Birth Order Effect Research Articles

Reexamining the effect of birth order on cognitive and non-cognitive abilities: New evidence from China

We present rich new evidence on birth order effects on cognitive and non-cognitive ability using a rural sample from China Family Panel Studies. Within families, being the later-born child confers both statistically and economically significant disadvantages in cognition, but has no effects on non-cognitive ability. In particular, the deficits in the cognition of the later-born are persistently large between the ages 10 and 18. We shed new light on the mediating role of school starting age, which explains more than a quarter of the total effect of birth order on cognition. We also find that birth order is negatively associated with home environment and parent–child interactions. In addition, we find a negative relationship between birth order and education among adults.

The fraternal birth-order effect as a statistical artefact: convergent evidence from probability calculus, simulated data, and multiverse meta-analysis.

The fraternal-birth order effect (FBOE) is a research claim which states that each older brother increases the odds of homosexual orientation in men via an immunoreactivity process known as the maternal immune hypothesis. Importantly, older sisters supposedly either do not affect these odds, or affect them to a lesser extent. Consequently, the fraternal birth-order effect predicts that the association between the number of older brothers and homosexual orientation in men is greater in magnitude than any association between the number of older sisters and homosexual orientation. This difference in magnitude represents the main theoretical estimand of the FBOE. In addition, no comparable effects should be observable among homosexual vs heterosexual women. Here, we triangulate the empirical foundations of the FBOE from three distinct, informative perspectives, complementing each other: first, drawing on basic probability calculus, we deduce mathematically that the body of statistical evidence used to make inferences about the main theoretical estimand of the FBOE rests on incorrect statistical reasoning. In particular, we show that throughout the literature researchers ascribe to the false assumptions that effects of family size should be adjusted for and that this could be achieved through the use of ratio variables. Second, using a data-simulation approach, we demonstrate that by using currently recommended statistical practices, researchers are bound to frequently draw incorrect conclusions. And third, we re-examine the empirical evidence of the fraternal birth-order effect in men and women by using a novel specification-curve and multiverse approach to meta-analysis (64 male and 17 female samples, N = 2,778,998). When analyzed correctly, the specific association between the number of older brothers and homosexual orientation is small, heterogenous in magnitude, and apparently not specific to men. In addition, existing research evidence seems to be exaggerated by small-study effects.

The Early Bird Catches the Worm: The Effect of Birth Order on Old‐Age Mortality

AbstractPrevious studies explore the role of birth order in children's and adults’ outcomes. This literature usually provides evidence of disadvantage of children with higher birth order. A narrow strand of this literature explores the association between birth order and old‐age mortality. This study re‐visits the birth‐order‐longevity relationship using US data. We employ Social Security Administration death records between the years 1988 and 2005 linked to the 1940 full‐count census and implement family fixed effect strategy to compare within‐sibling differences in the outcome. The findings suggest that later‐born children live, on average, 1–3 fewer months of life. The observed associations are exclusively concentrated among whites. However, the results do not point to significant heterogeneity based on family socioeconomic status, maternal education, and gender. Additional analyses suggest that higher birth order is associated with negative early educational outcomes.

Identifying the Relationship Between Economic Prosperity and Quality of Life in Chronic Obstructive Pulmonary Disease Patients.

Background Chronic obstructive pulmonary disease (COPD) places a significant economic burden on national healthcare systems, and the economic effects of diseases have long been known. The study aimed to evaluate the association of parental family financial wealth with current economic prosperity and the combined effect of both on health-related quality of life (HRQOL) in a sample of patients with COPD. The moderating effect of birth order is further investigated. Methods The results of the study are based on a purposive sample of 105 COPD patients at the Larisa University Hospital pulmonology clinic (94 males and 11 females), with an average age of 68.9 (SD = 9.2). The data collection was carried out in the spring and summer of 2020. Participants completed the 36-item Short Form Survey (SF-36) and a sociodemographic questionnaire with self-reported parental and current wealth items. A mediation model with the moderation of the indirect effect of parental wealth on current wealth and the direct effect of parental wealth on HRQOL was applied to test the research hypotheses among the variables studied. Results Parental wealth was found to affect current wealth significantly, and both were involved considerably in HRQOL. Birth order had a significant moderating effect on the relationship between parental wealth and HRQOL. Among parental families with lower financial status, patients who grew up as third or later children had significantly lower HRQOL than the first or second children of these families. Neither age nor COPD duration was related to current wealth or HRQOL. Conclusions An intergenerational transmission of poverty was found in our sample. In addition, a birth order effect can provide further insight into the harsher environment that the later children of a low-income family are exposed to and the long-term implications for their HRQOL.

