.1037/ebs0000280

Abstract: This study expanded upon Burch and Johnsen’s (2020) work on exaggerated bodies in Marvel comic book characters by also examining DC characters and actual humans. Compared to Marvel, DC men were not significantly taller but were significantly thinner and had significantly smaller shoulder to waist ratios. DC women were almost identical to Marvel women in height and weight, but DC women had smaller waist to hip ratios, making them curvier. Comic book bodies were then compared to actual humans; champion male bodybuilders, most frequently searched women on 1 of the most popular pornography websites, and a nationally representative U.S. sample. DC men had shoulder to waist ratios on par with champion bodybuilders while Marvel exceeded them. Both DC and Marvel women had lower waist to hip ratios than the Internet pornography sample. The average U.S. woman’s WHR was similar to the maximum WHR for the comic book and pornography sample, and the minimum U.S. woman’s WHR was similar to the average WHR for those samples. These findings support Burch and Johnsen (2020) and provide a better picture of how comic book depictions are hypersexualized supernormal stimuli.

Our review of the malevolent creative processes suggest that we have unintentionally avoided uncomfortable truths around who is capable of generating & instantiating malevolent ideas

Malevolent Creativity and Malevolent Innovation: A Critical but Tenuous Linkage. Samuel T. Hunter, Kayla Walters, Tin Nguyen, Caroline Manning & Scarlett Miller. Creativity Research Journal, Nov 21 2021. https://doi.org/10.1080/10400419.2021.1987735

Abstract: Interest is growing in the dark side of creativity and recent research has been instrumental in improving our understanding of the phenomenon. However, such efforts have also revealed confusion regarding the definition and operationalization of the dark side of creativity and malevolent creativity in particular. In response, we offer definitional clarity for both the generation of novel, malevolent ideas (i.e., malevolent creativity) as well as the implementation of those ideas (i.e., malevolent innovation). In addition, we present a framework outlining how and why malevolent ideas transition from ideation to implementation. This framework considers influences linked to both ability and willingness to engage in malevolent processes, spanning intrapersonal and interpersonal factors. Our review reveals a complex but tenuous link between malevolent creativity and innovation and one that requires consideration of the processes connecting the two. Moreover, our review of the malevolent creative processes suggest that we have unintentionally avoided uncomfortable truths around who is capable of generating and instantiating malevolent ideas. Implications and a plan for moving research forward are discussed.

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From the Encyclopedia of Creativity, 3rd ed, p 177.

Malevolent Creativity

Creativity is often beneficial, however, people also generate novel ways to harm and hurt (Baas et al., 2019). Examples of malevolent creativity include data fabrication of scientists, dirty tricks in political campaigns and firms falsifying information. Provocative and threatening circumstances trigger malevolent creativity (Baas et al., 2019), so it is likely that competition increases creative malevolent responses.

Anecdotes support this notion. For example, to compete with Virgin Atlantic, British Airways resorted to dirty tricks, which included circulating rumors that Virgin CEO Richard Branson had HIV and telling Virgin’s customers that their flights had been canceled. In addition, the fierce competition in science leads some scientists to perform biased peer review, sabotage competitors, and engage in questionable research practices.

There is also empirical support that competition breeds malevolent creativity. In studies conducted in our lab, people who were engaged in a competitive game against another person came up with more malevolent uses for a brick (e.g., using a brick as a weapon, or to sink a body) than non-competing others (see e.g., Baas et al., 2019). Together, these findings suggest that competition may also fuel a much darker side of creativity by facilitating the generation of ideas that are malevolent in nature.

Financial crises and political radicalization: How failing banks paved Hitler's path to power, and to more pogroms and deportations in the most affected areas

Financial crises and political radicalization: How failing banks paved Hitler's path to power. Sebastian Doerr, Stefan Gissler, Jose-Luis Peydro and Hans-Joachim Voth. BIS Working Papers No 978, November 22 2021. https://www.bis.org/publ/work978.htm

Summary

Focus: Do financial crises fan the flames of fanaticism? Many have argued that the financial crisis of 2007–09 not only wrought havoc on employment and output but that its problematic aftermath of failing financial institutions, public bailouts and austerity may also have paved the way for populists around the world. We examine the canonical case of a radical movement's rise to power: Hitler's Nazi party, which took office in the wake of the severe 1931 banking crisis in Germany – a turning point in modern history.

