Decreasing human body temperature in the United States since the industrial revolution

Decreasing human body temperature in the United States since the industrial revolution. Myroslava Protsiv, Catherine Ley, Joanna Lankester, Trevor Hastie, Julie Parsonnet.
eLife 2020;9:e49555, Jan 7, 2020, doi: 10.7554/eLife.49555

Abstract: In the US, the normal, oral temperature of adults is, on average, lower than the canonical 37°C established in the 19th century. We postulated that body temperature has decreased over time. Using measurements from three cohorts--the Union Army Veterans of the Civil War (N = 23,710; measurement years 1860–1940), the National Health and Nutrition Examination Survey I (N = 15,301; 1971–1975), and the Stanford Translational Research Integrated Database Environment (N = 150,280; 2007–2017)--we determined that mean body temperature in men and women, after adjusting for age, height, weight and, in some models date and time of day, has decreased monotonically by 0.03°C per birth decade. A similar decline within the Union Army cohort as between cohorts, makes measurement error an unlikely explanation. This substantive and continuing shift in body temperature—a marker for metabolic rate—provides a framework for understanding changes in human health and longevity over 157 years.

Discussion (links and full text at the original paper above)

In this study, we analyzed 677,423 human body temperature measurements from three different cohort populations spanning 157 years of measurement and 197 birth years. We found that men born in the early 19^th century had temperatures 0.59°C higher than men today, with a monotonic decrease of −0.03°C per birth decade. Temperature has also decreased in women by −0.32°C since the 1890s with a similar rate of decline (−0.029°C per birth decade). Although one might posit that the differences among cohorts reflect systematic measurement bias due to the varied thermometers and methods used to obtain temperatures, we believe this explanation to be unlikely. We observed similar temporal change within the UAVCW cohort—in which measurement were presumably obtained irrespective of the subject's birth decade—as we did between cohorts. Additionally, we saw a comparable magnitude of difference in temperature between two modern cohorts using thermometers that would be expected to be similarly calibrated. Moreover, biases introduced by the method of thermometry (axillary presumed in a subset of UAVCW vs. oral for other cohorts) would tend to underestimate change over time since axillary values typically average one degree Celsius lower than oral temperatures (Sund-Levander et al., 2002; Niven et al., 2015). Thus, we believe the observed drop in temperature reflects physiologic differences rather than measurement bias. Other findings in our study—for example increased temperature at younger ages, in women, with increased body mass and with later time of day—support a wealth of other studies dating back to the time of Wunderlich (Wunderlich and Sequin, 1871; Waalen and Buxbaum, 2011).

Resting metabolic rate is the largest component of a typical modern human’s energy expenditure, comprising around 65% of daily energy expenditure for a sedentary individual (Heymsfield et al., 2006). Heat is a byproduct of metabolic processes, the reason nearly all warm-blooded animals have temperatures within a narrow range despite drastic differences in environmental conditions. Over several decades, studies examining whether metabolism is related to body surface area or body weight (Du Bois, 1936; Kleiber, 1972), ultimately, converged on weight-dependent models (Mifflin et al., 1990; Schofield, 1985; Nelson et al., 1992). Since US residents have increased in mass since the mid-19^th century, we should have correspondingly expected increased body temperature. Thus, we interpret our finding of a decrease in body temperature as indicative of a decrease in metabolic rate independent of changes in anthropometrics. A decline in metabolic rate in recent years is supported in the literature when comparing modern experimental data to those from 1919 (Frankenfield et al., 2005).

Although there are many factors that influence resting metabolic rate, change in the population-level of inflammation seems the most plausible explanation for the observed decrease in temperature over time. Economic development, improved standards of living and sanitation, decreased chronic infections from war injuries, improved dental hygiene, the waning of tuberculosis and malaria infections, and the dawn of the antibiotic age together are likely to have decreased chronic inflammation since the 19^th century. For example, in the mid-19^th century, 2–3% of the population would have been living with active tuberculosis (Tiemersma et al., 2011). This figure is consistent with the UAVCW Surgeons' Certificates that reported 737 cases of active tuberculosis among 23,757 subjects (3.1%). That UAVCW veterans who reported either current tuberculosis or pneumonia had a higher temperature (0.19°C and 0.03°C respectively) than those without infectious conditions supports this theory (Supplementary file 1). Although we would have liked to have compared our modern results to those from a location with a continued high risk of chronic infection, we could identify no such database that included temperature measurements. However, a small study of healthy volunteers from Pakistan—a country with a continued high incidence of tuberculosis and other chronic infections—confirms temperatures more closely approximating the values reported by Wunderlich (mean, median and mode, respectively, of 36.89°C, 36.94°C, and 37°C) (Adhi et al., 2008).

Reduction in inflammation may also explain the continued drop in temperature observed between the two more modern cohorts: NHANES and STRIDE. Although many chronic infections had been conquered before the NHANES study, some—periodontitis as one example (Capilouto and Douglass, 1988)— continued to decrease over this short period. Moreover, the use of anti-inflammatory drugs including aspirin (Luepker et al., 2015), statins (Salami et al., 2017) and non-steroidal anti-inflammatory drugs (NSAIDs) (Lamont and Dias, 2008) increased over this interval, potentially reducing inflammation. NSAIDs have been specifically linked to blunting of body temperature, even in normal volunteers (Murphy et al., 1996). In support of declining inflammation in the modern era, a study of NHANES participants demonstrated a 5% decrease in abnormal C-reactive protein levels between 1999 and 2010 (Ong et al., 2013).

Changes in ambient temperature may also explain some of the observed change in body temperature over time. Maintaining constant body temperature despite fluctuations in ambient temperature consumes up to 50–70% of daily energy intake (Levine, 2007). Resting metabolic rate (RMR), for which body temperature is a crude proxy, increases when the ambient temperature decreases below or rises above the thermoneutral zone, that is the temperature of the environment at which humans can maintain normal temperature with minimum energy expenditure (Erikson et al., 1956). In the 19^th century, homes in the US were irregularly and inconsistently heated and never cooled. By the 1920s, however, heating systems reached a broad segment of the population with mean night-time temperature continuing to increase even in the modern era (Mavrogianni et al., 2013). Air conditioning is now found in more than 85% of US homes (US Energy Information Administration, 2011). Thus, the amount of time the population has spent at thermoneutral zones has markedly increased, potentially causing a decrease in RMR, and, by analogy, body temperature.

Some factors known to influence body temperature were not included in our final model due to missing data (ambient temperature and time of day) or complete lack of information (dew point)(Obermeyer et al., 2017). Adjusting for ambient temperature, however, would likely have amplified the changes over time due to lack of heating and cooling in the earlier cohorts. Time of day at which measurement was conducted had a more significant effect on temperature (Figure 1—figure supplement 4). Based on the distribution of times of day for temperature measurement available to us in STRIDE and NHANES, we estimate that even in the worst case scenario, that is the UAVCW measurements were all were obtained late in the afternoon, adjustment for time of day would have only a small influence (<0.05°C) on the −0.59°C change over time.

In summary, normal body temperature is assumed by many, including a great preponderance of physicians, to be 37°C. Those who have shown this value to be too high have concluded that Wunderlich’s 19^th century measurements were simply flawed (Mackowiak, 1997; Sund-Levander et al., 2002). Our investigation indicates that humans in high-income countries have changed physiologically over the last 200 birth years with a mean body temperature 1.6% lower than in the pre-industrial era. The role that this physiologic ‘evolution’ plays in human anthropometrics and longevity is unknown.

Democrats & Republicans equally dislike & dehumanize each other, but their estimate of how they are seen by members of the other party is more than twice the levels actually reported

Moore-Berg, Samantha, Lee-Or A. Karlinsky, Boaz Hameiri, and Emile Bruneau. 2020. “The Partisan Penumbra: Political Partisans’ Exaggerated Meta-perceptions Predict Intergroup Hostility.” PsyArXiv. January 9. doi:10.31234/osf.io/d6bpe

Abstract: People’s actions towards a competitive outgroup can be motivated not only by their perceptions of the outgroup, but also by how they think the outgroup perceives the ingroup (i.e., meta-perceptions). Here we examine the prevalence, accuracy, and consequences of meta-perceptions among American political partisans. Using representative samples (N=1053) and a longitudinal convenience sample (N=2707), we find that Democrats and Republicans equally dislike and dehumanize each other, but estimate that the levels of prejudice and dehumanization expressed by the outgroup party are more than twice the levels actually reported by representative samples of Democrats and Republicans. Finally, we show that meta-prejudice and meta-dehumanization are independently associated with outgroup hostility through their effects on prejudice and dehumanization. This research demonstrates that partisan meta-perceptions are subject to a strong negativity bias, with Democrats and Republicans agreeing that the shadow of partisanship is much larger than it actually is, which fosters mutual intergroup hostility.

