Saturday, November 20, 2021

Changes in Penile-Vaginal Intercourse Frequency and Sexual Repertoire from 2009 to 2018: Findings from the National Survey of Sexual Health and Behavior

Changes in Penile-Vaginal Intercourse Frequency and Sexual Repertoire from 2009 to 2018: Findings from the National Survey of Sexual Health and Behavior. Debby Herbenick, Molly Rosenberg, Lilian Golzarri-Arroyo, J. Dennis Fortenberry & Tsung-chieh Fu. Archives of Sexual Behavior, Nov 19 2021.

Abstract: Solo and partnered sexual behaviors are relevant to health, well-being, and relationships. Recent research shows that sexual frequency has declined in the U.S. and in other countries; however, measurement has been imprecise. We used data from 14- to 49-year-old participants in the 2009 and 2018 waves of the National Survey of Sexual Health and Behavior (NSSHB), a confidential U.S. nationally representative survey that is conducted online. We aimed to: (1) assess changes in frequency of past-year penile-vaginal intercourse and (2) examine combinations of past-year sexual behaviors for each of the two waves. We hypothesized that we would observe lower frequency of penile-vaginal intercourse (PVI) from 2009 to 2018 and that we would observe greater engagement in sexual repertoires involving non-coital partnered behaviors (e.g., partnered masturbation, oral sex) in 2018 as compared to 2009. Participants were 4155 individuals from the 2009 NSSHB (Adolescents: 406 females, 414 males; Adults: 1591 women, 1744 men) and 4547 individuals from the 2018 NSSHB (Adolescents: 416 females, 411 males; Adults: 2007 women, 1713 men). Compared to adult participants in the 2009 NSSHB, adults in the 2018 NSSHB were significantly more likely to report no PVI in the prior year (28% in 2018 vs. 24% in 2009). A similar difference in proportions reporting no PVI in the prior year was observed among 14–17-year-old adolescents (89% in 2018 vs. 79% in 2009). Additionally, for both adolescents and adults, we observed decreases in all modes of partnered sex queried and, for adolescents, decreases in solo masturbation.


The present study used data from two waves of US nationally representative survey data to examine changes in sexual frequency and sexual repertoire between 2009 and 2018. Our research adds to the literature by using detailed measures of sexual behaviors beyond oral, vaginal, and anal intercourse; we did this in order to examine whether an explanation for declines in coital frequency might be explained by increases in non-coital behaviors. However, in addition to finding decreased PVI frequency in 2018 as compared to 2009, we found significant decreases across all partnered sexual behaviors assessed and, for adolescents, decreases in the proportion of adolescents reporting solo masturbation in the prior year as well. Overall, our findings are consistent with studies from multiple countries that have documented declines in sexual frequency. Because our sample was limited to individuals ages 14–49, we were unable to examine sexual behavior trends among people aged 50 and older. However, our findings align with studies that have found greater proportions of young people reporting no partnered sexual behaviors in the prior year (e.g., Burghardt et al., 2020; Ghaznavi et al., 2019; Ueda & Mercer, 2019; Ueda et al., 2020).

Other than Natsal and ASHR, most population-representative studies examining sexual frequency trends have not included those under age 18 and thus less has been known at the population level about sexual trends among younger adolescents. Our study extends the literature by including adolescents as young as 14 years old in our analytic sample (the youngest participants in Natsal and ASHR were 16 years old). Findings from our research also align with the US Youth Risk Behavior Survey (YRBS) which has demonstrated declining rates of high school students reporting having ever had sex over a similar period of time (e.g., 46% in 2009 vs. 38% in 2019) (Centers for Disease Control & Prevention, 2020a). The lower rates of adolescents’ reports of solo masturbation and PVI in 2018 are striking and deserve further study. These differences aren’t trivial: for example, the proportion of adolescents reporting neither solo nor partnered sexual behaviors (Latent Class 2) increased from 28.8% of young men and 49.5% of young women in 2009 to 43.3% of young men and 74.0% of young women in 2018.

