Male more than female infants imitate propulsive motion

Few experimental studies investigate the mechanisms by which young children develop sex-typed activity preferences. Gender self-labeling followed by selective imitation of same-sex models currently is considered a primary socialization mechanism. Research with prenatally androgenized girls and non-human primates also suggests an innate male preference for activities that involve propulsive movement. Here we show that before children can label themselves by gender, 6- to 9-month-old male infants are more likely than female infants to imitate propulsive movements. Further, male infants’ increase in propulsive movement was linearly related to proportion of time viewing a male model’s propulsive movements. We propose that male sex-typed behavior develops from socialization mechanisms that build on a male predisposition to imitate propulsive motion.     

Heterosexual, lesbian, and gay male relationships: a comparison of couples in 1975 and 2000

This study examined the differences among lesbians, gay men, and heterosexuals at two points in time (1975 and 2000) using responses of 6,864 participants from two archival data sets. Groups were compared on variables representing equality of behaviors between partners in seven realms: traditionally "feminine" housework, traditionally "masculine" housework, finances, support, communication, requesting/refusing sex, and decision-making. In addition, the current study compared monogamy agreements and monogamy behaviors reported by the two cohorts of couple types. Overall, the results indicate that on the equality variables, there have been many statistically significant behavioral shifts among the different sexual orientations across 25 years. In addition, all couple types reported substantially greater rates of monogamy in the year 2000 than in 1975. The present study has important clinical implications for therapists working with couples because it provides new baseline evidence regarding how couples now interact with one another (especially about monogamy) and how this has shifted over time. In addition, it elucidates the differences that still exist between different couple types, which could serve to inform couple therapists as they strive to become more culturally competent working with same-sex couples.     

Effects of low survivability cues and participant sex on physiological and behavioral responses to sexual stimuli

According to life history theory, environmental cues indicating that one's future survivability is low increase reproductive effort. This suggests that exposure to low survivability cues will increase people's preparedness to engage in sex. However, according to sexual selection theory and parental investment theory, evolutionary pressures favored a more conservative sexual strategy among women compared to men. We therefore hypothesized that men, but not women, would respond to low survivability cues with increased sexual preparedness. Accordingly, both subliminal and supraliminal death primes (as compared with control primes) led men, but not women, to exhibit increased physiological arousal in response to sexual images (Study 1), and stronger approach-oriented behavioral responses to sexual images (Study 2). Theoretical implications for life history theory are discussed.     

The Flynn effect puzzle: A 30-year examination from the right tail of the ability distribution provides some missing pieces

The Flynn effect is the rise in IQ scores across the last eighty or more years documented in the general distribution of both industrialized and developing nations primarily on tests that require problem solving and non-verbal reasoning. However, whether the effect extends to the right tail (i.e., the top 5% of ability) remains unknown. The present study uses roughly 1.7 million scores of 7th-grade students on the SAT and ACT as well as scores of 5th- and 6th-grade students on the EXPLORE from 1981 to 2010 to investigate whether the effect operates in the right tail. The effect was found in the top 5% at a rate similar to the general distribution, providing evidence for the first time that the entire curve is likely increasing at a constant rate. The effect was also found for females as well as males, appears to still be continuing, is primarily concentrated on the mathematics subtests of the SAT, ACT, and EXPLORE, and operates similarly for both 5th and 6th as well as 7th graders in the right tail. These findings help clarify the nature of the effect and may suggest ways that potential causes can now be more meaningfully offered and evaluated.     

Digit ratio (2D:4D) and sex-role orientation: Further evidence and meta-analysis

Three new studies (N = 132, 623, 1112) did not yield hypothesized associations between digit ratio (2D:4D), an assumed negative correlate of prenatal testosterone, and psychometrically measured sex-role orientation (positive association with femininity, negative ones with masculinity and masculinity-femininity difference scores) among heterosexuals of either sex. Meta-analysis of the pertinent literature (N = 6311, 28 studies from 10 countries, 46% unpublished) showed only men’s (but not women’s) left-hand (but not right-hand) 2D:4D reliably related as expected (positively) to femininity. This effect was tiny (0.14% attributable variance) and possibly non-robust (crucially dependent on one large study included). Hence, the cumulative evidence does not support systematic, robust, noteworthy within-sex correlations between 2D:4D and the masculinity/femininity personality dimensions.     