Having a goal to change one’s level of Extraversion, Neuroticism, Agreeableness, & Conscientiousness does not lead to any subsequent change in trait levels over the course of 12 months

Personality change goals and plans as predictors of longitudinal trait change in young adults: A replication with an Iranian sample. Samaneh Asadi, Hamideh Mohammadi Dehaja, Oliver Robinson. Journal of Research in Personality, January 9 2020, 103912, https://doi.org/10.1016/j.jrp.2020.103912

Highlights
• Having a goal to change one’s level of Openness to Experience predicts becoming higher on this trait over the course of 12 months, in a sample of Iranian students.
• Having a goal to change one’s level of other traits within the Big Five model. (Extraversion, Neuroticism, Agreeableness, Conscientiousness) does not lead to any subsequent change in trait levels over the course of 12 months.
• 74% of the sample have a goal to reduce their current level of Neuroticism, and 61% have a goal to increase Conscientiousness.

Abstract: Goals and plans for changing one’s personality traits have been found to be commonly held, particularly in young adults. Evidence for whether such goals and plans can predict actual trait change is mixed. The current study replicated and extended the methodology of a previous study to investigate whether trait change goals and plans predict change over a year in an Iranian sample of students. It was found that goals and plans before and after the 12-month period predicted longitudinal change in Openness to Experience, but no association was found for other traits. To explore whether this relationship between goals and change in Openness to Experience is replicable, further research with samples of differing ages and cultures is needed.

Keywords: Personality change goalstrait changeplanslongitudinal

Check also In large part, the wish to change personality did not predict actual change in the desired direction; & desired increases in Extraversion, Agreeableness & Conscientiousness corresponded with decreases:

From Desire to Development? A Multi-Sample, Idiographic Examination of Volitional Personality Change. Erica Baransk et al. Journal of Research in Personality, December 26 2019, 103910. https://www.bipartisanalliance.com/2019/12/in-large-part-wish-to-change.html

Acquisition announcement returns and post-merger operating performance are significantly higher when the acquirer and the target have more similar political attitudes

Duchin, Ran and Farroukh, Abed El Karim and Harford, Jarrad and Patel, Tarun, Political Attitudes, Partisanship, and Merger Activity (Nov 30, 2019). SSRN: http://dx.doi.org/10.2139/ssrn.3497907

Abstract: This paper provides novel evidence that similarity in employees’ political attitudes plays a role in mergers and acquisitions. Using detailed data on individual campaign contributions to Democrats and Republicans, our estimates show that firms are considerably more likely to announce a merger, complete a merger, and a have shorter time-to-completion when their political attitudes are closer. Furthermore, acquisition announcement returns and post-merger operating performance are significantly higher when the acquirer and the target have more similar political attitudes. The effects of political partisanship on mergers are stronger in more recent years, when the political polarization in the U.S. is greater. Overall, we provide estimates that political attitudes and polarization have real effects on the allocation of assets in the economy.

Keywords: campaign contributions, mergers and acquisitions, politics, polarization
JEL Classification: G34, D72

When female speakers increased their pitch they were judged as more attractive; unexpected was that male speakers tended to rate other males who shifted their voice up in pitch as more attractive

Vocal attractiveness and voluntarily pitch-shifted voices. Yi Zheng et al. Evolution and Human Behavior, January 9 2020. https://doi.org/10.1016/j.evolhumbehav.2020.01.002

Abstract: Previous studies have found that using software to pitch shift people's voices can boost their perceived attractiveness to opposite-sex adults: men prefer women's voices when pitch-shifted up, and women prefer men's voices when pitch-shifted down. In this study, we sought to determine whether speakers could affect their perceived vocal attractiveness by voluntarily shifting their own voices to reach specific target pitches (+20 Hz or −20 Hz, a pitch increment that is based on prior research). Two sets of Chinese college students participated in the research: 115 who served as speakers whose voices were recorded, and 167 who served as raters who evaluated the speakers' voices. We found that when female speakers increased their pitch they were judged as more attractive to both opposite-sex and same-sex raters. An additional unexpected finding was that male speakers tended to rate other males who shifted their voice up in pitch as more attractive. These findings suggest that voluntary pitch shifts can affect attractiveness, but that they do not fully match the patterns observed when pitch shifting is done digitally.

Keywords: Vocal attractivenessPitch shifting

Humans, macaque monkeys, cats, horses, sheep, owls, falcons, & toads have stereopsis; in cuttlefish, stereopsis. works differently to vertebrates (extract stereopsis cues from anticorrelated stimuli)

Cuttlefish use stereopsis to strike at prey. R. C. Feord et al. Science Advances  Jan 08 2020: Vol. 6, no. 2, eaay6036. DOI: 10.1126/sciadv.aay6036

Abstract: The camera-type eyes of vertebrates and cephalopods exhibit remarkable convergence, but it is currently unknown whether the mechanisms for visual information processing in these brains, which exhibit wildly disparate architecture, are also shared. To investigate stereopsis in a cephalopod species, we affixed “anaglyph” glasses to cuttlefish and used a three-dimensional perception paradigm. We show that (i) cuttlefish have also evolved stereopsis (i.e., the ability to extract depth information from the disparity between left and right visual fields); (ii) when stereopsis information is intact, the time and distance covered before striking at a target are shorter; (iii) stereopsis in cuttlefish works differently to vertebrates, as cuttlefish can extract stereopsis cues from anticorrelated stimuli. These findings demonstrate that although there is convergent evolution in depth computation, cuttlefish stereopsis is likely afforded by a different algorithm than in humans, and not just a different implementation.

DISCUSSION

To ensure that cuttlefish hit their prey successfully, they must acquire information about its location before the strike. Here, we show that cuttlefish use the disparity between their left and right eyes to perceive depth (Fig. 1). Cuttlefish use this information to aid in prey capture, as animals with intact binocular vision take less time to strike at prey and do so from farther away (Fig. 2.). In animals tested with quasi-monocular stimuli, the significant difference in latency, travel distance, and strike location during the positioning phase is consistent with Messenger’s study (7), as he found that attack success in unilaterally blinded animals decreased to 56% (versus 91% in binocular animals). Nonetheless, binocular cues cannot be the only depth perception mechanism used by the cuttlefish, as many quasi-monocularly and binocularly stimulated animals behaved equally well, both in Messenger’s study and ours. The absence of pictorial cues in our stimulus (the shrimp silhouette lacks any shadowing, shading, or occlusion) leads us to conclude that for monocular but not binocular depth perception, cuttlefish may rely on motion cues such as parallax (13) and/or motion in depth (19).

Before our investigation, cuttlefish were not known to use stereopsis (i.e., calculate depth from disparity between left and right eye views). They had been shown only to have a variable range of binocular overlap (7). Using anaglyph glasses and this 3D perception assay, we provide strong support that cuttlefish have and use stereopsis during the positioning to prey seizure phases of the hunt. However, as suggested by Messenger (7), other depth estimation strategies, such as oculomotor proprioceptive cues provided by the vergence of the two eyes (20, 21), could be at play. Accommodation cues, as used by chameleons to judge distance (22), could also provide an additional explanation as lens movements have been observed in cuttlefish (23). However, if proprioceptive or accommodation cues were being used by cuttlefish for depth estimation, it should not fail as it did when presented with a completely uncorrelated stimulus, i.e., each eye should still fixate and converge on the moving target without requiring correspondence between the images (Fig. 3). We observed that cuttlefish consistently engaged and reached the positioning phase when presented with uncorrelated stimuli, but they quickly aborted and never advanced to the striking phase of the hunt (movie S4). Because they could not solve the uncorrelated stimuli test, we conclude that cuttlefish rely on interocular correspondence to integrate binocular cues and not simply use binocular optomotor cues (vergence) or accommodation to estimate depth. This also indicates that cuttlefish stereopsis is different from praying mantis (also known as mantids) stereopsis, because mantids can resolve targets based on “kinetic disparity” (the difference in the location of moving object between both eyes) (16). Mantids can do this in the absence of “static disparity” provided by the surrounding visual scene, something which humans are unable to do (16).

To see how binocular overlap may play a role in stereopsis, we investigated eye convergence. A disparity difference of up to 10° between the left and right eye angular positions at the moment when they strike may seem large (Fig. 4). However, cuttlefish have a relatively low-resolution retina, 2.5° to 0.57° per photoreceptor (24). Thus, cuttlefish image disparity relative to their eye resolution is comparable to the relative magnitudes observed for these measures in vertebrates. Cuttlefish’s lower spatial resolution makes it plausible that they may also have neurons that encode disparity across a larger array of visual angles, as known to be the case in mice (25). To coordinate the relative positions of the left and right receptive fields for object tracking, cuttlefish may have evolved similar circuits as those used by chameleons for synchronous and disconjugate saccades (26, 27) and by rats for a greater overhead binocular field (28).