A number of potentially convergent social and cultural changes may contribute to these substantial shifts in young people’s sexual behaviors. Widespread internet connectivity and emerging new technologies have added a new medium for providing sexual experiences outside of physical sex with a partner (e.g., sexting, easy access to sexually explicit media) (Doring et al., 2017; Twenge et al., 2017; Wright, 2013; Wright et al., 2013). Alcohol use has decreased among adolescents (Miech et al., 2019), and many young people have been engaged in conversations about sexual consent (such as through the #MeToo movement led by Tarana Burke, the Obama/Biden administration’s It’s On Us campaign, and recent high profile rape cases) (e.g., Armstrong & Mahone, 2017; PettyJohn et al., 2019). Also, more contemporary young people identify with non-heterosexual identities—including asexual identities—and more young people identify in gender expansive ways (Newport, 2018; Watson et al., 2020). It is also possible that secular trends reflect a tendency to have over-reported sexual behavior in earlier years, with more accurate reporting now as people become more comfortable with online presentations of themselves. These are among the many potential influences on adolescent sexual development and expression; subsequent research might examine how each of these may be contributing to changing patterns of sexual frequency and repertoire at the population level. Greater investment in understanding adolescent sexual development beyond risk is warranted, including how adolescents form, sustain, and interpret intimate relationships.

In terms of young adults, some research suggests that increasing use of computer games and social media may be implicated in young adults’ declining sexual activity (Lei & South, 2021). A recent analysis of 18–23-year-olds in 2007–2017 waves of the Transition to Adulthood Supplement of the Panel Study of Income Dynamics found that increased use of computer games, decreased alcohol use, decreased earnings, and declines in romantic relationship formation explained 76% of the decline in sexually active young adults in their sample (Lei & South, 2021). The median age at first marriage in the USA has also increased (US Census, 2020). It is worth noting that many published reports of adult sexual behavior (including ours) begin by describing the potential positive contributions of sex to health and quality of life. Media coverage of declining sexual activity tends to be similarly imbued with a sense that—in spite of risks that include unintended or mistimed pregnancy, sexually transmitted infections, and/or sad or lonely feelings connected to sex—partnered sex is generally pleasurable, joyful, connecting, and/or beneficial and thus declines in partnered sex among adults may be concerning (e.g., Feder, 2020; Julian, 2018). The age-old question on how much sex is too much and how little sex is not enough comes to mind. Given the impacts of the COVID-19 pandemic on physical and mental health, sexual behavior, relationships, and (for youth) in-person school and extracurricular activities, ongoing population-level research on sexual development and behaviors will be important (Finnerty et al., 2021; Rosenberg et al., 2021).

Positive aspects of adolescent partnered sex are less often highlighted. For example, in the section of the 2019 YRBS report that shows sexual behavior trends over time, the row that shows declining percentages of high school students who have “ever had sex” also features a green symbol (similar to the US traffic light system) which the legend describes as moving “in right direction” (Centers for Disease Control & Prevention, 2020b). The line between adolescence and adulthood has always been tenuous—perhaps particularly so when it comes to sexual behavior—but we must continue to interrogate how declining adolescent sexual activity is in the “right direction” yet declining adult sexual activity warrants concern. Solo and partnered adolescent sexual exploration are developmentally normative, offer opportunities for learning and joy, and are supportive of adult sexual development (Hensel et al., 2011; Robbins et al., 2011; Tolman & McClelland, 2011). Our findings have implications for those in policy roles, who might consider other helpful metrics of understanding changes in adolescent sexual experience—as an example, tracking the proportion of adolescent sex that is wanted, consensual, and even pleasurable may be illuminating.

Findings from our study also extend the existing literature by including solo masturbation among participants’ sexual behaviors. For both adults and adolescents, we found a latent class that was marked by engaging in solo masturbation. This highlights the important role of masturbation in people’s sexual expression; however, we note that the proportion of adolescents in the solitary masturbation Latent Class 1 decreased in 2018 compared to 2009, while the proportion reporting neither solo nor partnered sex increased. The 2009/2019 NSSHB waves did not ask participants how they feel about their sexual lives or whether they would like to have more sex or less sex than they are having; however, we note that Ueda and Mercer (2019) found that most Natsal participants who reported no prior year partnered sex but who did have prior partnered sexual experience were not dissatisfied with their sexual lives. Subsequent research should include more questions about people’s own subjective assessments of their sexual lives and feelings about their solo and partnered sexual behaviors.

