New research from the University of Granada found that stress could help determine sex.
- A new study found that women with elevated stress before, during, and after conception are twice as likely to deliver a girl.
- One factor could be that sperm carrying an X chromosome are better equipped to reach the egg under adverse conditions.
- Another factor could be miscarriage of male fetuses during times of stress.
Stress in the modern world is generally viewed as a hindrance to a healthy life.
Indeed, excess stress is associated with numerous problems, including cardiovascular disease, high blood pressure, insomnia, depression, obesity, and other conditions. While the physiological mechanisms associated with stress can be beneficial, as Kelly McGonigal points out in The Upside of Stress, the modern wellness industry is built on the foundation of stress relief.
The effects of stress on pregnant mothers is another longstanding area of research. For example, what potential negative effects do elevated levels of cortisol, epinephrine, and norepinephrine have on fetal development?
A new study, published in the Journal of Developmental Origins of Health and Disease, investigated a very specific aspect of stress on fetuses: does it affect sex? Their findings reveal that women with elevated stress are twice as likely to give birth to a girl.
For this research, the University of Granada scientists recorded the stress levels of 108 women before, during, and after conception. By testing cortisol concentration in their hair and subjecting the women to a variety of psychological tests, the researchers discovered that stress indeed influences sex. Specifically, stress made women twice as likely to deliver a baby girl.
The team points out that their research is consistent with other research that used saliva to show that stress resulted in a decreased likelihood of delivering a boy.
Maria Isabel Peralta RamírezPhoto courtesy of University of Granada
Lead author María Isabel Peralta Ramírez, a researcher at the UGR's Department of Personality, Evaluation and Psychological Treatment, says that prior research focused on stress levels leading up to and after birth. She was interested in stress's impact leading up to conception. She says:
"Specifically, our research group has shown in numerous publications how psychological stress in the mother generates a greater number of psychopathological symptoms during pregnancy: postpartum depression, a greater likelihood of assisted delivery, an increase in the time taken for lactation to commence (lactogenesis), or inferior neurodevelopment of the baby six months after birth."
While no conclusive evidence has been rendered, the research team believes that activation of the mother's endogenous stress system during conception sets the concentration of sex hormones that will be carried throughout development. As the team writes, "there is evidence that testosterone functions as a mechanism when determining the baby's sex, since the greater the prenatal stress levels, the higher the levels of female testosterone." Levels of paternal stress were not factored into this research.
Previous studies show that sperm carrying an X chromosome are better equipped to reach the egg under adverse conditions than sperm carrying the Y chromosome. Y fetuses also mature slowly and are more likely to produce complications than X fetuses. Peralta also noted that there might be more aborted male fetuses during times of early maternal stress, which would favor more girls being born under such circumstances.
In the future, Peralta and her team say an investigation into aborted fetuses should be undertaken. Right now, the research was limited to a small sample size that did not factor in a number of elements. Still, the team concludes, "the research presented here is pioneering to the extent that it links prenatal stress to the sex of newborns."
Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
Fifty years of research on children's toy preferences shows that kids generally prefer toys oriented toward their own gender.
- A recent meta-analysis overviewed 75 studies on children's gender-related toy preferences.
- The results found that "gender-related toy preferences may be considered a well-established finding."
- It's a controversial topic: Some people argue that these preferences stem from social pressure, while others say they're at least partly rooted in biology.
There's more gender equality in Western societies today than in the past. Inequalities still exist, of course, but research shows a general uptrend in women joining and rising within the workforce, obtaining degrees, and earning more money. The social expectations of men and women also seemed to have changed; this is harder to measure empirically, but it seems safe to say that our ideas about gender roles are more fluid today than they were, in say, the 1950s.
So, have these changes affected a crucial part of children's development: play? More specifically, as gender roles have become more fluid, have children's preferences toward gender-typed toys become more fluid, too?
The short answer seems to be no. For decades, studies have shown that boys and girls generally prefer playing with toys typically associated with their biological sex: toy trucks for boys and dolls for girls, to give a rough example.
These results have remained remarkably stable over the past 50 years, according to a 2020 meta-analysis of research on gender differences in toy preferences. Published in Archives of Sexual Behavior and titled "The Magnitude of Children's Gender‐Related Toy Interests Has Remained Stable Over 50 Years of Research," the analysis examined 75 previous studies, 113 effect sizes, and a range of toy preference measurements.
No matter what society wants, it's worth noting that there seems to be some biological drivers behind children's preferences for gender-typical toys.
The authors, Jac T. M. Davis and Melissa Hines, found "a broad consistency of results across the large body of research on children's gender-related toy preferences: children showed large and reliable preferences for toys that were related to their own gender. Thus, according to our review, gender-related toy preferences may be considered a well-established finding."