The evidence presented here establishes that cuttlefish make use of stereopsis when hunting and that this improves hunting performance by reducing the distance traveled, the time taken to strike at prey, and allowing it to strike from farther away. Further investigation is required to uncover the neural mechanisms underlying the computation of stereopsis in these animals.

During 2018, approximately 12 million (4.7%) U.S. residents aged ≥16 years reported driving under the influence of marijuana, and 2.3 million (0.9%) reported driving under the influence of illicit drugs other than marijuana

Azofeifa A, Rexach-Guzmán BD, Hagemeyer AN, Rudd RA, Sauber-Schatz EK. Driving Under the Influence of Marijuana and Illicit Drugs Among Persons Aged ≥16 Years — United States, 2018. MMWR Morb Mortal Wkly Rep 2019;68:1153–1157. https://www.cdc.gov/mmwr/volumes/68/wr/mm6850a1.htm

Summary
What is already known about this topic? The use and co-use of alcohol and drugs has been associated with impairment of psychomotor and cognitive functions while driving.

What is added by this report? During 2018, approximately 12 million (4.7%) U.S. residents aged ≥16 years reported driving under the influence of marijuana, and 2.3 million (0.9%) reported driving under the influence of illicit drugs other than marijuana during the past 12 months.

What are the implications for public health practice? Development, evaluation, and further implementation of strategies to prevent alcohol-, drug-, and polysubstance-impaired driving coupled with standardized testing of impaired drivers and drivers involved in fatal crashes could advance understanding of drug- and polysubstance-impaired driving and assist states and communities with prevention efforts.

Discussion

Although 4.7% of the U.S. population aged ≥16 years reported driving under the influence of marijuana and 0.9% reported driving under the influence of illicit drugs other than marijuana, these estimates are lower than the 8.0% (20.5 million) who reported driving under the influence of alcohol in 2018 (NSDUH, unpublished data, 2019). The highest prevalence of driving under the influence of marijuana was among persons aged 21–25 years. The second highest was among the youngest drivers (those aged 16–20 years), who already have a heightened crash risk because of inexperience^¶; thus, their substance use is of special concern. In a study of injured drivers aged 16–20 years evaluated at level 1 trauma centers in Arizona during 2008–2014 (3), 10% of tested drivers were simultaneously positive for both alcohol and tetrahydrocannabinol, the main psychoactive component of marijuana. Data from the 2018 NSDUH indicate a high prevalence (34.8%) of past-year marijuana use among young adults aged 18–25 years (4). Studies have reported that marijuana use among teenagers and young adults might alter perception, judgement, short-term memory, and cognitive abilities (5). Given these findings, states could consider developing, implementing, and evaluating targeted strategies to reduce marijuana use and potential subsequent impaired driving, especially among teenagers and young adults.
Research has determined that co-use of marijuana or illicit drugs with alcohol increases the risk for driving impairment (5,6). The use of these substances has been associated with impairment of psychomotor and cognitive functions while driving (6,7). In addition, previous research has demonstrated evidence of a statistical association between marijuana use and increased risk for motor vehicle crashes; however, methodologic limitations of studies limit inference of causation (8). Scientific studies have been unable to link blood tetrahydrocannabinol levels to driving impairment (8), and the effects of marijuana in drivers likely varies by dose, potency of the product consumed, means of consumption (e.g., smoking, eating, or vaping), length of use, and co-use of other substances, including alcohol. Additional data are needed to clarify the contribution of drug and polysubstance use to impaired driving prevalence and the resulting crashes, injuries, and deaths.
A national roadside survey using biochemical specimens among drivers aged ≥16 years found that during 2013–2014, the percentages of weekend nighttime drivers who tested positive for alcohol, marijuana (i.e., tetrahydrocannabinol) and illicit drugs were 8.3%, 12.6%, and 15.1%, respectively (9), although a positive test does not necessarily imply impairment. Collecting and testing biologic specimens (e.g., blood or oral fluids) currently required to test for drugs has challenges, including, in some circumstances, the need for a judge to order collection and testing (which can delay roadside testing, thus allowing drug levels to drop with time); variation in substances tested and methodology used by different toxicology laboratories; and the current state of development of oral fluid testing. The increased use of marijuana and some illicit drugs in the United States (4) along with the results of this report, point to the need for rapid and sensitive assessment tools to ascertain the presence of and impairment by marijuana and other illicit drugs. In addition, adoption and application of standards for toxicology testing and support for laboratories to implement recommendations are needed to improve understanding of the prevalence of drug- and polysubstance-impaired driving (10).
The findings in this report are subject to at least five limitations. First, because NSDUH data are self-reported, they are subject to recall and social desirability biases. Second, variations in laws and regulations among states and counties regarding marijuana could have resulted in negative responses to the NSDUH substance use survey questions for fear of legal consequences, leading to an underestimation of the prevalence of the use and driving under the influence in some jurisdictions. Third, the NSDUH questions are not limited to driving under the influence of marijuana only or each illegal substance only; therefore, persons might be driving under the influence of more than one substance at a given time. Fourth, self-reported data are subject to the respondents’ interpretations of being under the influence of a drug. Finally, NSDUH does not assess whether all respondents drive; therefore, reported percentages of impaired drivers might be underestimated.
Impaired driving is a serious public health concern that needs to be addressed to safeguard the health and safety of all who use the road, including drivers, passengers, pedestrians, bicyclists, and motorcyclists. Collaboration among public health, transportation safety, law enforcement, and federal and state officials is needed for the development, evaluation, and further implementation of strategies to prevent alcohol-, drug-, and polysubstance-impaired driving (2). In addition, standardized testing for alcohol and drugs among impaired drivers and drivers involved in fatal crashes could advance understanding of drug- and polysubstance-impaired driving and assist states and communities with targeted prevention efforts.

Subscription-based websites such as PollenTree.com and Modamily that match would-be parents who want to share custody of a child without any romantic expectations; it’s a lot like a divorce, without the wedding or the arguments

A new kind of online service matches people who want to have children, but not necessarily romance. Julie Jargon. The Wall Street Journal, Jan 7 2020. https://www.wsj.com/articles/co-parenting-sites-skip-love-and-marriage-go-right-to-the-baby-carriage-11578393000

When Jenica Andersen felt the tug for a second child at age 37, the single mom weighed her options: wait until she meets Mr. Right or choose a sperm donor and go it alone.

The first option didn’t look promising. The idea of a sperm donor wasn’t appealing, either, because she wanted her child to have an active father, just like her 4-year-old son has. After doing some research, Ms. Andersen discovered another option: subscription-based websites such as PollenTree.com and Modamily that match would-be parents who want to share custody of a child without any romantic expectations. It’s a lot like a divorce, without the wedding or the arguments.

Believing transgender status is biological is correlated with increased support for transgender rights; political conservatives are less likely to believe in biological attribution, but when they do, the impact on support for rights is big

What Drives Support for Transgender Rights? Assessing the Effects of Biological Attribution on U.S. Public Opinion of Transgender Rights. Melanie M. Bowers, Cameron T. Whitley. Sex Roles, January 9 2020. https://link.springer.com/article/10.1007/s11199-019-01118-9

Abstract: Scholars have a limited understanding of what drives opinion on transgender rights. The present study begins to fill this gap by applying attribution theory to data from a national quota-based (U.S. Census approximation) online survey of 1000 U.S. citizens to evaluate how individuals’ beliefs about the biological origin of a person’s transgender status influence support for transgender rights, including employment, housing, healthcare, and bathroom protections. Across all models, we find that believing transgender status is biological is correlated with increased support for transgender rights. Importantly, our results suggest that although political conservatives appear to be less likely to believe in biological attribution, when they do, the belief has a more dramatic impact on support for rights than it does among liberals. Our analysis builds on existing research demonstrating the importance of biological attribution for support of lesbian, gay, and bisexual (LGB) rights and extends our understanding of public opinion on transgender rights. Our findings have important implications for policy experts interested in approaches to addressing transgender rights as well as scholars and practitioners interested in better understanding opinion formation regarding transgender rights because they suggest that providing a biological basis for transgender status may be a way to increase support for protections, particularly among more conservative individuals.

Keywords: Transgender (attitudes toward) Explicit attitudes Public opinion Transgender

Our results show that body patterns corresponding to different moral violations are felt in different regions of the body depending on whether individuals are classified as liberals or conservatives

Body Maps of Moral Concerns. Mohammad Atari, Aida Mostafazadeh Davani, Morteza Dehghani. Psychological Science, January 8, 2020. https://doi.org/10.1177/0956797619895284

Abstract: It has been proposed that somatosensory reaction to varied social circumstances results in feelings (i.e., conscious emotional experiences). Here, we present two preregistered studies in which we examined the topographical maps of somatosensory reactions associated with violations of different moral concerns. Specifically, participants in Study 1 (N = 596) were randomly assigned to respond to scenarios involving various moral violations and were asked to draw key aspects of their subjective somatosensory experience on two 48,954-pixel silhouettes. Our results show that body patterns corresponding to different moral violations are felt in different regions of the body depending on whether individuals are classified as liberals or conservatives. We also investigated how individual differences in moral concerns relate to body maps of moral violations. Finally, we used natural-language processing to predict activation in body parts on the basis of the semantic representation of textual stimuli. We replicated these findings in a nationally representative sample in Study 2 (N = 300). Overall, our findings shed light on the complex relationships between moral processes and somatosensory experiences.

