Personality traits, immune function, and health are related: Inflammatory processes may be the mechanistic driver in these relationships; personality traits predict both in vivo and in vitro measures of inflammation

Exploring the links between personality and immune function. Summer Mengelkoch, Jeff Gassen, Emily K. Corrigan, Sarah E. Hill. Personality and Individual Differences, Volume 184, January 2022, 111179. https://doi.org/10.1016/j.paid.2021.111179

Highlights

• Personality traits, immune function, and health are related.

• Inflammatory processes may be the mechanistic driver in these relationships.

• Genetic polymorphisms known to impact cytokine release predict personality traits.

• Personality traits predict both in vivo and in vitro measures of inflammation.

• Relationships between personality and inflammation are sex and cytokine specific.

Abstract: Decades of research finds associations between personality traits and health. In recent years, it has become clear that the activities of the immune system play a key role in linking these variables. In the current work, we add to this research by exploring the relationship between Big Five personality traits and (Study 1) polymorphisms known to impact cytokine release and (Study 2) immunological parameters measured in vivo (differential white blood cell counts, plasma proinflammatory cytokine levels) and in vitro (proinflammatory cytokine release by peripheral blood mononuclear cells, S. aureus growth in plasma). Results provide insights into potential mechanistic drivers of the links between personality and immune function and the possibility that, in some cases, relationships between personality and immune function may be sex differentiated.

Keywords: PersonalityCytokinesInflammationExtraversionNeuroticismOpenness to experienceAgreeablenessConscientiousness

4. General discussion

Results of the current research provide continued support for links between personality traits and immune function (e.g., Allen & Laborde, 2017; Armon et al., 2013; D'Acquisto, 2017; Lopes, 2017; Segerstrom, 2000), some of which differed by sex. For example, results of Study 1 revealed that high TNF-α producers were more extraverted than low-producers and that men who were high IL-6 producers were less extraverted than low-producers, suggesting that the links between health-relevant variables and personality may be sex-, context-, and cytokine-dependent. Study 1 also revealed that high IL-10 producers were more open to experience than low-producers. This is consistent with animal research that finds IL-10 may have anxiolytic properties (Martinez et al., 2018; Mesquita et al., 2008; Munshi et al., 2019; Nava et al., 1997).

One particularly striking result from Study 1 was the regularity with which intermediate IFN-γ producers were found to differ from high- and low-producers across personality traits. Intermediate-producers, overall, reported being less agreeable, more neurotic, and, compared low-producers only, less conscientiousness and less extraverted. While we did not predict these results a priori, it is possible that this relationship could have emerged in response to these individuals' heightened risk for infectious disease. Researchers find that intermediate IFN-γ producers have an increased risk of certain infectious diseases relative to high- or low-producers (e.g., leishmaniasis: Kalani et al., 2019; tuberculosis: Amim et al., 2008). Accordingly, although the participants in the current study are unlikely to have come into contact with these infectious agents, it is possible that genetic predisposition to disease risk influences the development of personality traits (e.g., Bilbo & Schwarz, 2009). Additionally, separate research suggests that women with metabolic syndrome who are intermediate-producers of IFN-γ exhibit altered tryptophan metabolism compared to high- or low-producers (Szkup et al., 2019), which may influence personality traits. Although these interpretations are speculative, they raise interesting possibilities for future research.

Study 2 revealed additional associations between personality and immune measures. For example, higher extraversion was related to greater LPS-induced proinflammatory cytokine release by PBMCs in vitro, while higher conscientiousness was associated with lower levels of plasma IL-6, a result that is consistent with the results of previous research (e.g., Sutin et al., 2010). While similar results were found for the effect of conscientiousness on the remaining measures of inflammation, these effects were sex-differentiated with higher conscientiousness predicting lower levels of plasma TNF-α and diminished proinflammatory cytokine release by PBMCs in men and women, respectively. Results also revealed that higher levels of extraversion were associated with lower numbers of eosinophils and basophils (the latter in women only), potentially suggesting a skew towards Th1 over Th2 immunity in individuals high on this trait (Sokol et al., 2009; Spencer & Weller, 2010). This possibility is further supported by the finding that men high in extraversion had higher counts of monocytes than did men low in extraversion. Th1 immunity is primarily involved in the body's response to intracellular pathogens, like viruses, while Th2-biased responses are typically observed during macroparasite infection, such as with helminths, and also play a role in allergies (Romagnani, 2000). Interestingly, due to growing population density and urbanization, most modern human populations are exposed to much higher numbers of viruses than parasitic worms (Amoroso & Nunn, 2021). Accordingly, the heightened sociality associated with high extraversion likely increases one's exposure to viruses, specifically, which may lead to a Th1 skew.

Additionally, high levels of extraversion, and for women, high levels of agreeableness, were found to predict increased S. aureus growth in plasma in vitro. Additional research is needed to determine the exact differences in plasma composition that contribute to differences in rates of S. aureus growth (e.g., minerals: Cross et al., 2015, complement proteins: Walport, 2001); however, previous research has found lower S. aureus growth in the plasma of individuals whose PBMCs exhibit greater proliferation in response to antigen stimulation (Gassen, Leyva, et al., 2019), suggesting that this measure is related to well-characterized immunological parameters.

The current research finds certain personality traits are more consistently related to aspects of immune function than others. Across studies, conscientiousness and extraversion appear to be reliably related to levels of inflammation (although the directions of these relationships sometimes differ, e.g., Allen & Laborde, 2017; Armon et al., 2013; Sutin et al., 2010), while agreeableness is not. For example, the current research finds conscientiousness to be negatively related to plasma IL-6 levels, a pattern which is also reliably observed in others' work (e.g., Chapman et al., 2011; Luchetti et al., 2014; Sutin et al., 2010). Repeated replication of this result suggests that these two variables are likely interconnected in a meaningful way. For example, one possibility is that those with low IL-6 levels tend to utilize behavioral strategies, such as avoiding individuals who may be sick, visiting the doctor regularly for check-ups, washing hands often, etc., to compensate for their low levels of inflammation by avoiding pathogens in their environments. In this way, aspects of conscientiousness may develop as a strategy for managing infectious disease risk in a state of low inflammation or lack of immunological preparedness. Alternatively, it is also possible that the relationship between inflammation and conscientiousness primarily operates in the other direction. That is, individuals high in conscientiousness (compared to those lower in conscientiousness) may be more careful with their health and avoid circumstances that elicit inflammatory responses, such as eating unhealthy food or engaging in unsafe sexual practices. Future research is needed to test these, as well as other, hypotheses about the causal links between these variables.

