For some years now, teachers and parents have noted something about boys and girls. Starting in elementary school, young girls often score better on reading and math tests than young boys do.
The differences are uneven on different tests and do not describe the experience of every child, but empirical studies do document a difference.
Now, two economists are proposing a partial explanation for the disparity that might give some parents heartburn.
Michael Baker at the University of Toronto and Kevin Milligan at the University of British Columbia recently analyzed survey data of parents in three countries — the United States, Canada and Britain. They were especially interested to see how parents say they spend time with their children — and they turned up an intriguing gender difference in what they called "teaching activities."
"So, this would be, 'How often do you read with your child?' or 'Do you teach them the alphabet or numbers?' " Baker says. "Systematically parents spent more time doing these activities with girls."
The finding surprised them because, at least in popular lore, parents supposedly spend more time with boys than girls. And Baker says that perception does tend to hold true for older children — fathers tend to spend more time with boys once they are older than age 4 or 5. When children are smaller, Baker says, parents spend about the same total time with boys as they do with girls.
But the striking difference comes in the sorts of activities the parents said they engage the kids in. The survey data suggests that young girls are more likely to be taken to libraries than are boys, are more likely to own books than are boys, and are more likely to be read to for longer periods of time than boys.
The economists focused their analysis, recently published by the National Bureau of Economic Research, on first-born children in order to get at the disparity in parental investment. It would have muddied the waters to compare parents caring for an only child with parents caring for their second or third child, Baker says. But they did find that the disparity also shows up clearly among fraternal twins. Here again, the parents surveyed seemed to devote more time to girls when it came to cognitive activities.
Since parents say they spend the same amount of time overall with boys and girls, Baker's analysis suggests that if parents are spending more time with girls on cognitive activities, they must be spending more time with boys on other kinds of activities. While it's possible to speculate that those activities involve more active play, Baker says the surveys could not provide a definite answer.
The big question, of course, is why these disparities in parental investment come about at all. After all, as Baker notes, many parents are familiar with research showing that elementary school boys trail girls in test of vocabulary and math. And they've also likely heard about studies suggesting that early interventions might have a big impact on the lives of children.
Milligan says the short answer is that no one knows why parents spend more time with girls on cognitive activities. One theory holds that girls might have a greater inclination toward such activities. (Theories suggesting innate differences between boys and girls and between men and women are hotly debated.) Another theory is that parents may be following cultural scripts and unconscious biases that suggest they should read with their daughters, and have active play with sons.
It is also possible, Baker says, that the costs of investing in cognitive activities is different when it comes to boys and girls. As an economist, he isn't referring to cost in the sense of cash; he means cost in the sense of effort.
"It is just more costly to provide a unit of reading to a boy than to a girl because the boy doesn't sit still, you know, doesn't pay attention," he says, "these sorts of things."
Baker says that as the parent of a boy and girl, he noticed that his own daughter appeared to have a greater inclination toward cognitive activities than his son. Rather than theorize about what the difference might be about, he says, he and his wife systematically directed their boy toward more cognitive activities.
DAVID GREENE, HOST:
In elementary schools in the United States, educators have seen differences in test scores among girls and boys. On average, girls perform better. This is not the case with every single child, but there are broad differences. There's been intense debate about what might cause these differences. Studies have looked at whether these differences are innate, or shaped by how we raise kids.
NPR science correspondent Shankar Vedantam joins us regularly to discuss interesting social science findings. And he's found some new research that suggests the way parents interact with very young children might be playing a role here. Shankar, welcome back to the program.
SHANKAR VEDANTAM, BYLINE: Hi, David.
GREENE: So Shankar, it feels like we're talking about research here that touches on a lot of fields - education, psychology.
VEDANTAM: Yeah, I mean, there has been a ton of research in all of those fields, David. Interestingly, this piece of research comes from a pair of economists. Michael Baker, at the University of Toronto, and Kevin Milligan, at the University of British Columbia, they recently mined survey research done in three completely different countries - the United States, Canada and Britain. They looked at how parents reported interacting with very young children; these are preschool children in all these countries. And they found that when it came to some specific activities, there was an interesting disparity in how much time parents spend with boys, and how much time they spent with girls.
MICHAEL BAKER: When we looked at specific activities - what we call teaching activities; so this would be, how often do you read with your child or, how often do you teach them the alphabet or numbers - systematically, parents spent more time doing these activities with girls.
GREENE: I guess one important question, though, is, are parents spending the same amount of time with boys and girls? That seems like something important to sort out.
VEDANTAM: Yeah. That's a great question, David. Interestingly, Baker found that they do, indeed, spend the same amount of time with boys and girls. So they're not necessarily reporting that they're spending more time with girls overall. It's just when it comes to these specific activities, they seem to be spending more time with girls than boys.
GREENE: OK. So do we think that there's a link there to girls performing better on tests in elementary school?
VEDANTAM: So that's the $64 million question. And remember, these are economists. So what they're saying is look, we had these two, separate findings. First, we've known from previous research that there are these test-score differences in elementary school. And second, we're finding that there are these different investments from parents, when it comes to these cognitive activities.
Baker told me that he built a model that asked, what would happen to the test scores if we were to eliminate these disparities in parental investment? And remember, he's not actually changing what parents are doing in real life. He's building a statistical model that tries to control for these disparities. And he finds that the differences in parental investment might explain as much as a third of the test-score disparities, which is really quite a lot.
BAKER: If you look at the boy-girl difference in the test scores at age 4 and 5; and then you look at them again but this time are counting for the differences in how their parents read to them or taught them letters and numbers, the boy-girl difference in the test scores shrinks.
VEDANTAM: So Baker has multiple theories. And one of the theories he has - I mean, he's an economist, and so one of the things that economists do is, they say, what are the incentives for people to do different things - you know - and what are the costs involved? And when economists talk about costs, they're not necessarily talking about cash. They're also talking about the amount of effort that's involved. And Baker is asking, is it possible that there are different costs in investing these cognitive activities in boys versus girls, and could that be explaining the disparities?
BAKER: The costs of providing these inputs are different for boys and girls. So for example, it is just more costly to provide a unit of reading to a boy than to a girl because the boy doesn't sit still - you know, doesn't pay attention, these sorts of things.
VEDANTAM: So it's a feedback interaction between the parent and the child and - you know, that's being shaped by all kinds of things. But what he's suggesting is, it's possible that parents are getting signals from their children about what they're willing to do; and then that shapes the parents' behavior, and then the parents' behavior, in turn, shapes the child's behavior; and then you have these loops.
GREENE: So Shankar, I have to say, this is the kind of subject matter that some parents will probably have reactions to. I know this is just one study. Do these researchers, though, have any advice for parents?
VEDANTAM: Yeah. That's a tricky one, David. And I asked Baker about this, and he told me that in general, as a parent himself, he tries not to give advice to other parents.
GREENE: That's probably a safer position to stand on.
VEDANTAM: Yeah. He did tell me, though, that he has a boy and girl himself, and his girl showed greater interest in reading and math at a young age. But his response, and his wife's response, was to tailor far more attention to the boy as a result; and try and counter, perhaps, with this natural inclination may have been.
GREENE: Interesting - something for parents to think about. Shankar, thanks so much, as always.
VEDANTAM: Thanks, David.
GREENE: That's Shankar Verdantam, who regularly joins us to talk about interesting social science research. You can follow him on Twitter @Hidden Brain. And while you're at it, you can follow this program @NPRgreene, @NPRinskeep and @MORNING EDITION. Transcript provided by NPR, Copyright NPR.