Keywords: emotion, feeling, morality, moral-foundations theory, natural-language processing, open data, open materials, preregistered

Our cultural prioritization of penile-vaginal intercourse over more clitorally focused sexual activities is linked to the gendered orgasm gap

Orgasm Equality: Scientific Findings and Societal Implications. Elizabeth A. Mahar, Laurie B. Mintz & Brianna M. Akers. Current Sexual Health Reports, Jan 8 2020. https://link.springer.com/article/10.1007/s11930-020-00237-9

Abstract
Purpose of Review: Studies have consistently found that there is a gendered orgasm gap, with men experiencing orgasm more frequently than women in heterosexual sexual encounters. This literature review aims to highlight the current state of research on orgasm equality and to explore the reasons underlying this orgasm gap.

Recent Findings: Our review of recently published studies indicates that the gendered orgasm gap still exists today. Additionally, these studies underscore how sociocultural factors can contribute to the differences in reported orgasm frequency between men and women in heterosexual encounters.

Summary: This review suggests that our cultural prioritization of penile-vaginal intercourse over more clitorally focused sexual activities is linked to the gendered orgasm gap. Additional related contributing sociocultural factors may include women’s lack of entitlement to partnered sexual pleasure, societal scripts about masculinity, and women’s cognitive distractions during partnered sex. Recommendations to increase orgasm equality are discussed.


Sociocultural Explanations for the Gendered Orgasm Gap

In all sexual contexts in which women have the most orgasms
(e.g., masturbation, relationship sex, sex with other women),
there tends to be greater focus on clitoral stimulation.
Research finds that when women masturbate the vast majority
stimulate their clitoris, either alone or coupled with penetration [22, 29, 30]. Additionally, in casual sex, women receive
less oral sex and other forms of clitoral stimulation than they
do in relationship sex [31]. Finally, one study found that women in same-sex relationships reported more frequent orgasms
resulting from their partners’ stimulation of their clitoris and
from oral sex than women in heterosexual relationships [32•].
In short, these findings suggest that a likely reason for the
gendered orgasm gap is that during heterosexual sexual encounters, many women are not getting the clitoral stimulation
they may need to orgasm [19]. This lack of clitoral stimulation
has been theorized to be linked to several underlying cultural
factors including our cultural overvaluing of intercourse,
women’s lack of entitlement to sexual pleasure, a conflation
of penetration-based orgasms and masculinity, and our lacking
sex education system.


Cultural Overvaluing of Intercourse

Scholars have implicated our cultural devaluing of women’s
sexual pleasure and clitoral stimulation, and parallel
overvaluing of men’s sexual pleasure and intercourse to underlie the orgasm gap (e.g., [2, 33]). This overvaluing of intercourse is reflected in what has been termed our current
cultural script for heterosexual sex, which proceeds as follows: foreplay (just to get the woman ready for intercourse),
intercourse, male orgasm, and sex over [18, 33, 34]. In this
scenario, the man is responsible to give the woman an orgasm
during intercourse giving by lasting long and thrusting hard
[34].
This cultural prioritization of intercourse is reflected and
perpetuated in our language and media. We use the words sex
and intercourse5 as if they were one and the same and relegate
everything before to “foreplay,” implying it is a lesser form of
sex than intercourse [35]. Recent studies indicate that media
images of heterosexual sex generally portray women
orgasming from intercourse alone, if they orgasm at all. To
illustrate, content analyses of pornography indicate that the
orgasm gap is reflected there, with only about 17–18% of
women in comparison to 76–78% of men shown to reach
orgasm, and most of women’s orgasms shown to be achieved
through vaginal or anal intercourse [36, 37]. One recent study
used content analysis to code PornHub’s 50 most viewed
videos of all time and found that in the videos where women
are shown reaching orgasm, only 25% of the orgasms involve
some form of direct or indirect clitoral stimulation [36].
Additional evidence of media emphasizing intercourse is a
study that textually analyzed top articles from Men’s Health,
a popular men’s magazine, and discovered a focus on female
orgasms achieved through vaginal penetration [38]. Even in
instances where these articles encouraged sexual variety, they
spoke of variety almost exclusively in terms of intercourse
positions [38]. Such popular press advice runs counter not
only to research that indicates that most women do not orgasm
from penetration alone, but also to findings that combining
intercourse with other more clitorally focused sexual activities
during partnered sex is associated with women’s increased
3 orgasm frequency [9•, 39]. For example, one study found that Shirazi et al. [26] demonstrated that the way questions are phrased regarding
the occurrence of orgasm during intercourse modulates women’s reported
frequency of such orgasms, with the highest rate of orgasm reported when
the question specifies that intercourse include concurrent clitoral stimulation
and the lowest rate of orgasm reported when the question specifies no such
concurrent stimulation, with a mid-range rate found when this was left
unspecified.
4 In this convenience sample, 19% said they rarely if ever orgasmed with a
partner.
5 Given our cultural usage of the words sex and intercourse as equivalent,
research asking about women’s orgasms during “sex” could lead to lower
reports of orgasms than actually occur during partnered sexual activity because
many heterosexual women exclude activities that are associated with increased
likelihood of orgasm (e.g., receiving oral sex) from their personal definitions of
sex [9•, 35]. Researchers are thus advised to use precise wording in their
studies of orgasm.
women report more frequent orgasms if their sexual encounters include deep kissing, manual genital stimulation, and/or
oral sex in addition to intercourse [9•].

Women’s Lack of Entitlement to Sexual Pleasure

Research suggests that women may set the bar for satisfactory
sex quite low—specifically, the absence of pain and degradation rather than as the presence of pleasure and orgasm [40].
Indeed, research finds that many heterosexual women express
going into partnered sexual activity expecting not to orgasm
[41] and valuing their partners’ orgasms more than their own
[42, 43]. In fact, when women report on their sexual satisfaction, these reports often reflect their perception of their partners’ sexual satisfaction rather than their own [44, 45].
Women prioritizing providing their partners—rather than
themselves—pleasure during sexual encounters has been connected with them feeling less entitled to sexual pleasure and
also less likely to communicate to their partners how they need
to be stimulated in order to orgasm, two factors positively
associated with reaching orgasm in the research literature
[9•, 11, 46, 47].
Women’s lack of entitlement to sexual pleasure may be
especially pronounced during casual sex. One qualitative study
[31] found a double standard in which both men and women
question women’s (but not men’s) entitlement to pleasure in
hookups, while believing strongly in women’s (as well as
men’s) entitlement to pleasure during relationship sex. This
sexual double standard seems to translate directly to behaviors
focused on clitoral stimulation. A large-scale study [15] found
that “men are more likely to engage in cunnilingus—a practice
strongly associated with women’s orgasm—in relationships
than in hookups. In contrast, women engage in fellatio at high
rates across all contexts” (p. 362). Relatedly, another practice
strongly related to women’s orgasms—clitoral self-stimulation
during intercourse—was found to be more common in relationship sex than in casual sex. According to the authors, these
findings suggest that the orgasm gap is larger in casual sex
because women are less likely to feel entitled to seek their
own sexual pleasure and men are less motivated men to provide their partners with pleasure, with both resulting in less
clitoral stimulation for women.


