Has your TikTok For You Page bombarded you with influencers proclaiming that you might suffer from Eldest Daughter Syndrome? The app’s algorithm can’t diagnose you with a mental illness (yet), but, even if it could, Eldest Daughter Syndrome just refers to a collection of personality traits, not a real condition. The phrase is typically associated with the stereotyped personality of an oldest daughter: overachieving, perpetually anxious, and taking responsibility for younger siblings. Your friend who takes the lead at the airport, armed with digital boarding passes, nonperishable snacks, and 3.4 ounce containers of hand sanitizer, and breezes through security in 5 minutes flat despite having arrived 2 hours early? Eldest daughter. The woman in your office with a color-coordinated planner and Google Calendar? Eldest daughter. Your sister who plans the family Secret Santa gift exchange and schedules holiday cooking in between babysitting and cleaning house? You guessed it—eldest daughter. 

The original TikTok on Eldest Daughter Syndrome gathered thousands of likes and comments, indicating that these feelings resonate for many people. But do these personality traits and semi-dysfunctional familial relationships hold true in real life, or is Eldest Daughter Syndrome just another stereotyped label in a social media trend? To psychologically determine if eldest daughters really do have distinct personalities, there are a few research questions we have to take into account. 

First, we have to be able to accurately assess personality traits. In psychology, this is typically done via questionnaires. Most common is the Big Five (John, Donahue, & Kentle, 1991). This survey measures openness, conscientiousness, extroversion, agreeableness, and neuroticism. Participants might be asked to answer questions about themselves, or, in some studies, participants answer questions about others’ personalities. For example, in much of the research on siblings, parents are asked to answer questions about their children’s personalities. However, these measurements should be viewed with caution. Though you might be the greatest expert on yourself, it’s likely that your ratings of your own personality will change year-to-year or even week-to-week, as the context of your life changes. When parents rate children, they, too, are responding within a specific context. It’s unlikely that a parent would, for instance, rate their child as neurotic in one of these surveys. In addition, when people are told that a study is about examining personality differences among siblings, they may answer differently than if they are blind to the design of the experiment.  

Secondly, if we assume that personality traits are impacted by birth order, then it stands to reason that eldest daughters should have a personality distinct from their younger siblings. But does that mean there are traits universal to all eldest daughters? Let’s take two families, who we’ll call Family A and Family B. If Family A happens to be made up of doctors and scientists, and Family B happens to be made up of artists and actors, Eldest Daughter A might strongly differ from Younger Son A, and Eldest Daughter B might be quite different from Younger Daughter B. But that doesn’t mean that Eldest Daughter A and Eldest Daughter B will have similar personalities. Within the context of her family, Eldest Daughter B might be extremely organized, even if, compared to Eldest Daughter A, she’s all over the place. This is the conflict researchers face when determining how to analyze their data: should they compare personality traits within a family, between families, or use both methods? And what does each tactic tell us about personality and birth order as a whole?

Finally, one struggle that researchers face is quite obvious: firstborn children are born earlier, and so are older, and laterborn children are therefore younger. But researchers may choose to conduct their study when siblings are still growing and changing. If one sibling is in their late teens and another sibling hasn’t hit puberty, personality differences may come simply from age. In fact, differences in generation may also contribute to distinct personalities, whether we’re looking from baby boomers to Gen Z or within a family—think about a child born just before a parental divorce versus a child born years before! These variables have to be considered thoughtfully in order to get reliable results. 

After going through the experimental design rigmarole listed above, psychological researchers have generally concluded that there are almost no effects of birth order on personality (Mu et al., 2024; Dudek et al., 2022; Marini & Kurtz, 2011). Where differences in personality exist, they are typically small and virtually unnoticeable. In one study, it was found that firstborn children had a significantly higher intelligence than their laterborn counterparts by 5% of a standard deviation in 6 out of 10 cases (Rohrer, Egloff, and Schmukle, 2015). To paint a better statistical picture, 5% of a standard deviation difference in IQ scores is only 0.75 points. With such a small effect occurring only in 60% of cases, it’s nearly impossible to distinguish between an eldest daughter and a younger sibling simply by their intelligence. These authors ultimately concluded that there were no other significant differences. 

Another small conclusion comes from the scientists Boccio and Beaver. They found that laterborn children were more extroverted than firstborn children, but the effect size, or the strength of the relationship between these characteristics, was quite small (Boccio & Beaver, 2019). Once again, they otherwise found no differences in personality between siblings depending on birth order. The symptoms of Eldest Daughter Syndrome, therefore, seem tiny at best, and false at worst. 

But where do these effects, no matter how small, come from? Two theories abound: first, that older siblings receive more biological resources, such as better maternal health, and more psychological resources, like increased parental quality time, than their younger siblings. The second theory addresses a form of social Darwinism. Younger siblings are born into a family where their role as a child is already partially occupied by their older sibling. To make themselves essential within the family structure, younger children then might try to change their personality. This might indicate why Boccio and Beaver found younger siblings to be more extroverted—laterborn siblings could exert more social energy in order to differentiate themselves from their older siblings. 

