Not long ago, a single friend of mine observed something about the photos that men post of themselves on Match.com and other online dating sites. Many—too many for her taste—also include women. Ex-girlfriends, presumably, with their slender arms thrown around the men in question. Or possibly friends, but always attractive ones. Even when the woman in the photo had been cropped out, whatever boady part remained in the frame was comely. Long blond hair. Manicured nails.

Is it really a good strategy to include a picture of yourself with an attractive ex-girlfriend or boyfriend (or a hot friend) in your dating profile? My exasperated friend would say no, yet all too often the guys that she finds exceptional are the ones who have hot exes.

Are you having little luck in the search for your soulmate? When you finally meet a woman does she seem disinterested? What could it be? Your breath? Your clothes?

This is not an ad in the personals. It’s the opening line of the commentary in the straitlaced scientific journal, Proceedings of the National Academy of Sciences (PSAS). The authors, neuroscientists Liisa Galea and Cindy Barhain, intend to shock. Why, one wonders, would a man have no luck in love?

Findings from a new study suggest it may be your mother’s dietary exposure to bisphenol A (BPA).

Galea and Barha have all my attention now. Ever since my pregnancy, I have been tracking studies on BPA’s subtle yet shocking effects. One of the most common chemicals in the world, bisphenol A is found in the stuff we use every day of our lives. Soup and soda cans. Water pipes. Computers. Cell phones. Thermal paper receipts. Paper money. Even some baby bottles—at least in the U.S., because they are not banned here.

Much of the trouble with BPA lies in its ability to fool estrogen receptors into thinking it’s estrogen. Imagine a man doesn’t know that the woman he’s marrying is really an alien in drag, and you have a sense of the danger here. BPA disrupts any process that estrogen normally mediates, affecting brain, body, and behavior. It also tinkers with the way genes express themselves, turning up those that would otherwise be turned off or down. BPA exposure has been linked to breast cancer, heart disease, obesity, diabetes, attention-deficit disorder, increased anxiety, a decreased IQ in children and a low sperm count in men.

Pregnant women and new moms should be especially cautious. BPA has been found in umbilical cord blood and in breast milk. It crosses the placenta and flows in fetuses. Young bodies are especially vulnerable to pseudoestrogens. The toxin strikes us moms, too. Researchers worry that BPA may affect women’s brains in a way that alter their maternal instincts. In laboratory studies, BPA-exposed female rats are less likely to nurture their offspring—they lick them less—which in turn affects the emotional and cognitive system of their babies. They become more fearful and anxious.

And now, there’s more.

There is evidence that BPA emasculates males and makes them sexually undesirable. Galea and Barha’s opening lines in PSAS are tongue in cheek—they are describing a new study at the University of Missouri on the effects of BPA on deer mice—but the application to humans is implicit. Adult mice whose mothers were fed a dosage of BPA equivalent to what the USDA deems safe for pregnant women, were, well, different from other males.

“One of the prominent effects of early BPA exposure is that it eliminates a number of sex differences in brain and behavior,” the researchers wrote. It turned out that BPA-exposed males have impaired spatial ability (can’t find their way out of a maze or to their nest, considered unattractive to females). They also suffer from decreased exploratory ability (incurious and easily lost), and overall reduced attractiveness to the opposite sex. They may even smell different from their peers—in rodents, a sign of unhealthiness. Females are disgusted.

It’s not absurd to worry about similar effects of BPA-exposure on our babies. Men are not mice, but there is increasing evidence that BPA affects us as well, and in doses below the below the 50 µg/kg/day safety threshold in the United States. Almost every American pregnant woman (93 percent) has detectable BPA in her body, which is passed on to her fetus. The average BPA body burden of an American is high, alarmingly high, compared to other countries. We love our BPA-enriched Cokes and canned Campbell’s soups.

On a population level, how might BPA affect us? Might boys in the U.S. grow up to have poorer spatial skills—and, because it’s linked, weaker mathematical ability? Might they have little interest in exploring the world, preferring to hang out at home? Might our national temperament become more placid? Because BPA is lined with obesity and heart disease, will we become fatter and more sedate? And what about our sex lives?