The consistent relationships observed between inflammation and extraversion, both in the current work and in the work of others, further underscore that individual differences in human tendencies for behavior may be shaped by one's immunological vulnerabilities. For example, over human history, levels of extraversion would have been reliably linked to exposure to infectious diseases. That is, because humans are vectors for transmissible disease, increased sociality would have increased one's likelihood of coming in to contact with pathogens; however, elevated inflammation could be protective, rather than reactive, in this context, preventing an individual from becoming ill after encountering pathogens. Based on the results of Study 1, in which extraversion was associated with being a high-producer of TNF-α, our results suggest that differences in extraversion may be borne out of different immunological profiles, rather than the differences in levels of inflammation being exclusively the result of greater contact with others. Future research should explore this possibility, along with the threshold of inflammatory levels extraverted individuals must experience before exhibiting social withdrawal, one facet of inflammation-induced sickness behavior (Dantzer, 2001; Dantzer & Kelley, 2007), in response to elevated inflammation. While the levels of elevated inflammation explored in the current work are likely lower than what would be necessary to induce intense sickness behavior, it is possible that those high in extraversion require a larger release of proinflammatory cytokines before exhibiting social avoidance in response to inflammation compared to those lower in extraversion, given the potential for generally elevated inflammation and heightened stimulated proinflammatory cytokine release to buffer those high in extraversion from the somatic costs of elevated sociality. Identifying these thresholds would yield novel insights into the dynamic relationship between cytokines and the motivation to socially engage and withdraw.

The current work makes an important contribution to the literature by taking a step towards disentangling the directionality relationships between personality and immune function (Study 1), examining relationships between personality and novel measures of immunological functioning (Study 2), and examining sex differences in these effects (Studies 1 & 2). While Study 1 was cross-sectional, preventing us from drawing strong conclusions regarding causal directions, it is far more likely that one's genotype would predict their personality than vice versa. Relationships observed between cytokine genotypes and personality therefore provide initial support for the idea that immunological variables may impact aspects of personality in addition to personality having an impact on immune function, specifically in the case of extraversion. Further, Study 2 assessed the relationship between personality measures and novel measures of immunological functioning, including bacterial growth in plasma and stimulated proinflammatory cytokine release in PBMCs, both of which measure immune responses in the face of an immunological challenge. A better understanding of how personality relates to immunological responses to overt challenges will be informative for understanding how personality relates to immune function in the context of disease. Finally, this work also stands out from existing studies examining links between personality and immune function by reporting sex differences in these relationships. Much of the extant personality and health literature has not investigated sex differences, which may be important to consider as men and women consistently exhibit differences in immune function (e.g., Fish, 2008; Klein et al., 2015) and personality (e.g., Schmitt et al., 2008). This study was the first – to our knowledge – to investigate sex differences in relationships between personality traits and a comprehensive set of immune measures (e.g., bacterial growth in plasma, stimulated cytokine release, WBC composition, etc.).

The current studies do, however, have limitations to consider. First, the sample of participants in Study 2 was relatively homogenous and small, limiting the generalization of these results to all populations. Additionally, the measure used to assess personality was brief, and while validated in previous research (Gosling et al., 2003), the TIPI is not the most comprehensive measure of personality available. In light of these limitations, further research should include larger, more diverse samples of participants and administer a more comprehensive personality questionnaire, while also including a wide variety of immune measures capturing facets of immunity not assayed in the current research (e.g., adaptive immunity). A larger sample size would also allow for greater power to test for interactions between personality traits, sex, and immune function.

Furthermore, despite the hypothesized bi-directional nature of relationships between personality and health, in Study 1, we utilized genomic measures, and as such, investigated the impact of TNF-α, IL-10, IL-6, and IFN-γ genotypes on personality traits. In Study 2, we limited our analyses to the impact of personality on immune function to preserve power and limit the number of analyses ran. While this allowed us to test for relationships in both directions, we are nevertheless limited in the causal claims that can be made about the relationships found. Future longitudinal or experimental studies are warranted to provide a stronger test of directionality in relationships between personality and immunity.

Despite limitations, the current studies provide important data bearing on relationships between personality and immune function. The present results lend support for the growing body of theory and research suggesting covariation between psychological traits, like personality, and immunity. This research lays the foundation for future work that may provide groundbreaking insights into complex relationships between health, immune function, and behavior.

Trait charisma (having the ability to influence people, making people feel comfortable) is a trait linked with higher sexual communal motivation, associated with higher desire & sexual satisfaction in romantic relationships

Leading Better Sex Lives: Is Trait Charisma Associated with Higher Sexual Desire and Satisfaction in Romantic Relationships? Eric Tu, Stephanie Raposo & Amy Muise. Archives of Sexual Behavior, Sep 17 2021. https://link.springer.com/article/10.1007/s10508-021-02138-x

Abstract: Sexuality is a key predictor of relationship satisfaction, but sexual desire and satisfaction can be difficult to maintain over time. Past research has investigated who might be more likely to experience higher (compared to lower) levels of desire and sexual satisfaction in their relationships. Certain aspects of personality, such as extraversion, have been associated with sexual satisfaction and desire, but evidence linking personality to sexual outcomes has generally been mixed, meaning there is a lot left to learn about how personality is associated with sexual well-being. A promising, yet unexplored, trait that could be associated with higher sexual desire and satisfaction is charisma—a combination of influence and affability that has been identified as a desirable trait when people are selecting a romantic or sexual partner. Across two studies—a cross-sectional study of individuals in relationships (N = 413) and a 21-day dyadic daily experience study (N = 121 couples)—people higher in charisma reported being more communal during sex and reported higher sexual desire and satisfaction. Through higher sexual communal strength, people with a charismatic partner also reported higher daily sexual desire and sexual satisfaction. The effects were largely retained above and beyond general communal strength and Big Five personality dimensions, although in Study 1, charisma was no longer associated with sexual desire and satisfaction when controlling for extraversion. The current findings provide initial evidence that charismatic people tend to be responsive to their partner’s sexual needs, which is associated with higher desire and sexual satisfaction in romantic relationships.

Do Racial Differences in Coping Resources Explain the Black–White Paradox in Mental Health? (better mental health than whites despite experiencing greater stress exposure)

Do Racial Differences in Coping Resources Explain the Black–White Paradox in Mental Health? A Test of Multiple Mechanisms. Patricia Louie et al. Journal of Health and Social Behavior, September 22, 2021. https://doi.org/10.1177/00221465211041031

Abstract: A central paradox in the mental health literature is the tendency for black Americans to report similar or better mental health than white Americans despite experiencing greater stress exposure. However, black Americans’ higher levels of certain coping resources may explain this finding. Using data from the Nashville Stress and Health Study (n = 1,186), we examine whether black Americans have higher levels of self-esteem, social support, religious attendance, and divine control than white Americans and whether these resources, in turn, explain the black–white paradox in mental health. In adjusted models, the black–white paradox holds for depressive symptoms and any DSM-IV disorder. Findings indicate that black Americans have higher levels of self-esteem, family social support, and religiosity than white Americans. Causal mediation techniques reveal that self-esteem has the largest effect in explaining black–white differences in depressive symptoms, whereas divine control has the largest effect in explaining differences in disorder.

