Birth order and two marketing-related measures of aggression

Several bodies of research link birth order and aggression. With a sample of 144 women and 225 men business students, the present study investigated birth order and aggression using two measures from academic marketing. Neither measure detected significant influence of birth order. Implications are discussed regarding marketing and consumers' behavior.     

Birth order and intelligence: an immunological interpretation.

The literature indicates that the IQs and school performance of children tend to decline with increasing order of birth. A hypothesis is here presented that the effect of birth order upon intellectual performance may result from an increasing probability of maternal immune attack upon the fetal brain in utero with order of parity. In support of this hypothesis, evidence is adduced from the literature that the fetal brain is antigenic, that fetal antigens may reach the immune system of the mother, that the incidence of maternal sensitization to fetal antigens increases with parity, that antibodies may readily cross the placenta and reach the fetal brain, that antibodies can be highly teratogenic, and that certain antibodies may damage, in a lasting way, the structure, function, and learning capacity of brains in experimental animals and human infants.     

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 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.