Opposite-sex Pairs Research Articles

Examining perceptions of blame and homophobia: the impact of sexual orientation on non-consensual intimate image dissemination

ABSTRACT Our aim was to investigate whether blame attribution toward same-sex victims compared to heterosexual victims of NCII and offense severity evaluation were associated with homophobic attitudes. Two-hundred-and-sixty men and women, who described themselves as heterosexual, were presented with vignettes depicting an NCII offense in which the intimate material was released by the victim’s ex-intimate partner. Victim’s and perpetrator’s sex were manipulated (i.e. gay, lesbian, heterosexual). We found that higher levels of homophobic attitudes were linked with lower severity attributions for same-sex perpetrator-victim pairs, but not for opposite-sex pairs. Additionally, higher levels of homophobic attitudes were associated with lower blame attributed to the perpetrator, but higher blame attributed to the victim. Sex differences were found, revealing that men tended to attribute higher blame to same-sex victims compared to heterosexual victims, whereas women showed no significant differences in blame attribution based on victim’s sexual orientation. Men also exhibited higher levels of homophobic attitudes than did women. The study reveals the impact of homophobic attitudes on blame allocation in NCII cases, emphasizing the need for targeted interventions to reduce victim-blaming and promote inclusivity. The role of technology in shaping behavior was also underscored, urging consideration of sex and sexual orientation in response strategies.

Gene-environment interaction analysis of school quality and educational inequality

We study to what extent schools increase or decrease environmental and genetic influences on educational performance. Building on behavioral genetics literature on gene-environment interactions and sociological literature on the compensating and amplifying effects of schools on inequality, we investigate whether the role of genes and the shared environment is larger or smaller in higher-quality school environments. We apply twin models to Dutch administrative data on the educational performance of 18,384 same-sex and 11,050 opposite-sex twin pairs, enriched with data on the quality of primary schools. Our results show that school quality does not moderate genetic and shared-environmental influences on educational performance once the moderation by SES is considered. We find a gene-environment interplay for school SES: genetic variance decreases with increasing school SES. This school SES effect partly reflects parental SES influences. Yet, parental SES does not account for all the school SES moderation, suggesting that school-based processes play a role too.

A 10-Year Observational Study on Twin Pregnancy: Role of Fetal Sex Pairing on Obstetric Outcome.

Fetal sex contributes to the determination of obstetric outcome, as pregnancies carrying male babies seem to have an increased risk of maternal-fetal complications. Most studies have been conducted on singleton pregnancies, whereas less evidence is available for twins. A 10-year retrospective observational study was conducted on a cohort of 1180 women with twin pregnancy delivered at a single tertiary hospital. Clinical data on maternal characteristics, and obstetric and neonatal outcomes were collected, and the analysis was performed on monochorionic (MC) and dichorionic (DC) diamniotic twins separately. The group of DC twins included 837 cases, and those conceived by assisted reproductive technologies (ART) were more likely to have one or both female fetuses rather than males. The incidence of hypertensive disorders of pregnancy (HDP) was higher in same-sex pairs than in opposite-sex pairs. No differences were found regarding other obstetric and neonatal outcomes among the three sex-pairing groups. The MC twins group included 228 cases, and in female-carrying pregnancies a higher incidence of gestational diabetes (GDM) was observed compared to the male group. Furthermore, male pairs had significantly lower Apgar scores than females. Fetal sex seems to have a mild effect in twins compared to singleton pregnancies, suggesting a more complex set of factors contributing to pregnancy outcome in multiple pregnancies. However, we observed a higher incidence of HDP among same-sex DC pairs, a higher rate of GDM among MC female-female pairs, and a worse adaptation to extrauterine life among male-male pairs in MC twins.