Similarly, we need to understand more about how people’s subjective feelings about the sex they’ve experienced may shape their subsequent choices about sex. At the population level, the 2009 NSSHB demonstrated that anal intercourse had nearly doubled in lifetime prevalence since the National Health and Social Life Survey of the early 1990s. However, anal sex remained infrequent overall in any given year (though much more frequent among gay and bisexual men) (Dodge et al., 2016; Herbenick et al., 2010a). Anal sex has generally been rated as unappealing among US adults (Herbenick et al., 2017), and several qualitative studies examining anal intercourse between women and men found that—although anal sex behaviors were pleasurable to some—anal sex was often marked by pressure, coercion, lack of communication, fear, and pain among women (e.g., Fahs & Gonzalez, 2014; Fahs et al., 2015; Herbenick et al., 20152019a2019b; Jozkowski et al., 2014). Given these experiences, it is perhaps not surprising to have observed a decrease in anal intercourse between the 2009 and 2018 NSSHB, but that does not explain other decreases across all partnered sexual behaviors queried.

Recent research suggests that some sexual behaviors sometimes described as aggressive or as “rough sex” may have grown in prevalence in the USA, including choking during sex (which is technically a form of strangulation) (Herbenick et al., 2020; Herbenick et al., 2021a). Like anal sex behaviors, choking/strangulation is often wanted, asked for, and/or perceived as pleasurable (Herbenick et al., 2021a2021b). However, being choked/strangled has also been identified by many women as an example of something a partner has done during sex that made them feel scared (Herbenick et al., 2019a2019b), which is not surprising given that choking/strangulation is a common feature of sexual assault, intimate partner violence, and (in rare cases) is lethal even as part of consensual sex (e.g., Mcquown et al., 2016; Roma et al., 2013; Sendler, 2018). Subsequent research might examine the extent to which partnered sex may be declining, at least for some subset of the population, as a result of experiencing unpleasant or frightening experiences during otherwise consensual sex (e.g., being hit, punched, slapped, or choked without consent, or as a form of sexual compliance).

Strengths and Limitations

Our study was subject to several strengths and limitations. Among our strengths, we used data from the 2009 and 2018 waves of the NSSHB, a US nationally representative probability survey. The NSSHB is unique in that it includes items related to both sexual frequency and repertoire as well as a detailed assessment of solo and partnered sexual behaviors, which allowed for an examination of specific behavioral trends over two time periods. Other US national surveys, such as the GSS, YRBS, National Survey of Family Growth, and the National Longitudinal Study of Adolescent to Adult Health, are more limited in the scope of sexual behavior items assessed (Centers for Disease Control & Prevention, 2020a2020b; Harris et al., 2009; NORC at the University of Chicago, 2016). Both the 2009 and 2018 NSSHB waves were conducted through online, confidential surveys which has been shown to facilitate the reporting of sensitive behaviors. Among our limitations is that—in terms of frequency of sex—we were limited to comparisons of PVI (i.e., frequency of other sexual behaviors had not been assessed in both waves). Also, neither wave included an oversample of individuals who identify as lesbian, gay, bisexual, or asexual and thus—being a general population survey—findings largely reflect majority groups (e.g., heterosexual identified people). This becomes particularly apparent in examining the LCA classes, for which PVI loaded heavily on three of the four adult classes and two of the four adolescent classes. This is likely a fair representation of sex between males and females, given prior research showing the prevalence of PVI in many combinations of sex between women and men, and other research describing the intercourse imperative (Herbenick et al., 2010b; Richters et al., 2006). However, it does mean that these LCA classes do not reflect the rich diversity of all US adolescents and adults. Subsequent research might investigate similar constellations of intimate and/or sexual behaviors among dedicated samples of LGBTQ + individuals and/or among general population samples with sufficiently sized oversamples of LGBTQ + individuals.

Similarly, although the 2009/2018 NSSHB waves included a broad range of sexual behaviors for comparison, we would have liked to have been able to compare additional behaviors across waves but did not have additional items common among the two waves (e.g., kissing, cuddling, sex toy use, sexting, reading erotica, and/or watching pornography). As the NSSHB is focused on sexuality, we also did not have measures of more general behaviors (e.g., media use, substance use, mental health, physical health, perceived racism, political stress, etc.) that could have shed light on potential changes in sexual behaviors from 2009 to 2018. Finally, although our findings may help clinicians contextualize questions or concerns their clients have about how often people have sex, it is left to the client–clinician relationship, and to people themselves, to examine contexts of pleasure and satisfaction.

