Carnal Knowledge
Sex ratio dynamics and fluctuating selection on personality
Marco Del Giudice
Journal of Theoretical Biology, 21 March 2012, Pages 48-60
Abstract:
Fluctuating selection has often been proposed as an explanation for the maintenance of genetic variation in personality. Here I argue that the temporal dynamics of the sex ratio can be a powerful source of fluctuating selection on personality traits, and develop this hypothesis with respect to humans. First, I review evidence that sex ratios modulate a wide range of social processes related to mating and parenting. Since most personality traits affect mating and parenting behavior, changes in the sex ratio can be expected to result in variable selection on personality. I then show that the temporal dynamics of the sex ratio are intrinsically characterized by fluctuations at various timescales. Finally, I address a number of evolutionary genetic challenges to the hypothesis. I conclude that the sex ratio hypothesis is a plausible explanation of genetic variation in human personality, and may be fruitfully applied to other species as well.
----------------------
Anna Ziomkiewicz et al.
Hormones and Behavior, forthcoming
Abstract:
Personality and temperament were hypothesized to function as important factors affecting life history strategies. Recent research has demonstrated the association between temperamental traits and reproduction in humans, however, the underlying mechanisms are still poorly understood. This study presents evidence for an association between temperamental traits and woman's fecundity, as indicated by levels of ovarian steroid hormones during the menstrual cycle. On a large sample of urban, reproductive age women (n=108) we demonstrated that activity, endurance and emotional reactivity are associated with levels of estrogen and with a pattern of change of progesterone levels. Women high in activity, high in endurance and low in emotional reactivity had up to twice as high estradiol levels and more favorable progesterone profiles as women low in activity, low in endurance and high in emotional reactivity. The temperamental traits we measured highly overlap with extraversion, neuroticism and negative emotionality that were reported to correlate with reproductive success. Our findings thus suggest a possible explanation for these relationships, linking personality and women's reproductive success through a hormonal pathway.
----------------------
Changes in Women's Condom Use over the First Year of College
Jennifer Walsh et al.
Journal of Sex Research, forthcoming
Abstract:
Most college students are sexually active, engage in serially monogamous relationships, and use condoms inconsistently. Little is known about how condom use changes during college, and even less about variables predicting changes in use. Latent growth modeling (LGM) was used to examine changes in condom use during the first year of college among 279 women (mean age = 18.0; 74% White), who provided monthly reports on condom use frequency. At study entry, participants also reported on theoretically suggested risk and protective factors. Predictors of changes in use were examined after controlling for use of alternative contraception and partner type. LGM showed that women decreased their condom use during the first year of college. Levels of condom use were initially lower among women with strong alcohol-sexual risk expectancies, women with more previous sexual partners, women who did not smoke marijuana, and African American women. Decreases in condom use were greater among women with lower grade point averages, women from lower socioeconomic status families, and women who engaged in binge drinking. Reductions in condom use may place women at greater risk of unplanned pregnancy and sexually transmitted infections. Identification of factors associated with decreases in condom use will enable targeted educational and intervention efforts.
----------------------
I like who you like, but only if I like you: Female character affects mate-choice copying
Simon Chu
Personality and Individual Differences, April 2012, Pages 691-695
Abstract:
Mate-choice copying is shown when women imitate the mate-choice preferences of other women. We propose that the preferences of women with a pleasant character should be more influential than those of women with an unpleasant character and further suggest that this should apply only when the female demonstrates active interest in the male, rather than disinterest. Here, we presented women as having either a pleasant or unpleasant character and found that observing pleasant women looking at men increased women's preferences for those men, while observing unpleasant women looking at men had no effect on women's preferences. Furthermore, the effect of being looked at by a pleasant woman was heightened when she was smiling. This suggests that judgements of facial attractiveness can be socially influenced and that character affects the degree of influence.