Objectively measured facial traits predict in-person evaluations of facial attractiveness and prosociality in speed-dating partners

Many studies have investigated whether facial averageness, masculinity, and similarity are associated with facial attractiveness. These studies have relied on ratings of images of real or digitally morphed faces. It is important to establish whether past findings translate to real-life, face-to-face evaluations of potential partners; lack of effects in this context would cast doubt on the evolutionary relevance of previous findings. Further, previous studies have not considered that, by definition, faces that are more similar to the average face (i.e. higher in averageness) tend to be more similar to raters' faces. Therefore, these image-rating studies, which separately found that averageness and (in some cases) similarity are attractive, are confounded. To address these issues, we conducted a laboratory-based speed-dating study of 682 participants with objectively measured facial traits, where opposite-sex pairs rated each other on facial attractiveness and prosociality. We found that facial attractiveness was predicted separately by averageness and by similarity (to the rater), but with both variables in the same model, neither uniquely predicted attractiveness. Similarity, but not averageness, predicted prosociality ratings. Facial masculinity was positively and negatively associated with facial attractiveness ratings of men and women, respectively. These results confirm, in real-life interactions, some key findings from image-rating studies but raise questions about others, notably the attractiveness of facial averageness.

Sex differences in lifetime prevalence of low back pain: A multinational study of opposite-sex twin pairs.

Low back pain (LBP) is more likely to occur in people with a family history of this condition, highlighting the importance of accounting for familial factors when studying the individual risk of LBP. We conducted a study of opposite-sex twin pairs investigating sex differences in LBP while accounting for (genetic and shared environmental) familial factors. We applied a matched co-twin control design to study 795 adult opposite-sex pairs from Australia, Spain, and the United States (US). We used mixed-effects logistic regression to assess the within-pair association between female sex and lifetime prevalence of LBP in unadjusted and adjusted models for body-mass-index, and depression, as well as interactions between female sex and age (<median age vs. ≥median age) in this association. The mean age of the sample was 47.4 years (Standard Deviation = 16.5). The adjusted odds ratio (aOR) of the association between sex and LBP in the merged sample was 1.11 (95% Confidence Interval = 0.88-1.40), with 87.4% of the variance in the studied association explained by between-site heterogeneity (Q test; p = 0.001). Females had 2.37 (95% CI: 1.48-3.78) higher odds of LBP compared to their male co-twins in the Spanish sample (adjusted), but a sex association was not found in the Australian nor US samples. We found no evidence of the association between sex and LBP in our merged sample. Between-population differences (i.e. cultural background or health system characteristics) are likely to be major factors leading to variation in the sex association with LBP when familial factors are accounted for. Our study of adult opposite-sex twin pairs found no evidence of an association between female sex and lifetime prevalence of low back pain after controlling for familial factors in the merged sample from Australia, Spain and USA, contrary to findings from previous studies of unrelated individuals. Our findings indicate potentially relevant between-country genetic, cultural and environmental differences which may need to be considered for optimal and individualized strategies for the prevention and management of low back pain across the lifespan.

Odor exploration behavior of the domestic pig (Sus scrofa) as indicator of enriching properties of odors.

Although the sense of smell in pigs is widely recognized as being highly developed, surprisingly little is known about their sensory ability. This study aimed to (a) identify which non-social odors pigs were able to detect and distinguish between, (b) investigate the types of behavior expressed when exploring odors and, (c) compare pigs' responses to the different odors to evaluate their interest in the odors. Growing pigs (N = 192) of crossbred commercial breeds were enrolled in the experiment (32-110 days of age, weighing 64.9 ± 10.1kg). Littermate pairs of opposite sex were tested in test pens with two odor insertion points in the pen wall, 55 cm apart. All pigs were habituated to the test pens and experimenters. Twelve odors were tested (eight essential oils and four synthetic perfumes) in groups of three odors, with each pig pair tested once with one set of three odors (all possible orders of the three odors were tested on 24 pairs in total), always against a non-odor control (demineralized water). In a test, each of the three odors were presented during three trials in a row (a total of 9 trials per test; trial duration: 1 min; inter-trial breaks: 2 min; total test duration: 25 min). Response variables included: duration of sniffing, feeding-related behavior (licking, biting and rooting), agonistic behavior (biting, displacement and pushing) and no approach of the odor or control, recorded throughout each 1-min odor presentation. All pigs sniffed an odor less when repeatedly presented (LMM: all odors P < 0.05), and significantly longer at the subsequent presentation of a new odor [LMM (3rd vs. 1st presentations): P < 0.001]. Specific odor and odor type (essential oil vs. synthetic perfume) had no significant effect on sniffing duration. Overall, feeding-related behavior and agonistic behavior were expressed significantly more when pigs explored the odor compared with the control insertion point (Paired t-tests: P < 0.001), and specific odor only affected the expression of feeding-related behavior. Collectively, pigs express sniffing, agonistic, and feeding-related behavior when exploring odors, which suggests that pigs perceive odors of non-social origin as a resource. Odors may thus constitute relevant enrichment material for pigs.