Conflation of Penetration-Based Orgasms and Masculinity

While studies on casual sex [15, 31] position men as not
caring about women’s pleasure, other findings suggest that
men care deeply about women’s pleasure—although they
may be misguided about how to provide that pleasure. As
detailed above, our cultural script gives men responsibility
for “giving” women orgasms by lasting long and thrusting
hard [38]. A qualitative study found that men often felt distressed and sometimes emasculated when their female partner
does not orgasm [48]. Similarly, a recent vignette study found
that men reporting having higher sexual self-esteem and feeling more masculine when they imagined that their partner
orgasmed during sex versus imagining that she did not [49].
The female partner that the men were instructed to imagine
was an attractive woman that they had had sex three times
with, so neither a first-time hookup nor a relationship partner.
Whether and how men’s feelings of masculinity would change
when imagining differing types of partners (e.g., first time
hookup, girlfriend) is an empirical question awaiting study
and could shed light on the seemingly contradictory findings
that men do not care about women’s pleasure during hookups
and findings that men care so deeply about women’s orgasms
that they see “giving” one to be a reflection of their manhood.
Regardless of the results of such future research, existing
research indicates that women are expected to protect men’s
egos by orgasming during intercourse. One qualitative study
[28] found that female participants reported being concerned
that it would hurt the male partner’s ego if they did not have an
intercourse-based orgasm. The women in this study also believed that asking their partners for clitoral stimulation would
hurt their partners’ feelings. Given such findings, it is no wonder that a majority of women report having faked an orgasm
during intercourse, with some of the most common reasons for
faking being to protect their partners’ egos and to give their
partners pleasure [28, 34, 50]. Women also report faking orgasms to avoid appearing abnormal, because they, too, believe
they should be orgasm from intercourse alone [34]. A qualitative study found that women report feeling abnormal or
dysfunctional when they do not orgasm during penilevaginal intercourse [45].
In sum, several deeply intertwined sociocultural factors
related to expectations of female orgasm during intercourse
are linked to the gendered orgasm gap. Nevertheless, additional sociocultural factors have been implicated in women’s comparatively lower rate of orgasm when compared to men.


Additional Sociocultural Factors

Two additional cultural factors that may underlie the orgasm
gap are women’s cognitive distraction during sexual encounters and our lacking sex education system. Regarding the latter, the United States’sex education system often presents sex
as dangerous rather than pleasurable and particularly fails to
cover women’s sexual pleasure by excluding mention of
women’s external genital anatomy or women’s orgasms [20,
51, 52].
Women also report higher levels of both overall cognitive
distractions and appearance-focused cognitive distractions
during sexual activity than men [53] and these cognitive distractions are linked to lower levels of sexual satisfaction [54]
and orgasm [55]. One specific area of appearance-focused
cognitive distraction is women’s genital self-image, with
women’s positive feelings towards their genitals associated
with sexual satisfaction and enhanced orgasmic capacity with
a partner [56, 57]. Another common focus of cognitive distraction (for both women and men) is performance anxiety,
including worries about pleasing one’s partner and about if
one is going to orgasm. While for men, there is often concern
about orgasming too quickly, for women, the concern often
focused on taking too long to orgasm [24]. Regardless of the
content of the performance-based worry, there is evidence that
mindfulness, an approach characterized by “acceptance and
non-judgment of the present moment,” may enhance women’s
orgasmic capacity by decreasing cognitive distractions, such
as concerns about appearance or performance, during sexual
activity (p. 418) [58]. Mindfulness is useful in taking the focus
away from a performance-oriented view of sex and placing the
focus on pleasure and eroticism. Indeed, despite the focus of
this review on the gendered orgasm gap, it is essential to
underscore that pressure to achieve orgasm is linked to stress
in women [50] and that pressure to achieve orgasm (for both
women and men) makes orgasm less likely, given that orgasm
is often the result of a pleasuring/eroticism process rather than
a performance imperative [33]. Additionally, women differ
greatly in how important orgasm is to their sexual satisfaction
[24]. Thus, prior to turning to strategies to close the orgasm
gap, it is important to examine the issue of the importance of
orgasm to women’s sexual satisfaction.


How Important Is Orgasm to Women’s Sexual Satisfaction?

As detailed in a seminal review article [24], women differ
greatly in how important orgasm is to their sexual satisfaction.
Such individual differences may also be reflected in seemingly contradictory research findings, with some research finding
that many women report feeling sexual satisfaction even when
they do not orgasm [50] and other research reporting that
women’s orgasms are associated with increased sexual satisfaction and positive outcomes [10, 13, 31]. While we do not
dispute either set of findings, we also acknowledge that it is
difficult to separate the importance women place on their own
orgasms from the sociocultural factors that underlie the gendered orgasm gap. To explain, given our cultural scripts that
prioritize penetrative sex, when women are unable to reliably
orgasm through this method of stimulation, they may come
not to expect orgasms [41] and—as a way of reducing feelings
of abnormality—come to view their own orgasm as unimportant [59]. Potentially bolstering this view is the finding that
both men [44] and lesbian women are more likely than heterosexual women to include orgasm as a metric of their
partnered sexual pleasure [41, 46]. In other words, those most
likely to orgasm during partnered sexual encounters due to
being less negatively affected by the prioritization of intercourse are those most likely to view orgasm as most
important. While we are not suggesting that orgasm be set as
an imperative goal to achieve, that orgasm must be equally
important to all women, or that that every sexual encounter
needs to be completely synchronous (i.e., equally pleasurable
and orgasmic for both partners), consistent and robust research
findings concerning a gendered orgasm gap points to an underlying societal issue to be addressed.


Recommendations for Closing the Orgasm Gap

Given that sociocultural factors have been implicated in the
orgasm gap, it is likely that sociocultural interventions could
prove useful in closing the gap. In the conclusion of a recent
study on women’s pursuit of orgasm, it was proposed that an
effective societal intervention may be simply to “acknowledge
that broad claims about women’s biological capacity for orgasm are facile” (p. 8) [18]. Additionally, societal-level advocacy work aimed at women and men promoting clitoral
knowledge and the equal valuing of women’s and men’s most
reliable routes to orgasm will be useful.
Nevertheless, such awareness raising alone is likely insufficient, given that one study found that teaching women about
their clitoris is linked to orgasm frequency during masturbation but not during sex with a partner [2]. Instead, the most
empirically supported technique for women struggling with
orgasm concerns is to direct them to figure out what type of
clitoral stimulation they need via masturbation and then to
help them transfer this type of stimulation to partner sex or
in other words, helping them to engage in sexual behaviors in
which they get the same type of stimulation alone as with a
partner [33]. For women to get the same sexual stimulation
alone as with a partner entails replacing our current cultural
script for sex (i.e., foreplay, intercourse, male orgasm, sex
over) with turn-taking scripts (e.g., oral sex during which the
female orgasms followed by intercourse during which the
male orgasms; stimulation of the clitoris to prepare the woman
for intercourse, followed by intercourse during which the male
orgasms, then followed by vibrator stimulation during which
the woman orgasms) or scripts where penetration is consistently paired with clitoral stimulation (e.g., via an intercourse
position which provides clitoral stimulation to the women;
using a hand or a vibrator during intercourse). The underlying
strategy in teaching individuals to utilize such new scripts is
consistent with research finding that women are most orgasmic when including a variety of activities (e.g., oral sex, manual stimulation, intercourse) in their sexual encounter [9•]. In
short, closing the orgasm gap will require teaching women
and their male partners specific skills and methods with which
to apply clitoral knowledge to their sexual encounters [60].
Three recent studies show that this method holds promise.
One study found that undergraduate women who took a
Human Sexuality course covering topics such as women’s
genital anatomy and pleasure, cultural factors underlying the
orgasm gap, and evidence-based methods to enhance
women’s orgasm (e.g., mindfulness, masturbation training
with transfer to partner sex via sexual communication and
new sexual scripts) showed improvements on measures of
sexual functioning, including attitudes towards women’s genitals, cognitive distraction during sexual activity, and entitlement to pleasure when compared to students who took quasicontrol courses [61]. Another study found that women who
read a book (Becoming Cliterate [19]) combining feminist
analysis of the cultural reasons for the orgasm gap and the
same evidence-based methods to enhance women’s orgasm
improved on multiple measures of sexual well-being, including orgasm [62]. Finally, another study [63] found that men
who read a summary chapter aimed at male readers of this
same book (Becoming Cliterate [19]) showed improvement
on clitoral knowledge, sexual communication, dysfunctional
beliefs about women’s sexual satisfaction, and dysfunctional
beliefs conflating masculinity and sexual performance.
Additional interventions aimed at both women and men to
close the orgasm gap should continue to be developed and
empirically evaluated.
Importantly, such future interventions and research
should be more inclusive of individuals who are transgender or non-binary. We could locate only one study on orgasm frequency not exclusively focused on cisgender individuals. This study found that cisgender women in relationships with cisgender women orgasmed more than both
cisgender women in relationships with cisgender men and
individuals in relationships that include one or more transgender or non-binary partners [64]. Additional work should explore how the orgasm gap affects gender minority
individuals and aid in developing inclusive interventions
for these individuals.

Human self-domestication was done with sociosexual selection for dampened reactive aggression

Masculinity and the Mechanisms of Human Self-Domestication. Ben Thomas Gleeson. Adaptive Human Behavior and Physiology, Jan 6 2020. https://link.springer.com/article/10.1007/s40750-019-00126-z

Abstract
Objectives: Pre-historic decline in human craniofacial masculinity has been proposed as evidence of selection against reactive aggression and a process of ‘human self-domestication’ thought to have promoted complex capacities including language, culture, and cumulative technological development. This follows observations of similar morphological changes in non-human animals under selection for reduced aggression. Two distinct domestication hypotheses posit developmental explanations; involving dampened migration of embryonic neural crest cells (NCCs), and declining androgen influences, respectively. Here, I assess the operation and potential interaction of these two mechanisms and consider their role in human adaptation to a cooperative sociocultural niche.