Contribution: Several cross-country studies have concluded that a link exists between financial crises and right-wing populist movements. What is still missing are studies demonstrating that a financial shock can lead to a broad-based radicalisation of the electorate, with major political consequences. It has also remained unclear how economic and financial shocks interact with cultural identity in the turn toward radicalisation.

Findings: Using newly collected data on the exposure of individual cities to the failure of Danatbank – the bank at the heart of Germany's 1931 financial crisis – we show that a financial shock led to a generalised radicalisation of the electorate. This directly helped the Nazi party to gain power. Importantly, we demonstrate that the financial shock interacted with pre-existing cultural attitudes: the surge in support for the Nazis in response to the shock was greatest in places with a previous history of antisemitism. Voters were radicalised both at the ballot box and in their actions. Once the Nazis were in power, both pogroms and deportations were more likely to occur in places worse affected by the banking crisis.

Abstract: Do financial crises radicalize voters? We study Germany's 1931 banking crisis, collecting new data on bank branches and firm-bank connections. Exploiting cross- sectional variation in pre-crisis exposure to the bank at the center of the crisis, we show that Nazi votes surged in locations more affected by its failure. Radicalization in response to the shock was exacerbated in cities with a history of anti- Semitism. After the Nazis seized power, both pogroms and deportations were more frequent in places affected by the banking crisis. Our results suggest an important synergy between financial distress and cultural predispositions, with far-reaching consequences.

Keywords: financial crisis, political extremism, populism, anti-Semitism, culture, Great Depression.

JEL classification: E44, G01, G21, N20, P16.

Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women; our results imply that sniffing babies may increase aggression in mothers but decrease aggression in fathers

Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women. Eva Mishor et al. Science Advances, Vol 7, Issue 47. Nov 19 2021. DOI: 10.1126/sciadv.abg1530

Abstract: In terrestrial mammals, body volatiles can effectively trigger or block conspecific aggression. Here, we tested whether hexadecanal (HEX), a human body volatile implicated as a mammalian-wide social chemosignal, affects human aggression. Using validated behavioral paradigms, we observed a marked dissociation: Sniffing HEX blocked aggression in men but triggered aggression in women. Next, using functional brain imaging, we uncovered a pattern of brain activity mirroring behavior: In both men and women, HEX increased activity in the left angular gyrus, an area implicated in perception of social cues. HEX then modulated functional connectivity between the angular gyrus and a brain network implicated in social appraisal (temporal pole) and aggressive execution (amygdala and orbitofrontal cortex) in a sex-dependent manner consistent with behavior: increasing connectivity in men but decreasing connectivity in women. These findings implicate sex-specific social chemosignaling at the mechanistic heart of human aggressive behavior.