Prolonged partner separation erodes nucleus accumbens transcriptional signatures of pair bonding in male prairie voles.

The loss of a spouse is often cited as the most traumatic event in a person's life. However, for most people, the severity of grief and its maladaptive effects subside over time via an understudied adaptive process. Like humans, socially monogamous prairie voles (Microtus ochrogaster) form opposite-sex pair bonds, and upon partner separation, show stress phenotypes that diminish over time. We test the hypothesis that extended partner separation diminishes pair bond-associated behaviors and causes pair bond transcriptional signatures to erode. Pairs were cohoused for 2 weeks and then either remained paired or were separated for 48hrs or 4wks before collecting fresh nucleus accumbens tissue for RNAseq. In a separate cohort, we assessed partner-directed affiliation at these time points. We found that these behaviors persist despite prolonged separation in both same-sex and opposite-sex paired voles. Opposite-sex pair bonding led to changes in accumbal transcription that were stably maintained while animals remained paired but eroded following prolonged partner separation. Eroded genes are associated with gliogenesis and myelination, suggesting a previously undescribed role for glia in pair bonding and loss. Further, we pioneered neuron-specific translating ribosomal affinity purification in voles. Neuronally-enriched transcriptional changes revealed dopaminergic-, mitochondrial-, and steroid hormone signaling-associated gene clusters sensitive to acute pair bond disruption and loss adaptation. Our results suggest that partner separation erodes transcriptomic signatures of pair bonding despite core behavioral features of the bond remaining intact, revealing potential molecular processes priming a vole to be able to form a new bond.

Sex differences in ocular biometric measurements: A twin study.

Gender differences in ocular biometric measurements of opposite-sex and same-sex twin pairs are still unclear. We aimed to investigate the difference between ocular biometric measurements in adolescent twin pairs. This retrospective study included a total of 64 eyes of 64 adolescents from 32 twins. The ocular biometric measurements and refractive prediction error (RE) were acquired from four groups of dizygotic (DZ) twins: boys from same-sex twin-pairs (SSM, n = 20), boys from opposite-sex twin-pairs (OSM, n = 8), girls from opposite-sex twin-pairs (OSF, n = 8), and girls from same-sex twin-pairs (SSF, n = 29). The mean age of the patient was 9.92 ± 2.84 (range: 6-18) years. Overall, boys had higher height, AL, WTW, but lower Ks, and Kf than girls (p < 0.05). Specifically, SSF was found to have the lowest lens thickness (LT), anterior chamber depth (ACD), central corneal thickness (CCT), white to white (WTW), and axial length (AL) levels, while the highest keratometry readings in the flat (Kf) and steep (Ks) levels compared with OSM, OSF, and SSM adolescents (p < 0.05). Compared with the OSF adolescents, ACD levels of the SSF adolescents were significantly lower [(2.99 ± 0.35) and (3.26 ± 0.15) mm, p = 0.033)], but Kf indicator was significantly larger [(43.93 ± 1.64) and (42.91 ± 1.75), p = 0.016)]. Our study indicates that there was a significant difference in ocular biometric measurements between twin pairs, and sharing the uterus with a DZ twin SSF has smaller ocular indicator measurements. Our findings provide information on the eyeball and refractive development in adolescents.

Detecting Grooming Behaviors in Same-Sex versus Opposite-Sex Child Sexual Abuse

ABSTRACT Child sexual abuse (CSA) is a prevalent concern that often leads to severe, life-long consequences. Grooming is an early indicator of CSA, and it is imperative to be able to recognize these behaviors in adult-child relationships to prevent abuse from occurring. Research on CSA and grooming has primarily focused on opposite-sex (male adult and female child) abuse while little research has focused on same-sex (male adult and male child) abuse. The current study examined how the sex of the adult-child pair might impact the identification of grooming behaviors. Participants in this study were presented with a series of vignettes depicting grooming and non-grooming behaviors in either same-sex or opposite-sex adult-child pairs. Participants were more likely to label the behaviors presented as grooming when shown situations involving an opposite-sex adult-child pair as opposed to a same-sex adult-child pair.

