Birth order, family structure and personality variables

The birth order and family structure variables assessed included first or only child, position in multi-child family, position in dyadic family, age of parents at birth of given child, whether reared by one or both parents, whether reared under permissive or authoritarian family atmosphere. The personality variables assessed included Sociability, Anxiety, Dominance, Superego, Phlegmatic Temperament, Involvement, Self-Regard and other scales measured by the Howarth Personality Questionnaire. One hundred seventy female and 142 male undergraduates were tested. Significant relationships found included: anxiety lower in firstborns; superego higher in firstborns; persistence higher in those not dominated by elder sibling; phlegmatic temperament higher in permissive families; involvement and phlegmatic temperament lower in single parent families; self-pride higher in the elder of a sibling pair; individual tolerance higher in children reared by both rather than single parent.     

Birth order and a two-dimensional assessment of personality.

Higher order personality dimensions of extraversion-introversion and neuroticism were studied as functions of birth order in two-sib families, using 141 female subjects, with control over sex of sibling and sib age separation. No significant personality dimension variance was attributable to birth order in females. The results were considered briefly in terms of the importance of birth order, heritability questions, and the possible contribution of birth order to lower order traits.     

Birth order and personality: Some empirical findings and a biobehavioral theory

The birth-order variables assessed included sex and number of siblings, assignment to 2- or 3-child family for separate sample analysis, family position as appropriate to given sample, spacing effect—was the birth of the second child spaced 4 years or more after the first child—dominance relationships in the family, sex of nearest siblings, sex of other siblings as appropriate, whether raised by both original parents, whether raised by foster parent(s). The personality variables assessed included sociability, anxiety, dominance, superego, phlegmatic temperament, involvement, self-regard and other scales measured by the new Howarth Personality Questionnaire. Samples of 50 for the 2-child families and 58 for the 3-child families were analyzed and it was found that: (a) in the 2-child families eldest children were less cooperative than younger, that those reporting dominance by another sibling were higher in state anxiety and this also applied to the younger of the pair, that those spaced in birth order were less afraid of being socially unacceptable, that those raised by both parents were higher in involvement; (b) in the 3-child families those dominated by a sibling, regardless of position, had more hypochondriac symptoms (a sign of anxiety), and that those spaced in birth order showed less cooperativeness. A biobehavioral theory to encompass biological-hormonal spacing effects and dominance as well as other intrafamilial behaviors was proposed.     

Birth order and introversion-extraversion

The relationship between birth order and introversion-extraversion was investigated. Subjects were 70 male and 77 female undergraduates, all from three-child families. The measure of introversion employed was the Social Introversion Scale (Scale 0) of the Minnesota Multiphasic Personality Inventory. A two-way analysis of variance indicated that first borns were more introverted than either middle-horns or last-horns, with no difference between the latter two groups. It was suggested that inconsistent results in this area may be due to the use of different measures of introversion.     

Birth order differences in normal personality traits: Perspectives from within and outside the family

The hypotheses of Sulloway (1996) regarding birth order differences in five-factor model personality traits were tested in a sample of 231 college students with the NEO Five-Factor Inventory (NEO-FFI; Costa & McCrae, 1992). Data were collected from three sources (self, peer, and parent) to systematically evaluate previous observations that birth order differences are more commonly found when ratings are obtained from family members than from observers outside the family (Ernst & Angst, 1983). Using a between-family design, students were selected only from families with two or three full biological siblings and no half-siblings, step-siblings, or adopted siblings. Firstborn (n = 103) and laterborn (n = 128) students were compared using NEO-FFI ratings by the self, by a same-sex college peer, and by a biological parent. No birth order differences were found for any of the five NEO-FFI scores using any of the three rating sources. Effect sizes (Cohen’s d) were less than .20 for all comparisons. Suggestions for new approaches to the study of birth order differences are considered, including the use of within-family designs and more contextualized personality variables.     

Predicting vocational performance of engineers from selected vocational interest,personality, and scholastic aptitude variables

The study examines the validity of the ACE and selected subscales of the EPPS and SVIB in predicting the vocational performance of engineers. Multidimensional criteria of vocational performance assessed from both external and internal frames of reference were employed. Six predictors were related to 17 vocational performance criteria; of the 102 tests that were made, 7 were found to be statistically significant. The results indicate that, in general, vocational performance cannot be accurately predicted by vocational interest, personality, and scholastic aptitude variables. The only consistent finding was that subjective ratings of vocational performance were predicted by SVIB Group V scores; a “self-esteem” interpretation was posited. Implications of the results for counselors and employers were discussed.     

Birth order and person perception dispositions

The early social experiences of firstborn, laterborn, and only children were analyzed from the viewpoint of how those experiences influence the child's general image of human nature. It was hypothesized that there are some differences in the centrality of an evaluative dimension, that are related to birth order. Subjects in Poland and in the United States rated 20 known stimulus persons on 25 trait dimensions. The results supported the hypotheses and seem to point to some origins of individual differences in certain person perception processes.