Take a look at human history through the lens of hormones, as Harvard University’s Daniel Lord Smail did in his fascinating book, On Deep History and the Brain. Smail introduces a new view in which physiology and culture evolve symbiotically in a process driven by brain chemistry. Caffeine stimulated the body and mind, driving the industrial revolution and the modern corporation. Tobacco help us to focus and be calm. These substances changed the character of society. Now we have environmental toxins such as BPA (and other hormone disruptors such as phthlates and PCBs) that may also change our culture in subtle but very real ways.

BPA: Bad for your manhood. Bad for your sex life. Sensationalistic, sure—but would this get CEOs to pay attention? Hit them where it hurts.

Stubborn pushback—that’s the response from many corporations regarding BPA bans. The chemical is a mainstay in packaging, and to ditch it is disruptive for business. Coca Cola has famously refused to find an alternative. You can find BPA-free cans of beans from brands such as Eden, but not crushed tomatoes yet (in the meantime, buy them in glass jars). Avoid plastics that are marked with recycle codes 3 or 7; they may contain BPA. While Canada, Europe, and even China have banned the use of the chemical in baby bottles, the U.S. has not (although consumer demand has pushed many manufactuers to go BPA-free).

The good news, as I describe in my book, is that there is laboratory evidence that a diet high in folic acid and B12 may reverse at least some of the nasty effects of prenatal BPA exposure. How? One way that BPA tinkers with our systems is by attaching itself to strands of DNA and “turning on” certain genes (removing methyl groups) that are normally turned off—resulting in obesity, cancer, and other nasty effects. This is classic epigenetics—an environmental trigger affects the way that genes behave. Nutrients in green vegetables, beans, eggs, and soy may be protective (in those of us who include enough in our diet) because they turn off genes that BPA otherwise turns on.

Of course, the best protection is to turn corporations off BPA.  That would really be a turn-on for us moms.

 *If you like this blog, click here for previous posts. If you wish, check out my new book, Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy.

Check out in BOING BOING one of my favorite excerpts from Chocolate Lovers — on the very weird science of what fetal cells do in mothers’ bodies.

The best holiday gift: DO CHOCOLATE LOVERS HAVE SWEETER BABIES gets a STARRED REVIEW in Library Journal! Many thanks to Library Jrnl and the reviewer, Julianne Smith.

It reads:

What a charm! Science writer Pincott (Do Gentlemen Really Prefer Blondes?) tackles some myths and legends associated with pregnancy and compares them to peer-reviewed research on the matter. The book covers such questions as: “Do men prefer babies who resemble them?” “What does a baby’s birth season predict?” and “Do bossy broads have more sons?” This is an enjoyable, insightful, and fascinating look at pregnancy that explains what we know and identifies what we don’t. In discussing topics from stretch marks to mama’s boys, Pincott takes a conversational tone, making the science readily available to all readers. An ideal acquisition for public libraries, a great gift for expectant parents, and the perfect choice for the doctor’s waiting room, this winning title deserves some talking up. Way more fun than What To Expect.

LINK

Does stress sharpen your baby’s mind—or dull it? Can you predict your baby’s temperament? Why are babies born in the darker months of the year more likely to be risk-takers? Are bossy, dominant women more likely to have boys, which skinny women have more girls?

On Armin Brott’s Mr. Dad radio show, I talk about these topics from the book — and more.

Not long ago, someone emailed me a new study on chocolate and temperament. The study came from a group of psychologists at North Dakota State University and Gettysburg College, and it involved personality differences between people who liked sweet foods versus bitter, spicy, sour, salty, or umami flavors. The researchers wanted to know, “Is having a sweet tooth related to having a sweeter disposition?”

Here’s a sample of what they asked their hundred or so volunteers.

Candy, caramel, chocolate cake, honey, ice cream, maple syrup, pears, raisins, strawberries, and sugar. How fond were they of these dessert flavors?

The volunteers rated their taste preferences on a scale of 1-10.

Following that, they completed an agreeableness scale. That is, they were asked to indicate the extent to which they behave in ways reflective of high (e.g., “have a soft heart”) versus low (e.g., “insult people”) levels of agreeableness.

Pleasingly, the researchers found a significant correlation. People who loved sweets were likelier to be more agreeable.

“Further proof that chocolate lovers would have sweeter babies!” my sender gushed. There’s logic here: If people with a sweet tooth really have a sweeter disposition then women who love sweets might have more agreeable babies because disposition is heritable. Equally valid, people who have sweeter dispositions would have a gentler parenting style, resulting in babies with sweeter dispositions. Ergo, chocolate lovers have sweeter babies. Natch.

