A multilevel approach to the relationship between birth order and intelligence

Many studies show relationships between birth order and intelligence but use cross-sectional designs or manifest other threats to internal validity. Multilevel analyses with a control variable show that when these threats are removed, two major results emerge: (a) birth order has no significant influence on children's intelligence and (b) earlier reported birth order effects on intelligence are attributable to factors that vary between, not within, families. Analyses on 7- to 8 - and 13- to 14-year-old children from the National Longitudinal Survey of Youth support these conclusions. When hierarchical data structures, age variance of children, and within-family versus between-family variance sources are taken into account, previous research is seen in a new light.     

The birth order puzzle.

Studies relating intellectual performance to birth order report conflicting results, some finding intellectual scores to increase, others to decrease with birth order. In contrast, the relationship between intellectual performance and family size is stable and consistently replicable. Why do these two highly related variables generate such divergent results? This birth order puzzle is resolved by means of the confluence model that quantifies the influences upon intellectual growth arising within the family context. At the time of a new birth, two opposing influences act upon intellectual growth of the elder sibling: (a) his or her intellectual environment is "diluted" and (b) he or she loses the "last-born's handicap" and begins serving as an intellectual resource to the younger sibling. Since these opposite effects are not equal in magnitude, the differences in intellectual performance among birth ranks are shown to be age dependent. While elder children may surpass their younger siblings in intellectual performance at some ages, they may be overtaken by them at others. Thus when age is taken into consideration, the birth order literature loses its chaotic character and an orderly pattern of results emerges.     

Intelligence, birth order, and family size

The analysis of the National Child Development Study in the United Kingdom (n = 17,419) replicates some earlier findings and shows that genuine within-family data are not necessary to make the apparent birth-order effect on intelligence disappear. Birth order is not associated with intelligence in between-family data once the number of siblings is statistically controlled. The analyses support the admixture hypothesis, which avers that the apparent birth-order effect on intelligence is an artifact of family size, and cast doubt on the confluence and resource dilution models, both of which claim that birth order has a causal influence on children's cognitive development. The analyses suggest that birth order has no genuine causal effect on general intelligence.     

Possible Insomnia Predicts Some Risky Behaviors Among Adolescents When Controlling for Depressive Symptoms

Attachment theory asserts that secure attachment representations are developed through sensitive and consistent caregiving. If sensitive caregiving is a constant characteristic of the parent, then siblings should have concordant attachment classifications. The authors explored maternal attachment quality assessed by the Attachment Q-Set, maternal sensitivity, and specific mother–child interactions between siblings. Hour-long observations took place in the homes of 9 preschool sibling pairs and their immediate caregivers. The interactions were analyzed using a modified version of Bales’ Small Group Analysis. The results reveal attachment discordance in a third of sibling pairs. While maternal sensitivity was higher with older siblings and mothers displayed more positive emotions when interacting with their younger siblings, attachment quality was not associated with birth order. Therefore, a shift toward a more contextual, family-based perspective of attachment is recommended to further understand how attachment strategies are created and maintained within the child's everyday context.     

Représentations des pratiques éducatives parentales et estime de soi chez des enfants placés en fratrie versus séparément

Despite abuse, children placed in childcare homes have parental representations which are marked by ambivalence. This ambivalence is characterized by the coexistence of negative and positive representation towards their biological parents. However, the fact that positive representations towards neglecting parents persist can possibly harm self-esteem. Placement aims not only to protect the child, but also to offer him the possibility of reconstructing his self-image with more secure attachment figures. When a placement is decided, the children are entrusted to Child Welfare and are placed either with their siblings or separately. This study aims to examine the parental representations and the self-esteem of 33 children that are placed with siblings and 25 children that are placed alone; all children were between the ages of 10 and 18. Then, the relation between parental representations and self-esteem was examined in each group. Those two dimensions have been respectively measured with the Rosenberg Self-Esteem scale and the Parental Bonding Instrument (PBI). The results show that participants placed with their siblings were less depressed and had a better self-esteem than participants placed separately. Moreover, although the two groups had neglecting parents, the participants placed with their siblings had significantly better parental care representations. This study also put into light that the links between parental representations and self-esteem are significantly different whether the participant is placed with his siblings or not. Among children placed with siblings, the more positive the images of the father and the mother, the lower the self-esteem level. These results confirm the hypothesis according to which a positive parental care representation could reinforce the negative image those children have of themselves. The results also question the effects (positive or negative) of the defensive exclusion process on the evolution of self-representations among placed children. Finally, from a therapeutic point of view, they stress the importance of working on self-esteem with placed children.     