Birth order and intergenerational income mobility in Japan: Is the first‐born child different?

AbstractThis study examines how birth order affects intergenerational income mobility (IGM) in Japan, focusing on the difference in IGM between firstborn and later‐born children. The elasticities of sons’ income with respect to fathers’ income are separately estimated for sons who are firstborn and sons who are later born by family size using a two‐sample, two‐stage least squares approach. For sons born in 1926–1981, this study finds that in families with four or more children, intergenerational income elasticity (IGE) for firstborn sons is substantially and significantly higher than that for later‐born sons. However, no significant birth order effects are found in households with two or three children.

Birth order, socioeconomic background and educational attainment

ABSTRACT This paper examines the effect of birth order on educational attainment in the United States and the underlying mechanism producing these effects. Using a family fixed effects model, we find negative birth order effects on educational outcomes. However, this effect varies depending on the household's income, being the strongest for households with the highest income and diminishing as households' income decreases. In addition, we show that the timing of income across childhood is important for completed education, as the largest gap in educational attainment between siblings emerges between those who were born and spent their early childhood in wealthier households.

Growing up together: Differences between siblings in the development of compliance separating within-family and between-family effects.

This study applies a within-family, age-snapshot design to investigate differences between siblings in the development of compliance during the preschool years by disaggregating situational, within-family, and between-family effects. The aim of the study was to investigate the relation between sibling differences in compliance and the within-family factors birth order and differential parenting, as well as interactions between these factors. Using observational data of 311 Dutch families (self-identified as culturally Dutch) with 2 children when each child was 3 and 4 years old (firstborns: 36.2 months old; SD = 3.6; 48% girls, second-borns (2 years later): 36.67 months old; SD = .62; 47% girls) and both parents. Three-level cross-classified multilevel models showed main effects of observed sibling noncompliance and differential verbal discipline on noncompliance. In addition, second-born children were more compliant than their firstborn siblings, but only when the firstborn was disciplined physically more often than his/her younger sibling. The results provide evidence that birth-order effects may partially be explained by differential parenting and suggest that differences between siblings cannot be fully understood without taking into account the influence of both direct and indirect sibling effects. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Evaluation of the association of birth order and group childcare attendance with Kawasaki disease using data from a nationwide longitudinal survey.

Kawasaki disease (KD) is a form of pediatric systemic vasculitis. Although the etiology remains unclear, infections have been identified as possible triggers. Children with a later birth order and those who attend childcare are at a higher risk of infections due to exposure to pathogens from their older siblings and other childcare attendees. However, longitudinal studies exploring these associations are limited. Thus, we aimed to elucidate the relationship between birth order, group childcare attendance, and KD, using a nationwide longitudinal survey in Japan. In total, 36,885 children born in Japan in 2010 were included. The survey used questionnaires to identify hospitalized cases of KD. We evaluated the relationship between birth order classification, group childcare attendance, and KD prevalence every year, from 6 to 66 months of age. For each outcome, odds ratios (ORs), and 95% confidence intervals (CIs) were estimated after adjusting for child factors, parental factors, and region of residence. Children with higher birth orders were more likely to be hospitalized with KD at 6-18 months of age (second child OR: 1.77, 95% CI: 1.25-2.51; third child OR: 1.70, 95% CI: 1.08-2.65). This trend was stronger for children who did not attend group childcare (second child OR: 2.51, 95% CI: 1.57-4.01; third child OR: 2.41, 95% CI: 1.30-4.43). An increased risk of KD hospitalization owing to the birth order was not observed in any age group for children in the childcare group. Children with higher birth orders were at high risk for hospitalization due to KD at 6-18 months of age. The effect of birth order was more prominent among the children who did not attend group childcare.

Birth order effects and parenting behaviors

While it is well known that there are systematic birth order effects on life cycle outcomes, there is less consensus about underlying channels and mechanisms of birth order effects. We find negative birth order effects among Chinese adolescents, favoring earlier-born children within household in academic achievement, cognitive skill measures, and in parenting behaviors including harsh parenting and parental investment. We highlight harsh parenting as a novel channel of birth order effects, in which earlier-born children are less likely to be physically punished by their parents. Heterogeneity analysis results are consistent with parents reinforcing academic advantage of better-performing earlier-born children, but do not support resource dilution, son preference, or reputation concerns as primary mechanisms underlying birth order effects. Our findings are in contrast to positive birth order effects found among earlier generations of Chinese siblings reported in the literature.

