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The Truth About Only Children

More evidence that birth order is not destiny.

Key points

  • There's a long-held myth that only children become spoiled and demanding as adults.
  • A comprehensive personality study now shows that this myth is unfounded.
  • Not only is personality not determined by family position, but it can also change across the adult years.

The fate of the only child has long been debated, with some of the most attention on the personality theory of Alfred Adler, a Viennese psychologist who was a disciple of Sigmund Freud. Adler became essentially the founder of birth order research with his characterization of the baked-in traits that siblings, and those without siblings, carry throughout their lives.

Decades later, birth order research in personality has failed to establish reliable distinctions among oldest, middle, and youngest children. In part, the lack of clear differentiation may reflect the complexity within families based on child gender, age of parents, child age, and a host of other relationship qualities within families. Comparisons of children with siblings to only children thus become even more complicated.

As National Sibling Day in the U.S. approaches, April 10, 2022, it seems timely to examine the fate of children who, by definition, will be unable to celebrate this commemoration.

The Theory of the Only Child

In what might now be called the definitive study of personality comparisons between only children and those with siblings, University of Auckland’s Samantha Stronge and colleagues (2019) embarked on their mission to settle the matter for good. They began their quest with the observation that only children may indeed have a host of potential advantages due to being the sole focus of their parents, ranging from the financial to the emotional. On the other hand, the solo child's “sibling deprivation” can negatively affect their personality development due to their missing out on socialization experiences with fellow children in the home.

On balance, then, Stronge and her fellow researchers suggest that only children “should be more spoiled and self-centered, lack social skills, and struggle with anxiety.” However, the opposite can be true as well. Because they are the sole recipient of family attention and resources, they should also be “more mature…[and] do better academically.” The lack of other children in the home can also lead them to “engage in more imaginative play.” Yet, with polls consistently showing that only-child families are seen as less desirable in the U.S., plus those negative personal attributes most people associate with only children, even “clinicians expect a poorer prognosis” for them.

Although prior researchers failed to establish any reliable personality differences that might back up these negative characterizations, the New Zealand authors note that earlier work was limited by small sample sizes and inconsistencies in measurement. Small sample sizes in particular could be a problem given that comparisons between only children and those with siblings are made more complex by the varying family composition in multiple-sibling households. Stronge et al’s study was designed to overcome these limitations.

A Big Look at the Only Child

With this background in mind, you might wonder how Stronge and her collaborators could possibly tease out all the potential complexities of discovering how only children differ from their counterparts in multi-child families. To begin with, the authors were able to take advantage of an extensive multiyear probability sample of New Zealand adults, representing all adults eligible to vote. In 2016, the sample included nearly 21,000 adults averaging 50 years old (63 percent women), of whom 88 percent identified as New Zealand European.

To measure personality, the Auckland researchers asked participants to complete a brief Five-Factor Model questionnaire, which assessed the component traits of:

  • Openness to Experience (“I have a vivid imagination”)
  • Conscientiousness ("I get chores done right away”)
  • Extraversion (“I am the life of the party”)
  • Agreeableness (“I sympathize with other people’s feelings”)
  • And Neuroticism (“I have frequent mood swings”)
  • Adding the sixth factor often used in personality studies, Honesty-Humility, the authors also included items such as “I deserve more things in life.”

Have you already started to construct your own hypotheses about what the authors might find? Did that last factor about deserving more than everyone else seem to ring true as you thought about the only child’s feelings of entitlement? Are you imagining people growing up with other kids in the household as being better able to show empathy?

If so, then you will be surprised to learn that patterns of personality traits across age groups for only children were almost indistinguishable from the patterns in adulthood shown by individuals from multi-child households. The personality traits of neuroticism and openness did vary by age group, showing slight dips in later adulthood, and honesty-humility trended upward. The sibling-no sibling comparison, though, yielded differences that were negligible or, as the authors conclude “vanishingly small.”

Negligible didn’t mean insignificant, however, and some comparisons did yield “statistically significant” differences. However, with such a large sample, there’s a low threshold for showing that one mean score differs from another. Put slightly differently, as the authors note, there’s a 52.5 percent chance that an only child will have lower honesty-humility than one with siblings, which compares with the 92 percent chance that a man will be taller than a woman. In their words, “Even if people were astute enough to naturally observe such a small personality difference, it would not justify the extent of negative beliefs about only children."

Are You Ready to Give Up This Myth?

There’s a great deal of reassurance in the New Zealand study that, if you never had anyone with whom to celebrate National Sibling Day, there’s nothing wrong with you. Even if you are sending out the cards and flowers to your siblings, though, does this mean that you’re enjoying a lifelong dividend of a better-adjusted personality than your only-child friends? More importantly, though, has your birth order and or only-child status locked in your fate?

The child’s status in the family unquestionably becomes a key component of the identity that people mature into as adults. You will always be that member of the younger generation whose position is determined by when your parents had you and how many other children they also produced, even if those other children came from one or two different parents. However, based on the New Zealand findings, there’s no reason to equate that accident of your birth with your long-term prospects in life. Furthermore, the differences across age groups revealed in this study confirm prior work showing that personality can change in adulthood.

To sum up, it may be fun to kick around the idea that being an only child, or not, helps define the adult you are today. However, based on the New Zealand findings, it may finally be time to see your personal development as a function of the many other qualities that contribute to who you are as you continue on your own unique life's journey.

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Stronge, S., Shaver, J. H., Bulbulia, J., & Sibley, C. G. (2019). Only children in the 21st century: Personality differences between adults with and without siblings are very, very small. Journal of Research in Personality, 83. doi: 10.1016/j.jrp.2019.103868

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