What causes birth order-intelligence patterns? The admixture hypothesis, revived.

Recent evidence shows that the relation between birth order and intelligence is not the same in cross-sectional and within-family data. This simple empirical observation invalidates the conclusions from hundreds of previous birth order studies that relied on cross-sectional data. Simultaneously, the empirical foundation disappears from underneath theories like dilution and the confluence model that use explanatory processes occurring within the family. A theory proposed almost 25 years ago--the admixture hypothesis--effectively accounts for these empirical patterns. In this article, the author describes why birth order is of such intense interest to both parents and researchers (the birth order trap), discusses past birth order-intelligence patterns, shows that the admixture hypothesis accounts for those patterns, and reframes the original argument to support future productive research efforts.     

Estimating retest effects in longitudinal assessments of cognitive functioning in adults between 18 and 60 years of age

Several analyses were conducted on data from samples of adults between 18 and 58 years of age who completed the same cognitive tests after an interval ranging from less than 1 week to 35 years. Because the retest interval varied across individuals, it was possible to determine the length of time needed before the gains associated with a retest decreased to 0 and to obtain simultaneous estimates of the magnitude of effects associated with increased age and a prior assessment. The results indicated that for adults within this age range, 7 or more years were needed before positive retest effects were no longer detectable. Age effects in longitudinal comparisons could be interpreted in terms of large positive effects associated with a prior assessment and negative effects associated with age that were comparable in magnitude to those observed in cross-sectional comparisons.     

The influence of rearing order on personality development within two adoption cohorts

There is an extensive literature on the relationship between birth order and psychological traits, but no previous study has investigated the influence of ordinal position on personality development within adoptive siblings. Such a design is important because it effectively separates the effects of biological birth order and rearing order. Here we report data from two adoption cohorts in which subjects were biological first-borns reared in various ordinal positions. Data were analyzed with reference to Sulloway's (1996) evolutionarily based sibling rivalry theory of birth order effects. Between- and within-family analyses indicated that rearing order's influence on personality was very weak. The only clear difference was for conscientiousness, on which first-reared siblings scored higher. We draw possible implications for Sulloway's theory and speculate upon an alternative, prenatal biological process that may produce birth order differences.     

父母差别对待与青少年问题行为的关系：一个有调节的中介模型

通过问卷调查的方式,采用同胞不同经历问卷、关系网络问卷和问题行为量表对开封市1179名初高中学生进行研究。研究结果显示：（1）父母差别对待与外/内化问题行为呈显著正相关;同胞关系与外/内化问题行为呈显著负相关;父母差别对待和同胞关系呈显著负相关。（2）同胞关系在父母差别对待与外/内化问题行为之间起部分中介作用。（3）“父母差别对待→同胞关系→外/内化问题行为”这一中介路径的前半段受出生顺序调节;与年幼个体相比,父母差别对待对年长个体的同胞关系影响更大。出生顺序会调节父母差别对待对同胞关系的影响,提示二胎家庭要更关注年长个体的变化。     

Imitation as a Learning Strategy during Sibling Teaching

ABSTRACT

The sibling relationship represents a unique bond characterized by a high degree of closeness and intimacy, which fosters teaching and learning. Two studies investigated associations between sibling-directed teaching, imitation as a learning strategy, and learner involvement during a semi-structured, video-taped construction task. Study 1 also examined associations with the teacher’s Theory of Mind (ToM) abilities; Study 2 focused on associations with birth order and sibling relationship quality. In both studies, siblings ranged from preschool-age to the cusp of middle childhood (Study 1 n = 61; Study 2 n = 72). Findings across both studies indicated that learners engaged in significantly more nonverbal than verbal imitation and imitation was predominately immediate and not deferred. Teachers responded to both verbal and nonverbal learner imitation positively, corrected, or did not respond. In Study 1, learner task involvement was predicted by learner age and nonverbal imitation, while teaching strategies that were positively related to the teacher’s ToM abilities were associated with learner imitation. In Study 2, younger siblings’ reports of a positive sibling relationship were significantly associated with learner imitation. Birth order differences were only evident for younger (but not older) sibling learner imitation and task involvement. Findings are discussed in light of relationships and social constructivist theories of development.     