Impact of New Living Environment on Reactive Stress Tolerance in Preadolescent Sports Trainees of Jharkhand

Study purpose. The purpose of the study was to examine the effect of background experience related to family demography on the selected parameters of reactive stress tolerance in athletes who strictly lived in a training academy for a minimum of two years. Materials and methods. A total of 200 male sports cadets were chosen by the Jharkhand State Sports Promotion Society in Ranchi, with chronological age ranging from 11 to 14 years and 4 years of training. The demographic information (the size of the family, the type of family, the order of birth, the family monthly income, and the location of the home) were considered as independent variables. Stress tolerance parameters (PR correct, PR incorrect, PR omitted, and median reaction time) were chosen as dependent variables. The Shapiro-Wilk test was used to determine data normality, while Levene's test was used to determine homogeneity. The Mann-Whitney U and Kruskal-Wallis tests were used to draw comparisons. For post-hoc comparison, Dunn's test with Holm correction was employed. The threshold for significance was set at p = 0.05. Results. The percentile rank of correct responses (p = 0.005) and median reaction time (p = 0.033) related to birth orders showed significant results. Other factors related to family information and reactive stress tolerance were not significant. Conclusions. According to the findings, it was concluded that being in new environment for a long duration reduced the early living experience related to family demography but effect of birth order still continued.

Increased birth rank of homosexual males: disentangling the older brother effect and sexual antagonism hypothesis

Male homosexual orientation remains a Darwinian paradox, as there is no consensus on its evolutionary (ultimate) determinants. One intriguing feature of homosexual men is their higher male birth rank compared to heterosexual men. This can be explained by two non-exclusive mechanisms: an antagonistic effect (AE), implying that more fertile women have a higher chance of having a homosexual son and to produce children with a higher mean birth rank, or a fraternal birth effect (FBOE), where each additional older brother increases the chances for a male embryo to develop a homosexual orientation due to an immunoreactivity process. However, there is no consensus on whether both FBOE and AE are present in human populations, or if only one of these mechanisms is at play with its effect mimicking the signature of the other mechanism. An additional sororal birth order effect (SBOE) has also recently been proposed. To clarify this situation, we developed theoretical and statistical tools to study FBOE and AE independently or in combination, taking into account all known sampling biases. These tools were applied on new individual data, and on various available published data (two individual datasets, and all relevant aggregated data). Support for FBOE was apparent in aggregated data, with the FBOE increasing linearly with fertility. The FBOE was also supported in two individual datasets. An SBOE is generated when sampling in presence of FBOE, suggesting that controlling for FBOE is required to avoid artefactual SBOE. AE was not supported in individual datasets, including the analysis of the extended maternal family. The evolutionary implications of these findings are discussed.

Siblings in lockdown: International evidence for birth order effects on child adjustment in the Covid19 pandemic

AbstractSupportive family relationships may mitigate the impact of the Covid19 pandemic on young children's adjustment, but existing work is limited by its focus on within‐country variation and parental influences. Addressing these gaps, and drawing on reported buffering effects of older siblings on child mental health (Lawson and Mace, 2010), the current international study examined whether child adjustment problems were, on average, elevated by the pandemic and whether this buffering effect of older siblings would be maintained. In the first wave of the Covid19 pandemic (April to July 2020), 2516 parents of 3‐ to 8‐year‐old children living in Australia, China, Italy, Sweden, United Kingdom, and United States of America—six countries with contrasting governmental responses to the pandemic—completed an online survey about family experiences and relationships and child adjustment, as indexed by ratings on the Strengths and Difficulties Questionnaire (SDQ: R. Goodman, 1997). As expected, child SDQ total difficulty scores were elevated in all sites except Sweden (which notably did not enforce mass school closures). Compared to children without siblings, children with one or more older siblings showed fewer adjustment problems. Children from lone‐parent households displayed more adjustment problems, as did those whose parents reported increased sibling conflict. Finally, child adjustment problems were negatively associated with family socio‐economic status, but positively related to the indices of Covid‐19 family disruption and government stringency. We discuss these findings in relation to existing work on asymmetric effects of older versus younger siblings, and siblings as sources of support.

