In spite of sharing genes and environments, siblings are often not as similar in nature as one might think. But where do the supposed differences come from? Alfred Adler, a late-19th- and early-20th-century Austrian psychotherapist and founder of individual psychology, suspected that birth order leads to differences in siblings.
Such categorizations are popular because they’re rather intuitive, and one can always find an example of the sensible big sister or the rebellious young brother.
[I]n a 2015 study, which included 377,000 high school students, psychologist Rodica Damian and her colleague Brent W. Roberts, both then at the University of Illinois at Urbana-Champaign discovered that firstborns tended to be more conscientious, extraverted and willing to lead. Contrary to expectations, they were also more tolerant and emotionally stable than adolescents with older siblings. Yet the differences were very small, and the researchers concluded that the importance that is generally attached to sibling position in shaping one’s character is exaggerated.
“It is quite possible that the position in the sibling sequence shapes the personality—but not in every family in the same way,” says Frank Spinath, a psychologist at Saarland University in Germany. “In other words, there may be an influence but not a systematic one.”
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