The Role of Contextual Threat in Predicting Self-Reported Distress among Siblings of Children with Cancer

Each year, 14,000 children are diagnosed with cancer in the United States. Prolonged, intensive treatment regimens disrupt the entire family system, but effects on siblings are poorly understood. In this preliminary investigation, we employed a risk and resistance framework to study adjustment among 30 siblings (aged 10–17) of children undergoing cancer treatment. We examined whether or not objective stress associated with the cancer experience (contextual threat) predicted sibling distress and explored demographic and disease-related predictors of sibling adjustment. Contextual threat was positively associated with sibling-reported distress, independent of sibling age, gender, birth order relative to the child with cancer, and cancer treatment intensity. From among the demographic and disease-related factors, only younger birth order relative to the child with cancer was independently associated with sibling distress. These results suggest that a subset of siblings may be at increased risk for elevated distress in the face of their brother’s or sister’s illness.     

Antecedents of mirror self‐recognition of toddlers: Emotional availability,birth order,and gender

The present study employed a longitudinal design for examining the role of emotional availability of child–mother dyads, birth order of children, and their gender as determinants of mirror self‐recognition of toddlers. It was hypothesized that toddlers who maintained more optimal emotional availability with mother at the age of 12 months would tend to identify themselves more readily at the age of 20 months. We assumed further that first‐born children and females would identify themselves more readily than males and younger siblings. A sample of 54 nonrisk children and their mothers was investigated. Path analysis model showed that emotional availability partly predicted self‐recognition: responsive toddlers identified themselves more often than less responsive peers. No significant effects were found for the other scales of emotional availability. A nonlinear birth order effect was observed, with second‐born children being less likely to show mirror self‐recognition than first‐borns or third‐borns. Child gender was not significantly associated with self‐recognition at the age of 20 months. The data showed further that birth order was significantly linked with components of emotional availability. No significant correlations were found between emotional availability scores and child gender. Results were discussed in light of the different components of emotional availability, and the psychological correlates of ordinal position in the family. ©2002 Michigan Association for Infant Mental Health.     

Context-Specific Learning, Personality, and Birth Order

Most people believe that learning to get along (or not get along) with their siblings played an important role in shaping their personality, and that their position in the family—oldest, youngest, or in the middle—had lasting effects. Yet studies of birth order generally fail to support these beliefs. The apparent contradiction can be resolved by taking into account the context-specific nature of learned behavior. There is abundant evidence that people do not automatically transfer behavior from one context to another: They wait until they have evidence that what they learned in Context 1 will also be useful in Context 2. Because patterns of behavior acquired in the family of origin tend to be useless or inappropriate in other settings, birth order effects show up only in that context. Outside the family they grew up in, firstborns and later-borns are indistinguishable in personality.     

同胞共情：特点、影响因素及理论机制

同胞之间的交流和互动更能促进彼此共情的发展。随着“全面二孩”政策的实行,同胞共情成为国内外研究者共同关注的焦点。本文在同胞的视角下总结了同胞共情的共性特点和特异性特点,从个体、同胞、家庭三个维度阐述了同胞共情的影响因素。未来研究需要进一步注重文化,回归本土研究;加强双向机制研究,夯实理论框架;重视干预性研究,探索提升同胞共情的方法。     

Sex-related differences in the relationship between sibling status and responsivity to babies

Ninety-six middle-class subjects equally divided by age (4–5, 8–9, and 14–15 years), sex, and the presence or absence of younger siblings in the family were studied in two situations which assessed their interest in babies: responsivity to an unfamiliar baby in a waiting room situation and reactions to pictures of babies. Subjects' birth order does not affect degree of interest, only mode of expression. These findings held for boys, but not girls. Regardless of age, boys without younger siblings expressed their interest in babies in more distal, cautious ways. The results were discussed in terms of the contention that birth order effects are best understood as distinctive for each sex, especially when sex-role-related behavior is being investigated.This project was supported by funds from the Boys Town Center for the Study of Youth at Stanford. We are indebted to Barbara Aschenbrenner for her assistance in all phases of this study.     

Resolving the debate over birth order, family size, and intelligence

Hundreds of research articles have addressed the relationship between birth order and intelligence. Virtually all have used cross-sectional data, which are fundamentally flawed in the assessment of within-family (including birth order) processes. Although within-family models have been based on patterns in cross-sectional data, a number of equally plausible between-family explanations also exist. Within-family (preferably intact-family) data are prerequisite for separating within- and between-family causal processes. This observation reframes an old issue in a way that can be easily addressed by studying graphical patterns. Sibling data from the National Longitudinal Survey of Youth are evaluated, and the results are compared with those from other studies using within-family data. It appears that although low-IQ parents have been making large families, large families do not make low-IQ children in modern U.S. society. The apparent relation between birth order and intelligence has been a methodological illusion.     