----------------------
Consequences of Sex Education on Teen and Young Adult Sexual Behaviors and Outcomes
Laura Lindberg & Isaac Maddow-Zimet
Journal of Adolescent Health, February 2012, Page S26
Purpose: Formal sex education is a key strategy for promoting safer sexual behaviors and improved outcomes for American adolescents and young adults. This study examined whether formal sex education, particularly receipt of comprehensive sex education or abstinence-only instruction, is associated with safer sexual and reproductive health behaviors and outcomes using recent nationally-representative survey data.
Methods: Data used were from 4,691 males and females ages 15-24 from the 2006-08 National Survey of Family Growth. Weighted bivariate and multivariate analyses were conducted by gender using STATA, to estimate the associations of receipt of comprehensive (CSE) or only abstinence sex education before first sexual intercourse, and sexual behaviors and outcomes. We estimated a discrete-time logistic hazard rate model to examine the association between type of sex education received and the transition to first sexual intercourse, by age 19 and by age 24, incorporating censored cases.
Results: Two-thirds of females and 55% of males received CSE prior to first vaginal sex; about one in five respondents reported receiving only abstinence education prior to first sex. Sixteen percent of sexually experienced females and 24 % of sexually experienced males reported not receiving instruction in either topic prior to first sex. Receipt of formal sex education, regardless of type, was associated with a later onset of first sex for both genders, as compared to receiving no sex education. Receipt of comprehensive sex education was associated with being significantly more likely at first sex to use any contraception (OR=1.73, females, OR=1.91, males) or a condom (OR=1.62, females, OR=1.90, males), and being less likely to have an age discrepant partner (OR=.67, females, OR=.48, males). Females receiving comprehensive sex education were less likely to report that their first sex was unwanted (OR=.46). There were no significant associations between receiving only abstinence education and these outcomes. While there were no direct associations between receipt of comprehensive sex education and longer term behaviors and outcomes, there were indirect influences through later age at first sex, particularly among males, reducing their likelihood of having gotten a partner pregnant, multiple partnerships, and recent STD treatment, and indirectly increasing the likelihood of condom use at most recent sex.
Conclusions: Comprehensive sex education was associated with healthier sexual behaviors and outcomes as compared to not receiving instruction about either abstinence or methods of birth control. The protective influence of sex education is not limited to the questions of if or when to have sex, but extends to issues of partner selection, contraceptive use, and reproductive health outcomes. Creating access to medically accurate comprehensive sex education, and reducing socio-demographic disparities in the receipt of this education, should remain a primary goal of those concerned with the well-being of teens and young adults. Formal sex education offers one important opportunity to build a foundation of sexual health. At the same time, recognizing that maintaining sexual and reproductive health is a lifetime process, access to relevant information, services and support should remain available over the course of a lifetime.
----------------------
Unfortunate First Names: Effects of Name-Based Relational Devaluation and Interpersonal Neglect
Jochen Gebauer, Mark Leary & Wiebke Neberich
Social Psychological and Personality Science, forthcoming
Abstract:
Can negative first names cause interpersonal neglect? Study 1 (N = 968) compared extremely negatively named online-daters with extremely positively named online-daters. Study 2 (N = 4,070) compared less extreme groups - namely, online-daters with somewhat unattractive versus somewhat attractive first names. Study 3 (N = 6,775) compared online-daters with currently popular versus currently less popular first names, while controlling for name-popularity at birth. Across all studies, negatively named individuals were more neglected by other online-daters, as indicated by fewer first visits to their dating profiles. This form of neglect arguably mirrors a name-based life history of neglect, discrimination, prejudice, or even ostracism. Supporting this argument, neglect mediated the relation between negative names and lower self-esteem, more frequent smoking, and less education. These results are consistent with the name-based interpersonal neglect hypothesis: Negative names evoke negative interpersonal reactions, which in turn influence people's life outcomes for the worse.
----------------------
Relationship Formation and Stability in Emerging Adulthood: Do Sex Ratios Matter?
Tara Warner et al.
