Oldest siblings may be the conservatives of the family, according to new research from Italy.
The new study finds that the eldest child of a family is more likely to be conservative than the second-born, which supports a controversial theory that has been kicking around the social science community since at least 1928. The question of whether and how much birth order really shapes a person's personality remains open and contentious, however.
"We suggest that differences in conservatism between firstborns and second-borns stem from different strategies of optimizing the parental resources children can gain in the family system," study researcher Daniela Barni, a psychologist at the Catholic University of Milan in Italy, told Live Science. [11 Facts Every Parent Should Know About Their Baby's Brain]
Birth order controversy
Barni and her colleagues were investigating a question with a long history in psychology. The idea that a person's birth order can influence his or her entire life came from Alfred Adler, an Austrian psychiatrist who lived at the same time as Sigmund Freud. Adler theorized in 1928 that firstborn children are more conservative — in the sense of being resistant to change and preferring order and conformity — than their younger siblings, because the eldest child has had the experience of being toppled from his or her throne by the sudden arrival of a tiny competitor.
In 1997, psychologist Frank Sulloway expanded on the theory in his book, "Born to Rebel: Birth Order, Family Dynamics, and Creative Lives" (Knopf Doubleday Publishing Group, 1997). Sulloway suggested that firstborns are used to being dominant and prefer to uphold the status quo, while second-borns, looking for a unique niche to fill in their families, take a path of rebellion. Firstborns also stick to a conservative path in order to align themselves with their parents, Sulloway argued.
An initial study supported this theory, but follow-ups returned frustratingly mixed results. It's a problem that has long plagued birth order research: Studying differences between families is difficult, because there are so many variables, and those variables interact with each other. For example, parents who decide to have one child might be different (in either personality or in demographics) than parents who have two, three or more. Disentangling the effect of birth order from all the other potential family influences on a child is very difficult.
"Birth-order effects on values, personality, intelligence and many other psychological characteristics are definitively a controversial topic," Barni told Live Science, speaking for herself and her colleagues. "In our opinion, the inconsistency in results mostly comes from the poor methodological approaches traditionally used to study birth order and its effects."
Birth order's effect
Barni and her colleagues tried to overcome some of these problems by getting information from multiple family members in multiple families. The researchers recruited 96 Italian families and surveyed both parents, the firstborn child and the second-born child in each, for a total of 384 participants. [7 Personality Traits That Are Bad For You]
The family members filled out questionnaires about their own aversion to change and feelings about order, tradition and other facets of conservatism. The researchers analyzed their answers in relation to birth order, controlling for the gender, age and religiosity of the children, the religiosity and education level of the parents and the age of the parents at the birth of the first child.
The results of this analysis partly supported Sulloway's theories. Firstborn children were, indeed, more conservative on average. However, they were not more likely to be influenced by their parents' levels of conservatism than their younger siblings, suggesting that older kids aren't taking on a conservative personality in order to throw in their lot with Mom and Dad.
"In other words, firstborns are more conservative than are second-borns, independent from their parents' conservative values," Barni said. This tendency toward conservatism may be a canny way to maintain one's place in the family, she said.
"Firstborns, having experienced the undivided attention and care of their parents, and being stronger and more intellectually developed than their younger siblings, occupy a dominant position," she said. "Thus, they tend to safeguard their status advantage by developing conservative values helping them to uphold the status quo."
The study has some limitations, as it represents only a small slice of the Italian population and did not take the effect of blended or stepfamilies into account. Further research in larger populations and across cultures would be useful, the researchers wrote in the August 2014 issue of the journal Personality and Individual Differences. Future study should also examine how such personality traits might develop within families, Barni said.
Of course, any eldest siblings feeling affronted at being told they're sticks in the mud can soothe themselves with the results of another birth-order study. In 2007, Sulloway (who was not involved in Barni's research) found that firstborns had higher IQs than their younger siblings.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.