Methods: I provide a review and synthesis of related literature with a focus on physiological mechanisms affecting domesticated reductions in masculinity and sexual dimorphism. Further, I examine several modes of pre-historic sociosexual selection against aggressive reactivity which are proposed to have driven human self-domestication.

Results: I show that pluripotent NCCs provide progenitors for a wide range of vertebrate masculine features, acting as regular targets for sexually driven evolutionary change. This suggests hypoplasia of NCC-derived tissues due to dampened NCC migration is sufficient to explain declines in lineage specific masculine traits and features under domestication. However, lineage-specific androgen receptor variability likely moderates hypoplasia in NCC-derived tissues, and may influence NCC migration, though this latter influence requires further investigation.

Conclusions: These findings synthesise and extend theorised physiological mechanisms of domestication and human self-domestication. Self-domestication under sociosexual selection for dampened reactive aggression and correlated masculine physiology enabled human adaptation to an increasingly complex sociocultural niche. The analysis highlights several avenues for further productive investigation.

Rising individualism and emancipative values, as an outcome of modernization, diminish the importance of religious faith for people’s happiness, while increasing the importance of a feeling of life control

Cultural Evolution Shifts the Source of Happiness from Religion to Subjective Freedom. Michael Minkov, Christian Welzel & Michael Schachner. Journal of Happiness Studies, Jan 8 2020. https://link.springer.com/article/10.1007/s10902-019-00203-w

Abstract: Numerous studies have reported a positive individual-level association between happiness and two psychologically distinct states of mind: religious faith and subjective freedom (a feeling of life control). Although the strength of these relationships varies across countries, no general pattern driving this variation has been shown so far. After surveying 40,534 randomly selected respondents from 43 nations, we find that in countries where happiness is more closely related to religious faith, it is less strongly associated with subjective freedom, and vice versa. We have also identified the driving force behind this inverse relationship. Rising individualism and emancipative values, as an outcome of modernization, diminish the importance of religious faith for people’s happiness, while increasing the importance of subjective freedom. We conclude that the dominant emancipatory direction of cultural evolution favors freedom over religion.

An Initial Test of the Cosmetics Dehumanization Hypothesis: Heavy Makeup Diminishes Attributions of Humanness-Related Traits to Women

An Initial Test of the Cosmetics Dehumanization Hypothesis: Heavy Makeup Diminishes Attributions of Humanness-Related Traits to Women. Philippe Bernard, Joanne Content, Lara Servais, Robin Wollast & Sarah Gervais. Sex Roles, January 8 2020. https://link.springer.com/article/10.1007/s11199-019-01115-y

Abstract: Objectification theory suggests that sexualization has significant dehumanizing consequences for how perceivers see women. To date, research has mostly documented how sexualized bodies in the mass media are objectified and dehumanized. The purpose of the present work was to test the novel cosmetics dehumanization hypothesis (CDH), that is, that subtler manifestations of sexualization, such as heavy makeup, might influence the way people attribute humanness-related traits to women. Across four experiments, 1000 participants (mostly from the United Kingdom and United States) were asked to evaluate women’s faces with or without heavy makeup. Consistent with the CDH, results showed that faces with makeup were rated as less human while using complementary indicators of dehumanization: They were perceived as possessing less humanness, less agency, less experience (Experiment 1), less competence, less warmth, and less morality (Experiments 2–4) than faces without makeup. This pattern of results was observed for faces of both models (Experiments 1–2) and ordinary women (Experiments 3–4). In Experiment 4, we manipulated the part of the face that wore makeup (eye makeup vs. lipstick) and found that faces with eye makeup were attributed the least amount of warmth and competence. A meta-analysis based on Experiments 2–4 confirmed the robustness of the findings, which were not moderated by either participant gender or sexual orientation. Whereas prior studies suggested that a focus on faces may serve as an antidote for objectification and related dehumanization, the present set of experiments indicates that this strategy might not always be effective.

The green mate appeal: Men's pro‐environmental consumption is an honest signal of commitment to their partner

The green mate appeal: Men's pro‐environmental consumption is an honest signal of commitment to their partner. Sylvie Borau, Leila Elgaaied‐Gambier, Camilla Barbarossa. Psychology &amp; Marketing, January 7 2020. https://doi.org/10.1002/mar.21321

Abstract: Green consumption is associated with femininity. This green‐feminine stereotype has been accused of deterring men from buying green products to protect their gender identity. Here, we investigate whether men can benefit from this green‐feminine stereotype, beyond the status effect of green conspicuous consumption. We propose that green consumption can act as a signal of altruism and high commitment both as a partner and as a father. Based on evidence showing that these traits are sought in a long‐term partner, we predict that men can increase their value as long‐term mates by engaging in green consumption. We also investigate whether men involved in a long‐term mating relationship are indeed eco‐friendlier, testing the novel hypothesis that green consumption is an honest signal of commitment. Finally, we specify the type of commitment that is associated with men's green consumption. Across six studies, our findings suggest that green consumption is an honest signal of men's long‐term mating value and that it is a more reliable sign of partner commitment than of father commitment. We discuss how companies and governments can use these findings to increase green consumption among men.

Although appearing nervous and awkward during an initial encounter with an attractive other may seem counterproductive for future mating success, the reaction may have potential adaptive value

Perceived Nervous Reactions during Initial Attraction and Their Potential Adaptive Value. Susan M. Hughes, Marissa A. Harrison & Kathleen M. de Haan. Adaptive Human Behavior and Physiology, Jan 7 2020. https://link.springer.com/article/10.1007/s40750-019-00127-y

Abstract
Objective: We sought to examine perceived nervous reactions when first interacting with a particularly attractive person/potential romantic partner. From a theoretical standpoint, we cogitate on the possible adaptive nature of these reactions that appear seemingly counterproductive for future mating success.

Methods: We documented 280 participants’ retrospective self-reports of experiencing a variety of physiological, vocal, and behavioral reactions during an initial encounter with a person they found highly attractive. We also asked participants to rate the reactions of others that they used to determine if another person was attracted to them.

Results: Participants reported most frequently experiencing increased attentiveness, smiling, staring, heart rate, giggling/laughter, blushing, and difficulty concentrating during this first encounter. Both sexes reported speaking faster and being less able to express themselves clearly, and women reported using a higher pitch and having a more unsteady tone of voice during an initial encounter of attraction. Further, participants reported observing similar nervous reactions by others whom they perceived were attracted to them. These findings were examined while considering individual differences in sociosexual orientation (i.e., propensity toward uncommitted sex), self-perceived mate value, empathy, and gender.

Conclusions: Participants reported that they did, indeed, experience a cluster of anxiety-related physiological and behavioral reactions during an initial encounter with someone they found highly attractive. Although appearing nervous and awkward during an initial encounter with an attractive other may seem counterproductive for future mating success, we discuss potential adaptive functions for displaying these responses.

Reasons why Nervous Responses during Initial Attraction May be Adaptive

Whereas it was our aim to document the cluster of nervous reactions upon initial
encounter, it is of interest to explore the adaptive function of these physiological
responses reported in this study. At first glance, it would not appear adaptive for
someone to display nervous reactions during an initial encounter with an attractive,
potential mate. These reactions may make an individual seem awkward, clumsy,
ignorant, and uncomfortable and may deter one from considering that person as a
potential mate. Even though these reactions seem counterproductive for future mating
success, our data show that people report they are prevalent. Because the reproductive
consequences of a behavior affect the incidence of that behavior in subsequent
generations, this cluster of nervous signs may serve some adaptive function. Below we
present six possible adaptive reasons why nervous reactions during an initial encounter
with a potential mate are common.

Strong, Honest Sign of Mate Interest

These nervous reactions may serve an adaptive
function of being a salient signal of reproductive interest. In particular, attraction/
romantic interest can be easily distinguished through vocal tones (Hughes et al.,
2010). It may be difficult to mask anxious reactions during this encounter. Particularly
for men, because nervousness can cause problems with cognitive performance
(Karremans et al., 2009; Sarason, 1984), nervousness may make it more difficult for
a man to disguise his true feelings and display phony traits during an initial encounter.
Therefore, these reactions may serve as an honest signal of interest when in the
presence of a potential mate. It is also adaptive to attend to cues of romantic interest
to either avoid or engage in expending energy on individuals who may or may not be
interested or available (Bendixen et al., 2019; Floyd, Judd, & Hesse, 2008).
Both male and female participants indeed reported experiencing several physiological and behavioral reactions when first talking in person to someone whom they found
highly attractive and deem a potential romantic partner. Although the documented
responses occur typically under conditions of “fight or flight” (Marks & Neese, 1994),
we argue that this cluster of signals can be thought of as a psychobiological signature of
honest interest, and these reactions in the presence of a potential mate may serve an
adaptive function of signaling reproductive interest, enhancing the chances of obtaining
a desired mate. Given that our sample was a good representation of peak reproductive
years (a mean of 29.1 with a standard deviation of 12.7 years; Dunson, Baird, &
Colombo, 2004), our participants likely had an increased opportunity to experience
these reactions during initial attraction compared to younger, traditional, college-age
samples typically recruited in other research.