Keywords: coping resources, depression, disparities, mental disorder, race

Are people willing to pay to reduce others' income when inequalities are based on individual performance or based on arbitrary decisions?

Disadvantageous inequalities, effort and money burning: are people willing to pay to reduce others' income when inequalities are based on individual performance or based on arbitrary decisions? Jeremy Celse. Economics Bulletin, 2021, vol. 41, issue 3, 1719-1726, Sep 17 2021. http://www.accessecon.com/Pubs/EB/2021/Volume41/EB-21-V41-I3-P147.pdf

Abstract: Are people more or less willing to burn others' income if others deserve their advantage in the sense of having expended some efforts to get it? We investigated the impact of effort on burning decisions. To fulfil our research question, we conducted two experimental conditions: one in which participants received endowments randomly and another in which participants received endowments based on their performance in a real-effort task. Then participants could reduce others' income through incurring a cost. We found burning rates to be similar across conditions but participants cut a significantly larger fraction of others' income when endowments are attributed through effort rather than randomly.

Keywords: Money burning; Inequalities; Desert; Envy; Interdependent preferences

JEL-codes: C9 D6

Rather than being structurally unconscious, many higher mental processes might instead be victims of internal inattentional blindness: missing an otherwise consciously-accessible internal event because your attention was elsewhere

Morris, Adam. 2021. “Invisible Gorillas in the Mind: Internal Inattentional Blindness and the Prospect of Introspection Training.” PsyArXiv. September 26. doi:10.31234/osf.io/4nf5c

Abstract: Much of high-level cognition appears inaccessible to consciousness. Countless studies have revealed mental processes -- like those underlying our choices, beliefs, judgments, intuitions, etc. -- which people do not notice or report, and these findings have had a widespread influence on the theory and application of psychological science. However, the interpretation of these findings is uncertain. Making an analogy to perceptual consciousness research, I argue that much of the unconsciousness of high-level cognition is plausibly due to internal inattentional blindness: missing an otherwise consciously-accessible internal event because your attention was elsewhere. In other words, rather than being structurally unconscious, many higher mental processes might instead be "preconscious", and would become conscious if a person attended to them. I synthesize existing indirect evidence for this claim, argue that it is a foundational and largely untested assumption in many applied interventions (such as therapy and mindfulness practices), and suggest that, with careful experimentation, it could form the basis for a long-sought-after science of introspection training.

After 2 years, gaming positively impacted intelligence, but socializing had no effect, consistent with cognitive benefits documented; unexpectedly, watching videos also benefited intelligence, contrary to prior research on watching TV

Sauce, Bruno, Magnus Liebherr, Nicholas Judd, and Torkel Klingberg. 2021. “The Impact of Digital Media on Children’s Intelligence While Controlling for Genetic Differences in Cognition and Socioeconomic Background.” PsyArXiv. September 26. doi:10.31234/osf.io/jtwk7

Abstract: Digital media defines modern childhood, but its cognitive effects are unclear and hotly debated. We estimated the impact of different types of screen time (watching, socializing, or gaming) on children’s intelligence while controlling for genetic differences in cognition and socioeconomic background. We analyzed 9855 children from the ABCD dataset with measures of intelligence at baseline (ages 9-10) and after two years. At baseline, time watching and socializing were negatively correlated with intelligence, while gaming had no correlation. After two years, gaming positively impacted intelligence, but socializing had no effect. This is consistent with cognitive benefits documented in experimental studies on video gaming. Unexpectedly, watching videos also benefited intelligence, contrary to prior research on the effect of watching TV. Broadly, our results are in line with research on the malleability of cognitive abilities from environmental factors, such as cognitive training and the Flynn effect.

Lower socioeconomic status harms psychological well-being, effect assumed to weaken as nations develop economically; evidence is opposite to this assumption; lower national religiosity explains the burden

National religiosity eases the psychological burden of poverty. Jana B. Berkessel et al. Proceedings of the National Academy of Sciences, Sep 20 2021. https://www.pnas.org/content/pnas/118/39/e2103913118.full.pdf

Abstract: Lower socioeconomic status (SES) harms psychological well-being, an effect responsible for widespread human suffering. This effect has long been assumed to weaken as nations develop economically. Recent evidence, however, has contradicted this fundamental assumption, finding instead that the psychological burden of lower SES is even greater in developed nations than in developing ones. That evidence has elicited consternation because it suggests that economic development is no cure for the psychological burden of lower SES. So, why is that burden greatest in developed nations? Here, we test whether national religiosity can explain this puzzle. National religiosity is particularly low in developed nations. Consequently, developed nations lack religious norms that may ease the burden of lower SES. Drawing on three different data sets of 1,567,204, 1,493,207, and 274,393 people across 156, 85, and 92 nations, we show that low levels of national religiosity can account for the greater burden of lower SES in developed nations. This finding suggests that, as national religiosity continues to decline, lower SES will become increasingly harmful for well-being—a societal change that is socially consequential and demands political attention.

Keywords: socioeconomic status | well-being | religiosity | economic development 

Het women: Masculinized faces were perceived as slightly more attractive, slightly healthier, & much more formidable; pathogen prevalence lowered the preference for masculinized faces while resource scarcity weakly elevated it

Differential Effects of Resource Scarcity and Pathogen Prevalence on Heterosexual Women's Facial Masculinity Preferences. S. Adil Saribay et al. Evolutionary Human Sciences, September 16 2021. https://doi.org/10.1017/ehs.2021.42

Abstract: The present research focused on how environmental harshness may affect heterosexual women's preferences of potential male mates’ facial characteristics, namely masculinity-femininity. The evidence on this issue is mixed and mostly from Western samples. We aimed to provide causal evidence using a sample of Turkish women and Turkish male faces. A video-based manipulation was developed to heighten environmental harshness perceptions. In the main experiment, participants were primed with either resource scarcity, pathogen prevalence, or neither (control). They then saw masculinized versus feminized versions of the same faces and indicated the face they would prefer for a long-term relationship and separately rated the faces on various dimensions. In general, masculinized faces were perceived as slightly more attractive, slightly healthier, and much more formidable. A multilevel Bayesian model showed that pathogen prevalence lowered the preference for masculinized faces while resource scarcity weakly elevated it. The overall drop of attractiveness ratings in cases of high perceived pathogen prevalence, one of the strongest effects we observed, suggests that during epidemics, formation of new relationships is not a favourable strategy. Implications for evolutionary theories of mate preference are discussed.