Discussion

Impulsive aggression is a major factor in the human condition, yet how exactly aggression is triggered or blocked in the human brain remains unclear (11, 12). Moreover, real-world human impulsive aggression is one of the most sexually dimorphic behaviors (40), yet what brain mechanisms underlie this dimorphism also remains unclear (12). In animals ranging from insects to rodents, aggression is sexually dimorphic at levels ranging from genes to cells, and this dimorphism in aggression has been linked to dimorphism in the olfactory system (41). Here, we find the same in humans. We observed that sniffing a body volatile, namely, HEX, significantly decreased aggression in men yet significantly increased aggression in women. In both men and women, HEX increased brain activity in the AG, a cross-modal integrating hub involved in social cognition (42). In other words, in humans, like in rodents, a “social odor” activates the “social brain.” Moreover, HEX modulated functional connectivity between these substrates of social appraisal (AG) and a network previously associated with aggression. This included modulation of functional connectivity with the temporal pole (TP), an area similarly implicated in social appraisal (43) and aggression (44), and modulation of functional connectivity with the amygdala and OFC, namely, substrates implicated in aggressive execution (10, 12). All this modulation occurred in a sex-dependent manner consistent with behavior: HEX increased connectivity in men but decreased it in women. Thus, HEX may lead to increased or decreased aggression through increased or decreased control by the AG over the amygdala through a circuit involving the TP and OFC. This modulation of social behavior through modulation of functional brain connectivity was similarly observed following intranasal administration of oxytocin, which reduced OFC connectivity with the amygdala, and in this may have reduced negative emotional arousal (45). This further points to what may be considered a physiological counterpart of this brain mechanism: As stress increases, men become more aggressive and women become less aggressive (46). As stress decreases, men become less aggressive and women become more aggressive (47). In this manner, a non–sex-specific effect of HEX on the stress response (always reducing stress) may evolve into a sex-specific effect of HEX on aggression (increased aggression in women yet decreased aggression in men).

The above detailed neuroanatomy and mechanism may underlie a direct circuit from reception to action without the mediation of conscious perception. This echoes rodent circuitry, where OR37B projections bypass the olfactory cortex and connect directly to the paraventricular nucleus of the hypothalamus, where HEX reduces activity in corticotrophin-releasing cells, thus reducing activation of the hypothalamus-pituitary-adrenal axis (16). Although we cannot trace connectivity of a single olfactory receptor subtype in humans, it is tempting to liken the downstream activation in the absence of olfactory cortex activation we observed in response to HEX to the circuit detailed in rodents.

The sex dimorphism in our behavioral and brain results dovetails with previous findings obtained using functional brain imaging (48) and EEG (15) to depict a level of functional brain sex dimorphism in response to social odors that is not matched by any other sensory stimulus that we are aware of. Human functional brain responses to basic auditory and visual cues are generally nondissociable by sex (49), yet here, we could use them alone to discriminate men from women at 79.6% accuracy. This begs the question: what behavioral setting could underlie selection for a body volatile that increases aggression in women but decreases it in men? Or in other words, what could be the ecological relevance of these results? In this respect, we call attention to the setting of infant rearing. Parents across cultures are encouraged to sniff their babies (50), an action that activates brain reward circuits in women (51). Our results imply that sniffing babies may increase aggression in mothers but decrease aggression in fathers. Whereas maternal aggression has a direct positive impact on offspring survival in the animal world (52), paternal aggression has a negative impact on offspring survival (53). This is because maternal aggression (also termed maternal defense behavior) is typically directed at intruders, yet paternal aggression, and more so nonpaternal male aggression, is often directed at the offspring themselves (54, 55). If babies had a mechanism at their disposal that increased aggression in women but decreased it in men, this would likely increase their survival. With the hypothesis in mind that HEX provides babies with exactly such a mechanism, we first note that infant rearing is the one social setting where humans have extensive exposure to conspecific feces, a rich source of HEX (22). We also turned to a recently published analysis of baby-head volatiles (56), yet in contrast to our hypothesis, this report did not mention HEX. We turned to the authors of that report, who explained that the published analysis was not tuned to the near semivolatile range of HEX. With our question in mind, they (now coauthors T.U. and M.O.) sampled an additional 19 babies (fig. S10A), using gas chromatography (GC) × GC–mass spectrometry, and observed that HEX is one of the most abundant baby-head volatiles, evident in 17 of the 19 babies (fig. S10, B and C). Moreover, they also searched for the two additional known ligands of OR37, namely, pentadecanal and heptadecanal, and found both, albeit at levels much lower than HEX. Pentadecanal was evident in 15 babies but only at an average peak area of 56% that of HEX, and heptadecanal was evident in 16 babies but only at average peak area of 45.5% that of HEX (HEX greater than pentadecanal and peptadecanal: Kruskal-Wallis χ2 = 7.65, df = 2, P = 0.02) (fig. S10C). This outcome renders our overall ecological hypothesis plausible and retrospectively supports our selection of HEX as a testing target. In summary, babies emit HEX from their head. This is expected to trigger aggression in women but block aggression in men, and both of these impacts are expected to increase baby survival.