Retrospective Perceptions of Grooming in Same-Sex versus Opposite-Sex Child Sexual Abuse

ABSTRACT Research on child sexual abuse (CSA) has predominantly focused on opposite-sex (e.g., male adult-female child) adult-child pairs, neglecting same-sex (e.g., male adult-male child) adult-child pairs. Grooming behaviors are an early indicator of CSA and while it is important to recognize grooming to prevent abuse, research has shown that detecting these behaviors is a difficult task. Despite this difficulty, people retrospectively overestimate their ability to recognize abuse once it is clear that abuse has occurred. The current study investigated how outcome information (abuse did or did not occur) and the sex of the adult-child pair influenced perceptions of adult-child interactions. Participants evaluated vignettes depicting grooming and non-grooming behaviors in same-sex and opposite-sex adult-child conditions. Participants who were told CSA occurred provided higher likelihood ratings that abuse occurred than participants who were not given information about the abuse. There was some evidence that gender pairings influenced retrospective perceptions of these interactions.

Heritability of Psychotic Experiences in Adolescents and Interaction With Environmental Risk

Genetic risk factors are known to play a role in the etiology of psychotic experiences in the general population. Little is known about whether these risk factors interact with environmental risks for psychotic experiences. To assess etiological heterogeneity and exposure to environmental risks associated with psychotic experiences in adolescence using the twin design. This twin study, conducted from December 1, 2014, to August 31, 2020, included a UK-based sample of twin pairs aged 16 years. This investigation evaluated the extent to which the genetic variance underlying psychotic experiences and the magnitude of the heritability of psychotic experiences was moderated by exposure to 5 environmental risk factors (bullying, dependent life events, cannabis use, tobacco use, and low birth weight). Psychotic experiences were assessed by 5 self-reported measures and 1 parent-reported measure. Participants' exposure to environmental risks was assessed at birth and age 12 to 16 years. Structural equation models were used to assess differences in the variance in and heritability of psychotic experiences across these exposures, while controlling for gene-environment correlation effects. Analyses were repeated in an independent Swedish sample. Data analyses were performed from September 1, 2018, to August 31, 2020. Primary outcome measures were exposure to environmental factors, as measured by a composite score, and psychotic experiences. A total of 4855 twin pairs (1926 female same-sex pairs, 1397 male same-sex pairs, and 1532 opposite-sex pairs) were included from the Twins Early Development Study (TEDS), and 6435 twin pairs (2358 female same-sex pairs, 1861 male same-sex pairs, and 2216 opposite-sex pairs) were included from the Child and Adolescent Twin Study in Sweden (CATSS). Mean age of twins from TEDS was 16.5 years. Mean age of twins from CATSS was 18.6 years. More exposure to environmental risk factors was associated with having more psychotic experiences. The relative contribution of genetic influences to psychotic experiences was lower with increasing environmental exposure for paranoia (44%; 95% CI, 33%-53% to 38%; 95% CI, 14%-58%), cognitive disorganization (47%; 95% CI, 38%-51% to 32%; 95% CI, 11%-45%), grandiosity (41%; 95% CI, 29%-52% to 32%; 95% CI, 9%-48%), and anhedonia (49%; 95% CI, 42%-53% to 37%; 95% CI, 15%-54%). This pattern was replicated for the measure of psychotic experiences in the independent Swedish replication sample. The heritability of hallucinations and parent-rated negative symptoms remained relatively constant. Findings of this twin study suggest that environmental factors play a greater role in the etiology of psychotic experiences than genetic factors. The relative importance of environmental factors is even higher among individuals exposed to environmental risks for psychotic experiences, highlighting the importance of a diathesis-stress or bioecological framework for understanding adolescent psychotic experiences.

Interspecific variation in cooperative burrowing behavior by Peromyscus mice.