Trigger Reciprocal Feelings

Signs of romantic interest often trigger reciprocal feelings
(Kenny & La Voie, 1982; Montoya & Insko, 2008), and as reported by our participants,
people use these nervous reactions to assess whether another person is attracted to
them. Research shows that when one is made aware that a person is attracted to them,
they become more attracted to that person; but people need to be aware of other’s
feelings toward them for strong reciprocal liking to occur (Luo & Zhang, 2009).
Noticing reciprocation of interest would be particularly advantageous so as to decrease
the chances of missing a mating opportunity and avoid the risk of being rejected.
More Effective Communication Research has shown that when put in a stressful
situation, some aspects speech quality decreases such that speech fluency (as measured
by pause time) is significantly reduced and the frequency of flustered speech increases
(Buchanan, Laures-Gore, & Duff, 2014; Kasl & Mahl, 1965). However, several other
aspects of speech quality are actually enhanced during stressful situations, perhaps
unbeknownst to the speaker. For instance, under instances of stress, communication
rate (words per minute) increases, productive language (ratio of productive to nonproductive speech) increases (which is particularly pronounced during the early part of a
speech task), the use of non-fluencies (such as hmm, uh, um, etc.) is less likely, and
word-finding difficulties do not seem to impair speech (Buchanan et al., 2014). Thus, it
can be argued that when a person becomes anxious when first speaking to someone to
whom they are attracted, their semantic communication is essentially more effective.
We also found that women reported raising the pitch of their voice, which may have
made them sound more attractive. Thus, these speech patterns that occur under the
stress of an initial interaction may actually enhance the chances of impressing and
attaining the desired mate.

Indication of Desirable Traits Associated with those Who Exhibit Nervous Behavior

Anxious individuals have been shown to be more adept at conveying positive
qualities and appeared more willing to engage; they appeared nicer, more interesting,
and more conversational, all of which could increase their desirability (Brumbaugh &
Fraley, 2010). A person who exhibits nervous reactions during initial attraction could
serve as an indication to a potential mate (particularly women) that the suitor possesses
other personality traits that would be favorable in long-term relationships and for future
parenting such as being sensitive, caring, and responsive.
People generally like those who are more facially expressive, and it is seen
as more attractive (Sabatelli & Rubin, 1986). As such, people show greater
facial movement during high versus low anxiety situations (Harrigan &
O’Connell, 1996), and nonverbal expressiveness positively impacts interpersonal
perceptions (Sabatelli & Rubin, 1986). Having a more expressive nature, including displaying nervousness, could also demonstrate other positive characteristics that people find attractive (Sabatelli & Rubin, 1986). In fact, nonverbal
expressiveness could even compensate for a lack of physical attractiveness and
may enhance initial interpersonal impressions so as to allow the person to
appear more attractive (Sabetelli & Rubin, 1986). Along these lines, previous
research has shown that men were more likely to be accepted as a potential
romantic partner during a speed-dating event when they arrived with elevated
levels of the stress hormone, cortisol (van der Meij et al., 2019) suggesting that
being nervous may have its advantages.

Sweating Allows for the Release of Pheromones

Nervously sweating during an initial encounter with an attractive, potential mate may increase the release of pheromones
which can serve as a chemical signal of attraction to the recipient (Saxton et al., 2008).
When individuals become anxious, they tend to show increased palmar sweat (Kasl &
Mahl, 1965) and body perspiration (Galassi et al., 1981) and there is evidence to
suggest that human pheromones are released through these axillary sweat glands (Beier,
Ginez, & Schaller, 2005). Pheromones signal sexual readiness in other species and
likely do so in humans (Thornhill, Chapman, & Gangestad, 2013) and can affect
perceptions of attraction in humans (Rantala, Eriksson, Vainikka, & Kortet, 2006;
Thornhill & Gangestad, 1999; Wyart et al., 2007). For instance, women who were
exposed to androstadienone, a purported male pheromone released by axillary sweat
glands, gave men at a speed dating event higher attractiveness ratings than did women
with no exposure (Saxton, Lyndon, Little, & Roberts, 2008). Exposure to
androstadienone appears to increase sexual response, increase focus, and improve
mood in women (Jacob, Hayreh, & McClintock, 2001; Hummer & McClintock,
2009; Jacob, Garcia, Hayreh, & McClintock, 2002; Verhaeghe, Gheysen, & Enzlin,
2013). Further, release of pheromones has been shown to be valuable for making mate
assessments and can facilitate quick judgments (Hummer & McClintock, 2009;
Thornhill & Gangestad, 1999).
Pheromones may have other direct influences on the recipient. Pheromone exposure
affects skin temperature and conductance (Jacob et al., 2001) and cortisol levels (Wyart
et al., 2007). Thus, it is possible that the recipient could interpret one’s own physiological arousal caused by the pheromone exposure to be the result of their own attraction to
the sender. In addition, there is some evidence from the animal kingdom that pheromones serve to appease conspecifics (Pageat & Gaultier, 2003). Indeed, empathetic
responses to signals in sweat have been documented in humans. Prehn-Kristensen et al.
(2009) found that exposure to sweat from individuals in anxiety-provoking situations
activated areas of the brain related to emotional processing and empathy regulation.
Future studies may explore how pheromones released during this nervous interaction
with a potential mate could influence human opposite-sex conspecifics.

Aid in the Assessment of Matching Mate Value

Mutual nervousness could reveal
matching mate value whereas if only one person is nervous and the other is not, then
this could be a sign of a mismatch in mate value. In other words, whether one, both, or
neither persons of the dyad experiences nervousness when meeting for the first time
could help to differentiate between those who have a matching mate value from those
who are discordant. Individuals generally tend to desire mates with some level of
similarity to themselves and who are of matching social desirability (Berscheid,
Walster, & Walster, 1971; Buston & Emlen, 2003; Figueredo, Sefcek, & Jones,
2006), which often reflects a desire for someone of matching mate value. Back et al.
(2011) argued that knowing one’s own mate value is essential to reproductive to
success. Further, one could view any arousal felt when reciprocating that attention
from a potential mate as a signal of matching mate value.

Intellectual, narcissistic, or Machiavellian? How Twitter users differ from Facebook-only users

Marshall, T. C., Ferenczi, N., Lefringhausen, K., Hill, S., & Deng, J. (2020). Intellectual, narcissistic, or Machiavellian? How Twitter users differ from Facebook-only users, why they use Twitter, and what they tweet about. Psychology of Popular Media, 9(1), 14-30. Jan 2020. http://dx.doi.org/10.1037/ppm0000209

Abstract: Twitter is one of the world’s most popular social networking sites, yet gaps remain in our knowledge about the psychology of its users. The current studies sought to fill these gaps by examining whether the Big Five and Dark Triad personality traits predicted differences between Twitter users and Facebook-only users, motives for using Twitter, the frequency of tweeting about 4 topics—intellectual pursuits, personal achievements, diet/exercise, and social activities—and how much they liked to read tweets about these topics. Study 1 found that Twitter users (N = 346) were higher in openness (i.e., intellect and creativity) than Facebook-only users (N = 268). In Study 2, a preregistered replication, Twitter users (N = 255) were not only higher in openness than Facebook-only users (N = 248), but they were also more Machiavellian. In both studies, Twitter users who were higher in openness were more strongly motivated to use Twitter for career promotion, and in turn, they tweeted more frequently and most liked to read tweets about intellectual pursuits. Narcissists were more strongly motivated to use Twitter for career promotion, social connection, and attention-seeking, and in turn, they tweeted more frequently and most liked to read tweets about personal achievements and diet/exercise. On average, participants most liked to read tweets about intellectual pursuits and least liked tweets about diet/exercise. We discuss the implications of these findings for tailoring one’s tweets to retain followers and for drawing the boundary conditions when extrapolating from Twitter-based “big data” to larger populations.

Public Policy Relevance Statement: Twitter users significantly differed in their personality traits from Facebook-only users, suggesting that social scientists take caution when generalizing from Twitter-based “big data” to larger populations. Our finding that Twitter particularly attracts open-minded individuals who wish to advance their careers through tweeting about intellectual topics has relevance for not only individuals wishing to maximize their use of social media but also Twitter’s marketing and retention strategies.