A letter to the editor in the same journal sought to challenge these findings in a separate analysis, which concluded that children actually spend less time playing with gender-typical toys these days.
The authors of that analysis speculated that the reason for this decline "might reflect social pressures in recent times for children to be less gender-typical in their behavior." In other words, the decline stems from parents wanting to be more in line with progressive ideas about gender fluidity.
However, Davis and Hines disagreed, proposing that the supposed decline appeared in the analysis only because of the specific methodology employed by the researchers. What's more, they noted that toy advertisers have been using more gender stereotypes to boost sales in recent decades—a finding that potentially complicates the claim that social pressures are causing kids to spend less time playing with gender-typical toys.
Davis and Hines concluded:
"It may be tempting to think that social changes over time might be reducing children's play with gender-related toys, given arguments that play with a broader set of toys would be beneficial for both boys and girls. Unfortunately, however, broad change in the social roles of men and women do not seem to have influenced children's toy choices, perhaps because they have been counteracted by stronger marketing of different toys to girls and boys over recent time. If society wants girls and boys to play with the full range of toys, more targeted action is probably required."
Little boy playing mathematics wooden toy at nurseryCredit: Rawpixel.com via Adobe Stock
Why are we so concerned about which toys kids play with?
But does society really want kids to play with less gender-typical toys? Some research suggests the answer is yes. A 2017 survey from Pew Research Center found that a majority of Americans considered it a "somewhat or very good thing" to steer kids toward toys and activities traditionally associated with the opposite gender (though respondents were less enthusiastic about doing so for boys than girls).
Encouraging kids to play with a wider range of toys could yield benefits. For example, a 2020 study published in Frontiers in Human Neuroscience found that when both boys and girls play with dolls, they experience heightened activation within brain regions associated with empathy and perspective-taking.
But no matter what society wants, it's worth noting that there seem to be some biological drivers behind children's preferences for gender-typical toys.
For example, studies have shown that babies tend to prefer toys oriented to their own gender, a finding that suggests their preference is innate because they're in the pre-socialization stage of development. Supporting that argument are studies showing that baby monkeys also display gender-typical toy preferences.
Still, it's easy to see how social pressures might affect kids' toy preferences as they grow up. So, the question of why kids prefer the toys that they do likely boils down to a familiar answer: a tangled mix of environmental and biological factors.
"It would be extreme to claim zero influence of biology on gender differences in toy choices, and the research community is still divided on how important biology and social factors are," Davis told Big Think.
Flying that helicopter too low is counterproductive.
- A new study at Stanford finds that giving too much direction to children can be counterproductive.
- Children that are given too much advice display more difficulty regulating their behavior and emotions at other times.
- The researchers suggest a balance between being involved while allowing children to figure things out on their own.
In a scathing indictment of the growing influence of money in the private school educational system—and therefore on education, opportunity, and social mobility in America—The Atlantic's Caitlin Flanagan investigates the increasingly troublesome trend of parental involvement in their children's schooling. She points out an anecdotal instance when, as a private school teacher, she butted heads with the same parents twice after giving their child the unforgivable grade of an A-.
One of those irate phone calls came in less than 10 minutes after handing said student their creative writing paper. This meant they left the classroom and bolted straight to the school's pay phone to complain—this was the 1990s, after all. The parents immediately phoned the school. Back then, the school had her back; today, parents yield much more influence, often in the form of endowments.
Flanagan's article highlights two important questions beyond the unyielding influence of money on education: How involved should parents be in their children's education? And what is the emotional result of too much intervention on the child?A new study, published in the Journal of Family Psychology, attempts to answer both of those questions. Led by Stanford Graduate School of Education Associate Professor Jelena Obradović, the study finds that while it's important for parents to be involved, too much direction and influence can be counterproductive.
Why helicopter parenting backfires on kids | Heather Heying | Big Think
For this study, researchers watched videos of parental behavior around their kindergarten-age children. A total of 102 children, ages four to six, were brought into the Stanford lab by their primary caregivers. The children were tasked to clean up toys, learn new games, and discuss problems. The researchers timed the length of their interactions with caregivers, such as how much direction the parents gave them when trying to solve a novel puzzle.
The results were clear.
"The children of parents who more often stepped in to provide instructions, corrections or suggestions or to ask questions – despite the children being appropriately on task – displayed more difficulty regulating their behavior and emotions at other times. These children also performed worse on tasks that measured delayed gratification and other executive functions, skills associated with impulse control and the ability to shift between competing demands for their attention."
Given the laboratory conditions—parents knew they were being watched—Obradović and team noticed that parents did not yell or check their phones. How realistic this is for such a large cohort is difficult to gauge. The team was looking for "parental over-engagement," the tendency for parents to intervene too often and not allow their children to figure things out for themselves.
