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What effect can having an older sister have on a child's development? New research out of Kenya reveals some powerful differences, showing substantial benefits for younger brothers and sisters. NPR's Nurith Aizenman has the story.
NURITH AIZENMAN, BYLINE: One of the economists behind this study is Pamela Jakiela of Williams College in Massachusetts. She says she got the idea after reading that many parents in Kenya give their girl children a huge amount of responsibility when they're still very young.
PAMELA JAKIELA: By age kind of 6 to 8, older sisters are spending as much as half of their free time looking after younger children.
AIZENMAN: And that's much less common for older brothers. Anthropologists have been documenting this difference for decades, but Jakiela says there's not a lot of research on what effect do these young big sister babysitters have on the toddlers they're caring for.
JAKIELA: And so we thought that it would be interesting to compare young children who have an older sister as compared to an older brother.
AIZENMAN: Jakiela and her collaborator, Owen Ozier, also of Williams College, studied about 700 toddlers in a rural part of western Kenya to check. How well were they doing on measures of early vocabulary and fine motor skills? Their finding, released in a working paper through the think tank Center for Global Development - on average, the toddlers with an older sister did better. How much better? Well, Jakiela notes that researchers have long known that a significant predictor of a child's development is how much education their mother has. And she found that for these toddlers, having a big sister...
JAKIELA: It translates into about the same difference we see when we compare young children whose mothers finished secondary school to those whose mothers only finished primary school.
AIZENMAN: But what are the big sisters doing that's so helpful? Well, Jakiela and Ozier tried to answer that by coming up with a list of activities that would stimulate the toddlers.
JAKIELA: Having someone reading you stories or singing to you or practicing writing letters or doing physical play activities.
AIZENMAN: And then they checked. How often was someone doing these things for the toddlers, and who was doing it? They found that across all the families, the mothers engaged the toddlers this way about the same amount. But older sisters were far more likely to do so than older brothers, such that if the toddler happened to have an older sister, overall, they were getting a substantial boost in stimulation.
JAKIELA: We see more than a 10% increase.
AIZENMAN: Jakiela says that doesn't prove the extra stimulation is the reason the kids with older sisters performed better, but it certainly suggests it's a plausible explanation. Now, Jakiela has a warning about these findings.
JAKIELA: It's a charming story of everybody loving their old sister, seen through the lens of the younger child, but, you know, this uneven burden of care work has real costs for older girls.
AIZENMAN: They have less time for their own schoolwork, play. In fact, a growing number of researchers are investigating this effect. Marcella Alsan, an economist and public health expert at Harvard University, analyzed schooling data on more than 120,000 adolescents in 38 low and middle-income countries. She and her collaborators found that during weeks when a younger sibling in the household was sick, the older girls appeared more likely than the older boys to miss school so they could take care of the sick sibling. Specifically, when it came to attendance among these big sisters and big brothers...
MARCELLA ALSAN: The gender gap increased to almost eight percentage points if there had been one illness episode and increased further if there were two or more illness episodes.
AIZENMAN: But Alsan has also found that in Turkey, a vaccination campaign for toddlers had a positive spillover effect on their older sisters.
ALSAN: This did free up girls to attain more education.
AIZENMAN: In other words, improving conditions for toddlers may also be a way to help older girls. The larger point, say the researchers, is this - policymakers need to be a lot more mindful of how this unacknowledged work that so many older girls in poorer countries are doing affects them and to look for solutions. Nurith Aizenman, NPR News. Transcript provided by NPR, Copyright NPR.