Kevin Lewis

December 12, 2015

Interest in Babies Negatively Predicts Testosterone Responses to Sexual Visual Stimuli Among Heterosexual Young Men

Samuele Zilioli et al.
Psychological Science, forthcoming

Men's testosterone may be an important physiological mechanism mediating motivational and behavioral aspects of the mating/parenting trade-off not only over time but also in terms of stable differences between mating-oriented and parenting-oriented individuals. In this study, we tested the hypothesis that self-reported interest in babies is inversely related to testosterone reactivity to cues of short-term mating among heterosexual young men. Among 100 participants, interest in babies was related to a slow life-history strategy, as assessed by the Mini-K questionnaire, and negatively related to testosterone responses to an erotic video. Interest in babies was not associated with baseline testosterone levels or with testosterone reactivity to nonsexual social stimuli. These results provide the first evidence that differential testosterone reactivity to sexual stimuli may be an important aspect of individual differences in life-history strategies among human males.


Long-Term Consequences of Early Sexual Initiation on Young Adult Health: A Causal Inference Approach

Kari Kugler et al.
Journal of Early Adolescence, forthcoming

Although early sexual initiation has been linked to negative outcomes, it is unknown whether these effects are causal. In this study, we use propensity score methods to estimate the causal effect of early sexual initiation on young adult sexual risk behaviors and health outcomes using data from the National Longitudinal Study of Adolescent to Adult Health. We found that early sexual initiation predicted having two or more partners (for both males and females) and having a sexually transmitted infection in the past year (females only) but did not predict depressive symptoms in the past week (for either gender). These results underscore the importance of continued programmatic efforts to delay age of sexual initiation, particularly for females.


Men Ejaculate Larger Volumes of Semen, More Motile Sperm, and More Quickly when Exposed to Images of Novel Women

Paul Joseph et al.
Evolutionary Psychological Science, December 2015, Pages 195-200

Males in many species differentially allocate sperm and seminal fluid depending on certain social variables, including perceived sperm competition and female reproductive status. In some species, males reduce their investment in sperm quantity or quality upon repeated matings with the same female and increase such investment when mated to a novel female. We tested for effects of stimulus habituation and novelty on ejaculated semen parameters in humans. We analyzed ejaculates produced through masturbation with stimulation from sexually explicit films. When males were exposed successively to the same female six times, we saw no change in ejaculate parameters between the first and sixth exposures to the same female. However, ejaculate volume and total motile sperm count significantly increased when males were exposed to a novel female. Time to ejaculation also decreased significantly upon exposure to a novel female. Thus, our results suggest that human males ejaculate more quickly and invest more in ejaculates with novel females.


Do (non-American) Men Overestimate Women's Sexual Intentions?

Carin Perilloux et al.
Evolutionary Psychological Science, September 2015, Pages 150-154

Prior research has suggested that men overestimate women's sexual intentions. However, the bulk of the data supporting this view comes from participants from the USA. Here, we report three attempts to replicate this effect in samples from Chile, Spain, and France. While there was some evidence of overestimation of sexual intent by men on the aggregate measure, removing a single item decreases or even eliminates the sex difference in some of the cultures studied, suggesting that the aggregate effect is driven by a small number of particular behaviors. Furthermore, women from the USA appear to rate sexual intent differently from men and women in the other countries, whose ratings are relatively more homogeneous. While more work is needed, these results raise the possibility that the sex differences in sexual intent perception documented in the USA might not be cross-culturally universal.


Enhancing the Accuracy of Men's Perceptions of Women's Sexual Interest in the Laboratory

Teresa Treat et al.
Psychology of Violence, forthcoming

Objective: We evaluate a novel feedback-based procedure designed to enhance the accuracy of men's judgments of women's sexual interest in the laboratory, as misperception of sexual interest is implicated in male-initiated sexual aggression toward acquaintances.

Method: In an initial rating task, 183 undergraduate males judged the sexual interest of women in full-body photographs; the women varied along sexual interest, clothing style, and attractiveness dimensions. Half of the participants received feedback on their ratings. In a related transfer task, participants indicated whether women in photographs would respond positively to a sexual advance. History of sexual aggression and rape-supportive attitudes were assessed.