Determinants and transition of anaemia among under-five children from different social groups in India from 2005–06 to 2015-16

Anaemia among under-five children is a global health problem and a major cause of child morbidity and mortality, especially in Lower-Middle-Income countries including India. Despite a significant decrease over the last decade, nearly 58% of children in India suffered from anaemia in 2015-16. This national average hides the inequality in the prevalence of anaemia among indigenous people and other social groups. Therefore, the study focuses on identifying time-dependent significant determinants of the prevalence of anaemia from 2005–06 to 2015-16 among children belonging to Scheduled Tribe (ST), Scheduled Caste (SC), Other Backward Class (OBC) and Other or General social groups. Besides, it also identified social group-wise transition of anaemia among under-five children belonging to different socio-demographic, economic, residential and regional backgrounds in India. Time-dependent and independent logistic regression models were used to identify significant determinants of child anaemia and the mean probability of anaemia across different categories of explanatory backgrounds. Though the probability of anaemia has decreased more among marginalized children during the last decade, it remains relatively higher among them. The study has outlined the significant effects of child age, birth order, maternal anaemia, education level and geographic regions on the prevalence of anaemia among ST, SC, OBC and General social groups in India over the past decade. The effect of economic status on the prevalence of anaemia among ST and SC children was insignificant. Four subpopulations demonstrated a relatively greater magnitude of decadal anaemia risk reduction among children of early age groups, living with teenage, non-anaemic, less educated mothers and living in northeast India. The study suggests the arrangement of region-specific, social-group based strategies for reducing the prevalence of anaemia among under-five children in India. In this way, the nation can achieve “health and well-being for all” (SDG 03) by eliminating the geographical, and social inequality in the prevalence of child anaemia within the country (SDG 10).

Effects of parental age on salt stress tolerance in an aquatic plant

Parental age influences components of offspring fitness in many species. The ability to tolerate stress also affects fitness, but less is known regarding changes in offspring stress tolerance with increasing parental age, especially in plants. We examined first and fifth‐born clonal offspring (using birth order as a proxy for parental age), and compared their fitness in several sub‐lethal concentrations of salt (NaCl), to investigate the interactive effects of birth order and salt stress on the offspring of the aquatic plant Lemna minor L. We found that increasing salt concentration reduced reproduction particularly at early ages, which detrimentally affected fitness, as measured by the intrinsic rate of natural increase. Fifth offspring had greater fitness than first offspring, potentially due to the hump‐shaped relationship between offspring fitness and birth order observed in other studies on Lemna, with fifth offspring near the peak of the hump. We found no interactive effect of birth order and salt concentration on offspring fitness; however, there were interactive effects on the time to first reproduction and the size of fronds. Specifically, first offspring exposed to increasing salt concentrations exhibited longer delays to first reproduction and grew to a greater size, while fifth offspring showed little change in either variable with increasing salt concentration. Thus, variation in birth order affected offspring response to salt stress, although not in terms of fitness. These results help illuminate factors impacting the age‐specific strength of natural selection and stress responses, and may be environmentally relevant in the context of environmental salinization.

The Birth Order Effect: A Modern Phenomenon?

The Birth Order Effect: A Modern Phenomenon?

Birth Order Effects in the Developed and Developing World: Evidence from International Test Scores

Birth Order Effects in the Developed and Developing World: Evidence from International Test Scores

The effect of piglet vitality, birth order, and blood lactate on the piglet growth performances and preweaning survival

BackgroundLitter size is going up in modern pig production. Due to large litter size and increased farrowing duration, newborn piglets, during parturition, can suffer from asphyxiation. This alters their blood energy parameters and can contribute to their reduced vitality at birth, which is detrimental to their growth performance and survival. We aimed to evaluate the effects of vitality score, piglets’ umbilical cord blood lactate, glucose, and butyrate, and birth order on growth performance and the preweaning mortality of piglets.ResultsThe more vital (vitality score 2, VS2) piglets had higher umbilical cord blood glucose and butyrate, lower blood lactate, and higher colostrum intake (CI) at birth, and showed higher body weight at birth and at weaning than did less vital piglets (vitality score 1, VS1). Umbilical cord lactate negatively correlated with vitality, colostrum intake, and growth before weaning. Among the four birth-order groups (BOGs), piglets born earlier during parturition had a higher mean vitality score than those born later. BOG1 and BOG2 had significantly higher CI (p < 0.05) than BOG3 and BOG4.ConclusionChanges in piglets’ body weight, colostrum intake, and umbilical cord lactate are associated with piglet vitality and asphyxiation during farrowing. In addition, asphyxiation induced higher umbilical cord lactate may serve as an indicator of low vitality and low colostrum consumption. Overall, improvement in piglets’ vitality and in the farrowing process can help in reducing piglet mortality.