Associations between Birth Order and Personality Traits: Evidence from Self-Reports and Observer Ratings

Sulloway (1996) proposed that personality traits developed in childhood mediate the association of birth order with scientific radicalism. Birth-order effects on traits within the five-factor model of personality were examined in three studies. Self-reports on brief measures of Neuroticism, Extraversion, and Openness in a national sample (N= 9664) were unrelated to birth order. Self-reports on the 30 facet scales of the Revised NEO Personality Inventory (NEO-PI-R) in an adult sample (N= 612) showed only small effects for Altruism and Tender-Mindedness. Peer ratings (N= 166) supported the hypotheses that laterborn children would be higher in facets of Openness and Agreeableness, but spouse ratings (N= 88) did not replicate those findings. Birth order may have subtle effects on perceived personality, but it is unlikely that this effect mediates associations with scientific radicalism.     

Age and sex differences in behaviors mediated by the ventromedial hypothalamus.

Age and sex differences in behaviors mediated by the ventromedial hypothalamus (VMH) were examined in the rat. Circadian rhythm, emotionality, and taste responsiveness (except for responsiveness to quinine adulteration) were found to shift, in one or both sexes, toward a pattern suggesting decreased VMH functioning with increasing age. A post hoc analysis of the configuration of positive and negative results suggests that, for those behaviors known to show both immediate and sustained effects of VMH lesion, male rats show a marked trend toward the lesioned pattern of behavior with increasing age, whereas females show weaker or nonexistent age trends in the same behaviors. For those behaviors that have been shown to change only during the static, obese phase, or for which data re controversial as to whether changes take place as a result of the VMH lesion at all, this age and sex pattern does not emerge.     

Intelligence and fertility in the United States: 1912-1982

Results are presented for the 1st analysis of the relationship between IQ and completed fertility using a large, representative sample of the US population. Correlations are predominantly negative for cohorts born between 1894 and 1964 but are significantly more positive for cohorts whose fertility was concentrated in the baby boom years. Previous studies reporting slightly positive correlations appear to have been biased in their restriction of samples to atypical cohorts. The National Opinion Research Center (NORC), a nonprofit research organization affiliated with the University of Chicago, conducted the General Social Survey (GSS) in the US each year from 1972 to 1982, except for 1979. A combination of block quota and full probability sampling was employed. Hour-long interviews were completed with 12,120 respondents who were English-speaking, noninstitutionalized adults (18 years or older) living within the continental US. Such questions as age, place of birth, income and occupation, were asked in each interview. Other questions about attitudes on various social, political, and moral issues were rotated in different years. The unique opportunity this data set affords is an overview of the relationship between intelligence and fertility for a nationally representative sample of Americans whose major reproductive years fell between 1912 and 1982. Data were consolidated from the 4 surveys in which the vocabulary test was given (1974, 1976, 1978, and 1982). Respondents were divided into 15 birth cohorts of 5-year intervals ranging from before 1894 to 1964. Correlations between vocabulary scores and number of siblings are markedly negative across all 15 cohorts. Vocabulary sibling correlations are more negative in every cohort than vocabulary offspring correlations. Previous reports of a neutral or slightly eugenic relationship appear to be due to the nature of the samples used, in part because the cohorts chosen were atypical, and in part because they did not include nonwhites. Childless respondents averaged slightly higher scores than did those with 1 or more children, indicating that the automatic exclusion of the childless from sibling-IQ studies has not spuriously inflated negative correlations.     

Birth Order Effects on Personalityand Achievement Within Families

We investigated birth order effects on personality and achievement in four studies (N = 1,022 families) including both student and adult samples. Control over a wide range of variables was effected by collecting within-family data: Participants compared their siblings (and themselves) on a variety of personality and achievement dimensions. Across four diverse data sets, first-borns were nominated as most achieving and most conscientious. Later-borns were nominated as most rebellious, liberal, and agreeable. The same results obtained whether or not birth order was made salient (to activate stereotypes) during the personality ratings. Overall, the results support predictions from Sulloway's niche model of personality development, as well as Zajonc's confluence model of intellectual achievement.