The science is in: Big sisters are good for everyone

Now the managing director for a public-relations firm in Providence, Doucet-Albert believes that the amount of responsibility she carried growing up is inextricable from who she is today. "I never ask for help but always provide it. I am definitely a people pleaser and go out of my way to help others, almost like it's my obligation. I also have a hard time setting boundaries and saying no," she said. "It's something that I'm constantly working on."

Doucet-Albert counts herself among the scores of women who have recognized themselves in a flurry of memes and think pieces concerning an affliction of sorts: "eldest-daughter syndrome." Equal parts birth-order stereotyping and pop psychology, the term describes a heady cocktail of perfectionism, self-sacrifice, guilt, and sibling resentment thanks to the double whammy of being both the oldest child and a girl. In a post that has garnered 4.5 million views on TikTok, a poem titled "Oldest Daughter Guilt" sums up the strife, lamenting, "Why can't I be happy? / I need to put myself first. / But who even am I when / I'm not fixing someone's hurt?"

The premise of eldest-daughter syndrome relies on two core assumptions: that firstborn or only daughters are expected to be models of achievement and good behavior for their younger siblings and that daughters are asked to take on more of the family's housework than their brothers. Research is inconclusive (at best) as to whether birth order meaningfully predicts personality. But there may be more of a science to eldest daughters than meets the eye. While the cultural conversation has focused on the downsides — the burdens — of being the eldest girl, studies across disciplines point to very real benefits for firstborn daughters' parents and siblings, particularly in times of hardship. Whether those benefits carry over to the daughters in question, on the other hand, depends on how much they're expected to give up.

Everyone, in other words, should have an older sister. But not everyone may want to be one.

Older children also play an important role as babysitters — especially when parents and guardians have limited access to alternate caregiving help. In a survey of nearly 2,000 US parents, roughly half reported that they'd relied on their older children for some or all of their caregiving help between February and December 2020, through the height of COVID-19 lockdowns.

Although the survey didn't specify the gender of older-child caregivers, preexisting research supports an educated guess that girls did more of the lifting. "It's a well-established pattern across the anthropological literature in diverse human societies that older sisters participate in direct childcare more than older brothers," said Molly Fox, an associate professor of anthropology at the University of California, Los Angeles.

Fox led a team of researchers that recently uncovered a stunning evolutionary clue as to why it's so common for women to take on caregiving roles. The team's 15-year longitudinal study, published earlier this year, found a link between mothers who reported psychological distress during pregnancy and accelerated adrenal puberty in firstborn daughters. Adrenal puberty is when the body starts producing more of a hormone that gets converted into a host of other powerful chemicals, such as the sex hormones estrogen and testosterone. Crucially, adrenal puberty also kicks off a phase of cognitive development that's associated with emotional and behavioral maturity and typically occurs about two years before regular puberty. A child who has undergone adrenal puberty is better equipped to take on more adultlike responsibilities such as babysitting, cooking, and running household errands. Most striking of all, maternal distress was not found to speed up adrenal puberty in sons or younger daughters. So when a mother needed help, biology caused her eldest daughter to step up and mature faster to provide that help — but the same wasn't true for her other children.

Does this mean that eldest-daughter syndrome not only is real but also begins in the womb? As Fox sees it, the answer sure looks like a yes — at least some of the time. For moms in difficult circumstances, having a precocious firstborn daughter who can help out with subsequent siblings is a helpful adaptation. "This idea seems consistent with the 'eldest daughter' phenomenon," she said.

In low- and middle-income countries, having an older sister may even give younger siblings a leg up in their future success and well-being. A 2020 study examining patterns of early childhood development in rural Kenya found that young children with an older sister, as opposed to an older brother, scored significantly higher in vocabulary and development of fine motor skills — differences that were attributed to extra attention and interaction. "For comparison, this 'effect' of having a big sister is about as large as the difference in child development between young children whose mother completed secondary school and those whose mother only completed primary school," the researchers wrote in a blog post for the Center for Global Development.

Pamela Jakiela, an associate professor of economics at Williams College and a coauthor of the study, said it's hard to know whether older sisters in the US have a comparably significant impact on their younger siblings' early development. Mothers in rural Kenya tend to have more children than women in the US, which means there are more young children to care for at once. Less access to center-based childcare — such as preschool and day care — means that caring for infants and toddlers falls to household members. Gender roles and responsibilities remain more rigid than in the US, with housework and caregiving more explicitly placed on girls and women.

But the findings still hold clues for American households, where parents rely tremendously on their older children for help at home. And while familial roles and responsibilities aren't as preordained by gender as they once were, American women still do far more of the domestic labor.

Despite the potential for sacrifices, being an eldest daughter isn't without its perks. Firstborn girls tend to be the most ambitious and successful children in their families, a 2014 study by University of Essex researchers found. A 2018 study published in Child Development found that, irrespective of gender, an older sibling caring for a younger sibling helped both of them develop a sense of empathy.

Sibling relationships stand to benefit from these dynamics, too. Jonathan Westover, who grew up as the sixth of eight children in 1980s Utah, told me that his eldest sister acted like a third parent throughout much of his childhood. At the time, it felt special to be able to spend so much time with her, especially given their decade-plus age difference. "I have a closer relationship with her, to this day, than I do with many of my other older siblings," he said.

Westover's story lines up with my own experience as the firstborn, and only daughter, in a family of three kids. I'm not sure I would have spent much quality time with my younger brothers, given our respective four- and six-year age gaps, if I hadn't been tasked with taking care of them after school and during our parents' occasional nights out. Though I wasn't exactly Mary Poppins — as my brothers would be happy to attest to — my latchkey-parent position helped lay a foundation for the warm and affectionate bond I share with both of them as an adult.

I didn't develop the same negative view of my role as many others have, and the critical difference came from the fact my parents never expected me to put their childcare needs ahead of my own childhood experiences. If I needed to stay after school for play rehearsal or tennis practice, they found someone else to look after my brothers until one of us came home. (It's worth noting that, with two sets of grandparents living nearby, this was a fairly easy task.)

In contrast, Westover said his parents relied on his eldest sister to be their default childcare provider, at the expense of her social life and extracurriculars. "She got defensive about it with my parents and started acting out because they leaned on her so much — more than they should have, probably, and certainly more than she thought was fair," Westover said. "Even into her adult life, she held that against my parents." His wife grew up as part of a similarly large brood — and her eldest sister had a similar experience. In both families, older brothers were asked to shoulder a comparably minuscule share of the load.

Westover, who is now an associate professor of organizational leadership at Utah Valley University and a father of six, told me that he and his wife had been careful not to repeat their parents' mistakes. "We try not to put a burden on our kids to take care of things that are our responsibility," he said. "If we do have the kids helping, we make sure that they're helping equally. We're not making the girls do all of one thing and the boys do all of another thing." Their firstborn — a daughter — is now 20.

Those detriments may be especially pronounced in today's ultracompetitive scholastic environment. "While kids tend to do less in terms of chores now than they did when I was a child, expectations in terms of academic, athletic, and extracurricular achievement have also changed," Jakiela said. "I'm not sure that today's kids have the bandwidth to pick up the caregiving slack for their parents."

As with most things, the key is balance. Eldest or only daughters have a valuable role to play in the lives of their parents and younger siblings, but avoiding the drawbacks of that extra responsibility requires additional support for overwhelmed parents. The cure for eldest-daughter syndrome, in other words, isn't a culture shift; it's rebuilding the village.

Kelli María Korducki is a journalist whose work focuses on work, tech, and culture. She's based in New York City.