Animals often adjust their behavior according to social context, but the capacity for such behavioral flexibility can vary among species. Here, we test for interspecific variation in behavioral flexibility by comparing burrowing behavior across three species of deer mice (genus Peromyscus) with divergent social systems, ranging from promiscuous (Peromyscus leucopus and Peromyscus maniculatus) to monogamous (Peromyscus polionotus). First, we compared the burrows built by individual mice to those built by pairs of mice in all three species. Although burrow length did not differ in P. leucopus or P. maniculatus, we found that P. polionotus pairs cooperatively constructed burrows that were nearly twice as long as those built by individuals and that opposite‐sex pairs dug longer burrows than same‐sex pairs. Second, to directly observe cooperative digging behavior in P. polionotus, we designed a burrowing assay in which we could video‐record active digging in narrow, transparent enclosures. Using this novel assay, we found, unexpectedly, that neither males nor females spent more time digging with an opposite‐sex partner. Rather, we demonstrate that opposite‐sex pairs are more socially cohesive and thus more efficient digging partners than same‐sex pairs. Together, our study demonstrates how social context can modulate innate behavior and offers insight into how differences in behavioral flexibility may evolve among closely related species.

Are Metarhizium brunneum conidia transferred between male and female Agriotes obscurus adults?

ABSTRACT The success of autodissemination of entomopathogenic fungi depends to some degree on the transmission of infective conidia or spores from contaminated hosts to conspecifics. In the present study, we examined the potential for direct transmission of a lethal dose of Metarhizium brunneum (Petch) conidia between opposite sex pairs of Agriotes obscurus L in the laboratory. Male and female beetles were exposed to M. brunneum conidia prior to pairing with an uncontaminated opposite sex partner (‘indirectly exposed’ to M. brunnneum), 2, 21 and 45 h after M. brunneum exposure. Ninety-six percent of the female beetles that had been exposed to M. brunneum granules died by day 15, as compared to 59% and 53% of the indirectly exposed and control females. From 15 days after the beginning of the experiment, females indirectly exposed to M. brunneum had higher odds of dying at any point in time than unexposed females across all post-exposure time periods. There was no significant difference in the odds of dying between indirectly exposed males and their unexposed counterparts at any point during the experiment. When the female beetle was exposed to M. brunneum forty-five hours prior to pairing, the pairs engaged in fewer courtship interactions relative to the other treatment groups, however less than 50% of all the pairs engaged in courtship interactions. The low incidence of courtship interactions and limited transfer of conidia between A. obscurus beetle pairs suggests that negligible horizontal transmission of M. brunneum conidia may occur between conspecifics.

Mechanisms of inbreeding avoidance in a wild primate

Inbreeding often imposes net fitness costs,1-5 leading to the expectation that animals will engage in inbreeding avoidance when the costs of doing so are not prohibitive.4-9 However, one recent meta-analysis indicates that animals of many species do not avoid mating with kin in experimental settings,6 and another reports that behavioral inbreeding avoidance generally evolves only when kin regularly encounter each other and inbreeding costs are high.9 These results raise questions about the processes that separate kin, how these processes depend on kin class and context, and whether kin classes differ in how effectively they avoid inbreeding via mate choice-in turn, demanding detailed demographic and behavioral data within individual populations. Here, we address these questions in a wild mammal population, the baboons of the Amboseli ecosystem in Kenya. We find that death and dispersal are very effective at separating opposite-sex pairs of close adult kin. Nonetheless, adult kin pairs do sometimes co-reside, and we find strong evidence for inbreeding avoidance via mate choice in kin classes with relatedness ≥0.25. Notably, maternal kin avoid inbreeding more effectively than paternal kin despite having identical coefficients of relatedness, pointing to kin discrimination as a potential constraint on effective inbreeding avoidance. Overall, demographic and behavioral processes ensure that inbred offspring are rare in undisturbed social groups (1% of offspring). However, in an anthropogenically disturbed social group with reduced male dispersal, we find inbreeding rates 10× higher. Our study reinforces the importance of demographic and behavioral contexts for understanding the evolution of inbreeding avoidance.9.

Sex Differences in Migraine: A Twin Study.