However, neither of these theories have held up well under repeated psychological testing. Generally, the field agrees: birth order has no effect on personality. So why does popular perception remain? Why do we think of eldest siblings as responsible and uptight, middle children as quiet and unmemorable, and the youngest child as attention-seeking? The complications inherent in research design might provide an answer: age.

 Let’s say you meet a set of siblings who are all at different developmental stages, such as a trio of brothers aged 6, 11, and 14. You will perceive each of them differently on account of their age. The 14-year-old will seem mature, organized, and achievement-oriented compared to his 11-year-old brother, and the 11-year-old may seem awkward compared to his adorable 6-year-old brother. As they age, your opinion of them may remain heavily influenced by this first impression. 

In addition, stereotypes about sibling personalities may also create a psychological chicken-and-egg situation—except that we know which came first. If parents expect older siblings to take care of their younger siblings as they age, the parents may perceive the older sibling as more mature and responsible; as the older sibling learns to take care of their younger siblings, they may become more mature and responsible. The power of these expectations is that they reinforce themselves. Parental expectations may become their children’s expectations. As children grow up, they may also find themselves assuming their personality is because of their role as an older sibling. For example, an older child may assume that they are more organized because they are an older sibling, and that’s just how older siblings are—rather than recognizing the time spent taking care of young children, which ultimately taught them to be responsible. But any child tasked with large responsibilities from a young age would likely take on the same traits.

So what does this mean for Eldest Daughter Syndrome? Well, it’s not appearing on the pages of the DSM, the handbook used to diagnose mental disorders, anytime soon. In fact, with such limited scientific findings, we may find psychological researchers exploring sibling order less and less. But that doesn’t necessarily mean that eldest daughters everywhere are wrong. The social media phenomenon could be attributed to the weight of social expectations placed on oldest daughters. When expectations of oldest children are coupled with the gendered roles placed on women, it makes sense that these daughters might report being anxious, responsible, pseudo-caretakers of their siblings, since society expects them to take on the persona of parent and caretaker. It might also be that these personality traits are particularly strong only within familial settings; the eldest daughter might find herself displaying mature, organized traits when around her parents or siblings, but rarely breaking out a planner in day-to-day life. The cure, then, might not be in a psychologist’s office, but in unraveling societal norms, gender roles, and familial expectations. In the meantime, however, eldest daughters everywhere can continue booking out their calendars and scheduling family vacations. And, just to make sure your siblings appreciate all the work you’re doing, feel free to continue sending passive-aggressive Tik Toks to the family group chat. Your younger siblings are probably spoiled rotten, anyway. 

References

Black, Sandra, Erik Grönqvist, and Björn Öckert. “Born to Lead? The Effect of Birth Order on Non-Cognitive Abilities.” The Review of Economics and Statistics 100, no. 2 (2018): 274–86. https://doi.org/10.3386/w23393.

Boccio, Cashen M., and Kevin M. Beaver. “Further Examining the Potential Association between Birth Order and Personality: Null Results from a National Sample of American Siblings.” Personality and Individual Differences 139 (March 2019): 125–31. https://doi.org/10.1016/j.paid.2018.11.017.

Damian, Rodica Ioana, and Brent W. Roberts. “Settling the Debate on Birth Order and Personality.” Proceedings of the National Academy of Sciences 112, no. 46 (November 17, 2015): 14119–20. https://doi.org/10.1073/pnas.1519064112.

Dudek, Thomas, Anne Ardila Brenøe, Jan Feld, and Julia M Rohrer. “No Evidence That Siblings’ Gender Affects Personality Across Nine Countries.” Psychological Science 33, no. 9 (2022): 1574–87. https://doi.org/10.1177/09567976221094630.

Ioana Damian, Rodica, and Marion Spengler. “Negligible Effects of Birth Order on Selection into Scientific and Artistic Careers, Creativity, and Status Attainment.” European Journal of Personality 35, no. 6 (November 2021): 775–96. https://doi.org/10.1177/0890207020969010.

John, O. P., Donahue, E. M., & Kentle, R. L. (1991). Big Five Inventory. PsycTESTS Dataset. https://doi.org/10.1037/t07550-000 

Marini, Victoria A., and John E. Kurtz. “Birth Order Differences in Normal Personality Traits: Perspectives from within and Outside the Family.” Personality and Individual Differences 51, no. 8 (December 2011): 910–14. https://doi.org/10.1016/j.paid.2011.07.019.

Mu, Wenlong, Yumei Li, Shiyang Cui, Along He, and Tianyuan Liu. “Birth Order and Personality: Evidence from a Representative Sample of Chinese.” European Journal of Personality 38, no. 6 (November 2024): 896–906. https://doi.org/10.1177/08902070231224063.Rohrer, Julia M., Boris Egloff, and Stefan C. Schmukle. “Examining the Effects of Birth Order on Personality.” Proceedings of the National Academy of Sciences 112, no. 46 (November 17, 2015): 14224–29. https://doi.org/10.1073/pnas.1506451112.