Social Forces, September 2011, Pages 269-295
Abstract:
Research links sex ratios with the likelihood of marriage and divorce. However, whether sex ratios similarly influence precursors to marriage (transitions in and out of dating or cohabiting relationships) is unknown. Utilizing data from the Toledo Adolescent Relationships Study and the 2000 U.S. Census, this study assesses whether sex ratios influence the formation and stability of emerging adults' romantic relationships. Findings show that relationship formation is unaffected by partner availability, yet the presence of partners increases women's odds of cohabiting, decreases men's odds of cohabiting, and increases number of dating partners and cheating among men. It appears that sex ratios influence not only transitions in and out of marriage, but also the process through which individuals search for and evaluate partners prior to marriage.
----------------------
Jeni Loftus & Brian Kelly
Journal of Adolescent Health, February 2012, Pages 195-197
Purpose: To examine the short-term effects on the sexual health of adolescent boys in age discordant relationships.
Methods: Weighted logistic regression analyses were conducted using data from waves 1 and 2 of the National Survey of Adolescent Health to determine the health effects of entry into an age discordant relationship on adolescent boys.
Results: Results indicate that boys involved in an age discordant relationship, in comparison with boys in a similar age relationship, had higher odds of having had sexual intercourse (OR = 2.92), having got a partner pregnant (OR = 1.89), having been diagnosed with STD (OR = 4.41), and having lost one's virginity (OR = 3.39). Analyses on the sexually active subset reveal no significant relationship between involvement in an age discordant relationship and birth control use broadly, or condom use specifically, at their most recent sexual intercourse.
Conclusion: In general, entering into an age discordant relationship as a younger partner is associated with some adverse sexual health effects for adolescent boys. Thus, some outcomes that were demonstrated in previous research to be problematic for adolescent girls dating significantly older males are similarly problematic for adolescent boys dating older females.
----------------------
Managing an Attractive Impression by Using Alcohol: Evidence From Two Daily Diary Studies
Megan O'Grady et al.
Basic and Applied Social Psychology, Winter 2012, Pages 76-87
Abstract:
Two studies investigate impression management processes and alcohol use. In both studies, participants completed the Fear of Negative Evaluation scale and then a 21-day survey. In Study 1, participants reported daily desired impression and drinking. Men drank more than women; however, this effect was stronger on days in which they wanted to appear attractive as compared to other desired impressions. In Study 2, participants reported desired attractiveness, sex-composition, and drinking during social interactions. Attractiveness desires during social interactions related positively to drinking for men when interacting with mixed-sex others, and for women when interacting with mixed- and single-sex others.
----------------------
Social Exchange and the Progression of Sexual Relationships in Emerging Adulthood
Sharon Sassler & Kara Joyner
Social Forces, September 2011, Pages 223-245
Abstract:
Research has extensively examined matching on race and other characteristics in cohabitation and marriage, but it has generally disregarded sexual and romantic relationships. Using data from the 2002 National Survey of Family Growth and the National Longitudinal Study of Adolescent Health, we examine the tempo of key transitions in the recent relationships of young adults ages 18-24. We focus on how the racial mix of partners in relationships is associated with the timing of sex, cohabitation and marriage. We find evidence that relationships between white men and minority women proceed more rapidly from romance to sexual involvement and from sexual involvement to cohabitation compared to relationships involving other racial combinations. Our findings have important implications for social exchange perspectives on mate selection.
----------------------
The Role of Skin Color on Hispanic Women's Perceptions of Attractiveness
Dionne Stephens & Paula Fernández
Hispanic Journal of Behavioral Sciences, February 2012, Pages 77-94
Abstract:
This study relies on qualitative methods to investigate Hispanic women's skin color perceptions. The primary goal is to identify the relevance of these perceptions on their beliefs about their own physical attractiveness. Thirty-four self-identified White-Hispanic women attending a large Hispanic Serving Institution in the southeastern United States were interviewed for this study. Unlike previous research findings on Hispanic women's skin color preferences, findings identified a "tan" skin color as preferred; pale skin was viewed as "plain" and unattractive. This preference was associated with four themes about physical attractiveness: (1) desirability among their peer groups, (2) increased value in dating contexts, (3) sexual appeal to men, and (4) marker of Hispanic identity in social contexts. Findings from this study are important for those researchers addressing identity development and relationship issues among Hispanic populations in the United States.