Migraine is a neurological disorder with a prominent sex difference such that two thirds of sufferers are female. The mechanisms behind the preponderance of migraine in women have yet to be elucidated. With data on 51,872 participants from the Swedish Twin Registry, we report results from two distinct analyses intended to clarify the degree to which genetic and environmental factors contribute to sex differences in migraine. First, we fit a sex-limitation model to determine if quantitative genetic differences (i.e., is migraine equally heritable across men and women) and/or qualitative genetic differences (i.e., are different genes involved in migraine across men and women) were present. Next, we used a multilevel logistic regression model to compare the prevalence of migraine in individuals from opposite-sex and same-sex twin pairs to determine whether differences in the prenatal hormone environment contribute to migraine risk. In the final analytic sample, women were found to have a significantly higher rate of migraine without aura relative to men (17.6% vs. 5.5%). The results from an ADE sex-limitation model indicate that migraine is equally heritable in men and women, with a broad sense heritability of 0.45, (95% CI = 0.40–0.50), while results from a reduced AE sex-limitation model provide subtle evidence for differences in the genes underlying migraine across men and women. The logistic regression analysis revealed a significant increase in migraine risk for females with a male co-twin relative to females with a female co-twin (OR = 1.51, 95% CI = 1.26–1.81). These results suggest that the prominent sex difference in migraine prevalence is not entirely accounted for by genetic factors, while demonstrating that masculinization of the prenatal environment may increase migraine risk for females. This effect points to a potential prenatal neuroendocrine factor in the development of migraine.

The influence of social context on pinyon mouse (Peromyscus truei) vocalizations

Abstract Mice in the diverse genus Peromyscus are emerging as important models in the study of acoustic communication. However, reports on vocal repertoires exist for only 8 of the 56 currently recognized species. Descriptions of acoustic content and context are necessary to facilitate comparative studies. In this study, we present the first recordings of wild-captured pinyon mice (Peromyscus truei) in the laboratory in different social contexts. Similar to other Peromyscus species, pinyon mice produced four general types of vocalizations, including sustained vocalizations (SVs), barks, simple sweeps, and complex sweeps. SVs were produced primarily by females in social isolation, highlighting the potential significance of SVs in female advertisement behavior. While agonistic barks were rare, simple and complex sweeps were reliably produced in response to olfactory cues from same- and opposite-sex mice, and in paired contexts. Opposite-sex pairs produced significantly more complex sweeps than same-sex pairs, consistent with the well-supported function of sweeps in coordinating close-distance interactions. In addition, females produced sweeps with lower peak frequencies following separation from their social partner, indicative of a sex-specific mechanism to facilitate advertisement to potential mates and competitors. Together, our findings highlight the importance of social context in rodent vocal production, the significance of female vocal behavior, and the continued need to sample understudied species to better understand similarities and differences in rodent communication systems.

Do Epigenetic Clocks Provide Explanations for Sex Differences in Life Span? A Cross-Sectional Twin Study.

The sex gap in life expectancy has been narrowing in Finland over the past 4-5 decades; however, on average, women still live longer than men. Epigenetic clocks are markers for biological aging which predict life span. In this study, we examined the mediating role of lifestyle factors on the association between sex and biological aging in younger and older adults. Our sample consists of younger and older twins (21‒42 years, n = 1 477; 50‒76 years, n = 763) including 151 complete younger opposite-sex twin pairs (21‒30 years). Blood-based DNA methylation was used to compute epigenetic age acceleration by 4 epigenetic clocks as a measure of biological aging. Path modeling was used to study whether the association between sex and biological aging is mediated through lifestyle-related factors, that is, education, body mass index, smoking, alcohol use, and physical activity. In comparison to women, men were biologically older and, in general, they had unhealthier life habits. The effect of sex on biological aging was partly mediated by body mass index and, in older twins, by smoking. Sex was directly associated with biological aging and the association was stronger in older twins. Previously reported sex differences in life span are also evident in biological aging. Declining smoking prevalence among men is a plausible explanation for the narrowing of the difference in life expectancy between the sexes. Data generated by the epigenetic clocks may help in estimating the effects of lifestyle and environmental factors on aging and in predicting aging in future generations.

