diversifying in order to better compete

Were You 'Dethroned' In Your Birth Order? Birth order effects in the formation of long-term relationships

By Joshua K. Hartshorne of Harvard, Nancy Salem-Hartshorne and Timothy S. Hartshorne of Central Michigan University writing in the Journal of Individual Psychology

Researchers have debated for 134 years whether birth order has long-term effects on the development of a child, and so far no consensus has emerged. In addition to practical applications and relevance to the study of personality, birth order effects are an important test case for theories about how and whether home environment affects the adults children become. In two large surveys of diverse populations, we found that people are more likely to form close platonic and romantic relationships with other people of the same birth order. This effect cannot be explained by confounds of family size.

In 1874, Francis Galton noted that first-born sons and only sons were overrepresented among scientists (Galton, 1874), making birth order one of the first constructs studied in psychology. Presciently anticipating the next 134 years of debate, he attributed this effect to both practical circumstances – "they are more likely to become possessed of independent means, and therefore able to follow the pursuits that have most attraction to their tastes." – and their "independence of character," a result of having been treated more as companions by their parents.

Since then, numerous studies have investigated systematic differences in intelligence, achievement and personality between children of different birth orders. A number of theories have been postulated to account for such differences, generally focusing on the fact that each child’s home environment is at least partly a function of their birth order.

In 1918, Alfred Adler gave what is likely the first comprehensive account of birth order, focusing on "dethronement". The eldest child was, at some point, the center of attention; this is lost with the addition of a sibling.

Younger children, in contrast, see their elder siblings as "pacesetters," and race to catch up. The youngest child, in contrast, is never dethroned. A number of effects on personality are predicted on this basis.

Sulloway, in contrast, explains birth order effects in terms of children diversifying in order to better compete for scarce resources, such as parental investment. This leads, under his account, to the eldest child identifying with her parents and the establishment in general, while younger children are more open to new experiences and are generally more rebellious.

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In fact, there is at least one such behavior that appears to be uncontroversially liked to birth order: younger siblings engage in risky behavior earlier. However, this may have less to do with personality differences resulting from birth order, and more to do with older siblings exposing younger siblings to such behaviors earlier.

In this investigation, we focus on a stable, long-term and ecologically valid behavior: the formation of close platonic and romantic relationships. We assume that if birth order systematically affects personality, and personality systematically affects the formation of friendship and mating bonds, there should be a relationship between the birth orders of friends and between the birth orders of spouses.

Note that this should be true regardless of which positive theory of birth order effects is correct. Birth order studies typically consider one particular trait predicted by a theory to differ across birth orders, such as educational achievement, aggression, self-esteem or conservatism. Thus, a significant birth order effect can only be found if the birth orders differ on that particular construct (and if it is measured in a well-designed study). In contrast, our method casts a wider net.

A small number of studies have investigated birth order effects on mating patterns. The majority of these focused on testing Walter Toman’s "duplication theorem," which suggested that adults try to recreate in marriage the social dynamics of their childhood. Thus, men with only older sisters should be expected to marry women with only younger brothers, and such marriages should be more stable and successful than other birth order combinations.

Read the rest of the abstract to the paper, Birth order effects in the formation of long-term relationships. [Editor's Note: We did not retain citations in the abstract and did skip some paragraphs.]

Relationships and Going Places, Senior Women Web

Were You 'Dethroned' In Your Birth Order? Birth order effects in the formation of long-term relationships

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