KEYWORDS: Twitter, Facebook, social media, Big Five personality traits, Dark Triad

General Discussion

This research is the first to examine the Big Five and Dark Triad traits as simultaneous predictors of the likelihood of using Twitter versus Facebook-only, motives for using Twitter, frequency of tweeting about and likability of various topics, and the number of likes/retweets typically received. Our results confirmed that there does indeed appear to be something unique about people who use Twitter rather than just Facebook: They are higher in openness and Machiavellianism. We review these findings in more detail next, and discuss the implications for enhancing users’ experience of Twitter and the extent to which social scientists may generalize from Twitter data to larger populations.

Openness

We found, in both studies, that openness was positively associated with the likelihood of being a Twitter user, with using Twitter for career promotion and, in turn, with tweeting more frequently about intellectual topics. Highly open individuals, who are often entrepreneurial (Leutner, Ahmetoglu, Akhtar, & Chamorro-Premuzic, 2014) and pursuing scientific or artistic careers (Feist, 1998), may be particularly attracted to Twitter because it allows them to share their creative output, keep up-to-date on the latest work in their field, and network with colleagues. Indeed, almost half of scientists use social media to exchange research findings (Rainie, Funk, & Anderson, 2015). Surprisingly, we did not find that highly open individuals were more strongly motivated to use Twitter for information-seeking, as they tend to be in their use of Facebook (Marshall et al., 2015). Further research, with larger and more diverse samples, will need to confirm that highly open individuals are indeed attracted to Twitter, specifically for the career opportunities it affords rather than for its more general use as a tool for seeking and sharing information.

Extraversion

Extraverts tweeted more often about their social activities and everyday life in Study 1, but this finding was not replicated in Study 2. Moreover, extraverts were not more strongly motivated to use Twitter for social connection in either study, suggesting that, despite some of the social affordances Twitter provides (Chen, 2011), extraverts may still prefer to use other social media sites like Facebook for socializing (Hughes et al., 2012).

Narcissism

In both studies, narcissism was more strongly associated with the various motives for using Twitter and with tweeting about more topics than any other personality trait. Nonetheless, narcissists were not any more likely to use Twitter than Facebook-only, suggesting that Twitter’s affordances—particularly the potential to gain admiration from weak-tie contacts—may not be sufficiently alluring to narcissists. Still, the present studies confirmed several hypotheses. First, narcissists’ greater frequency of tweeting about personal achievements was motivated by their use of Twitter for career promotion (Studies 1 and 2) and attention-seeking (Study 2). Unexpectedly, it was also motivated by their use of Twitter for social connection (Studies 1 and 2), suggesting that narcissists may brag about their accomplishments not only for self-promotion but also to communicate with and feel closer to others. Perhaps they view these tweets simply as a way of sharing good news—a capitalization attempt that may enhance friendship quality (Demir, Doğan, & Procsal, 2013). Narcissists’ greater use of Twitter for social connection also motivated their more frequent tweets about their social activities and everyday life (Study 1), consistent with findings that narcissists’ tweets are more likely to refer to friends (Sumner et al., 2012) and everyday life (Preotiuc-Pietro et al., 2017).

Nevertheless, narcissists’ tweets about social activities were also motivated by their use of Twitter for attention-seeking, suggesting that their motives for posting such tweets may not be entirely prosocial; they may also be seeking social status and admiration. Indeed, narcissists may use social media for building social capital and for social grooming, especially if it enables them to take advantage of others (Garcia & Sikström, 2014). And if social capital and reward is embodied by the number of likes and retweets one’s tweets typically receives, then narcissists’ self-promoting strategy pays off. Their desire for attention not only explained why they reported receiving more likes and retweets, but also explained why they were more likely to tweet about diet and exercise in both studies. In line with narcissists’ vanity about their appearance (Vazire et al., 2008) and desire for admiration from Twitter followers (Davenport et al., 2014), they may tweet about their diet and exercise routine because they want attention for being physically fit.

Machiavellianism

As predicted, people with Machiavellian traits were more likely to use Twitter than Facebook-only (Study 2), but the data provided few clues to explain Twitter’s appeal for these individuals. Contrary to hypotheses, Machiavellians were not significantly more likely to use Twitter for information-seeking or career promotion, nor did they tweet more frequently about intellectual topics or personal achievements in a purported attempt to impress influential others. If anything, they were less likely to use Twitter for attention-seeking, which explained why they tweeted less frequently about intellectual topics and diet/exercise. Because Machiavellians are concerned with reputational management (Jones & Paulhus, 2014), they may avoid tweeting about topics that have the potential to make them look pretentious or boastful. But this cautious strategy may come at a cost: Their aversion to attention-seeking explained why they received fewer likes/retweets on average to their tweets, suggesting that their low-key presence on Twitter does not generate much social reward. Although these data tell us what does not motivate Machiavellians and what they do not tweet about, the data do not tell us what does motivate them and what they do tweet about. One possibility is that Machiavellians are more likely to use Twitter to keep a cunning eye on friends and enemies alike. Such surveillance may allow them to gather information that is later used for manipulation and to gain social status.

Likability of Tweet Topics

Study 2 revealed that Twitter users most liked to read tweets/retweets about intellectual topics and least liked to read tweets about diet and exercise, consistent with other findings that information-sharing tweets are liked the most and personal tweets the least (Andre et al., 2012). This is not surprising given that Twitter users, on average, were higher in openness than nonusers in Studies 1 and 2, and these were the tweet topics that highly open people liked most and least. These results suggest that highly open people, by gravitating toward Twitter for the intellectual stimulation and career opportunities that it affords, may be influential in setting trends and what is considered popular and entertaining on Twitter. This may be particularly true for “public intellectuals,” actors, musicians, writers, artists, or other celebrities, who tend to amass large numbers of followers and likes/retweets.

If indeed Twitter is the kingdom of the intellectual and creative, then the current results also suggested that it may not be for the diet- and fitness-oriented. Study 2 participants tweeted least frequently about diet/exercise and liked these tweets the least, suggesting that posts about diet and exercise may be received more favorably in a social networking site like Instagram, where the sharing of photos may be more appealing to people concerned with fitness, health, and physical appearance. Paradoxically, however, Study 2 also found that people who frequently tweeted about diet/exercise reported receiving a significantly greater number of likes/retweets. Should not people who post about unpopular topics on Twitter receive fewer, not more, likes and retweets? Although most Twitter users may favor and tweet about intellectual topics, there may be a cadre of individuals from a health and fitness-oriented community who use Twitter to connect with each other and encourage each other’s health-related goals by supplying likes and retweets to each other’s posts. Indeed, tweeting about diet/exercise was predicted by not only attention-seeking motives but also social connection motives. What may matter most, then, is not what topics are deemed most likable by Twitter users in general, but the topics deemed most likable within one’s own social network. Indeed, the various niches within Twitter—for example, those dominated by certain politicians or celebrities—may produce tweets that are only deemed likable by the people within that niche.

Limitations and Future Directions

Although this research had several strengths—notably, that we conducted a preregistered replication of our findings in a different country—it also had several limitations. First, participants self-reported the frequency with which they tweeted about various topics and the number of likes/retweets they received, which may be prone to memory or social desirability biases. In particular, Machiavellians’ concern with reputation management may mean that they downplayed how frequently they tweeted about less socially desirable topics (e.g., diet/exercise), whereas narcissists—who enjoy showing off—may be especially likely to inflate the number of likes/retweets they receive. Future research should code participants’ actual tweets for various topic themes and record the number of likes/retweets for each, then examine associations with personality traits and motives for using Twitter. Further research could also examine whether people who tweet about topics popular within their own social network do indeed receive more likes/retweets, and whether this form of social reward enhances feelings of inclusion and well-being (Tobin et al., 2015). It may be the case that likes/retweets only enhance well-being among Twitter users who crave attention (i.e., narcissists, psychopaths, and introverts).

Second, our measures may require further refinement and expansion. In particular, our measure of informational motives for using Twitter reflected passive consumption of Twitter content rather than active generation. If future versions of this measure included items that reflected more active information exchange on Twitter, such as posting links to news stories, we might find that it is associated with personality traits such as openness. Indeed, we found that openness was significantly associated with career promotion, which tapped more active content generation (e.g., using Twitter to publicize one’s own creative output). Furthermore, it would be useful to measure a wider range of tweet topics. That people with psychopathic and Machiavellian traits are more likely to swear, use negative emotion words, and express anger in their tweets (Preotiuc-Pietro et al., 2017; Sumner et al., 2012) suggests that future research could test the predictors of tweeting about and liking for “darker” topics.

Finally, although we sampled Twitter users from two different countries, they may not be representative of the overall population of Twitter users, just as Twitter users may not be representative of larger populations. Even though we found that Twitter users were higher in openness than Facebook-only users in both samples, the effect sizes were small (rs = .10 and .09 in Studies 1 and 2, respectively) and require further replication in larger and more diverse samples.