SOCIAL MEDIA SUMMARY 

It takes just ninety seconds to make women prefer less masculine faces: Video about the epidemic is the key! Petr Tureček

There are several studies which investigated how environmental harshness influences mate choice, in particular whether masculine or feminine faces are perceived as more attractive when the environment is harsh. Their results were inconsistent, probably because environmental harshness is not a monolithic concept: it is rather a set of unfavourable conditions which can, in principle, lead to opposing predictions regarding the preference for masculinity. Perhaps when resources are scarce, masculinity might be preferred, while when pathogens are prevalent, feminine faces could become more appealing because of the hypothesised immunosuppressive effect of testosterone. We used a video-based manipulation to tackle this issue. We recruited about 300 women and showed them videos to highten their awareness of a specific kind of environmental harshness. They viewed either a video about an impending economic crisis or a video about a dangerous bird flu. (The data were collected before the current pandemic.) Participants in the control condition were presented with a neutral video about space (planets and such). After video viewing, we presented our volunteers with photographs of men manipulated to be either 50% more masculine or 50% more feminine. We showed the manipulated photographs side by side and asked volunteers to indicate which of the two looks like a more suitable long-term partner. Then we showed the participants all photographs again, one by one, and asked them to rate their attractiveness, formidability, and health (in a random order). Because we were interested in potential mediating effects, we used an analysis comprised of several multiple regressions. We observed how the video influenced the level of perceived resource scarcity and pathogen prevalence, how these variables influenced the attractiveness, formidability, and healthiness ratings of the masculinised and feminised faces, and how the differences between ratings together with all the other predictors affected the outcome of the forced choice between a masculinised and feminised face. We included the effect of presentation laterality, because it is well known that people often select the face on the right even where the two displayed photographs are identical. Wherever suitable, we also included varying effects of targets, raters, and target-rater interactions. We confirmed our hunch! Masculinised faces were selected more often under the control and resource scarcity conditions, while the pathogen prevalence condition shifted the balance slightly in favour of the feminised face. The effect was small but clearly there! Although the videos did not change the perceived environmental harshness dramatically, the effect did turn out to be partly mediated by perceived pathogen prevalence and resource scarcity. Higher perceived pathogen prevalence indeed predicts a lower likelihood of selecting a masculinised face variant as a more suitable long-term partner, while the opposite holds of perceived resource scarcity. We had a few other notable findings. Masculinised faces are perceived as much more formidable, slightly healthier, and slightly more attractive. Under the condition of pathogen prevalence this difference becomes smaller, which is consistent with the higher preference for feminised faces under that condition. What is also interesting is that overall attractiveness ratings drop if perceived pathogen prevalence is high. This makes sense. During epidemics, when each contact poses a risk, formation of new relationships is just not so attractive: it is not a sensible strategy. Also, people seem very finetuned to assessments of attractiveness. There is a massive consensus between participants on target attractiveness (but not on their formidability and health). Still, there is space for perceived pathogen prevalence to influence attractiveness ratings and thereby also mate choice. When ninety seconds of a bird flu video can conclusively shift the preference of certain facial features, just imagine what the current pandemic is doing to them.

Petr Tureček is a poet who works as an evolutionary biologist (currently for Charles University and at the Center for Theoretical Study, both in Prague) because his poems suck. 

Facial structure and perception of sexual orientation: Research with face models based on photographs of real people

Facial structure and perception of sexual orientation: Research with face models based on photographs of real people. Julio González-Alvarez, Rosa Sos-Peña. International Journal of Psychology, September 25 2021. https://doi.org/10.1002/ijop.12811

Abstract: Some evidence suggests that lay persons are able to perceive sexual orientation from face stimuli above the chance level. A morphometric study of 390 heterosexual and homosexual Canadian people of both sexes reported that facial structure differed depending on the sexual orientation. Gay and heterosexual men differed on three metrics as the most robust multivariate predictors, and lesbian and heterosexual women differed on four metrics. A later study verified the perceptual validity of these multivariate predictors using artificial three-dimensional face models created by manipulating the key parameters. Nevertheless, there is evidence of important processing differences between the perception of real faces and the perception of artificial computer-generated faces. The present study which composed of two experiments tested the robustness of the previous findings and extended the research by experimentally manipulating the facial features in face models created from photographs of real people. Participants of the Experiment 1 achieved an overall accuracy (0.67) significantly above the chance level (0.50) in a binary hetero/homosexual judgement task, with some important differences between male and female judgements. On the other hand, results of the Experiment 2 showed that participants rated the apparent sexual orientation of series of face models created from natural photographs as a continuous linear function of the multivariate predictors. Theoretical implications are discussed.

Replication is positive: We All Believe Ourselves Less Risky and More Skillful Than Our Fellow Drivers

Koppel, Lina, David Andersson, Gustav Tinghög, Daniel Västfjäll, and Gilad Feldman. 2021. “We Are All Less Risky and More Skillful Than Our Fellow Drivers: Replication and Extension of Svenson (1981)‎.” PsyArXiv. September 25. doi:10.31234/osf.io/2ewb9

Abstract: The better-than-average effect refers to the tendency to rate oneself as better than the average ‎person on desirable traits and skills. In a classic study, Svenson (1981) asked participants to rate ‎their driving safety and skill compared to other participants in the experiment. Results showed ‎that the majority of participants rated themselves as far above the median, despite the statistical ‎impossibility of more than 50% of participants being above the median. We report a ‎preregistered, well-powered (total N = 1,203), very close replication and extension of the ‎Svenson (1981) study. Our results indicate that the majority of participants rated their driving ‎skill and safety as above average. We added different response scales as an extension and ‎findings were stable across all three mesaures. Thus, our findings are consistent with the ‎original findings by Svenson (1981). Materials, data, and code are available at ‎https://osf.io/fxpwb/

Depression and loneliness were elevated during the early US COVID-19 response; those who maintained very frequent in-person, but not remote, social & sexual connections had better mental health outcomes

Depression and loneliness during April 2020 COVID-19 restrictions in the United States, and their associations with frequency of social and sexual connections. Molly Rosenberg, Maya Luetke, Devon Hensel, Sina Kianersi, Tsung-chieh Fu & Debby Herbenick. Social Psychiatry and Psychiatric Epidemiology volume 56, pages1221–1232. https://link.springer.com/article/10.1007%2Fs00127-020-02002-8

Abstract

Purpose: To estimate the prevalence of depression and loneliness during the US COVID-19 response, and examine their associations with frequency of social and sexual connections.

Methods: We conducted an online cross-sectional survey of a nationally representative sample of American adults (n = 1010), aged 18–94, running from April 10–20, 2020. We assessed depressive symptoms (CES-D-10 scale), loneliness (UCLA 3-Item Loneliness scale), and frequency of in-person and remote social connections (4 items, e.g., hugging family member, video chats) and sexual connections (4 items, e.g., partnered sexual activity, dating app use).