----------------------
Megan Dillow, Walid Afifi & Masaki Matsunaga
Journal of Social and Personal Relationships, February 2012, Pages 28-51
Abstract:
This four-study investigation examines the role of perceived partner uniqueness (PPU) in determining the immediate communicative and relational consequences of transgressions in romantic relationships. Study 1 reports a psychometrically sound PPU measure distinct from similar constructs. Study 2 reveals that PPU is associated with conflict responses following the discovery of infidelity, which then predict termination intentions. Study 3 involves an experimentally manipulated flirting transgression between one partner and a confederate, witnessed by the other partner, which provides a controlled examination of PPU on partners' non-verbal immediacy. Study 4 expands and refines PPU measurement, and tests PPU's ability to predict relational decisions beyond other partner-focused constructs. Results support the utility of PPU as a unique construct with communicative and relational impacts.
----------------------
Evolution of ape and human mating systems
Wataru Nakahashi & Shiro Horiuchi
Journal of Theoretical Biology, 7 March 2012, Pages 56-64
Abstract:
Humans (Homo sapiens) generally form multiple-male-multiple-female groups that include multiple family units. This social structure is maintained because dominant males do not monopolize females and, thus, allow subordinate males to mate, and human females are not generally promiscuous. Although apes show great variation in mating systems, the human-type mating system is unique among primates. The mating systems of apes and humans have evolved in response to their adaptation to different ecological conditions. We created and analyzed a mathematical model to investigate the conditions for each type of mating system to evolve. We focused on the mating strategy of alpha males and the mating and grouping strategies of females. We defined the human-type mating system as one with multiple-male-multiple-female groups in which alpha males do not monopolize females and females are not promiscuous. We demonstrated that the human-type mating system could evolve when a large group is advantageous and the cost of female promiscuity is great. Moreover, the human- and Pan-type mating systems can be bistable. Our results shed light on the origin of the human family.
----------------------
Intrasexual competition among males: Competitive towards men, prosocial towards women
Abraham Buunk & Karlijn Massar
Personality and Individual Differences, forthcoming
Abstract:
In a study among 40 males and 56 females, participants engaged in a series of decomposed social games in which they had to divide resources between themselves and either a same-sex or an opposite sex other. As predicted on the basis of theorizing on sexual selection, males behaved more competitively towards another man than towards a woman, whereas women did not distinguish between men and women in their degree of competitiveness. At the same time, men behaved more prosocially towards women than women did towards men. In addition, after dividing resources between themselves and another man in the decomposed game task, men showed higher levels of intrasexual competition (assessed with a questionnaire) than after dividing resources between themselves and a woman, whereas for women the sex of the other did not affect their level of intrasexual competition.
----------------------
Pulling the strings: Effects of friend and parent opinions on dating choices
Brittany Wright & Colleen Sinclair
Personal Relationships, forthcoming
Abstract:
The current study examined how dating choices are affected when individuals are faced with social network opinions that are in agreement or disagreement about the quality of potential dates. In a virtual dating game paradigm, participants spoke to 2 potential romantic partners online and received positive and/or negative feedback ostensibly from their friend and parent about 1 of the partners. The study employed a 2 (parent opinion: approve, disapprove) × 2 (friend opinion: approve, disapprove) × 2 (interaction partner: evaluated target, control target-within subjects) mixed factorial design. Friend opinion influenced who the participants liked, whereas parental opinion was influential when participants relied on their parent for more resources than their friend. In the end, though, only friend opinion predicted dating choice.
----------------------
Jenée James et al.
