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Family Dynamics

3 Ways Birth Order Can Influence Who You Are

Research into key differences between oldest, middle, and younger children.

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Can birth order shape who we become? The theory that our position in our family might affect our character development began in earnest with Alfred Adler, a contemporary of Sigmund Freud. He proposed that, generally speaking, firstborns like to be in the spotlight, the youngest are pampered, and middle children are squeezed out.

Birth order effects remain a controversial area of research, but numerous studies have found that that it may have a profound impact on our lives. Here are three ways birth order has been found to influence who we are.

1. Doing Good

Can birth order influence how sensitive we are to the needs of others? One line of thinking goes that middle-borns are more “prosocial” in comparison to the eldest and youngest children. It has been argued from an evolutionary perspective that parents invest more in firstborns (since they have survived for a longer duration of time, and are closer to the age of reproductive maturity) and in last borns (since parents are older, and youngest children have fewer younger rivals). Middle-borns receive comparatively less from their parents; seem more inclined to develop relationships with people outside of the family; and tend to be less focused on the family. Indeed, research has found that middle children usually score higher on personality traits like agreeableness and extraversion, which facilitate close non-kin relationships. Consider a study of civil disobedience in which college students boycotted a chain store as a show of support for employee rights: An astounding 100 percent of those who were arrested more than once were later borns willing to take risks for the benefit of others.

2. Health

Research suggests that birth order can play a significant if complicated role in our health. In a study from Norway examined the influence of birth order on health and health-related behaviors, investigators found that on average, later borns have lower blood pressure, triglycerides, and Body Mass Index than firstborns. However, firstborns seem to have better self-reported physical and mental health, and tend to report being happier, which may partially explain why this group has been found to have lower suicide rates.

Firstborns are also much less likely to smoke, a finding in keeping with previous research that revealed a pattern of poorer health behaviors exhibited by later borns. This result may also explain the higher mortality rates found among later borns. What might account for these findings? Again, the researchers contend that higher maternal investment in firstborns may play a role. Alternatively, they suggest it could be that birth order effects may be biologically based—in particular, the in-utero programming hypothesis proposes that the maternal immune system changes with the number of births, and that this could lead to health-related differences both in-utero and once a child is born.

3. Income

Studies have found that birth order may influence income later in life. A study that examined data from 11 European countries for males born between 1935 and 1956 revealed that firstborns earn, on average, 13.7 percent more in their starting wages than later borns. But there's a twist: This benefit is only temporary and fades 10 years after a firstborn enters the job market. While firstborns tend to begin with better jobs, in part due to their higher levels of education, later-born children are able to make up the gap by changing jobs earlier and more often to positions with higher pay. Researchers argue that later borns may be less averse to risk than firstborns, and thus more willing to take chances in their professional lives.


  • Black, SE., Devereux, PJ., Salvanes, PJ, and Kjell KG. Healthy(?), Wealthy, and Wise Birth Order and Adult Health (February 8, 2016). NHH Dept. of Economics Discussion Paper No. 03/2016. Available at SSRN: or
  • Bertoni, M. & Brunello, G. Later-borns Don't Give Up: The Temporary Effects of Birth Order on European Earnings. Demography, 53 (2), 449-470, 2016.
  • Salmon, C., Cuthbertson, AM, Figueredo, AJ. Personality and Individual Differences, 2016, 96, 18-22. The relationship between birth order and prosociality: An evolutionary perspective.

Vinita Mehta, Ph.D. is a licensed clinical psychologist in Washington, D.C., and an expert on relationships, managing anxiety and stress, and building health and resilience. She provides speaking engagements for your organization and psychotherapy for adolescents and adults. She has worked with individuals struggling with depression, anxiety, trauma and abuse, and life transitions. She is also the author of the forthcoming book, Paleo Love: How Our Stone Age Bodies Complicate Modern Relationships.

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