Given all the above, should we label HEX as a human pheromone? Sniffing human bodily secretions such as sweat and tears drives assorted behavioral and physiological effects (7, 24), and body odors may reflect assorted emotional states (57), including aggression (13, 14), but the identity of specific molecular components involved in human social chemosignaling has remained elusive (58). Moreover, the current view on human social chemosignals is that, to the extent that they exist, they likely entail alterations in the ratios of components in complex body odor bouquets and not single molecular species (59). Yet, here, we identify one component, namely, HEX, whose effects can be seen as consistent with those of a mammalian pheromone (60). Previously, the steroidal molecules estratetraenol (EST) and androstadienone (AND) had been proposed as human pheromones, yet this labeling was often rejected, primarily because EST and AND do not clearly trigger or block behavior, nor do they have obvious ecological relevance (59, 61). Here, HEX had a pronounced effect on behavior and, moreover, on the behavior of aggression, a domain dominated by pheromonal communication in most mammals (3). The notion of pheromonal communication was once considered dependent on a functional vomeronasal system, a system that humans may not have (62). More recent views, however, blur this distinction and highlight pheromonal communication through the main olfactory system as well (63–65). Given all this, we think that had we presented an equivalent set of results obtained from mice, very few would argue the pheromone label. In turn, if HEX is a human pheromone, is it a cuing pheromone that is emitted consistently by the sender or a signaling pheromone that is emitted only during appropriate behavioral context (61)? Here, we reach at the primary limitation of this study: Although we think of HEX as a signal, we did not measure its emission as a function of behavior. Had we measured HEX emission under different conditions and found that its emission increased under the endurance of aggression, this would have closed the loop of a signaling pheromone. Such an effort, however, was far beyond the scope of the current study and remains the key missing component for labeling HEX a human signaling pheromone.

Beyond this, we would like to acknowledge several additional limitations in this study: First, although we used various control conditions across experiments (eugenol, mineral oil, and blank air), we did not test any other potential OR37 ligands. The rationale for selecting HEX was detailed in Introduction, but future testing of additional potential ligands remains an important question. Second, we do not know whether the concentrations of HEX that we used were physiological. This is because we do not know the concentrations that humans emit (the existing reports are relative), and we do not know the concentration that actually reached our participants using the current paradigms (e.g., experiment 1 sniff-jar versus experiment 2 olfactometer). Third, regarding our imaging results, we reiterate that correlation is not causation. We identify a brain pattern associated with HEX, and it is tempting to suggest that this pattern is responsible for the observed effects, yet this can only be proven by experiments where the brain mechanism is perturbed, experiments that are very difficult to conduct in human participants. Last, we also acknowledge that our suggested ecological relevance in infant rearing was not directly tested in this study. One may note that there are various forms of aggression, and whereas our tasks measured interpersonal aggression, our infant-rearing hypothesis alludes to paternal/maternal aggression. Thus, although we think it is a plausible hypothesis, it remains to be experimentally verified, and here serves only as an example of possible ecological relevance for our results.

Despite the above limitations, we conclude in stating that sniffing the body odor constituent HEX blocks aggression in men but triggers aggression in women. HEX may exert its effects by modulating functional connectivity between the brain substrates of social appraisal and the brain substrates of aggressive execution. This places chemosignaling at the mechanistic heart of human aggression and poses but one added example to the rapidly growing body of evidence implicating social chemosignaling as a major, albeit mostly subconscious, power in human behavior.