Developmental Psychology, forthcoming
Abstract:
The current study tested sex-specific pathways to early puberty, sexual debut, and sexual risk taking, as specified by an integrated evolutionary-developmental model of adolescent sexual development and behavior. In a prospective study of 238 adolescents (n = 129 girls and n = 109 boys) followed from approximately 12-18 years of age, we tested for longitudinal relations between ecological stressors, family relationships, pubertal maturation, self-perceived mate value, and sexual risk taking in both boys and girls. Consistent with the theory, (a) higher levels of familial and ecological stress predicted earlier sexual debut and greater sexual risk taking; (b) pubertal maturation partially mediated these relations among girls but not among boys; (c) father absence had unique effects on female sexual outcomes but not on male sexual outcomes; (d) higher self-perceived mate value directly predicted earlier sexual debut and, through it, greater sexual risk taking; and (e) relations between pubertal maturation and early sexual debut were partially mediated by higher self-perceived mate value in boys but not in girls. Discussion focuses on the contribution of an integrated evolutionary-developmental theory to the adolescent sexual health literature.
----------------------
Race and sexual behavior predict uptake of the human papillomavirus vaccine
Kate Keenan, Alison Hipwell & Stephanie Stepp
Health Psychology, January 2012, Pages 31-34
Objective: To identify predictors of human papillomavirus (HPV) vaccination initiation by girls at high risk for HPV infection.
Method: Participants were 2,098 girls enrolled in the ongoing Pittsburgh Girls Study, who were between the ages of 12 and 15 years in 2008, and their primary caregivers. The study was conducted in the 2 years after the deployment of the first HPV vaccine approved by the U.S. Food and Drug Administration. Primary caregivers were asked about HPV vaccine uptake. Girls were interviewed about pubertal development and sexually intimate behavior.
Results: Approximately 60% of the girls had initiated the HPV vaccine in the past year. Among the hypothesized predictors of initiation, African-American race decreased the likelihood and level of sexually intimate behavior in the previous year increased the likelihood of uptake. Controlling for receipt of public assistance, African-American girls were close to 40% less likely to be vaccinated than European-American girls.
Conclusion: Racial disparities in use of preventive interventions such as the HPV vaccine exist. Lack of information about public financing of the vaccine, timing of vaccination relative to sexual activity, and perceptions of preventive value may limit uptake among those at highest risk for infection and negative sequelae from infection. Further research to probe knowledge and attitudes toward HPV vaccination and the impact of the media on vaccine initiation and uptake may reveal specific targets of intervention.
----------------------
Sarah Clark, Peter Kilmarx & Katrina Kretsinger
Health Affairs, December 2011, Pages 2355-2361
Abstract:
Studies have shown that male circumcision greatly reduces the risk for heterosexual transmission of HIV, other sexually transmitted infections, infant urinary tract infections, penile cancer, and other adverse health outcomes. Given recent data regarding these health benefits and the cost-effectiveness of newborn male circumcision, national policy makers are developing new recommendations regarding circumcision for newborn, adolescent, and adult males. To investigate the implications, this study assessed insurance coverage and reimbursement for routine newborn and adult male circumcision in private and public health plans in 2009. We found that coverage varies across private and public payers. Private insurance provides far broader coverage than state Medicaid programs for routine newborn male circumcision. Specifically, Medicaid programs in seventeen states do not cover it, even though low-income populations have a higher risk of HIV and other sexually transmitted diseases compared to higher-income groups. For adult male circumcision, coverage is generally sparse across public and private plans. Presentation of evidence-based recommendations-for example, from the Centers for Disease Control and Prevention-may be necessary if coverage for newborn and adult male circumcision is to be expanded.