Results: One-third of participants (32%) reported depressive symptoms, and loneliness was high [mean (SD): 4.4 (1.7)]. Those with depressive symptoms were more likely to be women, aged 20–29, unmarried, and low-income. Very frequent in-person connections were generally associated with lower depression and loneliness; frequent remote connections were not.

Conclusions: Depression and loneliness were elevated during the early US COVID-19 response. Those who maintained very frequent in-person, but not remote, social and sexual connections had better mental health outcomes. While COVID-19 social restrictions remain necessary, it will be critical to expand mental health services to serve those most at-risk and identify effective ways of maintaining social and sexual connections from a distance.

Discussion

In a nationally representative probability survey of American adults taking place during the early phases of the COVID-19 response (April 2020), we found high levels of significant depressive symptoms and loneliness. Very frequent in-person social and sexual contacts during the time of COVID-19 restrictions in the last month were generally associated with lower prevalence of depression and loneliness, while remote contacts were not similarly protective. We also found that relationship tension due to COVID-19 spread and restrictions was strongly predictive of depression and loneliness. Our findings suggest that the COVID-19 spread and response has had a tremendous mental health impact on Americans.

We found that nearly one-third of Americans reported depressive symptoms in April 2020, notably much higher than previous estimates among American adults. From 2013 to 2016, the prevalence of major depression in a given 2 week period in US adults age 20 + years was 8%, nearly 4 times lower than our estimate [30]. Similarly, the mean loneliness score we found (4.4) was higher than prior estimates in three western European countries (3.5–3.7) [31], and the prevalence of loneliness we found in our general US population (Definition 1: 54%), is a similar magnitude as previously observed in older and elderly Americans (43–56%) [28, 29]. Patterns of higher depression prevalence among women, young adults, and people with lower incomes have been observed in previous studies [14, 30]. We also observed these gender, age, and socioeconomic patterns in our study, suggesting that while the magnitude of depression may be expanding during the time of COVID-19 spread and restrictions, the disproportionate burden continues to be felt in these populations.

The observed relationships between social and sexual connections and the outcomes of depression and loneliness are largely consistent with our understanding of the importance of human connection for mental health and well-being. Close touching in family interactions and among relationship partners has been associated with decreased heart rate, higher levels of oxytocin, and lower levels of cortisol [32, 33]; which, in turn could provide important mental health protections. These kinds of connections cannot easily be recreated with remote technology where direct touch is not possible, though some researchers have explored this through “huggable” and other similar communication devices [34]. We also know that common technical difficulties with video calls can cause misattributed negative feelings towards people on the call [35], perhaps contributing to the null effects we observed for remote connections and mental health outcomes. As the COVID-19 spread and response have dramatically limited access to many previously routine and familiar options for human connection, our findings are consistent with an explanation that the decreased frequency of social and sexual connections is contributing to poor mental health outcomes. In addition to limiting people’s social interactions, restrictions have also likely resulted in many people missing counseling or therapy appointments or other activities (e.g., exercise, massage, support group meetings, etc.) that may have been supportive of their mental health.

There are several other plausible explanations for the observed relationship between social and sexual connections and mental health outcomes. First, people who are struggling with poor mental health and feelings of isolation during COVID-19 restrictions may be reaching out more frequently for remote connections. As this was a cross-sectional study, our ability to infer temporality is limited. Future studies with a longitudinal design would be better able to disentangle the temporal relationships between social/sexual connections and mental health outcomes. Second, we used self-reported data for our key exposure and outcome assessments, with the potential for biased results. However, web-based surveys have shown to be effective modes to elicit sensitive sexual behaviors from study participants, alleviating some of the bias concern [36]. Similarly, our depression and loneliness scales are widely used in web-based surveys, are validated, and have good psychometric properties [24, 27]. However, their use could be complemented with clinical assessments in future studies. Relatedly, it is not yet known how these scales perform during times of social restrictions when daily lives have shifted so dramatically. It is possible that the wording of certain items (e.g., ‘How often do you feel isolated from others?’) may lose their discriminatory ability in times where isolation is essentially mandated. For this reason, we used a more conservative categorical definition of loneliness for our analyses than has been commonly used in prior studies. We also did not explore whether participants had run out of prescription medication supportive of their mental health or had missed counseling or therapy visits.

A key strength of this study is its external validity. Our findings are broadly representative of the US adult population during the early stages of the US COVID-19 response. However, these results may not hold during later phases of the COVID-19 response, or for countries outside of the US. Surveys should be conducted at frequent intervals and in other countries affected by COVID-19 to update our understanding of the changing mental health landscape across time and space.

Swearing fulfils positive functions including benefitting pain relief & physical strength; increased state disinhibition is a possible psychological mechanism for the effect on physical strength

Stephens, Richard. 2021. “Effect of Swearing on Strength: Disinhibition as a Potential Mediator.” PsyArXiv. September 24. doi:10.31234/osf.io/dfyc8

Abstract

Introduction: Swearing fulfils positive functions including benefitting pain relief and physical strength. Here we present three experiments assessing a possible psychological mechanism, increased state disinhibition, for the effect of swearing on physical strength.

Method: Three repeated measures experiments were carried out with sample sizes N=56, N=63 and N=118. All three included the Balloon Analogue Risk Task (BART) to measure risky behaviour. Experiments 1 and 3 included measures of physical performance assessing, respectively, grip and arm strength. Experiment 3, which was pre-registered, additionally assessed flow, self-confidence, anxiety, emotion including humour, and distraction including novelty.

Results: Experiments 1 and 3 found that repeating a swear word benefitted physical strength and increased risky behaviour, but risky behaviour did not mediate the strength effect. Experiment 2 showed no effect of listening to an audio track of a repeated swear word. Experiment 3 found that repeating a swear word increased flow, self-confidence, positive emotion, humour and distraction. Humour mediated the effect of swearing on physical strength.

Discussion: Consistent effects of swearing on physical strength indicate that this is a reliable effect. Swearing affected several constructs related to state disinhibition including increased self-confidence. Humour appeared to mediate the effect of swearing on physical strength, consistent with a hot cognitions explanation of swearing-induced state disinhibition. However, as this mediation effect was part of an exploratory analysis, further pre-registered experimental research including validated measures of humour is required.

Supplemental Materials osf.io/3eynk/ 

Mental Rotation Task Performance in Relation to Sexual and Gender Diversity in Thailand

Mental Rotation Task Performance in Relation to Sexual and Gender Diversity in Thailand. Lindsey T. Thurston et al. Psychoneuroendocrinology, September 23 2021, 105428. https://doi.org/10.1016/j.psyneuen.2021.105428

Highlights

• Visuospatial sex difference favoring cis men replicated in Thai population.

• Visuospatial organizational effect evident in Thai gay men and sao praphet song.

• Limited effect of sexual or gender diversity in participants assigned female at birth.