Mask-wearing improves the performance on a test that measures the capacity to infer other people mental states from their eye gaze

Trainin, N., & Yeshurun, Y. (2021). Reading the mind with a mask? Improvement in reading the mind in the eyes during the COVID-19 pandemic. Emotion. Nov 2021.

Abstract: The necessity to wear facial masks in public during the COVID-19 pandemic generated a unique situation where the eyes' importance as a visual source of information about individuals’ mental and emotional states greatly increased. In this study, we tested the hypothesis that experience in looking in interlocutor’s eyes (as a result of mask-wearing) will be correlated with enhanced performance on “reading the mind in the eyes test” (RMET). To test this, 87 participants performed an online version of the RMET at 2 different timepoints: when the mandatory mask wearing rules were put in place and a month later. We found that reported tendency to look at interlocutors' eyes, combined with experience in interacting with other people wearing masks, explained individual differences in RMET performance. Moreover, we found that individual’s tendency to look at interlocutors' eyes was correlated with change in performance in reading the mind in the eyes over this month. These results suggest that in addition to individual’s interest and motivation in understanding other’s mental state, continuous everyday experiences can result in an improved capacity for reading mental and emotional states by looking into individuals' eyes.

Pure 100% fruit juices – more than just a source of free sugars? A review of the evidence of their effect on risk of cardiovascular disease, type 2 diabetes and obesity

Pure 100% fruit juices – more than just a source of free sugars? A review of the evidence of their effect on risk of cardiovascular disease, type 2 diabetes and obesity. Carrie H. S. Ruxton, Emma Derbyshire, John L. Sievenpiper. Nutrition Bulletin, November 17 2021.

Abstract: Pure 100% fruit juice (100%FJ) provides a source of nutrients and bioactive substances, such as flavonoids, carotenoids and pectin, and counts as a serving of fruit in several countries. Nevertheless, 100%FJ has been the subject of debate since it also contains free sugars and provides less fibre than whole fruits. Sugar recommendations, when translated into policy, are designed to limit population consumption of free sugars. The World Health Organization (WHO) free sugars classification does not differentiate between added sugars and free sugars naturally occurring in 100%FJ and other foods. Hence, there is an implication that all sources of free sugars are equally detrimental and should be reduced. But is this the case? Since WHO’s original 2003 classification, a considerable amount of evidence has been published on 100%FJ and its impact on health. This paper provides an update, focussing on meta-analyses where available. These show protective associations for cardiovascular health at intakes of up to 200 ml/day, and significant improvements in vascular function, blood pressure and inflammation at higher intakes. Evidence on obesity, metabolic markers and type 2 diabetes risk – where studies have clearly differentiated consumption data for 100%FJ – suggests no clinically significant negative impact of 100%FJ at a wide range of intakes, unless diets are in positive energy balance. Data on nutrient adequacy from observational studies indicate positive associations between 100%FJ and intakes of whole fruits, vitamin C, vitamin A, folate and potassium. Since the evidence does not appear to show that drinking moderate amounts of 100%FJ is harmful to metabolic health or weight management, free sugars reduction policies should focus on sources that represent a genuine health risk and make a negligible contribution to nutrient adequacy. 100%FJ at intakes of up to 150 ml/day and consumed at mealtimes to protect dental health should remain part of 5 A DAY advice.

Both Trump & Clinton supporters display less positive attitudes towards the opposing supporters; significantly more wealth is destroyed if the opponent is an opposing voter, effect mainly driven by Clinton voters

The cost of a divided America: an experimental study into destructive behavior. Wladislaw Mill & John Morgan. Experimental Economics, Nov 19 2021.

Abstract: Does political polarization lead to dysfunctional behavior? To study this question, we investigate the attitudes of supporters of Donald Trump and of Hillary Clinton towards each other and how these attitudes affect spiteful behavior. We find that both Trump and Clinton supporters display less positive attitudes towards the opposing supporters compared to coinciding supporters. More importantly, we show that significantly more wealth is destroyed if the opponent is an opposing voter. This effect is mainly driven by Clinton voters. This provides the first experimental evidence that political polarization leads to destructive behavior.