Then the researchers took their study to the next level to see if sweet-toothed types not only test as more agreeable, but act sweeter too.

At the end of the session, participants were told that the study was over and that full participation credit would be awarded, thereby relieving them of any further obligations. However, it was mentioned that a colleague in the English department was collecting data on media preferences and was looking for volunteers.

Interestingly, people who had a sweet tooth were more likely to complete the voluntary survey, even though they weren’t getting any extra credit or compensation.

Such sweethearts!

I wonder: does the mere suggestion of sweet food make people act sweeter? Does sweet food make people less angry and aggressive? The researchers claim that metaphors can be predictive about behavior and personality. Because “sweet” in English applies to both taste and disposition, does the correlation still apply in different languages?

How sweet would that be?

Among the great mysteries — and horrible injustices — of aging is that dementia strikes more women than men. No one knows why exactly.  For years, scientists suspected that the culprit is estrogen. Implicated in memory formation, estrogen levels plummet after women reach menopause.

But here’s the catch.  If low estrogen levels are behind age-related dementia in women, then why did a massive study by the National Institute of Health find that women who had hormone replacement therapy (HRT) were no less likely to experience cognitive decline than women who didn’t have it?

Because not all estrogens are created equal, nor are all brains.  Motherhood may be the missing link.

This comes from an intriguing new study by Cindy Barha and Liisa Galea, neuroscientists at the University of British Columbia’s Brain Research Center.  Barha and Galea knew that the female brain is highly plastic; it literally restructures itself in the course of pregnancy and caring for a baby.  They were curious about whether motherhood might alter the brain in a way that protects against dementia under certain conditions.

One way to explore this is to study middle-aged rats that are genetically identical in every way with the exception of their reproductive lives.  The scientists divided the rats into groups — virgins and mothers — and injected each with a form of estrogen:  estradiol or estrone (the form in HRT).  Later, they looked at the rats’ brain tissue to see whether new cells had formed — a process called neurogenesis — in the hippocampus where memories are formed.  These new cells may reduce the risk of dementia.

It’s interesting, this contest between middle-aged virgins and mothers.  Compared to virgins who had been injected with estrogens (and mothers who hadn’t), the middle-aged mother rats that took the hormone replacement therapy grew significantly more new hippocampal cells.  The mothers — and only the mothers — grew many new neurons when exposed to the estrogens (especially a combination of estrone and 17a-estradiol).  The hormones helped the mothers’ minds to remain malleable.

Why did the mothers have a seeming advantage?  Anther mystery — which Barha and Galea say may be related to an enhanced ability of mothers’ hippocampuses, even late in life, to respond to estrogens.  Such responsiveness may come from hormone exposure during pregnancy or afterward, or enrichment from the experience of mothering.

Interestingly, estradiol’s effect on the brain is mediated by BDNF (brain derived neurotrophic factor levels), which may be higher in mothers than in those who have not given birth. The researchers note that BDNF may help explain an assocation between high levels of estrogen exposure across a lifespan and a decreased risk of cognitive decline and Alzheimer’s disease. Among rats, those who have been mothers have a reduced age-related decline in spatial memory and other cognitive decline.

The scientists conclude:

Therefore previous reproductive experience, which is associated with altered hormone exposure and greater enrichment, can result in higher levels of plasticity in the middle-aged brain and may protect the brain from the deleterious effects of aging in females.

But there’s a very real caveat.  Applied to humans, these findings are still highly speculative. First, the boost would depend on a woman taking hormone replacement therapy, which remains controversial due to its connection with breast cancer.  (Why hasn’t HRT been shown to improve cognition thus far?  It may because a combination of estrone and 17a-estradiol is much more effective than the current regimen of estrone and progestin.)

More importantly, there is no guarantee that new neurons will improve a person’s ability to learn and remember or decrease the risk of cognitive decline.  As Barha and Galhea warn, all that new growth might even lead to a sort of jungle effect if not properly integrated.  There are clearly other factors that determine what properties these new cells will have as they mature.  Do some mothers put their new neurons to use more effectively than others?  No one knows whether or how, but the question is fascinating.  (More research is underway in Barha and Galea’s lab.)

What’s clear is that motherhood results in permanent changes in the brain.  Will we mothers someday benefit cognitively more than childless women from new hormonal therapies? There’s a chance.  Wouldn’t it be marvelous if a cognitive boost later in life would compensate for all the sleepless nights now?