Immigration quotas in the 20s targeted “undesirable” nationalities to stem the inflow of low-skilled Eastern and Southern Europeans; this study measure effects in inventions and scientific production

Moser, Petra and San, Shmuel, Immigration, Science, and Invention. Lessons from the Quota Acts (March 21, 2020). SSRN: http://dx.doi.org/10.2139/ssrn.3558718

Abstract: Immigration quotas in the 1920s targeted “undesirable” nationalities to stem the inflow of low-skilled Eastern and Southern Europeans (ESE). Detailed biographical data for 91,638 American scientists reveal a dramatic decline in the arrival of ESE-born scientists after the quotas. Under the quotas, an estimated 1,165 ESE-born scientists were lost to US science. To identify effects on invention, we use k-means clustering to assign scientists to unique fields and then compare changes in patenting by US scientists in the pre-quota fields of ESE-born scientists with changes in other fields where US scientists were active inventors. Baseline estimates imply a 68 percent decline in invention. Decomposing this effect, we find that the quotas reduced both the number of US scientists working in ESE fields and the number of patents per scientist. Firms that employed ESE-born scientists experienced a 53 percent decline in invention. The quotas’ effects on invention persisted into the 1960s.

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Naturalization data indicate a dramatic decline in the arrival of new ESE-born scientists after the quotas. Until 1924, arrivals of new ESE-born immigrant scientists were comparable to arrivals from Northern and Western Europe (WNE), who were subject to comparable pull and push factors of migration.1 After the quotas, arrivals of ESE-born scientists decline significantly while arrivals from Northern and Western Europe continue to increase. Combining data on naturalizations with information on scientists’ university education and career histories, we estimate that 1,165 ESE-born scientists were lost to US science under the quota system. At an annual level, this implies a loss of 38 scientists per year, equivalent to eliminating the entire physics department of a major university each year between 1925 and 1955. For the physical sciences alone, an estimated 553 ESE-born scientists were lost to US science.

To estimate the effects of changes in immigration on US inventions, we compare changes in patenting per year after 1924 in the pre-quota fields of ESE-born US scientists with changes in patenting in other research fields in which US scientists were active inventors before the quotas. This identification strategy allows us to control for changes in invention by US scientists across fields, for example, as a result of changes in research funding. Year fixed effects further control for changes in patenting over time that are shared across fields. Field fixed effects control for variation in the intensity of patenting across fields, e.g., between basic and applied research.

Baseline estimates reveal a large and persistent decline in invention by US scientists in the pre-quota fields of ESE-born scientists. After the quotas, US scientists produced 68 percent fewer additional patents in the pre-quota fields of ESE-born scientists compared with the prequota fields of other US scientists. Time-varying effects show a large decline in invention by US scientists in the 1930s, which persisted into the 1960s. Importantly, these estimates show no preexisting differences in patenting for ESE and other fields before the quotas.

Special case of Paul Erdős:

A case study of co-authorships for the prolific Hungarian-born mathematician Paul Erdős illustrates how restrictions on immigration reduced collaborations between ESE-born scientists and US scientists. Erdős moved to the United States as a post-doctoral fellow at Princeton, and became a professor at Notre Dame, travelling and collaborating with many US scientists. As a Hungarian citizen, however, Erdős was denied a re-entry visa by the US immigration services in1954, and not granted re-entry until 1963. To examine how these denials affected Erdős’ collaborations with US scientists, we collect the location of Erdős top 100 coauthors at the time  of their first collaboration. These data show that Erdős’ collaborations shifted away from the United States when he was denied re-entry. Between 1954 and 1963, 24 percent of Erdős’ new co-authors were US scientists, compared with 60 percent until 1954. These patterns are confirmed in a broader analysis of patents by co-authors and co-authors of co-authors of ESEborn scientists, which indicates a 26 percent decline in invention by scientists who were directly or indirectly influenced by ESE-born scholars. 