Abstract: Neurohormonal theory argues that organizational effects of hormone exposure influence sexual orientation and gender identity, as well as sex differences in visuospatial cognition. This study examined mental rotation task (MRT) performance in a diverse Thai sample (N = 980). Thai culture has several third genders: individuals assigned male at birth (AMAB) who are feminine and attracted to cis men (i.e., sao praphet song); individuals assigned female at birth (AFAB) who are masculine and attracted to feminine individuals (i.e., toms); AFAB individuals who are feminine and attracted to toms (i.e., dees); and sexual orientation categories similar to Western culture (e.g., gay, lesbian, bi). On the MRT, straight cis men outperformed straight cis women. Results were consistent with organizational effects among AMAB individuals, with straight cis men outperforming gay cis men and sao praphet song. Among AFAB individuals, however, only bi and lesbian cis women outperformed dees. Overall, support for neurohormonal theory was limited among AFAB individuals, but MRT performance among AMAB individuals was consistent with organizational effects. This study informs our understanding of visuospatial sex/gender differences and the applicability of neurohormonal theory across cultures.

Keywords: visuospatial cognitionmental rotationneurohormonal theorygender identitysexual orientationThailand

From Hermit Kingdom to Miracle on the Han — Policy Decisions that Transformed South Korea into an Export Powerhouse

From Hermit Kingdom to Miracle on the Han — Policy Decisions that Transformed South Korea into an Export Powerhouse. Douglas A. Irwin. Peterson Institute for International Economics Working Paper 21-14, September 2021. https://www.piie.com/sites/default/files/documents/wp21-14.pdf

Abstract: In 1960, South Korea’s exports were about 1 percent of GDP, and the country’s  ability to import depended almost entirely on US aid. After changing its foreign exchange and trade policies in the mid-1960s, Korea saw a surge in exports to more than 10 percent of GDP by the end of the decade. What factors account for the shift in policy that enabled this dramatic export growth to occur? The United States helped initiate the process by withholding financial assistance, pressuring  Korea to devalue its currency and reform its foreign exchange regime. Initially, the Korean government resisted taking these steps, but in 1964 it became firmly committed to an export promotion strategy to boost foreign exchange earnings and end its dependence on American aid. 

JEL codes: F13, F31, N75

Keywords: export promotion, export orientation, devaluation, foreign exchange reform

According to the widely known ‘culture of honor’ hypothesis from social psychology, traditional herding practices are believed to have generated a value system that is conducive to revenge-taking and violence

Herding, Warfare, and a Culture of Honor: Global Evidence. Yiming Cao, Benjamin Enke, Armin Falk, Paola Giuliano & Nathan Nunn. NBER Working Paper 29250, September 2021. https://www.nber.org/papers/w29250

Abstract: According to the widely known ‘culture of honor’ hypothesis from social psychology, traditional herding practices are believed to have generated a value system that is conducive to revenge-taking and violence. We test this idea at a global scale using a combination of ethnographic records, historical folklore information, global data on contemporary conflict events, and large-scale surveys. The data show systematic links between traditional herding practices and a culture of honor. First, the culture of pre-industrial societies that relied on animal herding emphasizes violence, punishment, and revenge-taking. Second, contemporary ethnolinguistic groups that historically subsisted more strongly on herding have more frequent and severe conflict today. Third, the contemporary descendants of herders report being more willing to take revenge and punish unfair behavior in the globally representative Global Preferences Survey. In all, the evidence supports the idea that this form of economic subsistence generated a functional psychology that has persisted until today and plays a role in shaping conflict across the globe.

As already happens with other physiological indicators, the enlargement of pupils betrayed sexual interest only in men (both heterosexual and gay)

Measurement of Sexual Interests with Pupillary Responses: A Meta-Analysis. Janice Attard-Johnson, Martin R. Vasilev, Caoilte Ó Ciardha, Markus Bindemann & Kelly M. Babchishin. Archives of Sexual Behavior, Sep 23 2021. https://rd.springer.com/article/10.1007/s10508-021-02137-y

Abstract: Objective measures of sexual interest are important for research on human sexuality. There has been a resurgence in research examining pupil dilation as a potential index of sexual orientation. We carried out a meta-analytic review of studies published between 1965 and 2020 (Mdn year = 2016) measuring pupil responses to visual stimuli of adult men and women to assess sexual interest. Separate meta-analyses were performed for six sexual orientation categories. In the final analysis, 15 studies were included for heterosexual men (N = 550), 5 studies for gay men (N = 65), 4 studies for bisexual men (N = 124), 13 studies for heterosexual women (N = 403), and 3 studies for lesbian women (N = 132). Only heterosexual and gay men demonstrated discrimination in pupillary responses that was clearly in line with their sexual orientation, with greater pupil dilation to female and male stimuli, respectively. Bisexual men showed greater pupil dilation to male stimuli. Although heterosexual women exhibited larger pupils to male stimuli compared to female stimuli, the magnitude of the effect was small and non-significant. Finally, lesbian women displayed greater pupil dilation to male stimuli. Three methodological moderators were identified—the sexual explicitness of stimulus materials, the measurement technique of pupillary response, and inclusion of self-report measures of sexual interest. These meta-analyses are based on a limited number of studies and are therefore preliminary. However, the results suggest that pupillary measurement of sexual interest is promising for men and that standardization is essential to gain a better understanding of the validity of this measurement technique for sexual interest.

Discussion

This meta-analysis examined whether changes in pupil size in response to viewing images of adult males and females can provide a consistent measure of sexual orientation in men and women. Overall, this was found to be the case for gay and heterosexual men, whereby heterosexual men showed greater pupil dilation to other-sex (i.e., female) stimuli, and gay men showed greater pupil dilation to same-sex (i.e., male) stimuli. The overall effect sizes for these observer groups ranged from small to moderate across studies, similarly to other measures of sexual interest using cognitive tasks (e.g., Viewing Time, Ó Ciardha et al., 2018), but smaller effect sizes relative to those obtained with genital arousal measurements (e.g., Jabbour et al., 2020; Semon et al., 2017). Results for bisexual men demonstrated the same direction of effect as gay men, of greater pupil dilation to male than to female stimuli. In fact, this effect was larger for bisexual than for gay men. Previous studies recording pupil dilation and genital arousal have found varied response patterns such that men who identify as bisexual inconsistently demonstrate arousal to both men and women (Rieger & Savin-Williams, 2012; Rosenthal et al., 2011). However, in some studies this group has also exhibited a stronger arousal response to men (Rieger et al., 2005; Slettevold et al., 2019; Tollison et al., 1979). These diverse findings suggest that although sexual arousal is one facet in an individual’s identification with a sexual orientation, other aspects are likely to be involved, too. One such factor is sexual curiosity. This has been found to interact with arousal responses in bisexual men, whereby those with lower levels of sexual curiosity are more aroused by same-sex men compared to those with higher level of sexual curiosity, who record bisexual arousal patterns (Rieger et al., 2013).