Own spite measure

Our main measure was aimed to mimic basic market interactions where spite has been observed. More specifically, our measure reflects a simplified and condensed version of a second-price auction where one player can reduce the payoff of the opponent by increasing the own bid (see Kimbrough and Reiss 2012, for such a situation). This measure consists of three distribution-decisions upon money. These distributions are shown in Table 1. We call this our own spite measure. We asked the participants to decide three times among nine possible allocations, similar to the SVO-Slider measure by Murphy et al. (2011). The participants were told that either their decision or their opponent’s decision would be implemented, depending on a computerized random draw.

In all sets, the allocation with the highest payoff for the other player also maximizes the own payoff. However, any deviation from this allocation reduces the payoff of the other player and never increases the own payoff. In contrast to a standard dictator game—where there is a trade-off between the own payoff and the payoff of the opponent—in this game, the participants who do not choose the Pareto-efficient outcome do this in order to harm the other player. Therefore, any deviation from the Pareto-efficient outcome resembles spiteful behavior in a market setting and can be interpreted as spite or joy-of-destruction.Footnote25


This paper investigates whether partisanship—understood as the self-identified party affiliation—leads to dysfunctional behavior. In particular, we study which attitudes and, more importantly, which behavior voters show towards voters casting the same or the opposite vote. To the best of our knowledge, we are the first to study spite in a political context. For this purpose, we collected decisions of self-reported Clinton and Trump voters five times over a period of 4 years.

Most importantly, we were able to show that dysfunctional behavior—understood as the destruction of wealth—is significantly more likely if an opposing voter (outgroup) is impacted compared to a coinciding voter (ingroup). This effect is mainly driven by Clinton voters, who are significantly more likely to behave spitefully towards Trump voters compared towards fellow Clinton voters. This effect is not found for Trump voters—while Trump voters generally exhibit more spiteful behavior they do not differentiate between Trump voters and Clinton voters in their behavior.

These effects are supported by the attitudes of the voters: attitudes towards opposing voters are substantially and significantly more negative than attitudes towards coinciding voters. This effect is significantly stronger for Clinton voters. Further, the timing of the experiment does not substantially change attitudes, and it has no significant effect on dysfunctional behavior.

Several aspects of the results are worth elaborating on.

First, it is worth pointing out that we are not the first to find substantial polarization in the US (see Pew Research Center 2017a), but we are the first to show that this polarization leads to significantly increased destructive behavior (at least for Clinton voters). This is the main point of the paper, and this presents a significant and important contribution. We are able to show that even in a low key situation, like an online experiment, people are more likely to behave spitefully if matched with opposing voters. Hence, it seems plausible that in more salient situations where partisanship is even easier to detect and of more importance (e.g., collaborative work), the effect would be even stronger. More importantly, we know now that an increasing polarization leads to increased social and economic costs.

Second, it is interesting that the timing of the experiment hardly influenced attitudes and behavior. During this period Donald Trump won unexpectedly in 2016 and lost in 2020. However, these events seem not to spill over substantially into attitudes and behavior. This indicates that the destructive consequences of polarization are persistent and might be hard to eradicate.

Third, the differences between Clinton voters and Trump voters are worth elaborating on. On the one hand, it seems not too surprising that Trump voters did not differentiate between ingroup-members and outgroup-members because this would be perfectly in line with most papers on outgroup-bias who show that outgroup-bias lead rarely to purely hostile behavior (Brewer 1999, 2017; Balliet et al. 2014). It is also not too surprising that attitudes towards opposing voters are negative because this has also been shown in other papers (Tajfel 1970; Fowler and Kam 2007; Weisel and Böhm 2015).

However, it is puzzling that Clinton voters have significantly less positive attitudes towards their outgroup-members compared to Trump voters. More importantly, Clinton voters behave relatively more spitefully towards outgroup-members compared to ingroup-members—which cannot be found for Trump voters. This result is particularly interesting in the sense that it does not only show a mere group identity effect (as our aggregate results are driven by Clinton voters only) but an effect of political identity. The asymmetry in destructive behavior between Clinton and Trump voters suggests that political identity functions differently than just plain group identity.