Credit: Monkey Business / Adobe Stock
Of course, helping children is important as well. The team notes that aiding a child while they work on a new puzzle helps with cognitive development and independence. Striking a balance between lending a hand and letting the child struggle is important. As Obradović states, "there is a lot of variability within those averages, and our goal was to discover more subtle differences among parents who are generally doing fine."
This research is especially pertinent during the pandemic as parents and children are interacting more than ever. The overall message: if you're going to fly a helicopter, only descend when necessary.
This advice is critical for an educational system that, as Flanagan points out, is skewed to favor children from wealthy families. One startling statistic: only half of the public-school students in California are at grade reading levels; the numbers for math are even worse. As she writes, "Shouldn't the schools that serve poor children be the very best schools we have?"
Extrapolating from that idea, we can ask the same of all parents: shouldn't we work toward supporting children in the very best manner possible? Be it through influence or attention, it seems that too much of anything is usually counterproductive. Kids need to learn on their own terms, too.
Stay in touch with Derek on Twitter and Facebook. His most recent book is "Hero's Dose: The Case For Psychedelics in Ritual and Therapy."
More evidence that we're drowning in microplastic particles.
- Italian researchers have discovered microplastic particles in human placenta.
- Out of six collected placentas, four contained colored plastic microparticles.
- That petrochemical pollutants are present in such a critically important organ is alarming.
For the last few years, researchers have become increasingly alarmed at the degree to which microplastics—bits of plastic that are smaller than 5 millimeters in length—have invaded, well, basically everywhere and everything. In 2018, a small sampling of eight people from around the world found that all eight of them had microplastics in their stools; another study that same year found microplastics up and down the marine food chain. Researchers in 2019 found them in 100 percent of the whales, dolphins, and seals tested. Now a new study has found microplastics in human placentas, meaning that humans are now being exposed to bits of petrochemical waste as early as the womb.
The new research is published in the journal Science Direct.
The authors of the Italian study collected placentas from six mothers. They did this in a plastic-free environment so as to avoid contamination. Doctors and midwives wearing cotton gloves performed the collection from mothers covered only in cotton towels. Metal clippers and scalpels were used.
The six placentas were evaluated using microspectroscopy. Samples from four of the placentas contained colored microplastics. A total of 12 pieces, between 5 and 10 micrometers, were collected — at this size, the contaminants were small enough to be carried in the mother's or child's bloodstream.
Considering that the samples constituted just about 4 percent of the organs, it's reasonable to suspect that the researchers' findings represent just the tip of the iceberg.
Four of the pieces were found in tissues on the maternal side, the outside of the placenta, and five were found in the space in which the fetus had been. The remaining three were located in the fine membrane wall surrounding the amniotic fluid in the placenta.
All of the microplastics were colored, dyed red, blue, orange, and pink, but beyond that the researchers were only partially able to identify the materials with greater specificity, writing, "All of them were pigmented; three were identified as stained polypropylene a thermoplastic polymer, while for the other nine it was possible to identify only the pigments, which were all used for man-made coatings, paints, adhesives, plasters, finger paints, polymers and cosmetics and personal care products."
Understanding how the microplastics found their way in the mothers' placentas is beyond the scope of the research, but there's plenty of evidence that plastics are everywhere, from the products we use to the air we breathe, and so on. One study found that after babies are born, the infusion of microplastics begins right away— millions of particles a day are swallowed by infants drinking form plastic bottles.
Credit: Jonathan/Adobe Stock
A critical environment
The placenta plays a critical role in the development of a fetus, delivering nutrition and oxygen, handling waste disposal, and generally doing the job of keeping the fetus alive until its own organs develop enough to take over. The placenta also keeps the infant free of contaminants, or is supposed to, filtering out pathogens. It is also believed to be instrumental in facilitating the myriad chemical process involved in fetal development.
"Due to the crucial role of placenta in supporting the foetus's development and in acting as an interface with the external environment, the presence of potentially harmful plastic particles is a matter of great concern. Further studies need to be performed to assess if the presence of microplastics may trigger immune responses or may lead to the release of toxic contaminants, resulting in harm." — Ragusa, et al.
Study leader Antonio Ragusa, of the San Giovanni Calibita Fatebenefratelli hospital in Rome says, "It is like having a cyborg baby: no longer composed only of human cells, but a mixture of biological and inorganic entities." He adds, "The mothers were shocked."
Chemists Elizabeth Salter Green tells The Guardian, "Babies are being born pre-polluted. The study was very small but nevertheless flags a very worrying concern."
Having grown kids still at home is not likely to do you, or them, any permanent harm.
When the Pew Research Center recently reported that the proportion of 18-to-29-year-old Americans who live with their parents has increased during the COVID-19 pandemic, perhaps you saw some of the breathless headlines hyping how it's higher than at any time since the Great Depression.