A different pattern was observed with female observers. Heterosexual women showed a trend of larger pupil sizes during the viewing of other-sex (i.e., male) stimuli, but the magnitude of this effect was small and not significant. The gender differences in the strength of responses observed here are consistent with those found in the wider literature on the measurement of sexual interest in men and women using other physiological measurement techniques, such as direct measures of genital arousal (Chivers et al., 2004). Similarly to the inconsistent pattern of responding in bisexual men, it is possible that sexual arousal is only one element in women’s sexual identification and may form a smaller part in the makeup of their sexual orientation than in heterosexual men (Peplau & Garnets, 2000). We return to this issue in the “Moderators of Pupil Response Measures” section.

The responses of bisexual women were not analyzed due to an insufficient number of studies (Rieger et al., 2016; Snowden et al., 2019). Lesbian women showed greater dilation to other-sex stimuli. While this last result was unexpected, the analysis included only 3 studies (total N = 132) and was affected by one outlier study with a large negative effect size. As the analyses of gay and bisexual groups were also based on a limited number of either 3 or 4 studies, the meta-analysis of these should be considered as preliminary until more evidence becomes available.

Finally, we note that in this study the difference scores in pupil responses for images of men and women were calculated separately for male and female observers. This provides separate response patterns and effect size estimates for men and women of different self-reported sexual orientation. This approach is applied most frequently in this literature and was taken here to examine the potential applicability of pupillary response in assessing sexual interest within each group. However, some studies also include comparisons between male and female observers, or between sexual orientation groups, for each image category (Rieger et al., 2012; Savin-Williams et al., 2016). These between-subject comparisons would yield different effect sizes and may also produce a different pattern of results to this meta-analysis.

Moderators of Pupil Response Measures

We examined three moderators associated with methodological variations across studies: the sexual explicitness of stimuli, the methodological technique applied to measure pupillary response, and the inclusion of a subjective measure of sexual orientation or preference. Moderator analysis was only performed for heterosexual men and heterosexual women due to the insufficient number of studies for this analysis for the other participant groups. In heterosexual men, visual stimuli which comprised of partially nude images of people provided greater discrimination compared to studies using highly sexually explicit stimuli (i.e., complete nudity). Stimulus sets that comprised a mixture of explicitness level, such as dressed, partially nude, or completely nude, produced negligible effects. However, it is important to note that stimulus type might have been confounded with other possible moderators, such as the approach used to measure pupillary responses. Pupillary responses measured using an EyeLink eye trackers, for example, provided greater discrimination of pupil size change for male and female images in heterosexual men compared to other equipment.

These findings indicate that pupil response measurement and stimulus type can provide a source of variability. The specific effects of stimulus type and approach to measuring pupillary response are difficult to untangle because the three categories of explicitness (fully nude, partial or no nudity, and mixed nudity) do not span across the different types of pupillary response measures. For heterosexual men, for example, all studies with partially nude stimuli in the meta-analysis also applied EyeLink eye trackers to measure pupil response (Attard-Johnson et al., 2016; De Winter et al., 2021), while none of the studies using other techniques (i.e., SMI/Tobii eye trackers, manual measurement) included comparable stimuli of in low explicitness. In contrast, fully nude stimuli were employed by studies using EyeLink (Rieger et al., 2013; Watts et al., 2018) and SMI eye trackers (Finke et al., 2018), but not by any of the studies with Tobii eye trackers or manual pupil measurement. This could provide some explanation for a larger effect being observed for studies using partially nude compared to studies using more sexually explicit stimuli (i.e., complete nudity).

In heterosexual women, stimuli with low sexual explicitness demonstrated a moderate positive effect size (i.e., larger pupils when viewing persons of the same-sex), but a negative effect size (i.e., larger pupils when viewing other-sex stimuli) when mixed stimulus sets were used. The effect size for high sexual explicitness was negligible. These divergent findings could reflect the general pattern of inconsistency in female responding across studies and sexual arousal assessments more widely (Chivers, 2005; Chivers et al., 2010). Several theories have been proposed to explain inconsistencies in female sexual responding and comprehensive reviews have been published (see, for example, Chivers, 2005, 2017; Chivers et al., 2010). These theories include a range of methodological, biological, psychological and sociological factors. For example, potential differences could result from hormonal variations associated with fertility and menstrual cycle (Diamond, 2007; Shirazi et al., 2018), identification with the sexual pleasure that is perceived in other women leading to an arousal response to same-sex stimuli (Chivers, 2017), and greater malleability of sexuality by external contextual influences such as relationships (Baumeister, 2000). These possibilities have not been explored here (for a complete review of theories, see Chivers, 2017).

The comparatively small effect for stimuli of high sexual explicitness that was found in this meta-analysis could provide some support for the preparation hypothesis (Dawson et al., 2013; Lalumière et al., 2020), which suggests that any strong sexual cues provoke an indiscriminate arousal response to prepare a woman for the possibility of a sexual encounter (Chivers, 2017; Laan & Everaerd, 1995; Suschinsky & Lalumière, 2011). However, there is no clear explanation for the opposing effects of the mixed and low explicitness stimuli that were revealed in the current meta-analysis. Furthermore, the analysis considers difference scores of pupillary responses between male and female images, and from this it is therefore not possible to conclude whether the small effect is a result of no dilation or pupil dilation to a similar degree for both images. We also cannot exclude the possibility that other moderating factors could have contributed to this finding. For example, studies in both these subcategories included participants who were not asked to report their sexual orientation and were therefore assumed to be of heterosexual orientation (for example, De Winter et al., 2021; Hamel, 1974; Scott et al., 1967). Yet, the prevalence of same-sex behavior is reported to be higher in women compared to men (Diamond, 2016) with a difference of around 9% (7% of men versus 16% of women; Mercer et al., 2013). Thus, it is conceivable that the samples in these studies also contained a proportion of women who would have identified as bisexual or gay more so than samples of men. We note, however, that the moderator analysis also included measurement of sexual interest (i.e., whether researchers recorded self-reported sexual interest or assumed participants were heterosexual) and this was not found to moderate effect sizes.

Taken together, the findings from the present meta-analysis suggest that differences in type of stimulus and measurement technique across studies might not only influence the degree of pupillary response effects of sexual interest, but also the direction of these effects. Additional primary studies are required to draw firm conclusions on the individual influence of any of the moderators examined in the current meta-analysis.