These findings cast doubt on claims that a low-tax, low-regulation capitalism will generate extreme capital accumulation, & that persistent wealth equalization requires large shocks to capital coming from wars or progressive taxation

Wealth and History: An Update. Daniel Waldenström. CEPR DP16631, October 2021. cepr.org/active/publications/discussion_papers/dp.php?dpno=16631

Abstract: This paper analyzes new evidence on long-run trends in aggregate wealth accumulation and wealth inequality in Western countries. The new findings suggest that wealth-income ratios were lower before World War I than previously claimed, that wealth concentration fell over the past century and has remained low in Europe but increased in the United States, that wealth has changed from being dominated by elite-owned fortunes to consist mainly of popular wealth, and that capital shares in national income have been relatively stable over time, especially in the postwar era. These findings cast doubt on claims that a low-tax, low-regulation capitalism will generate extreme capital accumulation, and that persistent wealth equalization requires large shocks to capital coming from wars or progressive taxation. Instead, institutions that promote household wealth accumulation from below appear to be key for understanding the long-run evolution of wealth in Western societies.

Keyword(s): capital share, economic history, Wealth Inequality, Wealth-income ratios

JEL(s): D30, E21, N30

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Popular version: Wealth and history: A reappraisal Daniel Waldenström. November 17 2021. https://voxeu.org/article/wealth-and-history-reappraisal#.YZc-lJKvR6E.twitter

Revised historical wealth-income ratios

Figure 1 shows aggregate private wealth-income ratios in six countries for which consistent, long-run evidence is available: France, Germany, Spain, Sweden, the UK, and the US. The series of Piketty and Zucman show wealth-income ratios being historically high in 19th century Europe, around 600–800% of national income, and dramatic drops during the world wars after which they stayed low until the 1980s when they increased substantially.

The revised and new country series for Europe produces a different picture, especially for the pre-WWI period. The new German series has a wealth-income ratio of 500% instead of 600%, and the new UK series shows 450% instead of 700%. For newly added Spain and Sweden, pre-WWI wealth-income ratios are around 450–500% of national income (the series of France and the US have not been re-examined). The main reasons that the revised German and UK series differ from those of Piketty and Zucman is the use of new sources and adjusted computational assumptions (see Waldenström 2021 for further discussion). Looking at the 20th century, the new series present a less volatile trend, with some variation around the world wars but without any lasting trend breaks (except for Germany). The post-1990 increases are observed in both older and newer series.

Male researchers more often value and engage in research mainly aimed at scientific progress, which is more cited; females more often value & engage in research mainly aimed at contributing to societal progress, which has more abstract views (usage)

Gender differences in the aims and impacts of research. Lin Zhang, Gunnar Sivertsen, Huiying Du, Ying Huang & Wolfgang Glänzel. Scientometrics volume 126, pages 8861–8886, Nov 2021. https://link.springer.com/article/10.1007/s11192-021-04171-y

Abstract: This study uses mixed methods—classical citation analysis, altmetric analysis, a survey with researchers as respondents, and text analysis of the abstracts of scientific articles—to investigate gender differences in the aims and impacts of research. We find that male researchers more often value and engage in research mainly aimed at scientific progress, which is more cited. Female researchers more often value and engage in research mainly aimed at contributing to societal progress, which has more abstract views (usage). The gender differences are observed among researchers who work in the same field of research and have the same age and academic position. Our findings have implications for evaluation and funding policies and practices. A critical discussion of how societal engagement versus citation impact is valued, and how funding criteria reflect gender differences, is warranted.

Holding heavily invested political beliefs makes individuals reluctant to update their beliefs in the face of contradictory information; providing ambiguous information caused them to become further divided based on their political ideology

Updating Politicized Beliefs: How Motivated Reasoning Contributes to Polarization. Siyan Su. Journal of Behavioral and Experimental Economics, November 20 2021, 101799. https://doi.org/10.1016/j.socec.2021.101799

Highlights

• This experiment examined the effect of the political significance of information on motivated belief updating

• Holding heavily invested political beliefs makes individuals reluctant to update their beliefs in the face of contradictory information

• Providing subjects with ambiguous information caused them to become further divided based on their political ideology

• Subjects’ biased incorporation of new evidence is consistent with theories of belief-based utility, confirmation bias, and motivated reasoning