From my perspective, the real story here is less alarming than you might think. And it's actually quite a bit more interesting than the sound bite summary.
Even 30 years ago, adulthood – typically marked by a stable job, a long-term partnership and financial independence – was coming later than it had in the past.
Yes, a lot of emerging adults are now living with their parents. But this is part of a larger, longer trend, with the percentage going up only modestly since COVID-19 hit. Furthermore, having grown kids still at home is not likely to do you, or them, any permanent harm. In fact, until very recently, it's been the way adults have typically lived throughout history. Even now, it's a common practice in most of the world.
Staying home is not new or unusual
Drawing on the federal government's monthly Current Population Survey, the Pew Report showed that 52% of 18-to-29-year-olds are currently living with their parents, up from 47% in February. The increase was mostly among the younger emerging adults – ages 18 to 24 – and was primarily due to their coming home from colleges that shut down or to their having lost their jobs.
Although 52% is the highest percentage in over a century, this number has, in fact, been rising steadily since hitting a low of 29% in 1960. The main reason for the rise is that more and more young people continued their education into their 20s as the economy shifted from manufacturing to information and technology. When they're enrolled in school, most don't make enough money to live independently.
Before 1900 in the United States, it was typical for young people to live at home until they married in their mid-20s, and there was nothing shameful about it. They usually started working by their early teens – it was rare then for kids to get even a high school education – and their families relied upon the extra income. Virginity for young women was highly prized, so it was moving out before marriage that was scandalous, not staying home where they could be shielded from young men.
In most of the world today, it is still typical for emerging adults to stay home until at least their late 20s. In countries where collectivism is more highly valued than individualism – in places as diverse as Italy, Japan and Mexico – parents mostly prefer to have their emerging adults stay home until marriage. In fact, even after marriage it remains a common cultural tradition for a young man to bring his wife into his parents' household rather than move out.
Until the modern pension system arose about a century ago, aging parents were highly vulnerable and needed their adult children and daughters-in-law to care for them in their later years. This tradition persists in many countries, including the two most populous countries in the world, India and China.
In today's individualistic U.S., we mostly expect our kids to hit the road by age 18 or 19 so they can learn to be independent and self-sufficient. If they don't, we may worry that there is something wrong with them.
You'll miss them when they're gone
Because I've been researching emerging adults for a long time, I've been doing a lot of television, radio and print interviews since the Pew report was released.
Always, the premise seems to be the same: Isn't this awful?
I would readily agree that it's awful to have your education derailed or to lose your job because of the pandemic. But it's not awful to live with your parents during emerging adulthood. Like most of the rest of family life, it's a mixed bag: It's a pain in some ways, and rewarding in others.
In a national survey of 18-to-29-year-olds I directed before the pandemic, 76% of them agreed that they get along better with their parents now than they did in adolescence, but almost the same majority – 74% – agreed, "I would prefer to live independently of my parents, even if it means living on a tight budget."
Parents express similar ambivalence. In a separate national survey I directed, 61% of parents who had an 18-to-29-year-old living at home were "mostly positive" about that living arrangement, and about the same percentage agreed that living together resulted in greater emotional closeness and companionship with their emerging adults. On the other hand, 40% of the parents agreed that having their emerging adults at home meant worrying about them more, and about 25% said it resulted in more conflict and more disruption to their daily lives.
As much as most parents enjoy having their emerging adults around, they tend to be ready to move on to the next stage of their lives when their youngest kid reaches their 20s. They have plans they've been delaying for a long time – to travel, to take up new forms of recreation and perhaps to retire or change jobs.
Those who are married often view this new phase as a time to get to know their spouse again – or as a time to admit their marriage has run its course. Those who are divorced or widowed can now have an overnight guest without worrying about scrutiny from their adult child at the breakfast table the next morning.
My wife, Lene, and I have direct experience to draw on with our 20-year-old twins, who came home in March after their colleges closed, an experience shared with millions of students nationwide. I'll admit we were enjoying our time as a couple before they moved back in, but nevertheless it was a delight having them unexpectedly return, as they are full of love and add so much liveliness to the dinner table.
Now the fall semester has started and our daughter, Paris, is still home taking her courses via Zoom, whereas our son, Miles, has returned to college. We're savoring these months with Paris. She has a great sense of humor and makes an excellent Korean tofu rice bowl. And we all know it won't last.
That's something worth remembering for all of us during these strange times, especially for parents and emerging adults who find themselves sharing living quarters again. It won't last.
You could see this unexpected change as awful, as a royal pain and daily stress. Or you could see it as one more chance to get to know each other as adults, before the emerging adult sails once again over the horizon, this time never to return.