Results: Participants relied substantially on both affective and nonaffective cues when judging women's sexual interest. High-risk men relied less on affect and more on attractiveness. Feedback enhanced focus on women's affective cues and decreased focus on nonaffective cues for both low-risk and high-risk men. Feedback affected transfer performance indirectly, via altered cue usage in the training task.

Conclusions: The current work documents high-risk men's altered focus on women's affective and nonaffective cues and provides encouraging support for the potential use of a cognitive-training paradigm to enhance men's perceptions of women's sexual-interest cues, albeit to a lesser degree for high-risk men.


Time-Varying Risk Factors and Sexual Aggression Perpetration Among Male College Students

Martie Thompson et al.
Journal of Adolescent Health, December 2015, Pages 637-642

Purpose: Preventing sexual aggression (SA) can be informed by determining if time-varying risk factors differentiate men who follow different sexual aggression risk trajectories.

Methods: Data are from a longitudinal study with 795 college males surveyed at the end of each of their 4 years of college in 2008-2011. Repeated measures general linear models tested if changes in risk factors corresponded with sexual aggression trajectory membership.

Results: Changes in the risk factors corresponded with SA trajectories. Men who came to college with a history of SA but decreased their perpetration likelihood during college showed concurrent decreases in sexual compulsivity, impulsivity, hostile attitudes toward women, rape supportive beliefs, perceptions of peer approval of forced sex, and perceptions of peer pressure to have sex with many different women, and smaller increases in pornography use over their college years. Conversely, men who increased levels of SA over time demonstrated larger increases in risk factors in comparison to other trajectory groups.

Conclusions: The odds that males engaged in sexual aggression corresponded with changes in key risk factors. Risk factors were not static and interventions designed to alter them may lead to changes in sexual aggression risk.


Testosterone & gift-giving: Mating confidence moderates the association between digit ratios (2D:4D and rel2) and erotic gift-giving

Marcelo Vinhal Nepomuceno et al.
Personality and Individual Differences, March 2016, Pages 27-30

While prenatal testosterone and estrogen have been associated with various masculinized traits such as risk-taking, aggression, athletic ability, and sex drive, little is known regarding the impact of prenatal hormones on male romantic gift-giving. In a sample of 130 Caucasian men, we investigate the association between digit ratios (2D:4D and rel2), a proxy of exposure to prenatal testosterone-to-estrogen ratio, and the likelihood of offering erotic gifts to romantic partners. We hypothesize that men with highly masculinized (low) digit ratios and high mating confidence (i.e., the self-perceived ease with which one gains sexual access to others) will engage in greater erotic gift-giving. We find that masculinized digit ratios are associated with greater erotic gift-giving, but only among men with high mating confidence. Our findings suggest that high prenatal testosterone exposure and high prenatal estrogen exposure are likely to promote a greater desire to offer erotic gifts to a romantic partner, but that only men with high mating confidence have the courage to act on these desires.


Propose with a rose? Signaling in internet dating markets

Soohyung Lee & Muriel Niederle
Experimental Economics, December 2015, Pages 731-755

A growing number of papers theoretically study the effects of introducing a preference signaling mechanism. However, the empirical literature has had difficulty proving a basic tenet, namely that an agent has more success when the agent uses a signal. This paper provides evidence based on a field experiment in an online dating market. Participants are randomly endowed with two or eight "virtual roses" that a participant can use for free to signal special interest when asking for a date. Our results show that, by sending a rose, a person can substantially increase the chance of the offer being accepted, and this positive effect is neither because the rose attracts attention from recipients nor because the rose is associated with unobserved quality. Furthermore, we find evidence that roses increase the total number of dates, instead of crowding out offers without roses attached. Despite the positive effect of sending roses, a substantial fraction of participants do not fully utilize their endowment of roses and even those who exhaust their endowment on average do not properly use their roses to maximize their dating success.


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