Abstract: This paper examines how the political significance of information can affect subjects’ perceived reliability of that information and their motivated belief updating. In this study, 1,222 subjects were randomly assigned to receive low-reliability, high-reliability, or ambiguous information about neutral and political questions. For each question, subjects were first asked to give a numerical estimate. After receiving new information, subjects had the opportunity to update their previous numerical estimates, and then, they reported their perceived reliability of the information they received. I observed that subjects were more reluctant to update their beliefs for politically significant questions compared to neutral questions. I also found that subjects were more likely to discredit and reject new information when it challenged their preexisting ideology, indicating that one's rooted political beliefs can distort the belief updating process. In addition, subjects drew different conclusions from ambiguous information depending on their political ideology, illustrating how ambiguity may lead to greater polarization. Finally, I discuss possible explanations for subjects’ biased integration of new information using motivated reasoning and belief-based utility theories. The results of this study contribute to the understanding of why people remain divided on politically charged issues.

Keywords: belief updatingbelief-based utilitymotivated reasoningconfirmation biasambiguous informationbelief polarization

Social Networks Facilitate Informed Option Trading? Evidence from Alumni Reunion Networks

Cheong, Harvey and Kim, Joon Ho and Münkel, Florian and Spilker III, Harold D., Do Social Networks Facilitate Informed Option Trading? Evidence from Alumni Reunion Networks (February 27, 2021). Journal of Financial and Quantitative Analysis (Forthcoming), https://ssrn.com/abstract=3795685

Abstract: Material private information transmits through social networks. Using manually collected information on networks of alumni reunion cohorts, we show that hedge fund managers connected to directors of firms engaged in merger deals increase call option holdings on target firms before deal announcements. Effects are larger when reunion events for connected cohorts occur just before announcements. Independent directors, directors with short tenure, and directors with low stock ownership are more likely to transmit information. Our results are robust to confounding factors and alternative specifications. These findings highlight the role of social networks as channels of private information dissemination.

Keywords: Informed Trading, Social Networks, Hedge Funds, Mergers & Acquisitions, Options

JEL Classification: D82, G11, G12, G14, G34, L14, Z13

Loosening the definition of culture... An investigation of gender and cultural tightness: We find that American women felt their gender culture is “tighter” than men

Loosening the definition of culture: an investigation of gender and cultural tightness. Alexandra S. Wormley et al. Current Research in Ecological and Social Psychology, November 14 2021, 100021. https://doi.org/10.1016/j.cresp.2021.100021

Highlights

• Cultural tightness has previously been studied at the national or regional level.

• We find that American women felt their gender culture is “tighter” than men.

• This gender difference is mediated by gender related threats, in line with theories about tightness as a way of managing ecological threats

• We find a lack of measurement invariance comparing tightness in men and women in Singapore, pointing to a need for future work refining measurement

Abstract: To date, the study of cultural tightness has been largely limited to exploring the strictness of social norms and the severity of punishments at the level of nations or regions. However, cultural psychologists concur that humans gather cultural information from more than just their nationality. Gender is a cultural identity that confers its own social norms. Across three studies using multi-method designs, we find that American women feel the culture surrounding their gender is “tighter” than that for men, and that this relationship is mediated by perceived gender-related threats to the self. However, in a follow-up study in Singapore, we do not find measurement invariance, suggesting future work is necessary to refine the study of gender tightness cross-culturally. We close with an important discussion of understanding how tightness looks across a variety of cultural identities and introduce a novel, qualitative method for the study of the tightness of social norms within groups.

Keywords: gendertightness-loosenessculturepsychology

Discussion

Across hundreds of US participants, we found robust evidence for a difference in perceived tightness and looseness across men and women, such that women perceived greater tightness using a modified, 4 item scale and qualitatively reported more gender norms for themselves (Studies 1-2). Further, in line with ideas about tightness functioning to manage threat, we found that gender-specific threats mediated the relationship between gender and tightness (Study 3). This is in line with previous work which has suggested the broader adaptive purpose of cultural tightness is to manage environmental and social threats to the group. However, here we apply this to gender within a given society in a novel way.