One possible explanation for the asymmetry in behavior is that Trump voters are considered morally wrong in supporting Donald Trump. In that case, Mummendey and Wenzel (1999) argue theoretically that “inferior” groups are more likely to experience discrimination and hostility. Similarly, Brewer (1999) argues that negative discrimination might be present if participants are fighting for political power. Further support is provided by Parker and Janoff-Bulman (2013), who show that morality based groups lead to less positive emotions. More importantly, Weisel and Böhm (2015) demonstrate a significant increase in help avoidance if the group difference is morality-based: “When given the chance to benefit a strong-enmity outgroup, and even more so a morality-based outgroup, many group members decline to do so” (Weisel and Böhm 2015, p. 118). In Online Appendix we discuss differences in ascribed morality between Clinton and Trump voters in our experiment. We find that Clinton voters consider Trump voters substantially less moral than vice versa. In parallel, polls also reveal that a majority of Democrats express to feel angry going into the midterm elections of 2018 while only 30 percent of Republicans say the same.Footnote37 This indicates that the group difference might be morality-based and consequently drive hostile behavior.

Another possible explanation for the heterogeneous effects between Clinton and Trump voters is the expectation of Clinton voters that Trump voters will generally behave more spitefully and therefore retaliate in expectation. Trump voters on the other hand just generally are more prone to spiteful behavior independent of the opponent. Thus, Clinton voters just increase their spiteful behavior to match the spiteful behavior of Trump voters, which results in a heterogeneous effect.

However, these explanations are only conjectures and it might be valuable for future research to take a closer look at the justifications and motivations of Clinton and Trump supporters to engage in hostile behavior.

While we believe the results to be robust, some possible limitations should be noted. First, our experiment might be prone to experimenter demand effects as the opponent’s political orientation is made salient. While this saliency is essential for the treatment to work, it might reveal the experiment’s purpose and, thus, lead participants to shift their behavior. To obtain a bound on a possible demand effect we conducted a demand-effect treatment as suggested in de Quidt et al. (2018) and reported in detail in Online Appendix. Inducing demand does not change the behavior in our setting.Footnote38 Thus, while a demand effect cannot be excluded, we find that inducing a demand effect does not alter the behavior of participants substantially. Another limitation of our experiment is the non-representativeness of our sample. While our sample is much more representative of the US population than typical student samples, it is still not representative of the US population, as discussed in detail in supplementary material. Thus, such a selection might bias our results and reduce the generalizability of our findings. In Online Appendix, we try to deal with this issue by adjusting the weights of our estimations to make our sample artificially representative. While our results remain robust, we cannot exclude the possibility that our findings would differ using a representative sample. A similar concern is that sampling Trump and Clinton voters via MTurk might be problematic as, for example, Trump voters on MTurk are different from Trump voters in the general population. Reassuringly Huff and Tingley (2015) show that Mturkers behave similarly to the general population with regard to their voting behavior and suggest that Mturk is a great source to study voters. Further, we find striking similarities in demographics and voting patterns between our sample and nationally representative samples as discussed in supplementary material. Nevertheless, we should caution the reader that we cannot exclude the possibility that, for example, Clinton voters on Mturk are particularly spiteful compared to Clinton voters in general. It is also worth pointing out that we made our treatment rather salient by providing the political identity of their opponents to participants. While this was essential for the experiment it might reduce generalizablity. Partisan affiliation would most likely be less salient in the vast majority of human interaction. Thus, our experiment might not speak to everyday situations but primarily to environments where political identity is salient (such as around elections, rallies, etc.). Another concern we have to think about is possible spillover effects between the auction experiment (which is reported in Mill and Morgan (2020)) and the main task of this experiment (the spite task). It is possible that conducting an auction prior to the spite task might have increased spiteful behavior as participants might have been put into a competitive frame. Behavioral spillovers are discussed in detail in Dolan and Galizzi (2015). In particular, Cason and Gangadhara (2012), and Savikhin and Sheremeta (2012) find spillover effects between competitive games and cooperative games. However, we have two “competitive” games, which most likely will reduce the spillover effect. Further, we can see that the behavior in the SVO-task reported in Online Appendix is very similar to behavior reported in other studies (see also Footnote 19) which indicates that behavior has not been influenced substantially. More importantly, while such a spillover effect might shift overall behavior towards more spite, this spillover effect is identical between the treatments and also influences Clinton and Trump voters arguably to the same extend.Footnote39 Thus, while the absolute level of spite might have been affected by the auction, the auction is unlikely to account for our heterogeneous results.