Genetic and Environmental Influences on Perceived Social Support: Differences by Sex and Relationship.

Previous research has shown that self-reports of the amount of social support are heritable. Using the Kessler perceived social support (KPSS) measure, we explored sex differences in the genetic and environmental contributions to individual differences. We did this separately for subscales that captured the perceived support from different members of the network (spouse, twin, children, parents, relatives, friends and confidant). Our sample comprised 7059 male, female and opposite-sex twin pairs aged 18-95 years from the Australian Twin Registry. We found tentative support for different genetic mechanisms in males and females for support from friends and the average KPSS score of all subscales, but otherwise, there are no sex differences. For each subscale alone, the additive genetic (A) and unique environment (E) effects were significant. By contrast, the covariation among the subscales was explained - in roughly equal parts - by A, E and the common environment, with effects of different support constellations plausibly accounting for the latter. A single genetic and common environment factor accounted for between half and three-quarters of the variance across the subscales in both males and females, suggesting little heterogeneity in the genetic and environmental etiology of the different support sources.

THE RELATIONSHIP BETWEEN PLACENTAL GROWTH RATES AND THE BIRTH WEIGHT IN DICHORIONIC DIAMNIOTIC TWINS

Relevance. Birth weight is one of the main indicators of intrauterine fetal development. The condition of the placenta reflects the influence of the maternal environment on the fetus. It is important to find out which placental growth parameters significantly affect the mass of dichorionic diamniotic (DHDA) twins.&#x0D; Objective: to investigate the relationship between indicators of placental growth and birth weight of dichorionic diamniotic twins.&#x0D; Materials and methods. One hundred thirty-five DCDA twin pairs were studied during 2016-2020: 68 pairs were opposite-sex, 32 – same-sex females and 35 – same-sex males. The gestational age ranged from 29 to 39.5 weeks, averaging 36,4 ± V1,74 weeks. The influence of such parameters as maximum and minimum placental diameters, as well as perimeter, area, circularity (Circ), roundness, thickness, mass (PM), volume (V), displacement of the umbilical cord insertion site from the placental disc centre along its maximum (XCD) and the minimum axis (YCD).&#x0D; Results. A strong positive correlation was found between PM and birth weight in the whole cohort of DCDA twins (r = 0.7059, p &lt; 0.0001). It was strongest in the same-sex female group (r = 0.7886, p &lt; 0.0001), then in the opposite-sex pairs (r = 0.7093, p &lt; 0.0001), slightly weaker – in the same-sex male couples (r = 0.6065, p &lt; 0.0001). The birth weight and PM correlated with almost all indicators that characterize the placental shape. The strongest correlation was with V (rV_BW = 0.66, p &lt; 0.0001; rV_PM = 0.59, p &lt; 0.0001) and the area*Circ (rS*Circ_BW = 0.64; p &lt; 0.0001; rS*Circ_PM = 0.62; p &lt; 0.0001). The multiple regression analysis of the effect of different morphometric parameters of the placentas on the birth weight has demonstrated the statistical significance of the following parameters: XCD, PM, V, YCD and Circ. The general regression model for the whole DCDA group: birth weight = 2242,3 + 0,8*МП + V – 10,0* XCD (R2 = 0,7002). Similar equations were calculated for different types of DCDA tweens. Thus, morphometric measures account for the 67-85% variances of the birth weight of the DCDA tweens.&#x0D; Conclusion. In the DCDA pairs, placental mass strongly positively correlated with birth weight. Both indicators are in strong relationship with V and their area*Circ. The closer the placental shape is to the circle, the higher its functional ability. Deterioration of the latter may be due to the far fixation of the umbilical cord from the center of the placental disc. The displacement along the maximum axis has a stronger impact comparing to the displacement relative to the minimum axis. The multiple regression analysis has revealed that statistical significance had XCD and PM or V in the whole types of twins. Proposed models demonstrate that 67-85% of the variability of birth weight may be accounted for by the three or four simple placental measures

Educational attainment of same-sex and opposite-sex dizygotic twins: An individual-level pooled study of 19 twin cohorts

Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = −0.05 educational years, 95% CI −0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.