We attempted to replicate in a tight country, Singapore. We had thought perhaps national tightness might moderate the relationship between gender and tightness, such that a gender difference might appear in relatively loose cultures (like the US) but not in a culture in which there are very tight norms for everyone (like Singapore). We could not explore these novel questions because of bad model fit and a lack of measurement invariance. Once the measurement is sorted out in future work, we think that will open questions of how individuals, with their many cultural identities, manage competing expectations and prioritize certain parts of their identity (say, national identity) over others (like gender).

Other cultural dimensions may provide insight as to why Singaporean men and women reported similar numbers of norms in an open-ended prompt. Gender egalitarianism which varies by country is (somewhat paradoxically) known to increase gender differences since the equality allows the genders to pursue their different, respective goals (Schwartz & Rubel-Lifschitz, 2009). Singapore is higher than the United States on egalitarianism (Schwartz, 2007), suggesting that we should expect Singapore to have larger differences in gender norms than the United States. An interesting future direction would examine gender and tightness in societies that vary in gender equality and in tightness at the national level; we propose an interesting set of comparisons could be New Zealand (relatively loose, relative gender equality), Ukraine (relatively loose, relative gender inequality), Austria (relatively tight, relative gender equality), and India (relatively tight, relative gender inequality) (Gelfand et al., 2011; Schwartz, 2007). Do women report greater feelings of tightness in unequal societies? Do they report differences in the kinds of norms they must follow in comparison to men?

Additionally, our work presents a new qualitative method for studying cultural tightness. In having participants record social norms, we gain not only a proxy for the cognitive accessibility of social norms in their mind, but the content of these norms. This allows us to further dive into what threats are managed by social norms, revealing a cross-cultural convergence upon the importance of affiliation and appearance-related norms for women especially. Thus, we add yet another measure to the growing number of ways to capture perceptions of social norms and cultural tightness (Mu et al., 2015; Uz, 2015).

Theoretically, the most exciting prospect this line of research offers is the idea that tightness varies across different cultural identities, with identity-related threat as a mediator. What other differences might we then expect? Do African-Americans or other minority ethnic groups report tighter cultural norms than their White counterparts (US Census Bureau, 2019)? Do Jewish people, who have historically faced immense religious persecution (Phillips, 2018), have tighter norms than Christians do? Is a long history of threats needed to shape norm tightness or can tightness be affected by recent current threats to identity (e.g., a wave of hate crimes)? Do transgender individuals, who face four times the amount of violent crime as cisgender ones (Rude, 2021), have tighter in-group norms? Further, since threat influences cultural tightness, might norms be specific to the domain of threat? For example, in an environment where women outnumber men, might men face stricter mating norms (Bleu et al., 2012)?

Beyond replicating in other countries, gender differences in cultural tightness should be investigated from a more representative sample because student participants may not be entirely representative of the population. The consistent evolution of gender norms in developed countries means that generational, and perhaps social class, differences are likely to exist. Further, these studies cannot rule out the fact that women may overperceive norms in comparison to men. Is the observed difference in gender tightness due to a difference in sensitivity to threat or differences in actual threats? There is reason to think it may be beneficial for women to be especially attuned to the social landscape and the rules within it, in the same way they seem attuned to threat (Brebner, 2003; Burani & Nelson, 2020). To rule this out, women could be compared to men in their reporting of norms within other cultural contexts, like the workplace or the nation.

The tightness-looseness continuum represents an exciting trait of cultural groups that lie outside the traditional conception of “culture.” Through a mixed-method design, we establish that while other cultural groups may differ on these traits, special attention must be paid to measurement and the proper application of scales across group types. We leave the reader with two tools for continuing the study of gender and tightness—the GTS and the Gender Norm Perception Task—and further it beyond gender to other cultural identities.