----------------------
Lauren Papp, Jennifer Danielewicz & Crystal Cayemberg
Cyberpsychology, Behavior, and Social Networking, February 2012, Pages 85-90
Abstract:
Extending previous research on positive and negative correlates of Facebook use for individuals' outcomes, this study examined male and female dating partners' (n=58 couples) Facebook use and portrayals of their intimate relationship on the Facebook profile. Confirming hypotheses from compatibility theories of mate selection, partners demonstrated similar Facebook intensity (e.g., usage, connection to Facebook), and were highly likely to portray their relationship on their Facebook profiles in similar ways (i.e., display partnered status and show their partner in profile picture). These Facebook profile choices played a role in the overall functioning of the relationship, with males' indications of a partnered status linked with higher levels of their own and their partners' (marginal) relationship satisfaction, and females' displays of their partner in their profile picture linked with higher levels of their own and their partners' relationship satisfaction. Finally, male and female reports of having had disagreements over the Facebook relationship status was associated with lower level of females' but not males' relationship satisfaction, after accounting for global verbal conflict. Thus, the findings point to the unique contribution of Facebook disagreements to intimate relationship functioning. Results from this study encourage continued examination of technology use and behaviors in contexts of intimate relationships.
----------------------
Female Self-Sexualization in MySpace.com Personal Profile Photographs
Cougar Hall, Joshua West & Emily McIntyre
Sexuality & Culture, March 2012, Pages 1-16
Abstract:
This article reports the results of a content analysis of female self-sexualization in personal profile pictures on MySpace.com (N = 24,000). Photographs were analyzed according to three measures: ritualization of subordination, body display, and objectification. Trained evaluators coded the photographs for each measure by race/ethnicity, body type, sexual orientation, and education level. Findings reveal that rates of ritualization of subordination were significantly higher for Hispanics, average body types, and bisexuals. Body display and objectification were both significantly higher for Blacks and Hispanics, bisexuals, and women with higher education levels. Body display and objectification rates were significantly lower for larger body types while body display alone was significantly lower for lesbians. Overall self-sexualizing behavior in this study sample is low based upon study measures. Images presented on MySpace.com do reveal, however, an acceptance of constrained and stereotypical notions regarding both gender and sex roles.
----------------------
Ink and Holes: Correlates and Predictive Associations of Body Modification Among Adolescents
Richard Dukes & Judith Stein
Youth & Society, December 2011, Pages 1547-1569
Abstract:
We examined correlates and predictive associations of tattoos and body piercings among 1,462 Colorado students in grades 9 to 12. More boys (19%) than girls (17%) reported tattoos, but more girls (42%) than boys (16%) reported piercings (earlobes not included). Older students reported more body modification. Structural equation models showed that although girls generally reported less deviant behavior, the indirect effect of female gender mediated through piercings was toward greater deviance that was not an artifact of girls having more piercings. Pierced girls were less school oriented than girls without piercings; they reported more substance use than boys without piercings, and pierced girls did not differ from boys in weapons possession and delinquency. However, among pierced respondents, boys still reported a greater number of deviant behaviors than girls. Educators and other adults should become aware of the possible at-risk status of body-modified adolescents, especially among girls who have piercings.
----------------------
Female reproductive tract form drives the evolution of complex sperm morphology
Dawn Higginson et al.
Proceedings of the National Academy of Sciences, forthcoming
Abstract:
The coevolution of female mate preferences and exaggerated male traits is a fundamental prediction of many sexual selection models, but has largely defied testing due to the challenges of quantifying the sensory and cognitive bases of female preferences. We overcome this difficulty by focusing on postcopulatory sexual selection, where readily quantifiable female reproductive tract structures are capable of biasing paternity in favor of preferred sperm morphologies and thus represent a proximate mechanism of female mate choice when ejaculates from multiple males overlap within the tract. Here, we use phylogenetically controlled generalized least squares and logistic regression to test whether the evolution of female reproductive tract design might have driven the evolution of complex, multivariate sperm form in a family of aquatic beetles. The results indicate that female reproductive tracts have undergone extensive diversification in diving beetles, with remodeling of size and shape of several organs and structures being significantly associated with changes in sperm size, head shape, gains/losses of conjugation and conjugate size. Further, results of Bayesian analyses suggest that the loss of sperm conjugation is driven by elongation of the female reproductive tract. Behavioral and ultrastructural examination of sperm conjugates stored in the female tract indicates that conjugates anchor in optimal positions for fertilization. The results underscore the importance of postcopulatory sexual selection as an agent of diversification.