Birth order and health disparities throughout the life course

BackgroundResearch has shown ample evidence of how birth order affects health; however, these studies focus on specific health outcomes and ages. ObjectiveWe provide a comprehensive picture of the effects of birth order on health disparities over the life course. MethodWe study the effects of birth order from birth to age 70 on hospitalizations, visits to open care facilities and mortality using Swedish register data from 1987 to 2016. We identify the effects by comparing siblings within the same family. ResultsWe find that firstborns have worse health at birth. In adolescence, the birth-order effects switch direction, and younger siblings are more likely to be hospitalized and visit open care facilities. From early age younger siblings receive more care for injuries, in adolescence for drug and alcohol abuse, and from middle age for diseases of the circulatory system compared to older siblings. Younger siblings also stay longer in hospital. Age 0–2, younger siblings are more likely to be hospitalized for infections, diseases of the respiratory system, eyes and ears, whereas the pattern is the opposite for children age 3–6. Firstborns are more likely to receive care for depression and ADHD in childhood and endocrine diseases after age 50. InterpretationBirth order affects health over the life-cycle and this is likely due to biological factors as well as parental behavior and the family environment. Firstborns have worse health at birth, but in adolescence the effects switch direction due to health issues related to younger siblings engaging in more risky behavior. For small children, having siblings at home increases the risk of being hospitalized for infections, diseases of the respiratory system, eyes and ears. The adverse conditions in utero for firstborns may be the cause of increased risk of metabolic syndromes such as obesity and diabetes later in life.

Effects of lamb sex and ewe parity on suckling-related neonatal behaviors and weaning weight of small-tailed han lambs

Suckling behavior is essential for the growth, health, and welfare of the lamb. The factors that influence the suckling-related behavior varied across breeds, and they remain unclear in Small-tailed Han lamb. This study aims to investigate the effects of ewe parity, lamb sex, and birth order on the suckling-related behaviors of Small-tailed Han lamb. The neonatal behaviors of 36 lambs were observed during the first week after birth using focal-animal sampling methods, and the levels of cholecystokinin (CCK), endogenous opioid peptides and growth hormone (GH) were measured with ELISA methods before weaning. Results showed that male lambs began standing and suckling behaviors earlier than female lambs, and the duration of each suckling bout was longer in male lambs (P < 0.05). Lambs born to multiparous ewes more frequently suckled and attempted to stand earlier than lambs from primiparous ewes (P < 0.05). The weaning weights of male lambs and lambs from multiparous ewes were heavier, and the serum levels of CCK, opioid peptides, and GH were sometimes higher in these lambs before weaning (P < 0.05). Meanwhile, lamb birth order has no significant effect on the suckling-related behaviors of lambs (P > 0.05). In addition, the suckling-related behaviors of male lamb and lambs born to multiparous ewes were found to strongly correlate with each other. In conclusion, lamb sex and ewe parity could affect the suckling-related behaviors and weaning weights of Small-tailed Han lambs. Moreover, male lambs and lambs born to multiparous ewes seemed to have better suckling-related behaviors. Many of these behaviors were highly connected with one another. These phenomena may be related to the higher serum levels of CCK, opioid peptides, and GH. The effects of lamb sex on suckling-related behaviors were different from those of other breeds in previous research. The male lambs were observed to initiate sucking-related behaviors earlier in this study. Our findings will also help in extensively understanding the variability in the effects of these factors on suckling-related behavior across sheep breeds.

The role of deviant siblings in delinquency: A meta-analysis of longitudinal studies

Deviant siblings have been considered as role models for future delinquent behavior; however, previous studies have led to inconsistent results in this regard. The goal of the current meta-analysis was to analyze the effect of deviant non-twin siblings on future delinquency. The potential moderation effects of birth order, sex dyad, age of siblings, publication year, study length, and sample size were analyzed. Six databases were searched for studies: PsycInfo, MEDLINE, Criminal Justice Abstracts, Web of Science, SCOPUS, and Google Scholar. To analyze the prospective interdependence of delinquent siblings, only longitudinal studies were considered for inclusion in the meta-analysis. Two authors independently went through all the retrieved studies and coded those eligible for inclusion, with good interrater agreement. A total of 18 studies were included, which provided 24 independent effect sizes. The meta-analysis showed a significant prospective association between deviant siblings and delinquency. A moderate effect size was found from older sibling to younger sibling and vice versa, as well as between siblings when birth order was not specified. Likewise, significant associations were found in brother pairs, sister pairs, and mixed-sex sibling pairs. No moderation effects were found for age of siblings, publication year, study length, or sample size. The results highlight the role of siblings as a risk factor for future delinquency. • Deviant siblings are prospectively associated with future delinquency. • The effect of siblings is irrespective of birth order, age, and gender dyad. • Publication year, study length, and sample size are not significant moderators.