For centuries, humans have held beliefs about the birth order of their children. Some cultures believe that each child is predestined to have certain features and personality traits exclusively because of their birth order. In some countries, birth order is one of the most important factors in determining how to raise a child. Over the years, many researchers have attempted to discover the exact effects of birth order. In general, the vast majority of studies contradict and even debunk many of the traditional ideas around birth order.
One of the most common birth order beliefs is that first-born children are more likely to be dominant and become leaders. This stems from the idea that first-borns take on a leadership role among their siblings. Another common concept is that the youngest children are more playful. Most studies point out that these traits are likely the result of many more factors than simply the order in which a child was born.
Birth order has long affected the laws and traditions of cultures. Some groups expect their first-borns to act more assertive and take charge. This leads to some families driving their first child into career fields that allow them to have a leadership role. This also affects inheritance laws in some cultures, on the assumption that first-borns are better equipped to handle the responsibility than their siblings. These concepts of birth order even extend to only children. Mainland China’s little emperor syndrome stems from the idea that all only children will act bratty, snobbish, and spoiled.
In modern psychology, the vast majority of theories on birth order began with Francis Galton’s insistence in 1874 that too many first-borns were members of the Royal Society. Alfred Adler, a psychotherapist, wrote extensively on the topic. He considered first-borns “power-hungry conservatives” while describing middle children as competitive and last-borns as lazy and spoiled. He was a middle child. In the 90 years since his writings, thousands of psychologists and researchers have attempted to verify these claims.
Two of the largest critics of the concept that birth order affects personality were Cecile Ernst and Jules Angst. They studied all of the writings on this topic published between 1946 and 1980. They also performed a study of more than 6,000 men in Switzerland. The doctors not only failed to find substantial evidence that birth order has any effect on personality, but they also deemed previous research a “waste of time.” Their research and responses set the stage for future critics.
Nearly 70 years after Adler’s writings, psychologist Frank Sulloway proposed the Family Niche Theory. His theory was that siblings would naturally adapt to certain roles within a family to prevent competition. He went on to state that differences in age, power, and size would naturally lead to stable personality differences. His view was that these differences would be visible in the Big Five personality traits: emotional stability, extraversion, agreeableness, conscientiousness, and openness to experience. Sulloway’s theory stated that because firstborns were physically superior, that they would naturally be more aggressive and less agreeable than their siblings. Later-borns would rely more on social support and become more extraverted.
Following Sulloway’s theories, researchers have attempted to quantify the effects of birth order on the Big Five personality traits. A 2015 study in the PNAS journal researched more than 20,000 people from Great Britain, Germany, and the United States. It consistently found no birth-order effects on these traits. A similar study from the Association for Psychological Science confirmed these findings in relation to the Big Five and eight other personality aspects.
A 1998 study also found no birth-order effects but discovered some interesting issues. Many people hold the belief that birth order affects personality and insist that they could notice the effects once they were aware of a person’s birth position. Additionally, later-born children often self-report that they are more open and agreeable. However, when their spouses rated them, the results did not match up.
Beyond the Big Five personality traits, some studies do suggest that birth order affects other aspects. Many studies support that first-born children are slightly more likely to score a few points higher on IQ tests than later-born children. However, a study from the Indian Journal of Psychological Medicine found that first-borns are more inclined to have maladaptive perfectionism, driving them to a more negative mental state. They strive for perfection but receive no pleasure from their efforts.
One of the largest impacts on this research is that people tend to act differently in familial contexts than they do in non-familial situations. Interestingly, many studies performed within-family analyses and external analyses and could measure this. They found that people tend to revert to their familial role when they are with their family. This extends to other intimate relationships. Some smaller studies suggest that later-born spouses and roommates are more likely to be agreeable and extraverted, at least from outside perceptions.
Some of the most commonly believed effects of birth order are more likely the result of a Darwinian struggle for survival. Before the 20th century, most children didn’t survive to adulthood. Because of this, eldest children were more likely to reach the age of reproduction. This also meant that they were more likely to contribute to society in various ways. On the opposite end, later-born children are more likely to be born towards the end of the mother’s reproductive cycle. This makes their parents favor them more because they are viewed as irreplaceable. This could be why some people view later-borns as spoiled.
Those personality traits that aren’t the result of a Darwinian mentality could be due to natural struggles for attention. Children naturally crave their parents’ attention and time. Because of this, they will perform actions to gain that attention. Some children may become louder and more aggressive, while others become more conscientious. Additionally, the idea that first-borns are more mature may stem from a simple difference in age. People become more conscientious as they age, and parents will naturally compare their children. Even if they are aware that age plays a role, they can’t help but weigh the observable differences more heavily.
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