Limitations and Future Research Directions

Due to the low number of studies that were available, we were selective in the choices of variables that were used in the moderator analysis. Consequently, other potential variables associated with methodological techniques were not included in the meta-analysis, such as low-level stimulus characteristics. Image luminance, for example, has the potential to evoke bottom-up pupillary responses that might interfere with responses to the task-specific processes under investigation. One mechanism through which such interference could occur is the pupil light reflex, which refers to the constriction or dilation of the pupil in response to changes in the intensity of light levels that enter the eye (Ellis, 1981). The pupils begin to constrict within 200 ms after an increase in light, reaching a minimum diameter of approximately 2 mm at around 1500 ms (Mathôt, 2018). However, precise durations and pupil sizes vary depending on the intensity of the light change and individual differences (Ellis, 1981). In addition to luminance, color of the perceived light can also influence the duration of a constriction. For example, while blue light leads to sustained constriction of the pupil beyond 1500 ms, red light leads to a degree of re-dilation in the absence of light change, termed pupil escape (Mathôt, 2018). Variations in image luminance and color might, therefore, be a factor to consider when measuring pupillary responses to visual stimuli.

One method for controlling this factor is to equalize brightness across stimuli to match the mean luminance of the stimulus set (Attard-Johnson et al., 2016; Snowden et al., 2019). However, while this approach eliminates mean luminance differences across images, it could also create additional artifacts by introducing distortion of natural luminance levels within images, such as light–dark contrasts. Such image distortions might decrease the realism of images and could unwittingly interact with the attractiveness of a depicted person or draw the observer’s attention to information in images that is irrelevant for the task at hand. In the study of pupillary responses as an index of sexual interest, only a few studies have so far adopted such luminance manipulations, with results that are difficult to assimilate, demonstrating a need for further research (cf. Attard-Johnson et al., 2016; Snowden et al., 2019). However, most studies in this meta-analysis also demonstrate divergent pupillary responses to the same stimuli, based on differences in observers’ sex and sexual orientation, indicating that low-level image characteristics are unlikely to explain the study findings.

Another factor that was not included in the meta-analysis here is the approach that is taken to analyze pupillary response data, which also varies across research studies. A recent paper compared four widely used methods for analyzing pupil responses (Attard-Johnson et al., 2019). Specifically, Attard-Johnson et al. analyzed (unadjusted) raw pupil scores obtained from eye-tracking, z-scores of this data, a conversion of the pupil data that captures differences between conditions in terms of the percentage change in eye pupil size, and pupillary responses that have been adjusted on the basis of a baseline measure. They reported that fundamental pupillary response patterns were consistent across all methods.

Finally, although it was possible to obtain information on all three methodological moderators from published sources or from direct contact with the authors, we could not acquire the actual correlations for pupil responses between male and female stimuli for some of the earlier studies included in the meta-analysis. Therefore, estimated correlations were used as a proxy when coding these studies. Actual correlation data produced a larger effect size compared to estimated correlations for heterosexual men. For heterosexual women, actual and estimated correlations produced effect sizes of similar magnitude but in different directions. In order to facilitate accumulation of knowledge, studies on pupil responses should provide correlations between sets of stimuli.

Implications for the Measurement of Sexual Interest

The current meta-analysis offers some tentative guidance for the measurement of pupillary responses of sexual interest. Across both heterosexual men and women, the low sexual explicitness stimuli (comprising partial or no nudity) appeared to provide clearer discrimination in pupillary response to sexual interest compared to high explicitness stimuli (complete nudity). We note, however, that for heterosexual women this effect was not in the direction consistent with their sexual orientation. Current evidence is too limited to determine whether some eye-tracking apparatus are better suited to this research. The desk-mounted EyeLink provided the strongest effect for heterosexual male observers, but this did not extend to heterosexual women for whom the largest effect was obtained for manual recording, and there were insufficient eligible studies for inclusion of remote Tobii eye trackers. Thus, further investigation comparing these methods is warranted, especially in women.

Furthermore, it is also possible that the affective state underlying these arousal patterns could be attributed to states evoked from other interpretations of the stimulus being perceived by the observer as pleasant or unpleasant. For instance, an arousal response would also be evoked if the stimulus is perceived as threatening or unpleasant when viewing, for example, stimuli depicting illness or violence (Bradley et al., 2008). It may not be possible to establish for certain whether sexual arousal underpins pupil dilation responses to sexual stimuli. Equally, we cannot exclude the possibility that other ‘pleasant’ emotions, for instance affection or aesthetic appeal, could be underlying the pupil dilation responses to sexual stimuli. We would argue that it is implausible that, for example, heterosexual male arousal to female images is better explained by perceived threat or unpleasantness, or pleasant emotions given that correlations of pupillary responses to sexual stimuli with genital arousal patterns, subjective sexual arousal (Rieger et al., 2015) and sexual appeal ratings (Attard-Johnson et al., 2016). These correlations provide some evidence to support the notion that pupil dilation responses to sexual stimuli observed are related to sexual arousal—at least in men. However, we acknowledge that further research is needed to untangle the affective states underlying the arousal response when viewing these images.

This highlights the importance of obtaining confirmatory measure of sexual interest to validate against pupillary responses. In many studies this was obtained through subjective self-report of sexual orientation which, at least in men, demonstrates convergence with pupillary responses (Rieger et al., 2015), cognitive tasks (Ó Ciardha et al., 2018), and other physiological measures of sexual arousal (Chivers et al., 2010; Rieger et al., 2015). Few direct attempts have been made to examine the convergent validity of pupillary responses with self-report sexual orientation and cognitive-based measures of sexual interest (Attard-Johnson et al., 2016; Ó Ciardha et al., 2018; Rieger et al., 2015) and only one study with genital responses (Rieger et al., 2015). From these, men’s pupillary responses demonstrated modest correlations with genital response (average r = 0.59; Rieger et al., 2015), viewing time (average r = 0.51; Ó Ciardha et al., 2018; Rieger & Savin-Williams, 2012), self-report sexual orientation (average r = 0.56; Ó Ciardha et al., 2018; Rieger et al., 2015; Rieger & Savin-Williams, 2012), and subjective sexual appeal and arousal ratings (average r = 0.58; Attard-Johnson et al., 2016; Rieger et al., 2015). In contrast, women’s pupillary responses correlated weakly with genital response (average r = 0.19; Rieger et al., 2015), subjective sexual appeal, and arousal ratings (average r = 0.15; Attard-Johnson et al., 2016; Rieger et al., 2015), but demonstrated a moderate correlation with viewing time tasks (average r = 0.47; Ó Ciardha et al., 2018; Rieger & Savin-Williams, 2012) and self-report sexual orientation (average r = 0.31; Ó Ciardha et al., 2018; Rieger et al., 2015; Rieger & Savin-Williams, 2012). We recommend that future primary studies seeking to use pupillary responses as a measure of sexual interest include also one or more alternative measures of sexual orientation to strengthen our understanding of the validity of pupillary responses for the assessment of sexual interests in men and women.