Testosterone and domain-specific risk: Digit ratios (2D:4D and rel2) as predictors of recreational, financial, and social risk-taking behaviors

Prenatal testosterone has important effects on brain organization and future behavior. The second-to-fourth digit length ratio (2D:4D), a proxy of prenatal testosterone exposure, has been linked to a wide variety of sexually differentiated dispositions and behaviors. We examine the relationship between digit length ratios (2D:4D and rel2, the length of the second finger relative to the sum of the lengths of all four fingers) and risk-taking behaviors across five domains: financial, social, recreational, ethical, and health. In a sub-sample of male Caucasians (ethnically homogeneous), lower rel2 was predictive of greater financial, social, and recreational risk-taking, whereas lower 2D:4D was predictive of greater risk-taking in two domains (social and recreational). In the full male sub-sample (ethnically heterogeneous), the only significant correlation was a negative association between 2D:4D and financial risk. A composite measure of risk-taking across all five domains revealed that both rel2 and 2D:4D were negatively correlated with overall risk-taking in both male sub-samples. No significant correlations were found in the female sub-samples. Finally, men were more risk-seeking than women across all five contexts.     

Did you have sex with him? Do you love her? An in vivo test of sex differences in jealous interrogations

Abundant evidence suggests that between sex differences exist in the degree to which cues to sexual and emotional infidelity trigger jealousy. A criticism of this research is that this commonly found sex difference is a consequence of the hypothetical scenario and forced-choice methodology that is commonly employed. This study used a novel method to explore the nature of jealousy-fueled interrogations (N = 75) in the face of actual infidelities captured on video in the syndicated reality program Cheaters. Fifty-one episodes of Cheaters were content analyzed by six coders trained to watch each episode. As predicted, men were more likely than women to inquire about the sexual aspect of their partners’ infidelities, whereas women were more likely than men to inquire about the emotional aspect of their partners’ infidelities. These results suggest that humans have sex-differentiated damage assessment strategies dedicated to investigating the nature of their mates’ extra-pair relationships. Although previous studies have found sex differences in jealousy using prospective and retrospective reports, this is the first study to demonstrate sex differences in romantic jealousy in vivo. These findings refute the criticism that sex differences in jealousy are mere methodological artifacts. Discussion focuses on the benefits and limitations of content-analyzing Cheaters.     

Age-independent effects of pubertal status on behavioral constraint in healthy adolescents

Studies have examined age-related changes in personality traits from adolescence through young adulthood, finding that aspects of negative emotionality decrease while conscientiousness increases over time. Varied mechanisms may underlie these transitions, including puberty-driven hormonal changes. Here, healthy adolescents completed the Multidimensional Personality Questionnaire-Brief Form and self-report measures of pubertal status at baseline and after two years. Independent of age, pubertal status impacted primary trait scales of the MPQ-BF Constraint factor in a sex-specific manner. Females decreased in Constraint, and particularly Control, while males increased in Constraint, and particularly Harm Avoidance, with advancing puberty. Longitudinal analyses validated these findings for Control. Findings are discussed relative to males’ versus females’ achievement of optimal levels of behavioral control in adolescence.     

A longitudinal study of sex differences in intelligence at ages 7, 11 and 16 years

This paper presents the results of a longitudinal study of sex differences in intelligence as a test of Lynn’s (1994) hypothesis that from the age of 16 years males develop higher average intelligence than females. The results show that at the ages of 7 and 11 years girls have an IQ advantage of approximately 1 IQ point, but at the age of 16 years this changes in the same boys and girls to an IQ advantage of 1.8 IQ points for boys.     

Greed is good? Student disciplinary choice and self-reported psychopathy

The idea of the organisational psychopath has become not only popular in recent times, but increasingly relevant, thanks to the alleged role of high-profile members of the commercial sector in the global recession. To test the proposition that self-reported sub-clinical psychopathy might be disproportionately more common amongst those people electing to study commerce/business at University, 903 first-year students enrolled in a range of academic degrees completed a survey containing Levenson’s Self-Report Psychopathy Scale (Levenson, Kiehl, & Fitzpatrick, 1995) and Paulhus’ (1991) Balanced Inventory of Desirable Responding. Even after accounting for social desirability, commerce students reported higher levels of primary psychopathy than other students, regardless of sex.