*If you like this blog, click here for previous posts. If you wish, check out my new book,  Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy. 

Today I was thrilled to see a mention of Chocolate Lovers in one of my favorite parenting sites, Urban Baby.

Here’s my essay touching on some fun science behind  fatherhood, The Plight of the Pregnant Male, in this weekend’s WSJ review.

For months I’ve had a hunch that having a baby has been better for my husband’s image than mine. I don’t mean his looks. Neither of us has had much time to sleep and shower and pay attention to clothing and hair. What I mean is that I think first impressions favor fathers more than mothers.  Pushing our baby along in the stroller, holding a coffee cup and singing, I fall into an easy stereotype, but my husband doesn’t. Yes, in terms of public image, I believe a man benefits more from being a father than a woman benefits from being a mother.

Am I right?

A couple years ago, Ariane Kemkes, a researcher at the Tholius Institute for Research in Applied Demography in Scottsdale, Arizona, asked the same question. Kemkes wondered what would happen if you took a picture of a parent sitting next to his or child, and impartial judges rate that parent in terms of attractiveness, smarts, success, and so on.  Then, she wondered, what would happen if you crop the child out of the photo and ask a different set of judges to rate them on the same criteria?

Are men and women judged differently when they’re with kids than without?  And if so, do fathers benefit from a bigger boost in their social image than do mothers?

The results are intriguing to us new parents.

Men perceive mothers and fathers differently than women do. Looking at a photo of mother and child, male judges are 2.4 times more likely than female judges to believe that the woman is committed to family. Female judges were more cynical and critical of other women’s maternal commitment (but more interested in meeting them). Surprisingly – and to my relief – both sexes are marginally (1.1 times for men, 1.2 for women) more likely to think a woman looked more attractive with a child than when she was alone.  Men, however, were more ambivalent abot meeting women if they were mothers. A mother was also perceived by judges of both genders as slightly, but not significantly, more faithful, honest, and mature.

But what about her mind?  Here comes the crux of my argument about the drawbacks of motherhood.  If a woman was paired with her child, both male and female judges perceived that woman to be less ambitious than if she was alone.  The presence of a child around a woman reduced the woman’s likelihood of being regarded as ambitious by as much as 30 percent.  The assumption by men is unsurprising, but that the stereotype is held by other women is startling. The results may make one pause on bring-your-child-to-work day.

And now, what about men — what does fatherhood do to their image?

Only good things, as I presumed.

Men with children were perceived by all as being committed to family.  Interestingly, fatherhood was good for a man’s social life.  Men were 1.2 times more interested in meeting fellow a man with a child than the same man without a child. And here’s another perk of fatherhood: A man with a child  is perceived to be  of a higher social status.  This comes from judges of both genders. Fathers are also believed to be more faithful, mature, honest.  They’re also thought to be more generous – a perception not transferred to women with children.

Kemkes sums up the stereotype: females most often associate maternity as conflicting with career and leisured activities, while males emphasize financial sacrifices.  A childless woman is perceived as ambitious and a childless male is perceived as cash-strapped, immature, or having a lower social status.  For men, there is a strong association, explainable in evolutionary terms, between reproductive and financial status that does not exist for women.

Moreover, as Kemkes points out, men who are fathers are perceived as more generous than their childless counterparts because emotionally unstable men are more possessive and monopolize resources – traits not associated with fatherhood. Being a dad makes a man appear more “prosocial”; that is, generous and willing to cooperate.  Men are likelier to want to meet dads than childless men because fatherhood lowers expectations of inter-male competition.  It’s now established that fatherhood is linked to lower testosterone levels, especially in the first months after a baby’s birth.

There’s a lesson in research of this kind.  While parenthood generally boosts the social image of both genders, it still cripples career women more than men.  Although more fathers are taking care of the their kids while the mother goes to work, the stereotype that mothers aren’t as ambitious still hasn’t budged – in part, perhaps, because many workplaces continue to make it difficult to excel in both.  So the disappointing fact remains:  A man who prominently features a photo of himself with his children on his desk at work is doing more for his career than a woman who does the same.

*If you like this blog, click here for previous posts. If you wish, check out my new book — hot off the press! –  Do Chocolate Lovers Have Sweeter Babies?: The Surprising Science of Pregnancy.